Re: NiMH availablity ...

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Re: NiMH availablity ...

Sean Korb
It's 2014 now... a magic date for NiMH large format batteries.
http://www.winonarenewableenergy.com/1/post/2012/04/ev-batteries-are-being-held-hostage.html

Where are my cheap NiMH large format batteries?  Any news now that the
patents are expiring (expired?).

Just curious.

sean

On Thu, Jul 25, 2013 at 7:17 PM, Bruce EVangel Parmenter
<[hidden email]> wrote:

> [In reference to
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Ford-And-Tesla-Pushing-Toyota-To-Adopt-Li-ion-tp4664317.html
> EVLN: Ford And Tesla Pushing Toyota To Adopt Li-ion
> ]
>
> I pawed through the evdl nabble archive on this and found that ...
> Toyota had preferred to use NiMH for their hybrids for quite some time
> ...
>
> http://www.evdl.org/archive/index.html#nabble-td3085326
> Toyota will stay with NiMH for 10+ years, Chevron-out/ECD-in +
> Dec 13, 2010
>
>
> The following newswire explains that TMC improved on the NiMH design
> (along with some other money saving techniques) ...
>
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Building-hybrids-on-the-cheap-td4658568.html
> EVLN: Building hybrids on the cheap
> Oct 12, 2012 ... Toyota Motor Corporation, instead of switching to
> Lithium-ion [Li-ion] battery packs, which are more expensive, was able
> to make its current Nickel-Metal Hydride [NiMH] battery packs more
> efficient. They did this by changing the shape of individual cells from
> cylindrical to flat, and modified the case to improve cooling and
> lifespan. Toyota also switched from 500 V to 650 V, a decision that
> produced "a host of benefits," says Justin Ward, advanced power-train
> program manager at the Toyota Technical Center. Toyota was able to
> reduce the size of the drive motor without sacrificing performance. This
> small change reduced the amount of copper needed in the motor assembly,
> and therefore the cost of the component ...
>
>
> Ford had switched to using Li-ion in their hybrids a while ago
>
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Ford-s-New-Hybrid-Battery-Pack-Testing-Techniques-td4660294.html
> EVLN: Ford's New Hybrid Battery Pack Testing Techniques
> Jan 01, 2013 ... Unlike previous-generation vehicles from Ford's lineup
> that featured nickel-metal-hydride (NiMH) batteries, li-ion batteries
> offer numerous benefits - including a size 25 to 30 percent smaller, and
> the ability to provide about three times the amount of power per cell
> than the previous state-of-the-art NiMH battery technology ...
>
>
> With all this chatter about NiMH, it had me thinking, that maybe, just
> maybe NiMH would begin to be available the public (unlike before). We
> all know about the NiMH patent lockup so no one could get them:
> http://www.winonarenewableenergy.com/1/post/2012/04/ev-batteries-are-being-held-hostage.html
> http://en.wikipedia.org/wiki/Patent_encumbrance_of_large_automotive_NiMH_batteries
> http://en.wikipedia.org/wiki/Cobasys#Criticisms
>
> But the patent and manufacture of large format NiMH batteries has
> changed hands. Yet, a search really only shows individual cells yanked
> from hybrid vehicle packs for resale.
> http://www.google.com/search?hl=en&tbm=shop&q=nimh+batteries+prius
>
> -Where can a person buy large format NiMH cells to build a pack for
> their conversion?
>
>
> Some in the media may say it was the high energy density of Li-ion that
> got us where we are today. But it is more likely that the 'availability'
> of li-ion that really tells the story. So, I was wondering, what if NiMH
> 'had-been available' a decade ago and the CARB mandate had as much teeth
> (support) as it has today?
>
>
> {Dream mode on: let's assume NiMH large format cells/pack were available
> 10+years ago}
> So, if today's production EVs were using a NiMH pack of the same Ah
> density ...
>
> -The range would be the same, right? Or would a NiMH pack weigh more?
>
> -What would be the cost difference? Does the older NiMH technology cost
> less to manufacture? Perhaps now that li-ion is the standard, NiMH price
> will drop?
>
> If NiMH had not had the blockage to keep it from being available, (and
> political forces had allowed CARB to do their job), we could have had
> compliance EVs over ten years ago in the 2000's, right?
>
>
> Back then automakers would have to use their (older) ice sedan platforms
> for their compliance-car:
>
> http://en.wikipedia.org/wiki/Ford_Escort_%28North_America%29#Third_generation_.281997.E2.80.932002.29
> Ford Escort
>
> http://en.wikipedia.org/wiki/Chevrolet_Malibu#Fifth_generation_.281997.E2.80.932003.29
> Chevy Malibu
>
> http://en.wikipedia.org/wiki/Honda_Civic#Seventh_generation_.282000.E2.80.932005.29_-_EM2.2C_ES1.2C_EP1.2C_EP2.2C_EP3.2C_EU1.2C_EV1
> Honda Civic
>
>
> In those days, there wasn't any L3 EVSE standard. But what if one had
> been implemented?
>
> -What is the %SOC point one wants to stop charging NiMH at high current
> levels? Is it 80% like with Li-ion?
>
> -Does the pack heat up more or less than li-ion and require cooling?
>
>
>
> Corrections & comments are welcome.
>
>
> {brucedp.150m.com}
>
> --
> http://www.fastmail.fm - Or how I learned to stop worrying and
>                           love email again
>
> _______________________________________________
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>



--
Sean Korb [hidden email] http://www.spkorb.org
'65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso
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Re: NiMH availablity ...

brucedp5
Both the URL you referenced to below
EV Batteries are being held hostage  04/11/2012
 , and the URL of my post
EVLN: Ford And Tesla Pushing Toyota To Adopt Li-ion  Jul 20, 2013
 are quite old.

And a lot of information on NiMH is either old and or out of date,
including the Wikipedia listing found on a search
https://www.google.com/search?q=NiMH+large+format+batteries

http://en.wikipedia.org/wiki/Patent_encumbrance_of_large_automotive_NiMH_batteries#Current_status_of_the_Ovonics_battery_technology
  sez ... February 14, 2012 BASF acquired Ovonic Battery Company and has
  ownership of the NiMH patent.

