# Volt Battery Question



## evc3 (Oct 9, 2015)

I'm in the battery planning stages of my project. I basically need some help and insight on what I'm planning. I am doing a direct drive dual 9 inch motor conversion and was thinking about getting 2 Volt packs. My question is what would the operating voltage range be for this type of set up? And should I alter how the 24v and 48v modules are split up to get a higher kWh/volt rating? What type of power will I get from two packs and is it even necessary? I need this information to know which charger, controller (was looking at Zilla 2K to have reverse) and DC-DC set up that can handle this type of voltage to order.


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## Yabert (Feb 7, 2010)

Hello

Because you are planing dual 9'' motor I think your best bet it to use a Zilla 2K extra high voltage (EHV), but you will be limite to the max voltage of 375v.
For this reason you should remove 6 cells from the 96S Volt battery pack to have 90S (337,5v nominal, 375v full charge).
After you will need to link the two 90 cells battery pack in parallel to have one 337,5v and 90Ah battery.

You can expect over 500Kw of peak power from this kind of 30Kwh battery. http://www.diyelectriccar.com/forums/showthread.php/power-capability-chevy-volt-battery-109698.html
Of course, with water cooling you can expect to have a lot of power capability and a lot of fun... then destroy your motors... then restart with more motors


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## evc3 (Oct 9, 2015)

Yabert said:


> Hello
> 
> Because you are planing dual 9'' motor I think your best bet it to use a Zilla 2K extra high voltage (EHV), but you will be limite to the max voltage of 375v.
> For this reason you should remove 6 cells from the 96S Volt battery pack to have 90S (337,5v nominal, 375v full charge).
> ...


Sweet! Thanks for your reply. 
Is this set up achieved through one Volt battery modules or is it two?(basically, do I need one or two of these: http://www.ebay.com/itm/291613811071?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT )

Is it possible to use the Volt BMS system? Or how do people generally make BMS systems for these packs? 

I was also planning on running a liquid cooling system(http://www.evwest.com/catalog/product_info.php?products_id=155 for my controller and splitting it to batteries) - how does this affect power capability? 


Thanks for your help, it is much appreciated


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## piotrsko (Dec 9, 2007)

evc3 said:


> Sweet! Thanks for your reply.
> Is this set up achieved through one Volt battery modules or is it two?(basically, do I need one or two of these: http://www.ebay.com/itm/291613811071?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT )
> 
> Is it possible to use the Volt BMS system? Or how do people generally make BMS systems for these packs?
> ...


2 packs @$2000 ea. THE one in the ebay looks suspicious because of the duct tape. If it doesn't leak coolant it is probably ok.

Yes it is possible to use bms installed. EVtv.com or battery control system and charger out of wrecked car with harnesses. I dont run bms.

The cooling doesnt affect capacity much that I can see. Does affect battery life though. My batteries dont seem to get that hot during use. The other use for the coolant system if for WARMING Battery.


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## Brute Force (Aug 28, 2010)

Jack and his crew at EVTV have the Volt charger working, but not the BMS. Given his opinion of BMS in general, I don't see them hacking one any time in the near future.

The Volt drive system is incredibly complex, none of the components are stand alone. While you may eventually succeed at getting a battery control system pulled from a Vol to function, be aware that you're venturing into uncharted territory.


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## evc3 (Oct 9, 2015)

Brute Force said:


> Jack and his crew at EVTV have the Volt charger working, but not the BMS. Given his opinion of BMS in general, I don't see them hacking one any time in the near future.
> 
> The Volt drive system is incredibly complex, none of the components are stand alone. While you may eventually succeed at getting a battery control system pulled from a Vol to function, be aware that you're venturing into uncharted territory.


EDIT: Figured out I won't be using a BMS.

If I wanted to keep the voltage at 348 max. - what would the nominal voltage and minimum voltage be?


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## evc3 (Oct 9, 2015)

piotrsko said:


> 2 packs @$2000 ea. THE one in the ebay looks suspicious because of the duct tape. If it doesn't leak coolant it is probably ok.
> 
> Yes it is possible to use bms installed. EVtv.com or battery control system and charger out of wrecked car with harnesses. I dont run bms.
> 
> The cooling doesnt affect capacity much that I can see. Does affect battery life though. My batteries dont seem to get that hot during use. The other use for the coolant system if for WARMING Battery.


What type of controller can handle 375v on a DC motor system?


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## puddleglum (Oct 22, 2008)

You might want to check this out. http://electricporsche.ca/ He has reconfigured and installed a double pack in the 914 build.


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## probuild521 (May 3, 2009)

evc3 said:


> EDIT: Figured out I won't be using a BMS.
> 
> If I wanted to keep the voltage at 348 max. - what would the nominal voltage and minimum voltage be?


