no active bms

classic Classic list List threaded Threaded
86 messages Options
12345
Reply | Threaded
Open this post in threaded view
|

no active bms

Ben Jarrett


So I've been trying to decide between mini-bms and an EMUS bms.
I've read some of Jack's material and talked to various folks.

I'm starting to think that shunt balancing may not
be a good idea.  It allows you to balance voltages, but not necessarily energy storage.
I'm not sure if voltage balancing is that kind of balancing you actually want.  

I'm just starting to really think through this as I read pros/cons on BMS.
Since Li batteries in cars is still pretty new, I think it makes total sense to monitor
voltages and perhaps temperature of the individual cells. I'm not sure it makes sense
to actively do anything other than turn off the charger once a cell reaches max voltage
(3.6V for Calb, for example) or warn the controller if a min voltage is reached.

So I'm considering mini-bms and removing the shunt resistors.  

I realize that this is not a new topic, but what I'd like to questions is "what is balancing?"
Is it voltage?  It it charge (all the batteries see the same current during charging w/out active
balancing).

thanks!
-ben
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Bill Dube
There is more than one battery manufacturer that will not sell cells
to you if you do not have a BMS. They _require_ a BMS in all
applications. This should tell you something.

All OEM EVs and laptops and cellphones and cordless drills, etc. with
Li-Ion cells have a BMS. No exceptions. This should tell you something too.

There is Jack that says "No BMS" and then there is everyone else.

A malfunctioning BMS (manufacturing defect, poor design, or poor
installation) can indeed damage cells. No BMS will cause a pack fire.

Bill D.

At 10:32 AM 10/21/2011, you wrote:


>So I've been trying to decide between mini-bms and an EMUS bms.
>I've read some of Jack's material and talked to various folks.
>
>I'm starting to think that shunt balancing may not
>be a good idea.  It allows you to balance voltages, but not
>necessarily energy storage.
>I'm not sure if voltage balancing is that kind of balancing you
>actually want.
>
>I'm just starting to really think through this as I read pros/cons on BMS.
>Since Li batteries in cars is still pretty new, I think it makes
>total sense to monitor
>voltages and perhaps temperature of the individual cells. I'm not
>sure it makes sense
>to actively do anything other than turn off the charger once a cell
>reaches max voltage
>(3.6V for Calb, for example) or warn the controller if a min voltage
>is reached.
>
>So I'm considering mini-bms and removing the shunt resistors.
>
>I realize that this is not a new topic, but what I'd like to
>questions is "what is balancing?"
>Is it voltage?  It it charge (all the batteries see the same current
>during charging w/out active
>balancing).
>
>thanks!
>-ben
>-------------- next part --------------
>An HTML attachment was scrubbed...
>URL:
>http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html 
>
>_______________________________________________
>| Moratorium on drag racing discussion is in effect.
>| Please take those discussions elsewhere.  Thanks.
>|
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Peter Gabrielsson
In reply to this post by Ben Jarrett
The ideal balancing circuit would keep all cells at the same SOC at
all times regardless of capacity and cell drift. This is mostly not
practically achievable since it would mean charging and discharging
individual cells, think a bidirectional DCDC on each cell. Knowing the
exact SOC of individual cells at all times is also very difficult.

What we settle for is keeping the cells balanced enough that the
lowest capacity cell is limiting your discharge as well as your
charge, as long as this is the case there is not much need to muck
with the cells at all.

Brute force balancers such as voltage triggered shunt balancers
achieve it by always top balancing the cells whenever you charge the
pack full. I'm not convinced that's a good idea at all, it is the
cheap way to go, but prone to faults that leads to cell failure,
especially if the shunt balancers are poorly designed and don't
consider all failure modes.

More intelligent shunt balancers monitor the voltage and SOC of all
cells over one or more cycles and intelligently decide which shunts to
turn on in order to keep the pack in check. Such designs can have much
smaller shunt resistors since they can balance 24/7 and not just at
the end of charge.

As a hobbyist willing to work on your car and do the occasional manual
balancing all you really need is cell voltage monitoring to tell you
when it's time for pack maintenance, and of course with automatic high
and low cutoffs. I wouldn't trust a blind cell voltage monitor though,
you want something that will display the cell voltages to you so that
you can tell if it's measuring the voltage correctly and still
operating. If a miniBMS node blows an ADC and measures a static
voltage you'll have no idea until it's too late.

Temperature monitoring is also very important, it's you first line of
defense when something goes wrong.

I know this is a religious topic with lots of strong opinions so let
me just say that what I wrote above is my opinion based on 6 years of
designing and testing BMSs and batterypacks for aerospace and
automotive applications, and based on my experience driving a
partially lithium powered car with my own BMS design.