For a huge company like BASF, it would be no problem to tweak the NiMH
design enough to get another patent, so although that search (above URL)
did have some links wanting NiMH to be set free in 2014, it still may
not.

From what I can tell, NiMH is currently being used in hybrid packs, with
the reasoning being NiMH handles the higher amount of charges/discharges
of a small kWh hybrid pack (~1 mile of range) more affordably than a
small Li-ion pack, or so sez TMC.

It looks like it is still going to be a wait-n-see effort if NiMH ever
get s out of the grips of the legal tie-ups it has been put through.
IMO I would not wait. A long time ago I had posted my interest in
perhaps cheap China made NiMH batteries. But that did not happen. So,
waiting, and waiting for cheap large format NiMH batteries to be made
available for the public to purchase, may be a fruitless effort when
there are more affordable large format Li-ion batteries available for
the public to purchase now.


{brucedp.150m.com}



-
On Thu, Mar 6, 2014, at 07:52 AM, Sean Korb wrote:

> It's 2014 now... a magic date for NiMH large format batteries.
> http://www.winonarenewableenergy.com/1/post/2012/04/ev-batteries-are-being-held-hostage.html
>
> Where are my cheap NiMH large format batteries?  Any news now that the
> patents are expiring (expired?) ...
>
> On Thu, Jul 25, 2013 at 7:17 PM, Bruce EVangel Parmenter
> <[hidden email]> wrote:
> > [In reference to
> > http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Ford-And-Tesla-Pushing-Toyota-To-Adopt-Li-ion-tp4664317.html
> > EVLN: Ford And Tesla Pushing Toyota To Adopt Li-ion
> > ]
> >
> > I pawed through the evdl nabble archive on this and found that ...
> > Toyota [TMC] had preferred to use NiMH for their hybrids for quite some time ...
-

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  http://www.fastmail.fm/help/overview_quotes.html

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Re: NiMH availablity ...

Sean Korb
Well drat.  But it does look like Li-ion is getting incrementally
cheaper with every passing day. A $10k loan to get started for a 75
mile pack/management/charger is still a barrier.  I wish I could get
the same rates as I could for a car loan but it's really hard to
convince a bank that they could repossess my battery :)

On Thu, Mar 6, 2014 at 12:12 PM, Bruce EVangel Parmenter
<[hidden email]> wrote:

> Both the URL you referenced to below
> EV Batteries are being held hostage  04/11/2012
>  , and the URL of my post
> EVLN: Ford And Tesla Pushing Toyota To Adopt Li-ion  Jul 20, 2013
>  are quite old.
>
> And a lot of information on NiMH is either old and or out of date,
> including the Wikipedia listing found on a search
> https://www.google.com/search?q=NiMH+large+format+batteries
>
> http://en.wikipedia.org/wiki/Patent_encumbrance_of_large_automotive_NiMH_batteries#Current_status_of_the_Ovonics_battery_technology
>   sez ... February 14, 2012 BASF acquired Ovonic Battery Company and has
>   ownership of the NiMH patent.
>
> For a huge company like BASF, it would be no problem to tweak the NiMH
> design enough to get another patent, so although that search (above URL)
> did have some links wanting NiMH to be set free in 2014, it still may
> not.
>
> From what I can tell, NiMH is currently being used in hybrid packs, with
> the reasoning being NiMH handles the higher amount of charges/discharges
> of a small kWh hybrid pack (~1 mile of range) more affordably than a
> small Li-ion pack, or so sez TMC.
>
> It looks like it is still going to be a wait-n-see effort if NiMH ever
> get s out of the grips of the legal tie-ups it has been put through.
> IMO I would not wait. A long time ago I had posted my interest in
> perhaps cheap China made NiMH batteries. But that did not happen. So,
> waiting, and waiting for cheap large format NiMH batteries to be made
> available for the public to purchase, may be a fruitless effort when
> there are more affordable large format Li-ion batteries available for
> the public to purchase now.
>
>
> {brucedp.150m.com}
>
>
>
> -
> On Thu, Mar 6, 2014, at 07:52 AM, Sean Korb wrote:
>> It's 2014 now... a magic date for NiMH large format batteries.
>> http://www.winonarenewableenergy.com/1/post/2012/04/ev-batteries-are-being-held-hostage.html
>>
>> Where are my cheap NiMH large format batteries?  Any news now that the
>> patents are expiring (expired?) ...
>>
>> On Thu, Jul 25, 2013 at 7:17 PM, Bruce EVangel Parmenter
>> <[hidden email]> wrote:
>> > [In reference to
>> > http://electric-vehicle-discussion-list.413529.n4.nabble.com/EVLN-Ford-And-Tesla-Pushing-Toyota-To-Adopt-Li-ion-tp4664317.html
>> > EVLN: Ford And Tesla Pushing Toyota To Adopt Li-ion
>> > ]
>> >
>> > I pawed through the evdl nabble archive on this and found that ...
>> > Toyota [TMC] had preferred to use NiMH for their hybrids for quite some time ...
> -
>
> --
> http://www.fastmail.fm - One of many happy users:
>   http://www.fastmail.fm/help/overview_quotes.html
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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>



--
Sean Korb [hidden email] http://www.spkorb.org
'65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso
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Re: NiMH availablity ...

Cruisin
I have a 18kw Li-ion pack for $4000.00. You cant do better than that?
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Re: NiMH availablity ...

Sean Korb
I don't have regen on my GE forklift motor and Curtis controller so
that sounds about right.  I'd need 1.5 of those packs plus about $1000
in charger and BMS electronics.  I have a 40 mile round trip commute
and a 10 mile lunch/bank run but my car is very light so that only
uses.. well about 18kwh.

I should have at least 24kwh so I don't kill the battery and I have
some room to keep 18kwh over 8 years so that I can amortize the cost
fully.

Maybe I really only need 7 or $8000?


