# Best non lithium battery choice?



## dragonsgate (May 19, 2012)

It is either lead or lithium. If you can, budget lithium now to save the hassle of changing later. If you go lead don’t mess with 12 volts as they do not have the amp hours. An S10 will carry six volt batteries and give a lot more range than twelve or eight volt batteries. I have had good luck with Trojan batteries.


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## Ziggythewiz (May 16, 2010)

DC Marines will last you about a year, so they're an okay option if you're just stalling for time saving for lithium.

6 volt batteries will have double the capacity of 12V batteries, double the weight, and longer life, especially compared to marines.

I'm using cheap (~$90) 8V golf cart batteries. I'm sure more expensive ones may be better, but they can cost much more, getting close to lithium territory, and then there's no point.


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## Siwastaja (Aug 1, 2012)

adeyo said:


> For cost reasons right now, I cannot go the lithium route.


LiFePO4 being the cheapest option there currently is, the only other option is not doing the conversion at all.

Of course, if you are planning to ditch the conversion after a few years, then lead is cheaper. Otherwise, try getting a loan to be able to buy batteries that are much cheaper in the long run.

This is of course regarding new batteries. You might be able to find used lead acid, NiCd or even NiMH batteries for very low price or for free. But as these would probably have even shorter lifetime, they really need to be close to free.


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## adeyo (Jun 6, 2012)

Siwastaja said:


> LiFePO4 being the cheapest option there currently is, the only other option is not doing the conversion at all.
> ...
> 
> Of course, if you are planning to ditch the conversion after a few years, then lead is cheaper. .


Probably going to sell this conversion and attempt an ac one of this is successful. 

How much difference are we talking in price for 6v trojan and LiFePO4? What is the lowest amount I can get away with in batteries needing maybe only 30 mile range with a typical s10 (extended cab '98).... I know I can calculate that with the info here, I am just talking about a guesstimate in prices/minimal needs. 

Thanks everyone for the great input!


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## Ziggythewiz (May 16, 2010)

LiFePO4 would be $5-6k, no idea on the Trojans, would depend a lot on where you are located/get em.


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## dtbaker (Jan 5, 2008)

adeyo said:


> Probably going to sell this conversion and attempt an ac one of this is successful.
> 
> How much difference are we talking in price for 6v trojan and LiFePO4? What is the lowest amount I can get away with in batteries needing maybe only 30 mile range with a typical s10 (extended cab '98).... I know I can calculate that with the info here, I am just talking about a guesstimate in prices/minimal needs.
> 
> Thanks everyone for the great input!



for 30 mile range you are going to need at LEAST 120v traction pack of floodies, either 6v or 8v golf cart batteries. A set of new trojans or USBattery are going to run you between $1500-2000. 120v worth of 100ah Winstons from balqon.com are going to run about $5k, but will last 5x longer or maybe even more. you would be well advised to go a little bigger though, perhaps 144v x 130ah if you really expect to have daily use around 30 miles.

save your pennies, borrow, beg.... go lifepo4.


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## adeyo (Jun 6, 2012)

Thanks. I am going 144v, but if I sell after this 'experiment' then I would rather not invest in lithium. 

Never heard of the other batteries. They are more expensive but go 5 * longer? They're lead?


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## adeyo (Jun 6, 2012)

Btw, what kind of battery are Winstons? ( I. E. what chemistry?)


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## GerhardRP (Nov 17, 2009)

adeyo said:


> For cost reasons right now, I cannot go the lithium route. I am currently building an S 10 pickup DC conversion. 144 volt...
> 
> Any suggestions as to the best bang for my buck? With reasonable range and Power. I've also seen others using deep cycle marine batteries, is this a good option?
> 
> Also, is there any reason to go with 6 volt batteries over 12 volt batteries?


In estimating battery capacity with lead-acid you need to account for the Peukert effect. This calculator: http://dx9s.net/5-2/battcalc/ allows you to enter the usual specs which are the 20 hour capacity and the "reserve capaciry" which is the minutes it will deliver 25 amps to obtain the time the battery can deliver a selected current. Choose 100-200 Amps. You can then compare battery capacities at EV power levels


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## mk4gti (May 6, 2011)

adeyo said:


> Btw, what kind of battery are Winstons? ( I. E. what chemistry?)