On Fri, Oct 21, 2011 at 9:32 AM, Ben Jarrett <[hidden email]> wrote:

>
>
> So I've been trying to decide between mini-bms and an EMUS bms.
> I've read some of Jack's material and talked to various folks.
>
> I'm starting to think that shunt balancing may not
> be a good idea.  It allows you to balance voltages, but not necessarily energy storage.
> I'm not sure if voltage balancing is that kind of balancing you actually want.
>
> I'm just starting to really think through this as I read pros/cons on BMS.
> Since Li batteries in cars is still pretty new, I think it makes total sense to monitor
> voltages and perhaps temperature of the individual cells. I'm not sure it makes sense
> to actively do anything other than turn off the charger once a cell reaches max voltage
> (3.6V for Calb, for example) or warn the controller if a min voltage is reached.
>
> So I'm considering mini-bms and removing the shunt resistors.
>
> I realize that this is not a new topic, but what I'd like to questions is "what is balancing?"
> Is it voltage?  It it charge (all the batteries see the same current during charging w/out active
> balancing).
>
> thanks!
> -ben
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>



--
www.electric-lemon.com

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Bill Dube
Monitoring SOC on individual cells turns out to be impractical for
LiFePO4 because the cell voltage is virtually flat. However, the
self-discharge is tiny, so very little balance current is actually required.

A low-quality "bargain" BMS is like buying a low-quality "bargain"
parachute. You want to spend a few extra dollars on the proven,
reliable, high-quality BMS (and parachute.)

Forgoing the parachute or the BMS is not really a good idea.

At 11:25 AM 10/21/2011, you wrote:

>The ideal balancing circuit would keep all cells at the same SOC at
>all times regardless of capacity and cell drift. This is mostly not
>practically achievable since it would mean charging and discharging
>individual cells, think a bidirectional DCDC on each cell. Knowing the
>exact SOC of individual cells at all times is also very difficult.
>
>What we settle for is keeping the cells balanced enough that the
>lowest capacity cell is limiting your discharge as well as your
>charge, as long as this is the case there is not much need to muck
>with the cells at all.
>
>Brute force balancers such as voltage triggered shunt balancers
>achieve it by always top balancing the cells whenever you charge the
>pack full. I'm not convinced that's a good idea at all, it is the
>cheap way to go, but prone to faults that leads to cell failure,
>especially if the shunt balancers are poorly designed and don't
>consider all failure modes.
>
>More intelligent shunt balancers monitor the voltage and SOC of all
>cells over one or more cycles and intelligently decide which shunts to
>turn on in order to keep the pack in check. Such designs can have much
>smaller shunt resistors since they can balance 24/7 and not just at
>the end of charge.
>
>As a hobbyist willing to work on your car and do the occasional manual
>balancing all you really need is cell voltage monitoring to tell you
>when it's time for pack maintenance, and of course with automatic high
>and low cutoffs. I wouldn't trust a blind cell voltage monitor though,
>you want something that will display the cell voltages to you so that
>you can tell if it's measuring the voltage correctly and still
>operating. If a miniBMS node blows an ADC and measures a static
>voltage you'll have no idea until it's too late.
>
>Temperature monitoring is also very important, it's you first line of
>defense when something goes wrong.
>
>I know this is a religious topic with lots of strong opinions so let
>me just say that what I wrote above is my opinion based on 6 years of
>designing and testing BMSs and batterypacks for aerospace and
>automotive applications, and based on my experience driving a
>partially lithium powered car with my own BMS design.
>
>
>
>
>
>On Fri, Oct 21, 2011 at 9:32 AM, Ben Jarrett <[hidden email]> wrote:
> >
> >
> > So I've been trying to decide between mini-bms and an EMUS bms.
> > I've read some of Jack's material and talked to various folks.
> >
> > I'm starting to think that shunt balancing may not
> > be a good idea.  It allows you to balance voltages, but not
> necessarily energy storage.
> > I'm not sure if voltage balancing is that kind of balancing you
> actually want.
> >
> > I'm just starting to really think through this as I read pros/cons on BMS.
> > Since Li batteries in cars is still pretty new, I think it makes
> total sense to monitor
> > voltages and perhaps temperature of the individual cells. I'm not
> sure it makes sense
> > to actively do anything other than turn off the charger once a
> cell reaches max voltage
> > (3.6V for Calb, for example) or warn the controller if a min
> voltage is reached.
> >
> > So I'm considering mini-bms and removing the shunt resistors.
> >
> > I realize that this is not a new topic, but what I'd like to
> questions is "what is balancing?"
> > Is it voltage?  It it charge (all the batteries see the same
> current during charging w/out active
> > balancing).
> >
> > thanks!
> > -ben
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
> http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html
> > _______________________________________________
> > | Moratorium on drag racing discussion is in effect.
> > | Please take those discussions elsewhere.  Thanks.
> > |
> > | REPLYING: address your message to [hidden email] only.
> > | Multiple-address or CCed messages may be rejected.
> > | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > | OTHER HELP: http://evdl.org/help/
> > | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
>
>
>--
>www.electric-lemon.com
>
>_______________________________________________
>| Moratorium on drag racing discussion is in effect.
>| Please take those discussions elsewhere.  Thanks.
>|
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Peter Gabrielsson
It requires a lot more intelligent algorithms than just looking at the
voltage. Difficult, yes.

I think we're otherwise in agreement.