On Thu, Mar 6, 2014 at 12:27 PM, Cruisin <[hidden email]> wrote:

> I have a 18kw Li-ion pack for $4000.00. You cant do better than that?
>
>
>
> --
> View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-NiMH-availablity-tp4668269p4668273.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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>



--
Sean Korb [hidden email] http://www.spkorb.org
'65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso
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Re: NiMH availablity ...

Ruckus
BMS?  Sure, if you got extra cash, but it sounds like you are working a
tight budget.  If so, go bottom balance and cut charge a little early.
 Fairly easy to identify your weakest cell and monitor just that one to
prevent overcharge (it will get full first).

Cheers


On Thu, Mar 6, 2014 at 10:59 AM, Sean Korb <[hidden email]> wrote:

> I don't have regen on my GE forklift motor and Curtis controller so
> that sounds about right.  I'd need 1.5 of those packs plus about $1000
> in charger and BMS electronics.  I have a 40 mile round trip commute
> and a 10 mile lunch/bank run but my car is very light so that only
> uses.. well about 18kwh.
>
> I should have at least 24kwh so I don't kill the battery and I have
> some room to keep 18kwh over 8 years so that I can amortize the cost
> fully.
>
> Maybe I really only need 7 or $8000?
>
>
> On Thu, Mar 6, 2014 at 12:27 PM, Cruisin <[hidden email]> wrote:
> > I have a 18kw Li-ion pack for $4000.00. You cant do better than that?
> >
> >
> >
> > --
> > View this message in context:
> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-NiMH-availablity-tp4668269p4668273.html
> > Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
> > _______________________________________________
> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> > For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
> >
>
>
>
> --
> Sean Korb [hidden email] http://www.spkorb.org
> '65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
> "The more you drive, the less intelligent you get" --Miller
> "Computers are useless.  They can only give you answers." -P. Picasso
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>


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Re: NiMH availablity ...

Ruckus
ps.  I got 38 kWh blue Calb for $11,000, so deals are out there..


On Thu, Mar 6, 2014 at 4:22 PM, Marcus Reddish <[hidden email]>wrote:

> BMS?  Sure, if you got extra cash, but it sounds like you are working a
> tight budget.  If so, go bottom balance and cut charge a little early.
>  Fairly easy to identify your weakest cell and monitor just that one to
> prevent overcharge (it will get full first).
>
> Cheers
>
>
> On Thu, Mar 6, 2014 at 10:59 AM, Sean Korb <[hidden email]> wrote:
>
>> I don't have regen on my GE forklift motor and Curtis controller so
>> that sounds about right.  I'd need 1.5 of those packs plus about $1000
>> in charger and BMS electronics.  I have a 40 mile round trip commute
>> and a 10 mile lunch/bank run but my car is very light so that only
>> uses.. well about 18kwh.
>>
>> I should have at least 24kwh so I don't kill the battery and I have
>> some room to keep 18kwh over 8 years so that I can amortize the cost
>> fully.
>>
>> Maybe I really only need 7 or $8000?
>>
>>
>> On Thu, Mar 6, 2014 at 12:27 PM, Cruisin <[hidden email]> wrote:
>> > I have a 18kw Li-ion pack for $4000.00. You cant do better than that?
>> >
>> >
>> >
>> > --
>> > View this message in context:
>> http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-NiMH-availablity-tp4668269p4668273.html
>> > Sent from the Electric Vehicle Discussion List mailing list archive at
>> Nabble.com.
>> > _______________________________________________
>> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>> > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
>> > For EV drag racing discussion, please use NEDRA (
>> http://groups.yahoo.com/group/NEDRA)
>> >
>>
>>
>>
>> --
>> Sean Korb [hidden email] http://www.spkorb.org
>> '65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
>> "The more you drive, the less intelligent you get" --Miller
>> "Computers are useless.  They can only give you answers." -P. Picasso
>> _______________________________________________
>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
>> For EV drag racing discussion, please use NEDRA (
>> http://groups.yahoo.com/group/NEDRA)
>>
>>
>
>
> --
> Marcus Reddish
>



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Re: NiMH availablity ...

Sean Korb
In reply to this post by Ruckus
I think for many bottom balancing can be a real solution but it takes
a special talent.

I have an unreasonably heavy foot.  I think even when I build a BMS
I'll need to program it to cut out a bit early to save my pack from
myself.  I would need to identify and restrain the weaker battery at
the first sign of trouble and I'd like a computer to alert me.  Bottom
balancing requires that I become the BMS and I'm not fastidious enough
or rational enough to set battery limits in a reactive setting.

The other day my Honda (off topic) had a heater hose leak.  Instead of
pulling over to tape it up I drove the next mile to work and hoped for
the best.  It worked out but if it had been a voltage sag instead I
might have pushed it and ruined the pack.  I need to set up very firm
boundaries in advance.  Not as much a $$$ decision as it is a design
decision.

sean

On Thu, Mar 6, 2014 at 6:22 PM, Marcus Reddish <[hidden email]> wrote:

> BMS?  Sure, if you got extra cash, but it sounds like you are working a
> tight budget.  If so, go bottom balance and cut charge a little early.
> Fairly easy to identify your weakest cell and monitor just that one to
> prevent overcharge (it will get full first).
>
> Cheers
>
>
> On Thu, Mar 6, 2014 at 10:59 AM, Sean Korb <[hidden email]> wrote:
>>
>> I don't have regen on my GE forklift motor and Curtis controller so
>> that sounds about right.  I'd need 1.5 of those packs plus about $1000
>> in charger and BMS electronics.  I have a 40 mile round trip commute
>> and a 10 mile lunch/bank run but my car is very light so that only
>> uses.. well about 18kwh.
>>
>> I should have at least 24kwh so I don't kill the battery and I have
>> some room to keep 18kwh over 8 years so that I can amortize the cost
>> fully.
>>
>> Maybe I really only need 7 or $8000?
>>
>>
>> On Thu, Mar 6, 2014 at 12:27 PM, Cruisin <[hidden email]> wrote:
>> > I have a 18kw Li-ion pack for $4000.00. You cant do better than that?
>> >
>> >
>> >
>> > --
>> > View this message in context:
>> > http://electric-vehicle-discussion-list.413529.n4.nabble.com/Re-NiMH-availablity-tp4668269p4668273.html
>> > Sent from the Electric Vehicle Discussion List mailing list archive at
>> > Nabble.com.
>> > _______________________________________________
>> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>> > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
>> > For EV drag racing discussion, please use NEDRA
>> > (http://groups.yahoo.com/group/NEDRA)
>> >
>>
>>
>>
>> --
>> Sean Korb [hidden email] http://www.spkorb.org
>> '65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
>> "The more you drive, the less intelligent you get" --Miller
>> "Computers are useless.  They can only give you answers." -P. Picasso
>> _______________________________________________
>> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
>> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
>> For EV drag racing discussion, please use NEDRA
>> (http://groups.yahoo.com/group/NEDRA)
>>
>
>
>
> --
> Marcus Reddish