LiFepo4 or LiFeYPo4, depending....


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## dtbaker (Jan 5, 2008)

adeyo said:


> Btw, what kind of battery are Winstons? ( I. E. what chemistry?)


Winstons are LiFePO4. the old Thundersky mfg split into Winston and Sinopoly. They are the 'good value' prismatics. CALBs are 'better', but about 20% more expensive.

144v worth of good floody deep cycle lead like USBattery or Trojans are going to cost you close to $2k, plus a watering system like flow-rite. I would suggest you re-think your strategy; re-sale on lead DIY evs is not very good from what I've seen ... not that many people are willing to buy a lead conversion with dead batteries anywhere near what it will cost you in parts.

save up, and go lithium....


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## adeyo (Jun 6, 2012)

How do these look spec wise? I might be able to get a deal. 
www.aeesolar.com/catalog/lithium-ion-batteries 
They are lithium iron magnesium phosphate. Also, at 12.8 volts would I go 12 in series or 11 for a 144v system? I would probably go 36 if i can afford it and get approximately 414ah by adding 1500 lbs to my s10. Or, 276ah would only add about 1000 lbs. 

Any advice?


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## dtbaker (Jan 5, 2008)

adeyo said:


> How do these look spec wise? I might be able to get a deal.
> www.aeesolar.com/catalog/lithium-ion-batteries
> They are lithium iron magnesium phosphate.



I don't think these will support a high enough discharge rate for use in an EV... the spec is not shown on this page, but typically batteries intended for off-grid solar use do not support the 3C-5C output you'll need for decent acceleration.


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## adeyo (Jun 6, 2012)

Darn!! I was hoping they might work. How do i find out for sure? What specs exactly do I need to check? 
... 

Also, did you notice the Trojan t-105 RE model? Would those work like normal or does the 'renewable energy' model also change things?


***EDIT: I checked the Valence website. They seem to use these in automotive uses. I can't seem to confirm the exact model though.


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## dtbaker (Jan 5, 2008)

adeyo said:


> Darn!! I was hoping they might work. How do i find out for sure? What specs exactly do I need to check?
> .


you need to find the rated continuous output amps, and the 'burst' amps the cells will put out for 10 or 30 seconds. You need to find these for the 100ah capacity size.

Winstons for instance are rated at 1C continuous I think maybe 2C I can't remember for sure right this second, and 3C 'burst' without lowering expected life cycles. The new CALBs are rated at 3C continuous, and up to 10C burst I think.... C corresponds to the ah capacity.

you need to be able to accelerate with at least 200-300amps, and run at 100-200 amps continuously to maintain highway speeds.


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## adeyo (Jun 6, 2012)

www.valence.com/products/data-sheets 
I found the spec sheets but can't interpret them. I did notice a 150 A continuous and 300 A peak discharge rate. That should be good according to your last post, right?


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## jeffcoat (Apr 16, 2012)

As best I can tell, the Trojan T105RE is 5lbs heavier than the standard T105, and is designed for stationary applications. I would go with the regular T105s - I have had good luck with them and they are designed for mobile applications.


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## adeyo (Jun 6, 2012)

Thanks for the insight.... I have an option for a good price on the agm 245ah 12v batteries. (8a8d model)... Trying to find continuous rating etc. I would get 12 new for $2000. At about $125 for the Trojan, i would need 24 coating about a grand more.


... Do you have to do much maintenance on the Trojan batteries?


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## jeffcoat (Apr 16, 2012)

The only maintenance we do on the T105s is watering every 3-4 months - we have installed water miser battery caps. Our Ford Ranger with 16 Trojans is driven between 15 to 25 miles each weekday (on flat ground), and has had these cells since last March; we typically get 3-4 years of use out of them before we have to replace them so we can stay competitive in our competitions.

Of course, if our competition rules allowed us to use lithium in the truck, we would ditch the lead in about 2 seconds...