On Fri, Oct 21, 2011 at 10:46 AM, Bill Dube <[hidden email]> wrote:

> Monitoring SOC on individual cells turns out to be impractical for
> LiFePO4 because the cell voltage is virtually flat. However, the
> self-discharge is tiny, so very little balance current is actually required.
>
> A low-quality "bargain" BMS is like buying a low-quality "bargain"
> parachute. You want to spend a few extra dollars on the proven,
> reliable, high-quality BMS (and parachute.)
>
> Forgoing the parachute or the BMS is not really a good idea.
>
> At 11:25 AM 10/21/2011, you wrote:
>>The ideal balancing circuit would keep all cells at the same SOC at
>>all times regardless of capacity and cell drift. This is mostly not
>>practically achievable since it would mean charging and discharging
>>individual cells, think a bidirectional DCDC on each cell. Knowing the
>>exact SOC of individual cells at all times is also very difficult.
>>
>>What we settle for is keeping the cells balanced enough that the
>>lowest capacity cell is limiting your discharge as well as your
>>charge, as long as this is the case there is not much need to muck
>>with the cells at all.
>>
>>Brute force balancers such as voltage triggered shunt balancers
>>achieve it by always top balancing the cells whenever you charge the
>>pack full. I'm not convinced that's a good idea at all, it is the
>>cheap way to go, but prone to faults that leads to cell failure,
>>especially if the shunt balancers are poorly designed and don't
>>consider all failure modes.
>>
>>More intelligent shunt balancers monitor the voltage and SOC of all
>>cells over one or more cycles and intelligently decide which shunts to
>>turn on in order to keep the pack in check. Such designs can have much
>>smaller shunt resistors since they can balance 24/7 and not just at
>>the end of charge.
>>
>>As a hobbyist willing to work on your car and do the occasional manual
>>balancing all you really need is cell voltage monitoring to tell you
>>when it's time for pack maintenance, and of course with automatic high
>>and low cutoffs. I wouldn't trust a blind cell voltage monitor though,
>>you want something that will display the cell voltages to you so that
>>you can tell if it's measuring the voltage correctly and still
>>operating. If a miniBMS node blows an ADC and measures a static
>>voltage you'll have no idea until it's too late.
>>
>>Temperature monitoring is also very important, it's you first line of
>>defense when something goes wrong.
>>
>>I know this is a religious topic with lots of strong opinions so let
>>me just say that what I wrote above is my opinion based on 6 years of
>>designing and testing BMSs and batterypacks for aerospace and
>>automotive applications, and based on my experience driving a
>>partially lithium powered car with my own BMS design.
>>
>>
>>
>>
>>
>>On Fri, Oct 21, 2011 at 9:32 AM, Ben Jarrett <[hidden email]> wrote:
>> >
>> >
>> > So I've been trying to decide between mini-bms and an EMUS bms.
>> > I've read some of Jack's material and talked to various folks.
>> >
>> > I'm starting to think that shunt balancing may not
>> > be a good idea.  It allows you to balance voltages, but not
>> necessarily energy storage.
>> > I'm not sure if voltage balancing is that kind of balancing you
>> actually want.
>> >
>> > I'm just starting to really think through this as I read pros/cons on BMS.
>> > Since Li batteries in cars is still pretty new, I think it makes
>> total sense to monitor
>> > voltages and perhaps temperature of the individual cells. I'm not
>> sure it makes sense
>> > to actively do anything other than turn off the charger once a
>> cell reaches max voltage
>> > (3.6V for Calb, for example) or warn the controller if a min
>> voltage is reached.
>> >
>> > So I'm considering mini-bms and removing the shunt resistors.
>> >
>> > I realize that this is not a new topic, but what I'd like to
>> questions is "what is balancing?"
>> > Is it voltage?  It it charge (all the batteries see the same
>> current during charging w/out active
>> > balancing).
>> >
>> > thanks!
>> > -ben
>> > -------------- next part --------------
>> > An HTML attachment was scrubbed...
>> > URL:
>> http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html
>> > _______________________________________________
>> > | Moratorium on drag racing discussion is in effect.
>> > | Please take those discussions elsewhere.  Thanks.
>> > |
>> > | REPLYING: address your message to [hidden email] only.
>> > | Multiple-address or CCed messages may be rejected.
>> > | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>> > | OTHER HELP: http://evdl.org/help/
>> > | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>> >
>>
>>
>>
>>--
>>www.electric-lemon.com
>>
>>_______________________________________________
>>| Moratorium on drag racing discussion is in effect.
>>| Please take those discussions elsewhere.  Thanks.
>>|
>>| REPLYING: address your message to [hidden email] only.
>>| Multiple-address or CCed messages may be rejected.
>>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>>| OTHER HELP: http://evdl.org/help/
>>| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>



--
www.electric-lemon.com

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

"First do no harm" (was: no active bms)

Bill Dube
In reply to this post by Peter Gabrielsson
By the way, I fully agree that it is vital that the BMS be very
reliable. It needs to be designed in a way so that any type fault
that results in a failure, fails the BMS in a benign manner.

A high-quality BMS will be designed to fail in a benign, obvious, and
predictable manner. Like a skilled doctor, the well-designed BMS will
"First do no harm." Not all BMS on the market adhere to this motto.
Before you buy, ask in what ways the particular BMS fails when
subjected to abuse and external faults. Ask how the system behaves
when each of the types of failure occur.

Also ask, "Does the BMS draw its quiescent power 100% evenly from
every cell?" and ask "How much power does the BMS draw from each
cell?" A poor-quality BMS will draw many milliamps (or more)
continuously, while a high-quality BMS will draw a milliamp or less.
A BMS that draws operating power unevenly from the cells is
completely useless because it actively _unbalances_ the pack. (Hobby
store RC balancers are notorious for doing this, by the way.)

Bill D.

