Practical CALB SE100AHA 50% and 75% discharged voltage data

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Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms
1989 VW Cabby
Impulse 9 motor
Z1K-HV Motor Controller
52 SE100AHA cells (~170V)

Hi all -
I've been using my lithium batts for a year and a half, and usually go no further than 20 miles or so.
I have a smart battery meter that measures amphours expended, and usually this never goes above 30 Ah.  Theoretically, I can go much further than this, but I am trying not to get stuck somewhere where I would need a tow to get back home.

So, two questions.
1) How far can I *practically* go on amphours discharged, based on normal driving with hardware above?  I would appreciate NON-THEORETICAL data from folks who have similar batteries.
2) I have seen the CALB discharge voltage curves, and of course they are flat, but not completely.  The voltage per cell moves between 3.4VPC and 3.1VPC.  Where would I consider the average (unloaded) pack voltage as the 50% and 75% discharged state?  
Full charge = 173.5V (3.33VPC)
50% discharged = ??
75% discharged = ??

Knowing the answers to these questions will give me more confidence in longer trips!  Thanks in advance!

Rob
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

David Nelson-5
Rob,

Your amp-hour counter is far more accurate at telling you state of
charge than voltage is. Do NOT go by voltage to determine how far you
can go. Temperature variations do affect the open circuit voltage of
the batteries. You can reliably drive until you have used 70-80Ah from
your pack with no ill effects on your batteries. I have used 180Ah
from my 200Ah TS pack and only near the end did I notice much
difference in the drive-ability of my car.

To answer your first question we need more data from you. When you go
20 miles how many Ah did you use? This can be used to estimate rather
closely the answer to your question. Better yet, just drive until you
have used 70-80Ah and note the distance.

On Fri, Sep 16, 2011 at 7:27 PM, Rob Trahms <[hidden email]> wrote:

> 1989 VW Cabby
> Impulse 9 motor
> Z1K-HV Motor Controller
> 52 SE100AHA cells (~170V)
>
> Hi all -
> I've been using my lithium batts for a year and a half, and usually go no
> further than 20 miles or so.
> I have a smart battery meter that measures amphours expended, and usually
> this never goes above 30 Ah.  Theoretically, I can go much further than
> this, but I am trying not to get stuck somewhere where I would need a tow to
> get back home.
>
> So, two questions.
> 1) How far can I *practically* go on amphours discharged, based on normal
> driving with hardware above?  I would appreciate NON-THEORETICAL data from
> folks who have similar batteries.
> 2) I have seen the CALB discharge voltage curves, and of course they are
> flat, but not completely.  The voltage per cell moves between 3.4VPC and
> 3.1VPC.  Where would I consider the average (unloaded) pack voltage as the
> 50% and 75% discharged state?
> Full charge = 173.5V (3.33VPC)
> 50% discharged = ??
> 75% discharged = ??
>
> Knowing the answers to these questions will give me more confidence in
> longer trips!  Thanks in advance!
>
> Rob


--
David D. Nelson
http://evalbum.com/1328

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms
Hi David -
Good tip on the voltage - didn't think about temperature variations.

My daily commute is about 13 miles, and I expend 22-27Ah, depending on hills, traffic, freeway speeds, etc.
So that *roughly* is 1.7-2.1 Ah/mi.  Being conservative and extrapolating from that, my 50% discharge is 50 Ah/(2.1 Ah/mi) = 23.8 mi and 80% discharge is 80 Ah/(2.1 Ah/mi) = 38.1 mi.

So effectively, with 100Ah cells and my normal energy usage, I should drive no further than ~38 miles, just to be safe.

Does that sound right?  Any other practical experiences with CALB cells, 100AH or otherwise?  I know I can't read voltage, but is instantaneous current draw affected near the 80% discharge mark?  Will I notice any "softness" in acceleration/large current draws that deep into the cells?  Or should it remain pretty much the same right up to 80%?

