# LiFePO4 pack choices / advice



## racunniff (Jan 14, 2009)

With the ElectroJeep finally almost back on the road again I'm starting to dream of ditching the tired AGM batteries in the Volt914. It currently has an Azure Dynamics AC24 and DMOC445, with a nominal system voltage of 216V. I have three options which are rattling around in my head and spreadsheets:


80 CALB CA100FI cells - 256V nominal, 72 miles estimated range at 70% DOD, but continuous draw is going to probably be around 0.39C
63 CALB CA180FI cells - 202V nominal, 100+ miles estimated range at 70% DOD. Continuous draw will be around 0.28C, but weight is higher, voltage is lower, and therefore I expect acceleration to be somewhat less peppy
Change the controller to the new Curtis kit from HPEVS and go with 48 CALB CA180FI cells - 154V nominal, continuous draw of about 0.36C and a range of about 77 miles at 70% DOD

The CA100FI option is significantly less expensive than the other two. The CA180FI-only option is probably the least amount of labor. The Curtis option is tempting - a peak HP around 2000 RPM rather than 5000RPM and higher torque at lower RPM - but I bet I'd probably wish I added liquid cooling to it before I'm done. and I'll have to change out my DC-DC converter to one which works at lower voltage levels.

Right now I'm leaning toward the CA100FI option. Will I significantly shorten their lifespan by running at nearly 0.4C rather than 0.3C? Thoughts? Other opinions?


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## dcb (Dec 5, 2009)

Just curious, the dmoc445 says it can do 280 amps max and run on 120v min.

the ac24 (switching to delta I assume) says it can do 250amps max @ 156v

Do you really need a new controller for option 3? Just curious, I don't know much about 'em. The ac24 link shows a graph with it at 156v hooked up to a dmoc445.


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## dougingraham (Jul 26, 2011)

racunniff said:


> Right now I'm leaning toward the CA100FI option. Will I significantly shorten their lifespan by running at nearly 0.4C rather than 0.3C? Thoughts? Other opinions?


This is what I think I would do in your position. Most people worry about running them at 4C vs 3C. I doubt you will be able to tell any difference between 0.3C and 0.4C both of those being pretty low currents for these types of cells.

Best Wishes!


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## racunniff (Jan 14, 2009)

dcb said:


> Just curious, the dmoc445 says it can do 280 amps max and run on 120v min.
> 
> the ac24 (switching to delta I assume) says it can do 250amps max @ 156v
> 
> Do you really need a new controller for option 3? Just curious, I don't know much about 'em. The ac24 link shows a graph with it at 156v hooked up to a dmoc445.


I've run the DMOC at 144V before. It is a very unsatisfying experience - the low torque curve (peaking out at 4.5K RPM) is further un-enhanced by the low voltage levels. The specs on the Curtis/HPEVS controller seem better (if you can trust specs).

Specifically, the Curtis/HPEVS specs claim 177-160 Nm of torque up to 2K RPM, whereas the DMOC specs show flat torque of about 88 Nm up to 4K RPM (at 156V), both with an AC24 motor.

Having the peak kW output at 2K RPM is seriously tempting. It fits the gear ratio of the Porsche 914 transmission pretty nicely. The transmission screams like a banshee at 4500 RPM (and the car has sympathetic vibration right around that frequency as well).


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## dcb (Dec 5, 2009)

I see , the dmoc won't push the amps. But you are switching from PBuekert batteries too, at closer to rated volts. 49 c100 cells would be the cheapest option, dunno how much range you need, but peak amps of 280 shouldn't be a problem. so c100 or c180, you can always buy more batts or controller if it isn't good enough, no?

They say my ac24ls falls off a cliff below 156v.


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## steven4601 (Nov 11, 2010)

Perhaps not ideal, but I am running a 450V 36Ah headway pack (3x12Ah, 131 series) at approx 1C cruising @ 60mph and 10C hard acceleration.

So far no degredation after 1.5 years and 18000km...

LiFePo4 may not that sensitive to higher discharge rates.


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## major (Apr 4, 2008)

racunniff said:


> Right now I'm leaning toward the CA100FI option. Will I significantly shorten their lifespan by running at nearly 0.4C rather than 0.3C? Thoughts? Other opinions?


Hey racu,

I don't see where 0.4C or 0.3C enter into you decision. I recently looked into this on behalf of another member here: http://www.diyelectriccar.com/forums/showthread.php?p=385806#post385806 It appears these cells are rated at 3C discharge continuous. The 0.3C figure must just be a test condition or something and does not appear to be a rating.


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## Joey (Oct 12, 2007)

I have 60 cells of CA180 Calb. If I could do it over, I would pick a higher count, lower capacity pack for one reason: less mass. If you don't need the range, option one would be better. Fitting the shorter 100 Ah cells into the car without resorting to installing them sideways was a consideration for me.