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## adeyo (Jun 6, 2012)

Nice. What is your voltage? That should be at least close to my Chevy s10 I would think. If it's a 96v system how would this compare to a 144v one? Also, i probably need 20-30 miles but I am in the foothills of the blue Ridge mountains... So very hilly terrain.


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## jeffcoat (Apr 16, 2012)

We are at 96 volts which makes for very sluggish acceleration. If you can do 120v+, you will be much happier with the performance.


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## dtbaker (Jan 5, 2008)

adeyo said:


> www.valence.com/products/data-sheets
> I found the spec sheets but can't interpret them. I did notice a 150 A continuous and 300 A peak discharge rate. That should be good according to your last post, right?



to get the range and performance you want, 30 miles in hilly terrain, I would think 144v x 100ah would be advisable. with Li, the ah rating is pretty much what you get, with lead there is peukarts taking down the 20hr rating significantly for the typical EV 1-hr rating.

looking at the valence, the U24-12XP at 110ah, with 150amp continuous, 300 burst would be 'ok'. However, I dunno how you will be able to get them for less than Winstons or CALB? what kind of deal can you get?

There have not been any other builds I am familiar with using them, so I dunno..... your call.


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## piotrsko (Dec 9, 2007)

I'm at 192v @ 130 ah trojan 225's using a 11" Kostov 192 in a Ranger. 22 miles with long up hills to work, couple on the way back, 2 mile freeway at top of last hill. according to my data loggers I consume just about 13 kwh per trip perhaps 430wh per mile. low voltage alert goes off on last mile down hill to home, earlier if I catch the traffic lights red.

peak motor amps [email protected] peak battery 380 amps peak sag to 160v on way to work.

performance equal to ranger 2.9 with 1/2 ton in bed.

been doing this for a year so far


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## adeyo (Jun 6, 2012)

dtbaker said:


> looking at the valence, the U24-12XP at 110ah, with 150amp continuous, 300 burst would be 'ok'. However, I dunno how you will be able to get them for less than Winstons or CALB? what kind of deal can you get?


In a sales rep for Solar energy company. I can get them at cost. I don't know what the cost is yet, however. Our distributer (that can get those, tends to be a little high). 

... So, 100 ah might give me 30 miles at 144v in hilly terrain? (approximately anyways) 

Also, where is the best place to buy calb or Winston? (reliable place with best price?)


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## adeyo (Jun 6, 2012)

piotrsko said:


> I'm at 192v @ 130 ah trojan 225's using a 11" Kostov 192 in a Ranger. 22 miles with long up hills to work, couple on the way back, 2 mile freeway at top of last hill. according to my data loggers I consume just about 13 kwh per trip perhaps 430wh per mile. low voltage alert goes off on last mile down hill to home, earlier if I catch the traffic lights red.
> 
> peak motor amps [email protected] peak battery 380 amps peak sag to 160v on way to work.
> 
> ...


Great, thanks for that! Now I have an idea of what to expect.


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## dtbaker (Jan 5, 2008)

adeyo said:


> ... So, 100 ah might give me 30 miles at 144v in hilly terrain? (approximately anyways)


about...




adeyo said:


> Also, where is the best place to buy calb or Winston? (reliable place with best price?)


best price I've seen lately on Winstons has been from Balqon.com at around $1.10/ah , CALBs are more, I haven't priced the new gray ones, but would expect calibpower.com to have best price and most likely in stock.


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## adeyo (Jun 6, 2012)

Great, I'll check calibpower. Is it possible to "phase in" lithium ion batteries? I.e. Buy enough for 75ah now and another 75ah next year or the year after?

EDIT: I just saw Balqon carries 12 volt 90ah batteries. Is there any reason NOT to go with 12 volt lithium ion? It would be much easier and cheaper to go with 12 batteries in my 144v setup than 45 3.2v batteries!


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## Ziggythewiz (May 16, 2010)

You can't do 75AH because they don't make them...but you could do 70 and add more later.

Those aren't 12V lithium cells, they're 12V battery packs made of 4 cells. If they're cheaper that way though (I doubt it), sounds like a deal.