Thanks,
Rob
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

a.swackhammer
In reply to this post by Rob Trahms
Good evening Rob,  You and I have close to the same pack.  I have gone 90 miles and think I can go more.  I did the 90 miles with the BMS letting me know with two cells going to 2.5v.  You and I should go on a good trip some sunny afternoon.  Al


On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:

> 1989 VW Cabby
> Impulse 9 motor
> Z1K-HV Motor Controller
> 52 SE100AHA cells (~170V)
>
> Hi all -
> I've been using my lithium batts for a year and a half, and usually go no
> further than 20 miles or so.
> I have a smart battery meter that measures amphours expended, and usually
> this never goes above 30 Ah.  Theoretically, I can go much further than
> this, but I am trying not to get stuck somewhere where I would need a tow to
> get back home.
>
> So, two questions.
> 1) How far can I *practically* go on amphours discharged, based on normal
> driving with hardware above?  I would appreciate NON-THEORETICAL data from
> folks who have similar batteries.
> 2) I have seen the CALB discharge voltage curves, and of course they are
> flat, but not completely.  The voltage per cell moves between 3.4VPC and
> 3.1VPC.  Where would I consider the average (unloaded) pack voltage as the
> 50% and 75% discharged state?  
> Full charge = 173.5V (3.33VPC)
> 50% discharged = ??
> 75% discharged = ??
>
> Knowing the answers to these questions will give me more confidence in
> longer trips!  Thanks in advance!
>
> Rob
>
> -----
> Electro, the Cabby-EV
> http://chaosmgmt.blogspot.com 
> http://www.evalbum.com/1426 
> --
> View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Practical-CALB-SE100AHA-50-and-75-discharged-voltage-data-tp3819532p3819532.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
>
> _______________________________________________
> | Moratorium on drag racing discussion is in effect.
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> |
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms

Hi Al -
90 miles - impressive!  How many AH of the 100AH did you expend doing that - did you get close to 80% discharge, or beyond it?  What was your experience with "performance" of the pack toward the end of the trip?

I would imagine your Auto Union expends considerably less energy per mile than does my cabby (while small, the cabby still is around 2500 lbs.  You also know how I drive ;) ).

A drive sometime sounds good!  Let me make sure my estimated range is correct first though!  Should be doing this range testing out over the next couple of weekends.

Rob

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

corbin dunn
In reply to this post by Rob Trahms

On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:

> 1989 VW Cabby
> Impulse 9 motor
> Z1K-HV Motor Controller
> 52 SE100AHA cells (~170V)

Based on my experience with 48 200ah cells (and simply halving my distances), I'd say you can safely go 35 miles, and probably (if you drive slowly and don't have a lot of hills) go up to 50 miles.

> Full charge = 173.5V (3.33VPC)
> 50% discharged = ??
> 75% discharged = ??

You can't use pack voltage to determine where you are at in your SOC. It isn't reliable until it is too late.

corbin

>
> Knowing the answers to these questions will give me more confidence in
> longer trips!  Thanks in advance!
>
> Rob
>
> -----
> Electro, the Cabby-EV
> http://chaosmgmt.blogspot.com 
> http://www.evalbum.com/1426 
> --
> View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Practical-CALB-SE100AHA-50-and-75-discharged-voltage-data-tp3819532p3819532.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.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.
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

David Nelson-5
In reply to this post by Rob Trahms
Hi Rob,

On Fri, Sep 16, 2011 at 9:21 PM, Rob Trahms <[hidden email]> wrote:

> Hi David -
> Good tip on the voltage - didn't think about temperature variations.
>
> My daily commute is about 13 miles, and I expend 22-27Ah, depending on
> hills, traffic, freeway speeds, etc.
> So that *roughly* is 1.7-2.1 Ah/mi.  Being conservative and extrapolating
> from that, my 50% discharge is 50 Ah/(2.1 Ah/mi) = *23.8 mi* and 80%
> discharge is 80 Ah/(2.1 Ah/mi) = *38.1 mi*.
>
> So effectively, with 100Ah cells and my normal energy usage, I should drive
> no further than ~38 miles, just to be safe.