--
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'65,'68 Mustangs,'68 Cougar,'78 R100/7,'60 Metro,'59 A35,'71 Pantera #1382
"The more you drive, the less intelligent you get" --Miller
"Computers are useless.  They can only give you answers." -P. Picasso
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Re: NiMH availablity ...

EVDL Administrator
In reply to this post by Sean Korb
True, lithium (even LiFePO4) beats NiMH for specific energy.  However, I'm
not yet sure that it can beat NiMH for cycle life.  Look at the RAV4-EVs
running around on their original NiMH batteries at 100k miles and more.  

Practically speaking, though, NiMH wasn't available when the EV world needed
it, so the EV world has moved on.  Even if NiMH were "liberated" today, I
can't imagine enough manufacturers jumping on the wagon to make for a
competitive marketplace like we have in lead and is developing in lithium.  

Suppose a LiFePO4 battery lasts 5 years and an NiMH battery lasts 15 years
but costs 3 times as much and has less specific energy.  That probably
doesn't sound attractive to EV hobbyists, but there might be some EV
engineers who would appreciate the reliability, and EV bean-counters who
might want reduced warranty claims. Isn't Toyota pretty well married to NiMH
for those reasons?  They've had all these years for NiMH to prove itself to
them in Priuses.

But for most, I suspect it's a weak pull against the intensity of current
trends and fashion.  I'd guess that EV engineers don't much think about NiMH
any more.  They go straight to lithium because (1) it's available and (2)
everyone else does.

Interestig to muse about what might have been.  If Ovonics hadn't dropped
the ball in selling NiMH's future to GM, they COULD have been a major player
in the EV business.  Ah well, the EV world is thickly populated with such
missteps.

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: NiMH availablity ...

Michael Ross
Dave,

Do you think if LiFePO4 are BB'd and limited to operating between 20% and
80%, or 10% and 90% SOC that they will have degraded cycle life?

They don't have any fancy elements in them (Co, Ni,  Mg)  Which helps cost
a lot.  They are safer (higher burn temperature).

I read that some OEM EVs with Li Ion packs limited there SOC range between
25% and 75% - only 50% of capacity actually used.  That makes sense if you
are willing to over design that much.  You  can charge faster if you never
go near 100%, and very long life is attractive.  I think the S Model is
limited in SOC range too.  BUT I don't remember where that came from.

I have a salvaged pack of 40Ah Thundersky cells for my little pedal assist
EV, and I am thinking of operating this way; so I am interested in
opinions.  I am willing to  do the work to  BB them and set up a cut off
system.  It is a good learning experience.

I am thinking of using 17 cells instead of 16 and charging with 60V and not
worry about a charging cut off.  Just a discharge cut off.


On Thu, Mar 6, 2014 at 6:54 PM, EVDL Administrator <[hidden email]> wrote:

> True, lithium (even LiFePO4) beats NiMH for specific energy.  However, I'm
> not yet sure that it can beat NiMH for cycle life.  Look at the RAV4-EVs
> running around on their original NiMH batteries at 100k miles and more.
>
> Practically speaking, though, NiMH wasn't available when the EV world
> needed
> it, so the EV world has moved on.  Even if NiMH were "liberated" today, I
> can't imagine enough manufacturers jumping on the wagon to make for a
> competitive marketplace like we have in lead and is developing in lithium.
>
> Suppose a LiFePO4 battery lasts 5 years and an NiMH battery lasts 15 years
> but costs 3 times as much and has less specific energy.  That probably
> doesn't sound attractive to EV hobbyists, but there might be some EV
> engineers who would appreciate the reliability, and EV bean-counters who
> might want reduced warranty claims. Isn't Toyota pretty well married to
> NiMH
> for those reasons?  They've had all these years for NiMH to prove itself to
> them in Priuses.
>
> But for most, I suspect it's a weak pull against the intensity of current
> trends and fashion.  I'd guess that EV engineers don't much think about
> NiMH
> any more.  They go straight to lithium because (1) it's available and (2)
> everyone else does.
>
> Interestig to muse about what might have been.  If Ovonics hadn't dropped
> the ball in selling NiMH's future to GM, they COULD have been a major
> player
> in the EV business.  Ah well, the EV world is thickly populated with such
> missteps.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
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Re: NiMH availablity ...

EVDL Administrator
On 6 Mar 2014 at 20:01, Michael Ross wrote:

> Do you think if LiFePO4 are BB'd and limited to operating between 20% and
> 80%, or 10% and 90% SOC that they will have degraded cycle life?

I'm guessing that by "BB" you mean "bottom balanced."  Yes?

Sorry, I don't have the experience to answer this question.  I'm sure
someone else will tackle it, though.

It does seem to me that there's still a fair bit of varying opinion among
hobbyists on how to charge LiFePO4s.  No surprise; it's still pretty new
technology.  Heck, there are still plenty of differences among us about
charging AGM lead batteries and even flooded batteries.  

I suppose that somewhat more definitive answers will emerge as time goes on,
though, just as they have for lead batteries.