At 11:25 AM 10/21/2011, you wrote:

>The ideal balancing circuit would keep all cells at the same SOC at
>all times regardless of capacity and cell drift. This is mostly not
>practically achievable since it would mean charging and discharging
>individual cells, think a bidirectional DCDC on each cell. Knowing the
>exact SOC of individual cells at all times is also very difficult.
>
>What we settle for is keeping the cells balanced enough that the
>lowest capacity cell is limiting your discharge as well as your
>charge, as long as this is the case there is not much need to muck
>with the cells at all.
>
>Brute force balancers such as voltage triggered shunt balancers
>achieve it by always top balancing the cells whenever you charge the
>pack full. I'm not convinced that's a good idea at all, it is the
>cheap way to go, but prone to faults that leads to cell failure,
>especially if the shunt balancers are poorly designed and don't
>consider all failure modes.
>
>More intelligent shunt balancers monitor the voltage and SOC of all
>cells over one or more cycles and intelligently decide which shunts to
>turn on in order to keep the pack in check. Such designs can have much
>smaller shunt resistors since they can balance 24/7 and not just at
>the end of charge.
>
>As a hobbyist willing to work on your car and do the occasional manual
>balancing all you really need is cell voltage monitoring to tell you
>when it's time for pack maintenance, and of course with automatic high
>and low cutoffs. I wouldn't trust a blind cell voltage monitor though,
>you want something that will display the cell voltages to you so that
>you can tell if it's measuring the voltage correctly and still
>operating. If a miniBMS node blows an ADC and measures a static
>voltage you'll have no idea until it's too late.
>
>Temperature monitoring is also very important, it's you first line of
>defense when something goes wrong.
>
>I know this is a religious topic with lots of strong opinions so let
>me just say that what I wrote above is my opinion based on 6 years of
>designing and testing BMSs and batterypacks for aerospace and
>automotive applications, and based on my experience driving a
>partially lithium powered car with my own BMS design.
>
>
>
>
>
>On Fri, Oct 21, 2011 at 9:32 AM, Ben Jarrett <[hidden email]> wrote:
> >
> >
> > So I've been trying to decide between mini-bms and an EMUS bms.
> > I've read some of Jack's material and talked to various folks.
> >
> > I'm starting to think that shunt balancing may not
> > be a good idea.  It allows you to balance voltages, but not
> necessarily energy storage.
> > I'm not sure if voltage balancing is that kind of balancing you
> actually want.
> >
> > I'm just starting to really think through this as I read pros/cons on BMS.
> > Since Li batteries in cars is still pretty new, I think it makes
> total sense to monitor
> > voltages and perhaps temperature of the individual cells. I'm not
> sure it makes sense
> > to actively do anything other than turn off the charger once a
> cell reaches max voltage
> > (3.6V for Calb, for example) or warn the controller if a min
> voltage is reached.
> >
> > So I'm considering mini-bms and removing the shunt resistors.
> >
> > I realize that this is not a new topic, but what I'd like to
> questions is "what is balancing?"
> > Is it voltage?  It it charge (all the batteries see the same
> current during charging w/out active
> > balancing).
> >
> > thanks!
> > -ben
> > -------------- next part --------------
> > An HTML attachment was scrubbed...
> > URL:
> http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html
> > _______________________________________________
> > | Moratorium on drag racing discussion is in effect.
> > | Please take those discussions elsewhere.  Thanks.
> > |
> > | REPLYING: address your message to [hidden email] only.
> > | Multiple-address or CCed messages may be rejected.
> > | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > | OTHER HELP: http://evdl.org/help/
> > | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
>
>
>--
>www.electric-lemon.com
>
>_______________________________________________
>| Moratorium on drag racing discussion is in effect.
>| Please take those discussions elsewhere.  Thanks.
>|
>| REPLYING: address your message to [hidden email] only.
>| Multiple-address or CCed messages may be rejected.
>| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>| OTHER HELP: http://evdl.org/help/
>| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Cell SOC determination (was: no active bms)

Bill Dube
In reply to this post by Peter Gabrielsson
I have seen the SOC "black hole" happen countless times in BMS design for EVs.

Folks get focused on individual cell SOC and then other, more vital,
BMS requirements tend to get pushed aside. The system gets very
complicated. The cost goes way up. The reliability tends to go down.
The quiescent current tends to go up. You end up with an expensive,
complicated, unreliable BMS that draws a lot of current and does a
slipshod job of SOC measurement in exchange.

In a hybrid, you care (somewhat) about individual cell SOC and
capacity measurement while at partial state of charge. In an EV, you
can make sure every cell is 100% SOC at the end of charge (daily) and
that is _really_ simple to do. In an EV, you can "remember" which
cell ran out of juice sooner than all the others, and this takes care
of the capacity determination. Thus, in an EV application, the
designer needs to first focus on reliability, modes of failure, "Do
no harm", and cost.

SOC determination at partial charge is a detrimental distraction for
EV applications in every BMS design I have seen that has implemented
it. Needed in hybrids, so it is worth the effort and cost for that
application, but not for BEVs. You are paying a lot for something a
BEV does not really need.

Bill D.

At 11:57 AM 10/21/2011, you wrote:
>It requires a lot more intelligent algorithms than just looking at the
>voltage. Difficult, yes.
>
>I think we're otherwise in agreement.