That sounds right. You will know by watching your Ah counter so if
your driving style, terrain, temperature, etc changes you will still
know what your SOC is and can then plan accordingly.

> Does that sound right?  Any other practical experiences with CALB cells,
> 100AH or otherwise?  I know I can't read voltage, but is instantaneous
> current draw affected near the 80% discharge mark?  Will I notice any
> "softness" in acceleration/large current draws that deep into the cells?  Or
> should it remain pretty much the same right up to 80%?

I find that the pack gets soft under two different situations. Low SOC
like around 75% and at low temperature at even at 100%SOC. I have TS
cells which are not generally as stiff as CALB so you may not see the
softness as much as I do. When my pack is below ~10°C a >1.5C draw can
drop the cells below 2.9V. At 0°C it takes even less of a draw. The
good thing is, however, that the pack will self heat. I have had my
pack stiffen up because of warming up over the course of a drive where
over 60% of the capacity was used over the course of a little over an
hour of driving. I have a 70mile range and can only go about 50mph in
my rig.


--
David D. Nelson
http://evalbum.com/1328

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Willie McKemie
In reply to this post by Rob Trahms
http://www.evalbum.com/1426

I find no mention, in your EVAlbum page or your EVDL post, of BMS.
If you are running without BMS, it would be best to state that fact.

If you don't have something to tell you when a single cell drops below
a low threshold of perhaps 2.5v, I don't believe you can comfortably
get below the last 20%-30% of your pack.  Indeed, it seems you are
having trouble getting down below 50%.

If you DO have a BMS that warns you when a cell goes low, then you just
drive until you get that alarm to test the true capacity of your pack.  
Do that once and you have confidence that you know where the bottom of
the pack is and future trips will have less anxiety.

--
Willie, ONWARD!  Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime  86 days 21 hours 15 minutes

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms
Hi Willie -
Yes, sorry, forgot to mention that.  I have an EV Power BMS configuration (monitors on all cells tied to an MCU).  I will get an alarm when any cell goes below 2.5V for more than 10 seconds.

Rob
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

martinwinlow
In reply to this post by Rob Trahms

On 17 Sep 2011, at 03:27, Rob Trahms wrote:

> 1989 VW Cabby
> Impulse 9 motor
> Z1K-HV Motor Controller
> 52 SE100AHA cells (~170V)
>
> Hi all -
> I've been using my lithium batts for a year and a half, and usually  
> go no
> further than 20 miles or so.
> I have a smart battery meter that measures amphours expended, and  
> usually
> this never goes above 30 Ah.  Theoretically, I can go much further  
> than
> this, but I am trying not to get stuck somewhere where I would need  
> a tow to
> get back home.
>
> So, two questions.
> 1) How far can I *practically* go on amphours discharged, based on  
> normal
> driving with hardware above?  I would appreciate NON-THEORETICAL  
> data from
> folks who have similar batteries.
> 2) I have seen the CALB discharge voltage curves, and of course they  
> are
> flat, but not completely.  The voltage per cell moves between 3.4VPC  
> and
> 3.1VPC.  Where would I consider the average (unloaded) pack voltage  
> as the
> 50% and 75% discharged state?
> Full charge = 173.5V (3.33VPC)
> 50% discharged = ??
> 75% discharged = ??
>
> Knowing the answers to these questions will give me more confidence in
> longer trips!  Thanks in advance!
>
> Rob


Rob,  In my view based on the numbers you have given and the type of  
car you have (a VW Golf = US Rabbit?)  60 miles would be a safe max  
range but your cells probably have a 'new' capacity of nearer 110Ah so  
perhaps 65 miles and still 'safe'.