My poorly-informed view of bottom balancing is that I'd better not try it. I
get the impression that it takes more time and attention than I care to give
to charging batteries.  Not that I want to sound cavalier or anything, but
dang it, I have too many other things I like doing!  Without a smart BMS
looking after my battery, I'd probably murder it.

What little personal experience I have with lithium is based entirely on
Ping's bike/scooter batteries.  They come pre-configured with a charger and
BMS - wire 'em up and go.  While they're not suited to a high-power EV, at a
fairly reasonable (IMO) cost, they're about as close to idiot-proof as
you'll find.  

They're 24v nominal.  I run them until they fall to about 20-21v under load.
 (I read in one of the Ebike forums that 2.5 vpc is a good place to stop.)  
This is actually pretty convenient, because 21v under load (1.75 vpc) is
where I'd stop using a 24v lead battery anyway.  This gives me a little
margin of error.

So, when they hit 20-21v, I charge.  On most cycles, I try to manually stop
the charger when the first BMS cell light goes on.  However, as I say, I
tend to do other things while charging, so I miss that light fairly often.  
I just consider that an opportunity to top-balance them.  ;-)

So far I'm pleased with the results I'm getting.  I see no loss of capacity
after 2+ years.  (Probably not more than 100-150 cycles, though.)  

Based on my experience to date, if I were to put LiFePO4 in a road EV, I'd
probably look for a BMS similar to the one Ping uses.  I appreciate its
"idiot-proofness."  As always, your mileage may vary.

David Roden
EVDL Administrator
http://www.evdl.org/


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Re: NiMH availablity ...

Lee Hart
In reply to this post by Michael Ross
Michael Ross wrote:
> Do you think if LiFePO4 are BB'd and limited to operating between 20% and
> 80%, or 10% and 90% SOC that they will have degraded cycle life?

Lithium cells have been around for almost 20 years now. If you look,
there are lots of examples that can tell us how long they lasted, and
how did usage affect their life.

Laptops are a classic example. They almost all use Li-Co or Li-Mn
formulations, because it's cheap and provides the highest energy storage
per pound. We find that:

  - cycle life is fairly short (a few hundred deep discharge cycles)
  - calendar life is fairly short (a few years)
  - higher temperatures drastically shorten life
        and, most laptops tend to run their batteries hot
        which is a major contributor of their short life
  - deep discharges shorten life
        so the less deeply you run it down, the longer it lasts
        some systems prevent deep discharges; their cells last longer
  - overcharging shortens life
        many cheap chargers chronically overcharge, because it's a way
                to increase operating time per charge in the short run
        but it shortens life in the long run
        some systems limit charging, to extend life but shorten run time
  - a BMS system is mandatory (or you get fires!)

Note that many of the current auto company produced EVs are using Li-Mn
based cells. That implies that their life will follow a similar pattern
(marketing claims notwithstanding). They are depending on limiting depth
of discharge and charging, and better temperature control to compensate.
Will their efforts be enough? Time will tell.

Li-Fe based lithiums are newer, and there is less field data on their
life. They cost more and store less energy per pound, and so are less
popular in consumer products (where price and long running time matters
more than life). But safety testing has shown them to be safer. They
have the potential for longer life (have done so under ideal controlled
conditions in the lab).

  - consumer products that have used Li-Fe cells (like cordless
        drills) don't seem to have any longer life
  - they still "die young" from deep discharge cycles, or chronic
        overcharging, or high temperatures
  - so, their life is dependent on initial quality control, limiting
        depth of discharge, charging, and temperature
  - a BMS is not as important to prevent fires; but it is necessary
        to avoid abusive events that would seriously shorten life

> They don't have any fancy elements in them (Co, Ni,  Mg)  Which helps cost
> a lot.  They are safer (higher burn temperature).

Well, this is true for pretty much all rechargeable batteries. The
higher the energy storage, the more fragile they are, and the more
dangerous their failure modes are.

> I read that some OEM EVs with Li Ion packs limited there SOC range between
> 25% and 75% - only 50% of capacity actually used.  That makes sense if you
> are willing to over design that much.

My understanding is that they are doing this to prevent early battery
failures, and the resulting high warranty costs and bad publicity.

> You  can charge faster if you never go near 100%, and very long life
> is attractive.  I think the S Model is limited in SOC range too.

Yes, everything I've read says they are doing this.

There is a *long* history of companies making exaggerated claims about
their EV's range. They depended on overcharging, and deep discharging to
get that range. The result was short battery life. This cost them dearly
in sales and reputation.

It does appear that the auto companies have learned from this, and have
quit exaggerating their claims quite so much. But that could be due to
fear of warranty claims, lawsuits, or government regulations.

> I have a salvaged pack of 40Ah Thundersky cells for my little pedal assist
> EV, and I am thinking of operating this way; so I am interested in
> opinions.  I am willing to  do the work to  BB them and set up a cut off
> system.  It is a good learning experience.
>
> I am thinking of using 17 cells instead of 16 and charging with 60V and not
> worry about a charging cut off.  Just a discharge cut off.

Ultimately, the only way you'll know is to TEST FOR YOURSELF. No one
will go to the trouble and expense to test, and then give all the data
away for their competitors to take advantage of.

It's not that hard to set up a BMS for 17 cells. Watch what they do, and
control your driving and charging to limit the stress on them. Just
about *everything* lasts longer if not overstressed.

--
There is hardly anything in the world that someone cannot make a
little worse and sell a little cheaper. Those who consider price
alone are that person's lawful prey. -- John Ruskin
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/projects.htm
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Re: NiMH availablity ...

Michael Ross
In reply to this post by EVDL Administrator
Dave,

Thanks for the no BS answer.  Very respectable.

I gather that bottom balancing depends on cells that don't self discharge -
not the thing at all for PbSO4.

There is little charge left in LFP cells above and below the flat  voltage
region that is so pronounced.  I think 2.5V is a reasonable choice.  On the
high side above 3.5V very little more can be stored in them.