348V max would be ~82s which isnt an easy configuration with the volt battery pack (needs to be a multiple of 6s). So 78s would put you at 327.6V peak (4.2v/cell). I'd recommend not discharging below 3.0v/cell so that'd be 234V minimum to increase battery cycle life.


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## puddleglum (Oct 22, 2008)

I would think that an 84s configuration would be better for a 348v peak at 4.14v/cell. The Volt does not charge the cells higher than that. Nominal would be 323.4v at 3.85v/cell. Minimum is still 252 at 3v/cell if you want to go there.


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## probuild521 (May 3, 2009)

puddleglum said:


> I would think that an 84s configuration would be better for a 348v peak at 4.14v/cell. The Volt does not charge the cells higher than that. Nominal would be 323.4v at 3.85v/cell. Minimum is still 252 at 3v/cell if you want to go there.


Good point, that's certainly the best route to go.


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## Frank (Dec 6, 2008)

I'm pretty sure a z2k can handle 96S...


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## dougingraham (Jul 26, 2011)

Frank said:


> I'm pretty sure a z2k can handle 96S...


Of LiFe cells yes. Of LiMn or LiCo types no. 96S of LiFe would be a peak voltage (3.6 vpc) of only 345.6 volts. The others go to 4.2 volts per cell so 96S is 403.2 volts. Manzanita suggests not exceeding 375 volts. With that in mind you shouldn't exceed 89 cells if you take them up to 4.2 vpc. And 88 if you take them to 4.15 volts.


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## Hollie Maea (Dec 9, 2009)

Probably shouldn't take these cells up to 4.2V...you get a lot more life cycles out of them if you top off at 4.15 or even 4.1 (the voltage curve isn't as flat as LiFePO4 so you don't lose that much capacity going down a bit).


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## dougingraham (Jul 26, 2011)

Hollie Maea said:


> Probably shouldn't take these cells up to 4.2V...you get a lot more life cycles out of them if you top off at 4.15 or even 4.1 (the voltage curve isn't as flat as LiFePO4 so you don't lose that much capacity going down a bit).


While not specifically tested on Volt cells I have tested capacity change due to undercharging of some RC hobby LiPo.

Baseline was charging to 4.20 at a 1C rate with CV stage stopping at C/40. Capacity was measured with a 1C discharge to 3.0 volts.

4.15 volt cutoff gives 90.2% of baseline capacity.
4.10 volt cutoff gives 82.8% of baseline capacity.
4.05 volt cutoff gives 77.8% of baseline capacity.
4.00 volt cutoff gives 75.2% of baseline capacity.
3.95 volt cutoff gives 66.3% of baseline capacity.
3.90 volt cutoff gives 60.3% of baseline capacity.

GM probably stops at 4.15 with a higher ending current so that it comes out at about 80% of full. Has anyone watched the voltage and current as it charges to see what they do for the termination condition?


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## Yabert (Feb 7, 2010)

I only have a discharge curve from a Volt cell at 1/8C.
It's not a lot of discharging power (20w), but my graph seem confirmed that there isn't a lot of energy between 4,2v and 4,15v.
Only around 1% of capacity between 4,2 and 4,15v. 
And around 4% of capacity between 4,2 and 4,1v.


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## dougingraham (Jul 26, 2011)

Yabert said:


> I only have a discharge curve from a Volt cell at 1/8C.
> It's not a lot of discharging power (20w), but my graph seem confirmed that there isn't a lot of energy between 4,2v and 4,15v.
> Only around 1% of capacity between 4,2 and 4,15v.
> And around 4% of capacity between 4,2 and 4,1v.


A discharge curve will not show you what I am talking about. A standard charging algorithm does a constant current up to a particular voltage. In the case of the Volt and Leaf type batteries (LiMn type cells) this is generally considered to be 4.2 volts for a 100% state of charge. You can choose any current you like to get there (within reason) but once you get to 4.2 volts per cell you hold the voltage at 4.2 volts by lowering the current until you reach a certain reduced current value. This part of the charge is called the constant voltage portion. With LiMn cells (LiPo) this is often until the current reaches C/5 or C/10 or in my case I set the charger to C/40 which gives a really complete and repeatable level of charge. The C I mention is the Capacity of the cell in Amp Hours. A 60 amp hour cell would terminate charge at 12 amps if a C/5 termination was used or 6 amps if a C/10 termination was used. Changing the CV to 4.15 reduced the amount of energy the cell accepted by almost 10% when I used a C/40 termination level. I have not tested at other C/X levels and it could be different at other values.

A lot of people believe that these cells will have longer life if undercharged. I am in that camp because I have seen some evidence of this in test data that has been published. Chevy only charges to 80% and they probably have good data telling them that this will allow them to meet their warranty period.


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