As for relying on the pack voltage for measuring SOC, I wouldn't  
bother even trying.  Using an Ah counter - for both discharging and  
charging - is far more accurate and therefore safer than measuring  
volts.  You should really do a run down test to fully flat to see but  
you must have some way of ensuring you do not over do it - hence my  
belief that at least a cell-level BMonS is essential for us  
'experimenters'.  Jack Rickard has won the argument (IMO) that a BManS  
(cell balancing) is not necessary for lithiums in a properly designed  
system - ie principally one which has no cells with unbalanced drains  
on them.

Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk



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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Willie McKemie
In reply to this post by Rob Trahms
On Sat, Sep 17, 2011 at 07:28:01AM -0700, Rob Trahms wrote:
> Hi Willie -
> Yes, sorry, forgot to mention that.  I have an EV Power BMS configuration
> (monitors on all cells tied to an MCU).  I will get an alarm when any cell
> goes below 2.5V for more than 10 seconds.

I haven't heard of the 10 second feature.  My EVPower unit is probably
one of the very early ones and alarms immediately upon a cell dropping
to the threshold.  I like the early warning that the immediate alarm
gives; I can slack off the throttle and travel quite some distance as
my low cell runs out of juice.  I'm alerted well before I have real
trouble.

You should be able to test your capacity as I've outlined.  You just
need to be more careful and be prepared to walk home since you will
likely be nearer to the end (or at the end) when you get the alarm.

BTW, I've swapped out all my EVPower cell modules for miniBMS units.  
Spares are easier to get and I've configured such that the modules are
easier and safer to install and replace.

--
Willie, ONWARD!  Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime  87 days  3 hours 30 minutes

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

martinwinlow
In reply to this post by a.swackhammer
AL, OK, but what are your aerodynamics like?  My brick-shaped van  
would be lucky to get 500Wh/mile at 55mph or so.  I bet Robs car would  
be twice as good as that - what do you drive for comparison purposes?  
MW

On 17 Sep 2011, at 06:03, Al Swackhammer wrote:

> Good evening Rob,  You and I have close to the same pack.  I have  
> gone 90 miles and think I can go more.  I did the 90 miles with the  
> BMS letting me know with two cells going to 2.5v.  You and I should  
> go on a good trip some sunny afternoon.  Al
>
>
> On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:
>
>> 1989 VW Cabby
>> Impulse 9 motor
>> Z1K-HV Motor Controller
>> 52 SE100AHA cells (~170V)
>>
>> Hi all -
>> I've been using my lithium batts for a year and a half, and usually  
>> go no
>> further than 20 miles or so.
>> I have a smart battery meter that measures amphours expended, and  
>> usually
>> this never goes above 30 Ah.  Theoretically, I can go much further  
>> than
>> this, but I am trying not to get stuck somewhere where I would need  
>> a tow to
>> get back home.
>>
>> So, two questions.
>> 1) How far can I *practically* go on amphours discharged, based on  
>> normal
>> driving with hardware above?  I would appreciate NON-THEORETICAL  
>> data from
>> folks who have similar batteries.
>> 2) I have seen the CALB discharge voltage curves, and of course  
>> they are
>> flat, but not completely.  The voltage per cell moves between  
>> 3.4VPC and
>> 3.1VPC.  Where would I consider the average (unloaded) pack voltage  
>> as the
>> 50% and 75% discharged state?
>> Full charge = 173.5V (3.33VPC)
>> 50% discharged = ??
>> 75% discharged = ??
>>
>> Knowing the answers to these questions will give me more confidence  
>> in
>> longer trips!  Thanks in advance!
>>
>> Rob



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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

martinwinlow
In reply to this post by corbin dunn
Corbin, Rob, Al - EVERYone - Comparing ranges without specifying the  
conditions is completely pointless.  At 70mph you use twice the power  
used at 50mph, and 10 times as much used at 20mph.  So, seriously, can  
we have some slightly more scientific guesstimations, puh-lease?