Anyway, I think I will try it.  I don't have a BMS for my salvaged pack.
 And buying a low cost one from China means you know almost nothing about
its function before confirming a payment.  Then there is the question of
quality and it is one more thing to fail on the road.  So there is an
appeal to bottom balancing in terms of life, cost (ignoring labor, but we
are DIY'ing so that is ignored always), and ease of use.

Best,

M




On Fri, Mar 7, 2014 at 12:43 AM, EVDL Administrator <[hidden email]> wrote:

> On 6 Mar 2014 at 20:01, Michael Ross wrote:
>
> > Do you think if LiFePO4 are BB'd and limited to operating between 20% and
> > 80%, or 10% and 90% SOC that they will have degraded cycle life?
>
> I'm guessing that by "BB" you mean "bottom balanced."  Yes?
>
> Sorry, I don't have the experience to answer this question.  I'm sure
> someone else will tackle it, though.
>
> It does seem to me that there's still a fair bit of varying opinion among
> hobbyists on how to charge LiFePO4s.  No surprise; it's still pretty new
> technology.  Heck, there are still plenty of differences among us about
> charging AGM lead batteries and even flooded batteries.
>
> I suppose that somewhat more definitive answers will emerge as time goes
> on,
> though, just as they have for lead batteries.
>
> My poorly-informed view of bottom balancing is that I'd better not try it.
> I
> get the impression that it takes more time and attention than I care to
> give
> to charging batteries.  Not that I want to sound cavalier or anything, but
> dang it, I have too many other things I like doing!  Without a smart BMS
> looking after my battery, I'd probably murder it.
>
> What little personal experience I have with lithium is based entirely on
> Ping's bike/scooter batteries.  They come pre-configured with a charger and
> BMS - wire 'em up and go.  While they're not suited to a high-power EV, at
> a
> fairly reasonable (IMO) cost, they're about as close to idiot-proof as
> you'll find.
>
> They're 24v nominal.  I run them until they fall to about 20-21v under
> load.
>  (I read in one of the Ebike forums that 2.5 vpc is a good place to stop.)
> This is actually pretty convenient, because 21v under load (1.75 vpc) is
> where I'd stop using a 24v lead battery anyway.  This gives me a little
> margin of error.
>
> So, when they hit 20-21v, I charge.  On most cycles, I try to manually stop
> the charger when the first BMS cell light goes on.  However, as I say, I
> tend to do other things while charging, so I miss that light fairly often.
> I just consider that an opportunity to top-balance them.  ;-)
>
> So far I'm pleased with the results I'm getting.  I see no loss of capacity
> after 2+ years.  (Probably not more than 100-150 cycles, though.)
>
> Based on my experience to date, if I were to put LiFePO4 in a road EV, I'd
> probably look for a BMS similar to the one Ping uses.  I appreciate its
> "idiot-proofness."  As always, your mileage may vary.
>
> David Roden
> EVDL Administrator
> http://www.evdl.org/
>
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
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(919) 513-0418 Desk

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Re: NiMH availablity ...

Rick Beebe
In reply to this post by EVDL Administrator
On 03/07/2014 12:43 AM, EVDL Administrator wrote:
> My poorly-informed view of bottom balancing is that I'd better not try it. I
> get the impression that it takes more time and attention than I care to give
> to charging batteries.  Not that I want to sound cavalier or anything, but
> dang it, I have too many other things I like doing!  Without a smart BMS
> looking after my battery, I'd probably murder it.

Bottom balancing--in general--in a one shot deal. It's a pain in the
butt to set the pack up. You trying to make sure all the cells are
depleted to the exact same level. The idea is that once they are, they
will charge and discharge at the same rate and stay together. By
subsequently avoiding the very top and bottom of the charge curve you
compensate for any slight differences.

Of course it assumes that the internal resistance of these cells is
close enough that you won't get substantial cell drift. You should check
the cells on occasion to make sure none have gone walkabout but the
difficult part of bottom balancing is just done once.

The purported advantage of bottom balancing--in addition to a simple or
no BMS--is that if you drive the pack too low all your cells will run
out of juice at the same time. It becomes very obvious to you that the
pack is dead and none of the cells has enough power left in them to do
any damage to their neighbors.

--Rick
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Re: NiMH availablity ...

Michael Ross
Yes, that is my understanding too.  It is a redundant protection.  The
cells don't get hurt if they overdischarge - that is a root cause solution.
 When you top balance you are setting up the possibility for a significant
over-discharge and are completely dependent on the active lower cutoff
function to protect the pack.

WIth BB'ing you may want a lower cutoff (like from a JLD404) if you want to
limit the %SOC you use for long life.  That is my plan anyway.  I
understand the JLD, I don't understand the anonymous BMS that I get with
the small LFP packs that I use.

The recipe for BB'in includes checking the cells or banks to see which
reaches the per cell upper cutoff voltage first.  Then setting the upper
cutoff for the whole pack at the pack voltage when that first cell (the one
with the least capacity) is topped out.  As a CYA most people want to look
at cell voltages periodically to see if a cell is dieing.  WIth all new,
good quality cells, maybe this is a waste of time.  Some think so.

If I run 17 cells and charge with 60VDC the upper limit is 3.53V for cells
that are similar.  I am not sure what happens with my salvage pack that
clearly has some cells of uncertain condition.  I think I may also
implement an upper cut off.

I don't know how BB'ing could be implemented in an OEM production process,
it seems much more appropriate for DIY'ers that like the tedium.   Top
balancing solves needing to provide individual attention to each cell or
bank that BB'ing requires.

A company that has smart vendor management  (I have actually seen such a
thing in practice) you could get the battery vendor to provide cells of
appropriate quality that are bottom balanced.  Then you could omit BMS
entirely.  Perhaps monitoring cell voltages to flag problem cells, but not
trying to adjust them.  You would also need to have separate batteries for
asymmetrical tasks.  Like having a 12VDC system and the encapsulated higher
voltage propulsion pack.

I see that Jack Rickard is toying with offering "life time" LFP packs for
his golf cart business.  BB'd, and armored, insulated, and tamper proof.
He even encapsulates them so they can't be mucked about with.   I am
curious to see how this works out over years.  He has to charge a lot of
money for them because the BB'ing is so laborious.