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Jukka Järvinen-2
In reply to this post by Ben Jarrett
Ah ! This is wonderfull Peter. Our 'SOC' camp is getting larger.  :)

You do not need to keep the cells in exact same soc in the early days of the pack life. By modeling out individual cell behaviour you can keep notching the cells during normal usage in a way that eventually become more identical from their properties. So eventually BMS makes it self more of just a monitoring system. BMS couldmean battery manipulation system too :)

Current through the series is the same but efficiencies of the cells are not. Differencies were huge with LCP when comparing now to the LFPs. I have not yet figured out the right notching method since overcharging has reversed effect compared to LCP... :/

Allowing heat differencies could work..

-akkuJukka

@my N8
---- alkuperäinen viesti ----
Lähett.: Peter Gabrielsson
Lähet.:  21.10.2011, 20:25
Vast.ott.: Ben Jarrett; Electric Vehicle Discussion List
Aihe: Re: [EVDL] no active bms


The ideal balancing circuit would keep all cells at the same SOC at
all times regardless of capacity and cell drift. This is mostly not
practically achievable since it would mean charging and discharging
individual cells, think a bidirectional DCDC on each cell. Knowing the
exact SOC of individual cells at all times is also very difficult.

What we settle for is keeping the cells balanced enough that the
lowest capacity cell is limiting your discharge as well as your
charge, as long as this is the case there is not much need to muck
with the cells at all.

Brute force balancers such as voltage triggered shunt balancers
achieve it by always top balancing the cells whenever you charge the
pack full. I'm not convinced that's a good idea at all, it is the
cheap way to go, but prone to faults that leads to cell failure,
especially if the shunt balancers are poorly designed and don't
consider all failure modes.

More intelligent shunt balancers monitor the voltage and SOC of all
cells over one or more cycles and intelligently decide which shunts to
turn on in order to keep the pack in check. Such designs can have much
smaller shunt resistors since they can balance 24/7 and not just at
the end of charge.

As a hobbyist willing to work on your car and do the occasional manual
balancing all you really need is cell voltage monitoring to tell you
when it's time for pack maintenance, and of course with automatic high
and low cutoffs. I wouldn't trust a blind cell voltage monitor though,
you want something that will display the cell voltages to you so that
you can tell if it's measuring the voltage correctly and still
operating. If a miniBMS node blows an ADC and measures a static
voltage you'll have no idea until it's too late.

Temperature monitoring is also very important, it's you first line of
defense when something goes wrong.

I know this is a religious topic with lots of strong opinions so let
me just say that what I wrote above is my opinion based on 6 years of
designing and testing BMSs and batterypacks for aerospace and
automotive applications, and based on my experience driving a
partially lithium powered car with my own BMS design.





On Fri, Oct 21, 2011 at 9:32 AM, Ben Jarrett <[hidden email]> wrote:

>
>
> So I've been trying to decide between mini-bms and an EMUS bms.
> I've read some of Jack's material and talked to various folks.
>
> I'm starting to think that shunt balancing may not
> be a good idea.  It allows you to balance voltages, but not necessarily energy storage.
> I'm not sure if voltage balancing is that kind of balancing you actually want.
>
> I'm just starting to really think through this as I read pros/cons on BMS.
> Since Li batteries in cars is still pretty new, I think it makes total sense to monitor
> voltages and perhaps temperature of the individual cells. I'm not sure it makes sense
> to actively do anything other than turn off the charger once a cell reaches max voltage
> (3.6V for Calb, for example) or warn the controller if a min voltage is reached.
>
> So I'm considering mini-bms and removing the shunt resistors.
>
> I realize that this is not a new topic, but what I'd like to questions is "what is balancing?"
> Is it voltage?  It it charge (all the batteries see the same current during charging w/out active
> balancing).
>
> thanks!
> -ben
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/3c803275/attachment.html
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>



--
www.electric-lemon.com

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Robert MacDowell-2
In reply to this post by Bill Dube
On Fri, Oct 21, 2011 at 10:21 AM, Bill Dube <[hidden email]> wrote:

> There is more than one battery manufacturer that will not sell cells
> to you if you do not have a BMS. They _require_ a BMS in all
> applications. This should tell you something.
>


That's the opposite of the battery I just worked with this week.  It is 12V
(10 cells) about 200 pounds and 40-50 years old.  It had been neglected
completely since about 1988 and been through many cold winters.  I cleaned
up piles of electrolyte spoo on top of the cells; saw the electrolyte levels
were above the plates, and threw a charger on it.  Common 6-amp lead-acid
charger, for 5 minutes.  It gulped up "max amps" quickly rolling down to 3.
Uh-oh.  I unhooked it and it burned a 2-amp load for 5 minutes and it didn't
fade.  I stuck the charger back on it for 4 hours.  3 days later (no
charging since) it still handles loads just fine and I've cleared folks to
use it without restriction.  I would not have believed it, but there it is
working.

I'm told this type is healed by overcharge and to go ahead and give it the
works.  This seems nonsensical but nothing so far has refuted it.