Corbin, my 160Ah (x38) TS cells took my hopelessly inefficient van 60+  
miles at 50-55  mph so I think Rob's car should do at least that with  
his vastly superior aerodynamics.

But Rob,  please prove me wrong!  Do a test and let us know. MW

On 17 Sep 2011, at 06:32, corbin dunn wrote:

>
> On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:
>
>> 1989 VW Cabby
>> Impulse 9 motor
>> Z1K-HV Motor Controller
>> 52 SE100AHA cells (~170V)
>
> Based on my experience with 48 200ah cells (and simply halving my  
> distances), I'd say you can safely go 35 miles, and probably (if you  
> drive slowly and don't have a lot of hills) go up to 50 miles.
>
>> Full charge = 173.5V (3.33VPC)
>> 50% discharged = ??
>> 75% discharged = ??
>
> You can't use pack voltage to determine where you are at in your  
> SOC. It isn't reliable until it is too late.
>
> corbin
>
>>
>> Knowing the answers to these questions will give me more confidence  
>> in
>> longer trips!  Thanks in advance!
>>
>> Rob
>>
>> -----
>> Electro, the Cabby-EV
>> http://chaosmgmt.blogspot.com
>> http://www.evalbum.com/1426
>> --
>> View this message in context: http://electric-vehicle-discussion-list.413529.n4.nabble.com/Practical-CALB-SE100AHA-50-and-75-discharged-voltage-data-tp3819532p3819532.html
>> Sent from the Electric Vehicle Discussion List mailing list archive  
>> at Nabble.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
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>
> _______________________________________________
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Regards, Martin Winlow
Herts, UK
http://www.evalbum.com/2092
www.winlow.co.uk



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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Willie McKemie
In reply to this post by Rob Trahms
Back to your original question not that we know you have cell level
monitoring and an amp-hour counter.

On Fri, Sep 16, 2011 at 07:27:51PM -0700, Rob Trahms wrote:

> So, two questions.
> 1) How far can I *practically* go on amphours discharged, based on normal
> driving with hardware above?  I would appreciate NON-THEORETICAL data from
> folks who have similar batteries.

Gain confidence in your ah meter and rely on it.  Does your meter come
back to near zero when you charge?  If it does so repeatedly, have
confidence in it.  You should be able to safely draw out 70-80 ah.  
Range might be as low as 50 miles but could easily be as high as 75
miles.  Test your capacity to learn the truth.

> 2) I have seen the CALB discharge voltage curves, and of course they are
> flat, but not completely.  The voltage per cell moves between 3.4VPC and
> 3.1VPC.  Where would I consider the average (unloaded) pack voltage as the
> 50% and 75% discharged state?  
> Full charge = 173.5V (3.33VPC)
> 50% discharged = ??
> 75% discharged = ??

People coming to lithium from lead ALWAYS want to do this.  It is not
appropriate for lithium.  I've had experienced EV people put a voltmeter
on my cells and tell me the pack was well balanced just because the
voltages were all the same to about three digits.  Not so, just ignore
the voltages when they are between 3.2 and 3.4.

--
Willie, ONWARD!  Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime  87 days  3 hours 49 minutes

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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

AMPhibian
In reply to this post by martinwinlow
martinwinlow wrote
As for relying on the pack voltage for measuring SOC, I wouldn't  
bother even trying.  
I'll be the contrarian here and disagree somewhat since I drove around for a while before I got my amp hour counter and only used pack voltage and a trip odometer quite successfully.  I did run a bottom balanced pack so no single cell could be driven lower than the others, but with my 36 cell 100ah SE pack the difference between 120V full and 108V empty was quite obvious and was easy to check when off throttle.  Obviously a few seconds off throttle would still show lower than resting voltage but that simply gave a bit more cushion.  114V  or so off throttle meant I needed to be getting near an outlet.  I've gotten a little over 50 miles range in mixed driving in a hilly area in my 2500lb Fiero on a near 100% discharge.
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

a.swackhammer
In reply to this post by martinwinlow
Martin,  It is a 1960 Auto Union 1000.  www.evalbum.com/2430  Pretty aerodynamic compared to the VW cabby.  I did revise my stats as to an speedo error.  I did very close to 78 miles on that charge and used 22KW to recharge with Zivan NG3 charger @ 240v.  Al