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## green_EV 2000 (May 2, 2014)

suggestion:

63 CALB CA180FI cells - 202V nominal, 100+ miles estimated range at 70% DOD. Continuous draw will be around 0.28C, 

CALB ,winston (thunder-sky), sinopoly and our is all same, it is good for long life at continuous 0.3C 

in china,dMany authoritative standard battery life tests are 0.3C, I uploaded 201 of China's most authoritative test reports, you can see the way life is also testing 0.3C continuous discharge， because 0.3C is the best current for battery good in terms of the life, which is long battery manufacturers to test and experimental results also.

reports: http://www.liyuanbattery.com.cn/En/Certificate.aspx?UserInfo_ID=788672


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## halestorm (Apr 28, 2009)

hi Ross,

It looks like you went with a combination of your first two choices, 63 CA100FI cells (http://volt914.blogspot.com/2014/06/out-with-old.html). Just curious how you came to this. This should put you in the ~ 50+ mi range, correct? Since my 914ev lead acid pack died I never upgraded it. I couldn't stand to put messy PbA back in, and couldn't swallow dropping another $12k on LFP. Anyway, I'm thinking about reviving the car again, so am interested to know some of the things you've considered. Thanks,

Dave


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## racunniff (Jan 14, 2009)

halestorm said:


> hi Ross,
> 
> It looks like you went with a combination of your first two choices, 63 CA100FI cells (http://volt914.blogspot.com/2014/06/out-with-old.html). Just curious how you came to this. This should put you in the ~ 50+ mi range, correct? Since my 914ev lead acid pack died I never upgraded it. I couldn't stand to put messy PbA back in, and couldn't swallow dropping another $12k on LFP. Anyway, I'm thinking about reviving the car again, so am interested to know some of the things you've considered. Thanks,
> 
> Dave


I went with 68 of the CA100FI cells. This is because it matches the various voltage levels of the 18 AGM batteries pretty closely, and so I won't have to change the fuses, DC-DC converter, voltmeter, etc. I expect to get about 60 miles range at 70% DOD. The pack weight will be 476 pounds, which will get the curb weight of the car almost down to where it started as an ICE.


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## PThompson509 (Jul 9, 2009)

I assume you've got the motor in the Delta configuration - that will work fine with the lower voltage. If you want a bit more torque, you could reconsider and go for the higher voltage. You would need to change the motor over to Wye configuration, and a bunch of other stuff do that that tho. I had my DMOC445 up to 370v with no problem.

Out of curiosity, how are you dealing with the heat in your 914? I live in San Diego and it gets HOT here (so I couldn't use the AC24 during the really hot spells).

Cheers!


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## racunniff (Jan 14, 2009)

PThompson509 said:


> I assume you've got the motor in the Delta configuration - that will work fine with the lower voltage. If you want a bit more torque, you could reconsider and go for the higher voltage. You would need to change the motor over to Wye configuration, and a bunch of other stuff do that that tho. I had my DMOC445 up to 370v with no problem.
> 
> Out of curiosity, how are you dealing with the heat in your 914? I live in San Diego and it gets HOT here (so I couldn't use the AC24 during the really hot spells).
> 
> Cheers!


Yes, it is in delta. I asked AZD about delta vs. wye at the lower voltage, and their advice was that it is probably better for delta. The ElectroJeep has an AZD AC55/DMOC445, at 307V nominal, and it is in wye. This was originally an Electro Automotive AC kit, so started out at 144V. I think the 216V nominal is a reasonable compromise - 144V is way too low, and much above 216V you start to get into the delta/wye gray zone. Unless you can go above 288V, of course.

Regarding heat in the 914 - in Colorado, heat is not the problem, cold is the problem  I have battery warmers and an electric cabin heater.


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## halestorm (Apr 28, 2009)

PThompson509 said:


> I had my DMOC445 up to 370v with no problem.


Is that where you run it now? Did you try it also in Delta? I'm curious for a side-by-side comparison. As I think I mentioned, I'm considering reviving my 914ev, which has been sitting garaged since the FLA batteries died three years ago.  I know I need to get my voltage >> 160, as the car was always rather anemic with the 18 * 8.4V FLAs. The question I have is HOW much do I need and where I will really see a difference.



PThompson509 said:


> Out of curiosity, how are you dealing with the heat in your 914? I live in San Diego and it gets HOT here (so I couldn't use the AC24 during the really hot spells).


I'm in Los Angeles; the heat is a problem and one which I've not properly dealt with. On hot days the DMOC would reduce power, making my already anemic drive even more so. Sometimes, if I couldn't park in the shade, it would over-temp before I even started driving, as the controller baked in the hot trunk of the car. I had various ideas for how to cool it but never implemented any of them. The one I always favored was getting the DMOC out of the trunk altogether and mounting it in a box alongside the motor. I built a mock-up, and it's tight, but I still think it might be possible. The easiest idea I had was building some duct work around the DMOC's heat sink and venting it outside with fans... but ugly.