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## adeyo (Jun 6, 2012)

Good to know. Balqon has them for the same price (200amp =$220 vs. 100 amp = $110)... But I figure less connections etc. Plus, easier to hook up.


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## Ziggythewiz (May 16, 2010)

Where do you see that?


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## PStechPaul (May 1, 2012)

I have found some "good deals" on NiMH batteries that might be better than lead. I have ordered some and will do testing to see if their specs are "real" or hugely inflated. One advantage of NiMH is they are possibly safer and less critical for charging. I'm looking at AA cells which are rated at 1.2V 3.5 Ah, so for a 10 kWh pack you would need 2380 cells. But they can be easily stacked 20 in series in a tube for 24V modules. Here are some that I found:
http://www.ebay.com/itm/4pcs-UltraFire-3500mAh-1-2V-Ni-MH-AA-Rechareable-Battery-Battery-Box-Yellow-/190704654165 ($0.40/Wh)
http://www.ebay.com/itm/4x-UltraFire-AA-1-2V-3500mAh-Ni-MH-rechareable-Batteries-High-quality-/110999656639 ($0.31/Wh)
http://www.ebay.com/itm/16-2500-mAh-AA-1-2V-Rechargeable-Ni-MH-Batteries-SHIPS-FROM-TX-WITHIN-24-HRS-/110991494981 ($0.30/Wh)
http://www.ebay.com/itm/20-pcs-AA-2A-LR06-3000mAh-Ni-MH-1-2V-Rechargeable-Battery-Cell-BTY-HR6-Green-/400380315685 ($0.20/Wh)

So a 10 kWh pack could be built for $2000. The last ones listed are 16 grams each, so total weight is 38 kg. They are 14x50 mm (7700 mm^3) so total volume is 18,000 cc, or a cube 26 cm (10 inches) per side. Rated charge/discharge cycles is 1000.

Another option is SLA batteries. The best deal I have found is 12V 12 Ah for $20 each, or about $0.14/Wh, and 12 lb each. Considering Peukert, you would need a 20 kWh pack to get the equivalent of 10 kWh. The cost would be $2800 for 140 batteries, and weight would be 1680 pounds. Truly a lead sled. SLAs may last better than flooded lead-acid deep cycle 12V marine batteries, which are about $80 or 100 Ah, or $0.07/Wh. These are about 80 pounds each, so 67 lb/kWh and 1333 lb for a 20k Whr pack (10 kWh effective).

I think NiMH is worth looking into, although of course LiFePO4 are the most economical when considered over their 10 year expected life.

There are 9500 mAh C cells for $0.24/Wh:
http://www.ebay.com/itm/8-x-C-size-...US_Rechargeable_Batteries&hash=item2326df58e7
or $0.19/Wh
http://www.ebay.com/itm/40-x-C-size...US_Rechargeable_Batteries&hash=item53f2e2ae10

Note: All prices above INCLUDE shipping from Hong Kong. 

Now, if these specs are real....


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## Siwastaja (Aug 1, 2012)

PStechPaul said:


> One advantage of NiMH is they are possibly safer and less critical for charging.


Do your homework -- within all typical battery chemistries, NiMH is the most difficult to charge. Most chargers for past two decades have included microprocessor control, temperature sensors and precise voltage measuring for dV/dt cutoff. Basically, you can't charge NiMH fully with CV like you can do with lithium; NiMH starts do degrade and heat up from overcharge. There happens to be a very small notch in voltage when the battery is full; you need a processor to detect that notch and stop charging. Then, you need a temperature sensor in order the notch goes undetected, to stop charging when only minimal damage has happened.

For a big pack, you'd need to DIY that.

Yes you can do with constant current charge and no cell level BMS, but it works only for very slow charge (C/10, giving typically 14 - 15 hours charge time due to poor charging efficiency - this is more than "overnight".) At those currents, the "overcharge" won't do much damage, mostly just convert to heat.

There have been some "semi-quick" 5-hour chargers without processor control, but I think they compromise the battery life. Not sure, but at least these are things you need to consider. 

Me included, people did not have very good experience using NiMH. Lithium just works better. Even NiCd is better, just worse at Wh/kg and environmental aspects.