On Sep 17, 2011, at 8:55 AM, Martin WINLOW wrote:

> AL, OK, but what are your aerodynamics like?  My brick-shaped van  
> would be lucky to get 500Wh/mile at 55mph or so.  I bet Robs car would  
> be twice as good as that - what do you drive for comparison purposes?  
> MW
>
> On 17 Sep 2011, at 06:03, Al Swackhammer wrote:
>
>> Good evening Rob,  You and I have close to the same pack.  I have  
>> gone 90 miles and think I can go more.  I did the 90 miles with the  
>> BMS letting me know with two cells going to 2.5v.  You and I should  
>> go on a good trip some sunny afternoon.  Al
>>
>>
>> On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:
>>
>>> 1989 VW Cabby
>>> Impulse 9 motor
>>> Z1K-HV Motor Controller
>>> 52 SE100AHA cells (~170V)
>>>
>>> Hi all -
>>> I've been using my lithium batts for a year and a half, and usually  
>>> go no
>>> further than 20 miles or so.
>>> I have a smart battery meter that measures amphours expended, and  
>>> usually
>>> this never goes above 30 Ah.  Theoretically, I can go much further  
>>> than
>>> this, but I am trying not to get stuck somewhere where I would need  
>>> a tow to
>>> get back home.
>>>
>>> So, two questions.
>>> 1) How far can I *practically* go on amphours discharged, based on  
>>> normal
>>> driving with hardware above?  I would appreciate NON-THEORETICAL  
>>> data from
>>> folks who have similar batteries.
>>> 2) I have seen the CALB discharge voltage curves, and of course  
>>> they are
>>> flat, but not completely.  The voltage per cell moves between  
>>> 3.4VPC and
>>> 3.1VPC.  Where would I consider the average (unloaded) pack voltage  
>>> as the
>>> 50% and 75% discharged state?
>>> Full charge = 173.5V (3.33VPC)
>>> 50% discharged = ??
>>> 75% discharged = ??
>>>
>>> Knowing the answers to these questions will give me more confidence  
>>> in
>>> longer trips!  Thanks in advance!
>>>
>>> Rob
>
>
>
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms
In reply to this post by martinwinlow
Data point #1 (drive today)

28.2 miles, half freeway driving, half 30-40 mph.
51.4 Ah expended, just over theoretical halfway on the batts.

No noticeable performance differences, no complaints from any cells (nor do I expect any here).

Tomorrow I go for 75% discharge!
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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

David Nelson-5
In reply to this post by AMPhibian
The difference is that you were using more than just voltage. You had
a bottom balanced pack for one, and you also watched the trip meter
for the other. Remove those two and I don't think you would be quite
as comfortable using only voltage.

Did you also take into account pack temperature or did you just not
drive to as low or a SOC when they were colder? In the last 24 hours
my pack voltage dropped nearly 1V due just to a drop in pack
temperature from around 23°C to 17°C.