As I'm considering reviving the car, I'm also considering this replacement controller, http://www.hpevs.com/ac24-hpevs-controller-kit.htm as it looks smaller and maybe I could get it out of the oven which is the trunk of the 914.


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## racunniff (Jan 14, 2009)

halestorm said:


> I'm in Los Angeles; the heat is a problem and one which I've not properly dealt with. On hot days the DMOC would reduce power, making my already anemic drive even more so. Sometimes, if I couldn't park in the shade, it would over-temp before I even started driving, as the controller baked in the hot trunk of the car.
> Dave


Although I joke about cold, I did actually do a little something about heat and the DMOC and charger. See http://volt914.blogspot.com/2010/02/pushing-toward-completion.html - I installed vents and fans in the rear trunk, plus some relays to have them come on appropriately when the DMOC or charger is running


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## PThompson509 (Jul 9, 2009)

halestorm said:


> Is that where you run it now? Did you try it also in Delta? I'm curious for a side-by-side comparison. As I think I mentioned, I'm considering reviving my 914ev, which has been sitting garaged since the FLA batteries died three years ago.  I know I need to get my voltage >> 160, as the car was always rather anemic with the 18 * 8.4V FLAs. The question I have is HOW much do I need and where I will really see a difference.
> 
> 
> 
> ...


Hi Dave, I started off with Delta (probably same kit as yours), and went with Wye. I got more torque with less current (but can't remember how much). If I remember correctly, you need to keep your voltage above 120v to keep the controller happy with delta. The higher the better - up until you get near that grey area.

If you decide to switch to Wye, then you are good for up to 400v max.

For the heat, I mounted an 11" cooling fan to the front of the motor. Looked like a terrible hack, but it worked for the motor. I was also seriously looking into a water spray that would mist the motor during really serious heat. However, there wasn't anything I could do for the controller, short of putting liquid cooling pad under it (which is what I have now for my current system).

The Curtis controller for the AC24 would be a great solution - it is common in the market, and there are several cooling solutions for it. Richard R has the AC50 and Curtis combo, and I believe he added some extra cooling for it (he lives in North San Diego County).


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## www.3xE.pl (Nov 22, 2008)

@racunniff: You could also choose A123 - 20Ah cells. These are still available from stock (we have access to their stock). Price is quite acceptable: 28 USD
I know that company is bankrupt, but their products are really good


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## halestorm (Apr 28, 2009)

I guess what I'm trying to get at with the voltage question is this.

The min/max range for Delta is 144/240 (nominal 156v).
The min/max range for Wye is 288/336 (nominal 312v).

We already know that operating in delta with 144v is rather anemic. Ross is going to run with 218v. That's going to be better, I'd think. But what is the ideal target? The datasheet shows tests in delta at 156v and test data in wye at 312v. What's special about 156v? Would 172v be better? How about 180v or is it just as good as 160v? is 205v just as good as 218v? Wye might be better but is the high end of delta better than the low end of wye?

Maybe no one knows the answer to this but I'm also trying to select a lithium pack for my 914ev with AC24LS/DMOC445 and I feel like I'm completely guessing when it comes to target voltage. I'm pretty sure I'm decided on staying within the delta range (based on available space in the car and the desire to have Ah >= 90), and I know I need to be at least 156v, but after that it's total guesswork (to me, so far). Hopefully someone can enlighten me.

Thanks


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## PThompson509 (Jul 9, 2009)

halestorm said:


> I guess what I'm trying to get at with the voltage question is this.
> 
> The min/max range for Delta is 144/240 (nominal 156v).
> The min/max range for Wye is 288/336 (nominal 312v).
> ...


When I was talking to the factory, they said that the higher the voltage the better. With Delta, you stop losing efficiency gains above 220v (may be 240, dunno, can't recall). There is that grey area where neither Delta nor Wye are really good (e.g. 240 to 290v).

The other thing is that you can get more torque out of the Wye configuration. 

So for my 914, I have 108 CALB60 stuffed into every nook and cranny. I no longer have any trunk space. In retrospect, I would prefer to have at least 100Ah batteries, as I could really use the extra current.

My suggestion: stick with Delta and go for the largest Ah batteries you can fit into the car, and try to get close to the top of the voltage range. 

Cheers, Peter


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## racunniff (Jan 14, 2009)

PThompson509 said:


> When I was talking to the factory, they said that the higher the voltage the better. With Delta, you stop losing efficiency gains above 220v (may be 240, dunno, can't recall). There is that grey area where neither Delta nor Wye are really good (e.g. 240 to 290v).


This is the same info I got from AZD back when they were still operational - you will see performance increases all the way to 240v in delta. I second Peter's recommendation - get as close to 240 as you can get with as many Ah as you can make fit.

Which is kind of how I ended up at 218V (I could make 216V of AGM fit, and I'm just putting LiFePO4 in essentially the same place).


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