And again, NiMH has poor efficiency (round-trip at something like 65-70% compared to 90-95% of li-ion) and you'll probably need a cooling system at EV power levels. Self-discharge is also a real problem. If you don't go straight from the charger but wait just for one day, it may be a 20% drop in range. There is now a new NiMH technology called low self discharge or LSD, but those won't be cheap.

And lastly, do not believe that 3500 mAh rating for AA size. 3000 mAh is well possible for a good brand -- those cheap ones would be about 2000 mAh, probably.



> So a 10 kWh pack could be built for $2000.


I would only do it if I could get those cells for $500 absolute max.

A 10 kWh lithium pack can be had for $4000, and will probably last for 5 times longer than those cheap, low-quality NiMHs without proper BMS.

So to sum up my opinion, don't use NiMH unless you can get it _very_ cheap. The prices you are quoting are not much better at all than for well tested LiFePO4 prismatics. And if you get a 500 cycles out of those, you'll be lucky. Again, in a few years when you are changing your battery pack you will see that these "cheaper" batteries become the more expensive battery technology, just like lead does.

If you want easy charging, why not go no-BMS top-balanced LiFePO4? IMO, BMS should be used but people have good experience without and that would be simple at least if that is your goal.

Believe me, I am piss poor and open to any technical solution, and I've done my homework regarding cheapest battery solution in an EV; and it boils down to: just don't use any non-LiFePO4 battery unless you get them for VERY cheap, for 1/5 of the Wh price of the LiFePO4, which currently is about $0.35/Wh. So if you can get something that is in working order for $0.07/Wh, consider using it. So, it basically needs to be free stuff.


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## dtbaker (Jan 5, 2008)

adeyo said:


> Great, I'll check calibpower. Is it possible to "phase in" lithium ion batteries? I.e. Buy enough for 75ah now and another 75ah next year or the year after?


really NOT a good idea to mix sizes, types or even ages... makes it hard to balance and they will require a good BMS to keep them in line if they are mixed. Second, if you go below about 100ah size cells, you will be straining the crap out of them when accelerating at 300 amps.




adeyo said:


> EDIT: I just saw Balqon carries 12 volt 90ah batteries. Is there any reason NOT to go with 12 volt lithium ion? It would be much easier and cheaper to go with 12 batteries in my 144v setup than 45 3.2v batteries!


I would guess you are looking at pre-packaged sets of 4 cells made to fit in standard lead size battery footprint. Introduces a whole second level of complexity in balancing. Just go with 100ah cells, and go with a 120v or 144v system you'll be happy you did.


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## adeyo (Jun 6, 2012)

Ziggythewiz said:


> Where do you see that?


Balqon.com then click products tab.


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## PStechPaul (May 1, 2012)

Siwastaja said:


> Do your homework -- within all typical battery chemistries, NiMH is the most difficult to charge. Most chargers for past two decades have included microprocessor control, temperature sensors and precise voltage measuring for dV/dt cutoff. Basically, you can't charge NiMH fully with CV like you can do with lithium; NiMH starts do degrade and heat up from overcharge. There happens to be a very small notch in voltage when the battery is full; you need a processor to detect that notch and stop charging. Then, you need a temperature sensor in order the notch goes undetected, to stop charging when only minimal damage has happened.
> 
> For a big pack, you'd need to DIY that.


That is what I plan to do. I'm working on a BMS that will be open source and suitable for DIY. It will be able to handle NiMH, Lead-acid, Li-Ion, and LiFePO4.



> Yes you can do with constant current charge and no cell level BMS, but it works only for very slow charge (C/10, giving typically 14 - 15 hours charge time due to poor charging efficiency - this is more than "overnight".) At those currents, the "overcharge" won't do much damage, mostly just convert to heat.


That charging rate would be acceptable for my initial application of a lawn tractor, or possibly a small car used infrequently.