It says something about my nerdiness and pedantry that I find this topic so
interesting.


On Fri, Mar 7, 2014 at 11:27 AM, Rick Beebe <[hidden email]> wrote:

> On 03/07/2014 12:43 AM, EVDL Administrator wrote:
> > My poorly-informed view of bottom balancing is that I'd better not try
> it. I
> > get the impression that it takes more time and attention than I care to
> give
> > to charging batteries.  Not that I want to sound cavalier or anything,
> but
> > dang it, I have too many other things I like doing!  Without a smart BMS
> > looking after my battery, I'd probably murder it.
>
> Bottom balancing--in general--in a one shot deal. It's a pain in the
> butt to set the pack up. You trying to make sure all the cells are
> depleted to the exact same level. The idea is that once they are, they
> will charge and discharge at the same rate and stay together. By
> subsequently avoiding the very top and bottom of the charge curve you
> compensate for any slight differences.
>
> Of course it assumes that the internal resistance of these cells is
> close enough that you won't get substantial cell drift. You should check
> the cells on occasion to make sure none have gone walkabout but the
> difficult part of bottom balancing is just done once.
>
> The purported advantage of bottom balancing--in addition to a simple or
> no BMS--is that if you drive the pack too low all your cells will run
> out of juice at the same time. It becomes very obvious to you that the
> pack is dead and none of the cells has enough power left in them to do
> any damage to their neighbors.
>
> --Rick
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> For EV drag racing discussion, please use NEDRA (
> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

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Re: NiMH availablity ...

EVDL Administrator
In reply to this post by Michael Ross
On 7 Mar 2014 at 3:08, Michael Ross wrote:

> So there is an appeal to bottom balancing in terms of life, cost
> (ignoring labor, but we are DIY'ing so that is ignored always), and
> ease of use.

I see your point, but I don't agree that DIY labor cost is "ignored always."
OK, it's not like I'm paying a mechanic, but every hour I spend under the
hood or under the car is an hour I don't have for other things I like doing
just as much or more.  

But hey - if you have the time and you enjoy it, why not try?  

David Roden - Akron, Ohio, USA
EVDL Administrator

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Re: NiMH availablity ...

Michael Ross
There is a real possibility that BB'ing saves you more than you put into
it, but this is pretty speculative.

There are hidden costs too - I have to come up with a resistive load than
can dump significant amps (rebar and an 200Ohm wire wound).  Some people
just jack up the vehicle and spin it, but that is unappealing to me when I
can always use an excuse to weld something.  You need contactors, and
JLD404s and shunts, stuff like that.  Once you have it you can do more
packs. The tools are general purpose.

I investigated DIY BMS and this all seemed easier.





On Fri, Mar 7, 2014 at 3:06 PM, EVDL Administrator <[hidden email]> wrote:

> On 7 Mar 2014 at 3:08, Michael Ross wrote:
>
> > So there is an appeal to bottom balancing in terms of life, cost
> > (ignoring labor, but we are DIY'ing so that is ignored always), and
> > ease of use.
>
> I see your point, but I don't agree that DIY labor cost is "ignored
> always."
> OK, it's not like I'm paying a mechanic, but every hour I spend under the
> hood or under the car is an hour I don't have for other things I like doing
> just as much or more.
>
> But hey - if you have the time and you enjoy it, why not try?
>
> 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/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
> _______________________________________________
> UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> http://lists.evdl.org/listinfo.cgi/ev-evdl.org
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> http://groups.yahoo.com/group/NEDRA)
>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

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Re: NiMH availablity ...

Ruckus
Am I crazy or could bottom balancing be done at 3V with all the cells in
parallel?  They will all be perfectly balanced together at 2.75V or
whatever you chose.  Use a JLD and contactor with a resistive load to get
down to the target voltage.  Reconnect them in series and charge.

Please note that hooking them in parallel for balancing would only work at
the extremes (low for BB, high for TB).  If you hook them in parallel at
half full (3.2v) they won't be balanced at either extreme.  Obviously, this
only would work for groups of individual cells, not pre-made modules.  Are
there any issues with this approach?


On Fri, Mar 7, 2014 at 1:36 PM, Michael Ross <[hidden email]>wrote:

> There is a real possibility that BB'ing saves you more than you put into
> it, but this is pretty speculative.
>
> There are hidden costs too - I have to come up with a resistive load than
> can dump significant amps (rebar and an 200Ohm wire wound).  Some people
> just jack up the vehicle and spin it, but that is unappealing to me when I
> can always use an excuse to weld something.  You need contactors, and
> JLD404s and shunts, stuff like that.  Once you have it you can do more
> packs. The tools are general purpose.
>
> I investigated DIY BMS and this all seemed easier.
>
>
>
>
>
> On Fri, Mar 7, 2014 at 3:06 PM, EVDL Administrator <[hidden email]>
> wrote:
>
> > On 7 Mar 2014 at 3:08, Michael Ross wrote:
> >
> > > So there is an appeal to bottom balancing in terms of life, cost
> > > (ignoring labor, but we are DIY'ing so that is ignored always), and
> > > ease of use.
> >
> > I see your point, but I don't agree that DIY labor cost is "ignored
> > always."
> > OK, it's not like I'm paying a mechanic, but every hour I spend under the
> > hood or under the car is an hour I don't have for other things I like
> doing
> > just as much or more.
> >
> > But hey - if you have the time and you enjoy it, why not try?
> >
> > 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/ .
> > = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> >
> >
> > _______________________________________________
> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> > For EV drag racing discussion, please use NEDRA (
> > http://groups.yahoo.com/group/NEDRA)
> >
> >
>
>
> --
> Put this question to yourself: should I use everyone else to attain
> happiness, or should I help others gain happiness?
> *Dalai Lama *
>
> Tell me what it is you plan to do
> With your one wild and precious life?
> Mary Oliver, "The summer day."
>
> To invent, you need a good imagination and a pile of junk.
> Thomas A. Edison<
> http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
>
> A public-opinion poll is no substitute for thought.
> *Warren Buffet*
>
> Michael E. Ross
> (919) 550-2430 Land
> (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> Phone
> (919) 631-1451 Cell
> (919) 513-0418 Desk
>
> [hidden email]
> <[hidden email]>
> -------------- next part --------------
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>