On Sat, Sep 17, 2011 at 10:59 AM, AMPhibian <[hidden email]> wrote:

>
> martinwinlow wrote:
>>
>>
>> As for relying on the pack voltage for measuring SOC, I wouldn't
>> bother even trying.
>>
> I'll be the contrarian here and disagree somewhat since I drove around for a
> while before I got my amp hour counter and only used pack voltage and a trip
> odometer quite successfully.  I did run a bottom balanced pack so no single
> cell could be driven lower than the others, but with my 36 cell 100ah SE
> pack the difference between 120V full and 108V empty was quite obvious and
> was easy to check when off throttle.  Obviously a few seconds off throttle
> would still show lower than resting voltage but that simply gave a bit more
> cushion.  114V  or so off throttle meant I needed to be getting near an
> outlet.  I've gotten a little over 50 miles range in mixed driving in a
> hilly area in my 2500lb Fiero on a near 100% discharge.
>

--
David D. Nelson
http://evalbum.com/1328

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Re: Practical CALB SE100AHA 50% and 75% discharged voltagedata

Cor van de Water
In reply to this post by martinwinlow
Martin,
I agree that going from about 55 to 70 MPH
(my truck's max speed was rev-limited to 72)
the power draw more than doubles while the
speed clearly does not, so the Wh/mi shoots
up sharply, but while staying at 55 my S10 truck only
drew 15kW or 272 Wh/mi which is pretty good for a
5000 lbs truck (driver included).
I did have LRR tires and they were pumped up to
50 PSI to give low drag, also brakes were not dragging
and in general, staying at constant speed of 55 even
these non-airodynamic vehicles can perform pretty good
if you know how to drive for best energy efficiency
(not stop-n-go traffic).
 
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

________________________________

From: [hidden email] on behalf of Martin WINLOW
Sent: Sat 9/17/2011 9:25 PM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Practical CALB SE100AHA 50% and 75% discharged voltagedata



AL, OK, but what are your aerodynamics like?  My brick-shaped van
would be lucky to get 500Wh/mile at 55mph or so.  I bet Robs car would
be twice as good as that - what do you drive for comparison purposes?  
MW

On 17 Sep 2011, at 06:03, Al Swackhammer wrote:

> Good evening Rob,  You and I have close to the same pack.  I have
> gone 90 miles and think I can go more.  I did the 90 miles with the
> BMS letting me know with two cells going to 2.5v.  You and I should
> go on a good trip some sunny afternoon.  Al
>
>
> On Sep 16, 2011, at 7:27 PM, Rob Trahms wrote:
>
>> 1989 VW Cabby
>> Impulse 9 motor
>> Z1K-HV Motor Controller
>> 52 SE100AHA cells (~170V)
>>
>> Hi all -
>> I've been using my lithium batts for a year and a half, and usually
>> go no
>> further than 20 miles or so.
>> I have a smart battery meter that measures amphours expended, and
>> usually
>> this never goes above 30 Ah.  Theoretically, I can go much further
>> than
>> this, but I am trying not to get stuck somewhere where I would need
>> a tow to
>> get back home.
>>
>> So, two questions.
>> 1) How far can I *practically* go on amphours discharged, based on
>> normal
>> driving with hardware above?  I would appreciate NON-THEORETICAL
>> data from
>> folks who have similar batteries.
>> 2) I have seen the CALB discharge voltage curves, and of course
>> they are
>> flat, but not completely.  The voltage per cell moves between
>> 3.4VPC and
>> 3.1VPC.  Where would I consider the average (unloaded) pack voltage
>> as the
>> 50% and 75% discharged state?
>> Full charge = 173.5V (3.33VPC)
>> 50% discharged = ??
>> 75% discharged = ??
>>
>> Knowing the answers to these questions will give me more confidence
>> in
>> longer trips!  Thanks in advance!
>>
>> Rob



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Re: Practical CALB SE100AHA 50% and 75% discharged voltage data

Rob Trahms
In reply to this post by Rob Trahms
Data point #2:

32.5 mi, all freeway driving @ ~65 MPH this time except the last mile home, significant headwinds
64.8 Ah expended (about 65% of theoretical)

Again, so far no noticeable performance differences in acceleration, etc toward the end of the drive, and no BMS alarms.

Inching my confidence toward 80Ah...
12