Robert
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/866213c3/attachment.html 
_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

corbin dunn

On Oct 21, 2011, at 12:44 PM, Robert MacDowell wrote:

> On Fri, Oct 21, 2011 at 10:21 AM, Bill Dube <[hidden email]> wrote:
>
>> There is more than one battery manufacturer that will not sell cells
>> to you if you do not have a BMS. They _require_ a BMS in all
>> applications. This should tell you something.
>>
>
>
> That's the opposite of the battery I just worked with this week.  It is 12V
> (10 cells) about 200 pounds and 40-50 years old.  

Yeah, but Bill is talking about lithium based cells. I'm gathering your cells weren't lithium if they were that old.

corbin

> It had been neglected
> completely since about 1988 and been through many cold winters.  I cleaned
> up piles of electrolyte spoo on top of the cells; saw the electrolyte levels
> were above the plates, and threw a charger on it.  Common 6-amp lead-acid
> charger, for 5 minutes.  It gulped up "max amps" quickly rolling down to 3.
> Uh-oh.  I unhooked it and it burned a 2-amp load for 5 minutes and it didn't
> fade.  I stuck the charger back on it for 4 hours.  3 days later (no
> charging since) it still handles loads just fine and I've cleared folks to
> use it without restriction.  I would not have believed it, but there it is
> working.
>
> I'm told this type is healed by overcharge and to go ahead and give it the
> works.  This seems nonsensical but nothing so far has refuted it.
>
> Robert
> -------------- next part --------------
> An HTML attachment was scrubbed...
> URL: http://lists.sjsu.edu/mailman/private/ev/attachments/20111021/866213c3/attachment.html 
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

EVDL Administrator
In reply to this post by Robert MacDowell-2
On 21 Oct 2011 at 12:44, Robert MacDowell wrote:

> That's the opposite of the battery I just worked with this week.  It
> is 12V (10 cells) about 200 pounds and 40-50 years old.  It had been
> neglected completely since about 1988 and been through many cold
> winters.  ...  I would not have believed it, but there it is working.

Sounds like a flooded NiCd battery.  The good ones are nigh onto
bulletproof.  

They're bothered very little by overcharging.  Nor is overdischarging a big
deal; even cell reversal, while it's not good for them, is seldom fatal.  
They can sit for years at low (or, better, zero) SOC with no harm.  They
won't freeze.  They aren't affected by sulfation since the electrolyte is
strictly an ion carrier.  Voltage is nearly flat over discharge.  They can
be cycled thousands of times with little loss of capacity.

So why don't EVs use them?  For one thing, cadmium is considered evil these
days and tightly regulated.  They are also just plain out of fashion.  
Finally, most people consider flooded batteries a nonstarter for "Joe and
Jane Average" EVs, and with some justification.

Their updated and more benign couisin is NiMH, but regrettably that battery
is imprisoned by deliberate anti-BEV restrictions placed on it by the patent
holder.

David Roden - Akron, Ohio, USA
EVDL Administrator

= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
EVDL Information: http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Note: mail sent to "evpost" and "etpost" addresses will not
reach me.  To send a private message, please obtain my
email address from the webpage http://www.evdl.org/help/ .
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Chris Zach
In reply to this post by Robert MacDowell-2
On 10/21/2011 3:44 PM, Robert MacDowell wrote:
> I'm told this type is healed by overcharge and to go ahead and give it the
> works.  This seems nonsensical but nothing so far has refuted it.

Yup. Even the 100 year old Edison cells still work fine. Worst case is
you need to replace the pig intestines that they used as a plate
separator, those had to be replaced every... 50? years or so.

The flooded NiCDs I use in the tractor are indestructible. Pulling 300a
for the snowblower in the dead of winter is kind of the ultimate test,
and they passed with flying colors. Note that it is *best* to store the
batteries dead-shorted.

Just keep vinegar and other acids away from them and don't way overheat
them. I've heard that some of the older Marathon BB600 cells would have
seperator issues when seriously overheted, but the SAFT BB600's have
improved separators.

Speaking of which, anyone got a set of 100ah SAFT NICds? I would be so
more than glad to take them off your hands....

Chris

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Rush Dougherty
In reply to this post by corbin dunn
.
>
> Yeah, but Bill is talking about lithium based cells. I'm gathering your cells weren't lithium if
> they were that old.
>

Back from the future...

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Lee Hart
In reply to this post by Robert MacDowell-2
>> There is more than one battery manufacturer that will not sell cells
>> to you if you do not have a BMS. They _require_ a BMS in all
>> applications. This should tell you something.

Robert MacDowell wrote:
> That's the opposite of the battery I just worked with this week.  It is 12V
> (10 cells) about 200 pounds and 40-50 years old... neglected since 1988...
> it still handles loads just fine...

Sounds like nickel-iron (Edison cells). When built right, they are darn
near immortal.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Lee Hart
In reply to this post by Jukka Järvinen-2
jukka järvinen wrote:

> Ah ! This is wonderfull Peter. Our 'SOC' camp is getting larger.  :)
>
> You do not need to keep the cells in exact same soc in the early days
> of the pack life. By modeling out individual cell behaviour you can
> keep notching the cells during normal usage in a way that eventually
> become more identical from their properties. So eventually BMS makes
> it self more of just a monitoring system. BMS could mean battery
> manipulation system too :)
>
> Current through the series is the same but efficiencies of the cells
> are not. Differences were huge with LCP when comparing now to the
> LFPs. I have not yet figured out the right notching method since
> overcharging has reversed effect compared to LCP... :/
>
> Allowing heat differencies could work..