--
Marcus Reddish
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Re: NiMH availablity ...

tomw
In reply to this post by Michael Ross
I have to come up with a resistive load than can dump significant amps (rebar and an 200Ohm wire wound).  Some people just jack up the vehicle and spin it, but that is unappealing to me when I can always use an excuse to weld something.  You need contactors, and JLD404s and shunts, stuff like that.  Once you have it you can do more packs. The tools are general purpose.  Sounds a lot like this:
http://www.diyelectriccar.com/forums/showthread.php?t=84591

The bms/no bms, and top vs bottom balancing debates mostly occurred back in 2009-2010.  Most that were in them long since quit discussing it.  Here's some history:
http://www.diyelectriccar.com/forums/showthread.php?t=84252
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Re: NiMH availablity ...

Michael Ross
In reply to this post by Ruckus
Marcus,

A reasonable question.  For LFP I think you want to go lower like 1.5V
maybe.   I think a lot of the historically acceptable target voltages are
arbitrary (adopting a RIckard opinion).  1.5V might even be higher than
necessary.  1.5V is perhaps a reasonable cut off voltage for a bottom
balanced LFP pack.  I don't think there is anything definitive about this.

Voltage being such a crappy surrogate for State Of Charge  you definitely
want to be far away from the flat part of the V/SOC curve where small
changes in V are large changes in SOC.  Around 1.5V there a la much greater
change in V for a small change in SOC.

When BB'ing you want a low open circuit voltage....the way I have seen it
done, the cell is loaded down, and at a target voltage the load is lifted,
the voltage recovers, the load is added, the load is lifted, again and
again until the voltage settles where you want it and the recovery is very
small.  Best to automate this if you can.    You can throw a 20 foot rebar
out on the sand and run 1000A through it if that works for the cell in
question and the C rate you desire.

I think if you put two cells in parallel, and you run them to a low target,
you have the same old issue that BB'ing is trying to cure maybe? If one
cell goes empty before the other , the other cell has significant charge
left in it, then a loop gets going between them lots of current flows
backwards through the empty cell and one or both of them are cooked.

I think. FWTW




On Sat, Mar 8, 2014 at 7:04 AM, Marcus Reddish <[hidden email]>wrote:

> Am I crazy or could bottom balancing be done at 3V with all the cells in
> parallel?  They will all be perfectly balanced together at 2.75V or
> whatever you chose.  Use a JLD and contactor with a resistive load to get
> down to the target voltage.  Reconnect them in series and charge.
>
> Please note that hooking them in parallel for balancing would only work at
> the extremes (low for BB, high for TB).  If you hook them in parallel at
> half full (3.2v) they won't be balanced at either extreme.  Obviously, this
> only would work for groups of individual cells, not pre-made modules.  Are
> there any issues with this approach?
>
>
> On Fri, Mar 7, 2014 at 1:36 PM, Michael Ross <[hidden email]
> >wrote:
>
> > There is a real possibility that BB'ing saves you more than you put into
> > it, but this is pretty speculative.
> >
> > There are hidden costs too - I have to come up with a resistive load than
> > can dump significant amps (rebar and an 200Ohm wire wound).  Some people
> > just jack up the vehicle and spin it, but that is unappealing to me when
> I
> > can always use an excuse to weld something.  You need contactors, and
> > JLD404s and shunts, stuff like that.  Once you have it you can do more
> > packs. The tools are general purpose.
> >
> > I investigated DIY BMS and this all seemed easier.
> >
> >
> >
> >
> >
> > On Fri, Mar 7, 2014 at 3:06 PM, EVDL Administrator <[hidden email]>
> > wrote:
> >
> > > On 7 Mar 2014 at 3:08, Michael Ross wrote:
> > >
> > > > So there is an appeal to bottom balancing in terms of life, cost
> > > > (ignoring labor, but we are DIY'ing so that is ignored always), and
> > > > ease of use.
> > >
> > > I see your point, but I don't agree that DIY labor cost is "ignored
> > > always."
> > > OK, it's not like I'm paying a mechanic, but every hour I spend under
> the
> > > hood or under the car is an hour I don't have for other things I like
> > doing
> > > just as much or more.
> > >
> > > But hey - if you have the time and you enjoy it, why not try?
> > >
> > > 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/ .
> > > = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> > >
> > >
> > > _______________________________________________
> > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
> > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org
> > > For EV drag racing discussion, please use NEDRA (
> > > http://groups.yahoo.com/group/NEDRA)
> > >
> > >
> >
> >
> > --
> > Put this question to yourself: should I use everyone else to attain
> > happiness, or should I help others gain happiness?
> > *Dalai Lama *
> >
> > Tell me what it is you plan to do
> > With your one wild and precious life?
> > Mary Oliver, "The summer day."
> >
> > To invent, you need a good imagination and a pile of junk.
> > Thomas A. Edison<
> > http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>
> >
> > A public-opinion poll is no substitute for thought.
> > *Warren Buffet*
> >
> > Michael E. Ross
> > (919) 550-2430 Land
> > (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google
> > Phone
> > (919) 631-1451 Cell
> > (919) 513-0418 Desk
> >
> > [hidden email]
> > <[hidden email]>
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> > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub
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> >
> >
>
>
> --
> Marcus Reddish
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>
>


--
Put this question to yourself: should I use everyone else to attain
happiness, or should I help others gain happiness?
*Dalai Lama *

Tell me what it is you plan to do
With your one wild and precious life?
Mary Oliver, "The summer day."

To invent, you need a good imagination and a pile of junk.
Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html>

A public-opinion poll is no substitute for thought.
*Warren Buffet*

Michael E. Ross
(919) 550-2430 Land
(919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone
(919) 631-1451 Cell
(919) 513-0418 Desk

[hidden email]
<[hidden email]>
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