It does this "Hart" good to see so many constructive comments on this
topic. :-) It saves me from have to repeat what I've been saying for
over ten years; that a BMS is necessary and useful, but has to be
constructed carefully so it won't cause more problems than it solves.

My earlier balancers just measured voltage. This is good for detecting
problems (dead or overcharged cells), and adequate for approximate
balancing.

But there are additional advantages to SOC based balancing. When the
differences between cells is large (due to initial quality or
degradation from age), a balancer that knows each cell's capacity and
can transfer charge between them can extend your vehicle's range, and
extend pack life. The more expensive the batteries, the more important
this becomes.

Suppose we had an "Einstein" BMS, with perfect knowledge about each
cell, and the ability to charge or discharge each one individually. It
can then lighten the load on the weaker cells to extend their life, by
increasing the load on the stronger cells. Thus you won't face the
prospect of having to replace your whole pack when only a few cells are
bad. This also extends your range, since it "props up" the weaker cells
with power from the stronger ones.
--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

EVDL Administrator
In reply to this post by Chris Zach
On 21 Oct 2011 at 17:17, Chris Zach wrote:

> Speaking of which, anyone got a set of 100ah SAFT NICds? I would be so
> more than glad to take them off your hands....

Early STM5-100s (with the removeable vent caps) are pretty much what you
expect - very sturdy and long-lived.  The closed top MR and MRE (reduced
maintenance) type made after 2000 are reportedly also good, though perhaps
not as long-lived as the oldest ones.

However, the early MR and MRE modules are subject to separator failures.  
They should never be asked to produce more than 200 or perhaps 250 amps, not
even for a few seconds.  It's better to avoid these modules.  

More info :

http://www.evdl.org/docs/saft-failures.pdf

David Roden - Akron, Ohio, USA
EVDL Administrator

= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
EVDL Information: http://www.evdl.org/help/
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Note: mail sent to "evpost" and "etpost" addresses will not
reach me.  To send a private message, please obtain my
email address from the webpage http://www.evdl.org/help/ .
= = = = = = = = = = = = = = = = = = = = = = = = = = = = =


_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Jukka Järvinen-2
In reply to this post by Lee Hart
As if no one in the field has yet seen this patent document:
http://www.freepatentsonline.com/20090218986.pdf

:P

Anyway.. the active data collection to draft out the algorithms for
better management methods is essential (in my opinion) since there are
always some differences in the cells (manufacturing patches,
chemistry, new innovations, etc.). You can actually modify the cell
properties by using them (wearing off) unevenly and eventually calls
become more and more identical. This seems to work well with LCP cells
that are more fragile than LFP.

Now.. does the LFP cells in EVs already deliver crushing numbers
against ICEs ? Pretty much so unless you intentionally murder the
cells with No- or Poor-BMS -strategy. What is the "next step" in BMS
and batteries.

I feel now strongly that it is in the recycling and reusing the cell
materials. Next big thing to me is to find the right way to finish-off
the cells when they are ready to be dismantled and recycled. Most of
the materials in the cell can be used just as they are over and over
again. So why go for the virginity and not use proven old-good ? And
pay more and more to the same IPR-pool ?

So how much more effective investment for EV hobbyist it would be to
use recycled materials and pay 20% the price of new cells ? Could the
grass-root level still be doing the wonderful work with prices and
resources big industry is crying for ? Too many questions ? Ok.. I'll
stop here. :)

About the "Einstein" BMS. Is it really bad-bad if the BMS is 10% of
the price of the whole pack ? We could do that already 6 years ago.
With 20W DC/DC on every cell with controller logic. The actual wisdom
was shared between our work remotely over wireless data transfers and
local Embedded Linux PC. Biggest issue was the energy consumption of
the system which was about 50 W continuously. But we gained a lot of
knowledge from real application usage. Few of the vehicles are STILL
running after 7 years (or so). LCP cells are also used :P

So.. we've had Apple MiniMac PCs in the vehicles for 7 years and they
are still running with the original Linux SW. And some super experts
shoot us down telling us our setups are most unreliable stuff they've
ever seen.  HA!

I'll wrote more about the experiences as soon as I have more time.

-akkuJukka

http://www.google.com/profiles/jarviju#about



2011/10/22 Lee Hart <[hidden email]>:

> jukka järvinen wrote:
>> Ah ! This is wonderfull Peter. Our 'SOC' camp is getting larger.  :)
>>
>> You do not need to keep the cells in exact same soc in the early days
>> of the pack life. By modeling out individual cell behaviour you can
>> keep notching the cells during normal usage in a way that eventually
>> become more identical from their properties. So eventually BMS makes
>> it self more of just a monitoring system. BMS could mean battery
>> manipulation system too :)
>>
>> Current through the series is the same but efficiencies of the cells
>> are not. Differences were huge with LCP when comparing now to the
>> LFPs. I have not yet figured out the right notching method since
>> overcharging has reversed effect compared to LCP... :/
>>
>> Allowing heat differencies could work..
>
> It does this "Hart" good to see so many constructive comments on this
> topic. :-) It saves me from have to repeat what I've been saying for
> over ten years; that a BMS is necessary and useful, but has to be
> constructed carefully so it won't cause more problems than it solves.
>
> My earlier balancers just measured voltage. This is good for detecting
> problems (dead or overcharged cells), and adequate for approximate
> balancing.
>
> But there are additional advantages to SOC based balancing. When the
> differences between cells is large (due to initial quality or
> degradation from age), a balancer that knows each cell's capacity and
> can transfer charge between them can extend your vehicle's range, and
> extend pack life. The more expensive the batteries, the more important
> this becomes.
>
> Suppose we had an "Einstein" BMS, with perfect knowledge about each
> cell, and the ability to charge or discharge each one individually. It
> can then lighten the load on the weaker cells to extend their life, by
> increasing the load on the stronger cells. Thus you won't face the
> prospect of having to replace your whole pack when only a few cells are
> bad. This also extends your range, since it "props up" the weaker cells
> with power from the stronger ones.
> --
> Lee A. Hart             | Ring the bells that still can ring
> 814 8th Ave N           | Forget the perfect offering
> Sartell MN 56377        | There is a crack in everything
> leeahart earthlink.net  | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
> | Please take those discussions elsewhere.  Thanks.
> |
> | REPLYING: address your message to [hidden email] only.
> | Multiple-address or CCed messages may be rejected.
> | UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> | OTHER HELP: http://evdl.org/help/
> | CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

mark at evie-systems
I'm curious what the consequence of this patent is?  Does it negate the
possibility of anyone else "inventing" such a technology without paying
royalties to said patent holder?

Jukka Järvinen wrote:
> As if no one in the field has yet seen this patent document:
> http://www.freepatentsonline.com/20090218986.pdf
>
> :P
>

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
~ ~ ~ ~ ~ ~
mark@evie-systems.com
"Delay is preferable to error", Thomas Jefferson.
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Cor van de Water
Mark,

I have the opinion that this patent will do nothing to
promote or reduce the use of BMS'es and - sorry for Jukka -
it is again my opinion that his patent has zero value with
maybe an exception for claim 12.
The way that Patents work is that you can claim something
and you can defend it *only* if there has not been a public
presentation of the subject that has taken place before the
Priority Date of the invention.
In addition, anyone who has something that would fall under
the claims, already developed and/or selling in products,
by the Priority Date, can continue to do so after the Patent
is awarded without infringing, because the Patent does not
give rights on things that already exist.

Now, looking through the claims, I recognise the general
operation of a Battery Management System and one of those
that has been published widely and certainly before the
2007 Prio Date of this patent is the Lee Hart Battery Balancer.
So, that takes care of the claims 1 - 11 because they all
either call on claim 1 or describe directly that they work
on individual cells to monitor and influence their relative
properties (such as state of charge).

Only claim 12 is something that I am not sure if it has not
been published before, having the central management part of
the BMS running on a remote server.

Since Patents can be a tricky proposition in relation to
your business (NOTE that you can always build the device as
claimed in the Patent for your own use without infringing,
even building it with the purpose of improving it so you
do no longer infringe this patent and you can actually file for
your own patent, can never be forbidden. You cannot manufacture
and sell the claimed inventions without infringing, but then
there is the situation that I described here, whether the
patent has actually any value and can be defended depends on
whether you can prove there is already "Prior Art" that makes
the patent claims which you infringe, void.
So - don't just rely on my words, get a patent lawyer or other
professional advice as I do not accept liability for following
what I present here as my opinion, because I am not a lawyer.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
Skype: cor_van_de_water     XoIP: +31877841130
Tel: +1 408 383 7626        Tel: +91 (040)23117400 x203

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf Of mark at evie-systems
Sent: Saturday, October 22, 2011 3:19 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] no active bms

I'm curious what the consequence of this patent is?  Does it negate the possibility of anyone else "inventing" such a technology without paying royalties to said patent holder?

Jukka Järvinen wrote:
> As if no one in the field has yet seen this patent document:
> http://www.freepatentsonline.com/20090218986.pdf
>
> :P
>

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
Reply | Threaded
Open this post in threaded view
|

Re: no active bms

Jukka Järvinen-2
In reply to this post by Ben Jarrett
I hope that in this forum it would bring in a bit more info what has been already done in the field. I have nothing to do anymore with the company which holds the patent. What it comes to patents in general that is another question. I think they are supposed to bring some sort of monopoly to the patent holder. I do admit that it would be wonderfull to be able to pay back the research work of dozens of people over several years.
Now.. It is always possible to make things better. Should we put our efforts on that ?
-akkuJukka
@my N8
---- alkuperäinen viesti ----
Lähett.: mark at evie-systems
Lähet.:  22.10.2011, 12:48
Vast.ott.: Electric Vehicle Discussion List
Aihe: Re: [EVDL] no active bms


I'm curious what the consequence of this patent is?  Does it negate the
possibility of anyone else "inventing" such a technology without paying
royalties to said patent holder?

Jukka Järvinen wrote:
> As if no one in the field has yet seen this patent document:
> http://www.freepatentsonline.com/20090218986.pdf
>
> :P
>

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev

_______________________________________________
| Moratorium on drag racing discussion is in effect.
| Please take those discussions elsewhere.  Thanks.
|
| REPLYING: address your message to [hidden email] only.
| Multiple-address or CCed messages may be rejected.
| UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
| OTHER HELP: http://evdl.org/help/
| CONFIGURE: http://lists.sjsu.edu/mailman/listinfo/ev
12345