> There have been some "semi-quick" 5-hour chargers without processor control, but I think they compromise the battery life. Not sure, but at least these are things you need to consider.
> 
> Me included, people did not have very good experience using NiMH. Lithium just works better. Even NiCd is better, just worse at Wh/kg and environmental aspects.
> 
> And again, NiMH has poor efficiency (round-trip at something like 65-70% compared to 90-95% of li-ion) and you'll probably need a cooling system at EV power levels. Self-discharge is also a real problem. If you don't go straight from the charger but wait just for one day, it may be a 20% drop in range. There is now a new NiMH technology called low self discharge or LSD, but those won't be cheap.


Those drawbacks won't be a major problem for my application, but I can see the point for a practical commuter EV.



> And lastly, do not believe that 3500 mAh rating for AA size. 3000 mAh is well possible for a good brand -- those cheap ones would be about 2000 mAh, probably.
> 
> I would only do it if I could get those cells for $500 absolute max.
> 
> A 10 kWh lithium pack can be had for $4000, and will probably last for 5 times longer than those cheap, low-quality NiMHs without proper BMS.


I plan to test them thoroughly. I, too, will be surprised if they meet specs, but I'd accept 70% of what they claim. I am also going to test the 18650 Li-Ion cells which I found for $0.26/Wh. I'll be even more surprised if they meet spec. 



> So to sum up my opinion, don't use NiMH unless you can get it _very_ cheap. The prices you are quoting are not much better at all than for well tested LiFePO4 prismatics. And if you get a 500 cycles out of those, you'll be lucky. Again, in a few years when you are changing your battery pack you will see that these "cheaper" batteries become the more expensive battery technology, just like lead does.
> 
> If you want easy charging, why not go no-BMS top-balanced LiFePO4? IMO, BMS should be used but people have good experience without and that would be simple at least if that is your goal.


I have sent an email to one eBay seller to see if they can provide quantities of 250 and 500 (for 300/600 VDC VFD). I would expect to be able to get them for a little less than $0.20/Wh for true capacity.



> Believe me, I am piss poor and open to any technical solution, and I've done my homework regarding cheapest battery solution in an EV; and it boils down to: just don't use any non-LiFePO4 battery unless you get them for VERY cheap, for 1/5 of the Wh price of the LiFePO4, which currently is about $0.35/Wh. So if you can get something that is in working order for $0.07/Wh, consider using it. So, it basically needs to be free stuff.


There is no real argument for an automotive EV, as the OP plans, but I wanted to present the possibilities of NiMH and lead. Obviously lead is far too heavy for his needs, but if the disadvantages as you describe can be overcome, NiMH may be viable.

For my tractor I am looking at possibly 24 SLAs for $480 and 3.5 kWh which should give me 1-2 hours of mowing or other general use, and the 288 pounds is actually an asset. If the NiMH seem to be OK, I could use 300 of them for 360V and 3 Ah for about 1.2 kWh and maybe 1/2 hour of mowing or 1 hour of riding for $240. If the cheap Li-Ion 18650 cells prove good, I can get about the same kWh with 100 of them for about $320. I'd be willing to pay $0.35/Wh for good LiFePO4 cells of the same size, but most of the cells I've seen from the reputable dealers are about 40 Ah minimum. If you know of any sources for cheap 18650s, even used cells, please let me know. 

Thanks for the valuable information. I am looking forward to the challenge of dealing with these various battery chemistries for my small applications, but also perhaps provide some new ideas for the BMS and using standard industrial motors and VFDs for EVs.


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## Siwastaja (Aug 1, 2012)

PStechPaul said:


> but if the disadvantages as you describe can be overcome, NiMH may be viable.


I'm still missing something: why?

If there are two technologies available, A and B, and A is better in every single aspect, theoretical and practical, but also cheaper, with better availability, easier to use than B, and with a lot of practical experience and know-how around the DIY community, why would anyone want to choose B?

Building packs from single cells is not practical for a DIYer. Maybe it could be done if those small cells were somehow the best tech available, but they are worst and the most expensive (in real operating costs).

BTW, I did a lot "series in tube" thing when I was 7-8 years old. No, it does not really work well, the contact is not good enough. You really need to have spot welding equipment.


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## Siwastaja (Aug 1, 2012)

dtbaker said:


> really NOT a good idea to mix sizes, types or even ages... makes it hard to balance and they will require a good BMS to keep them in line if they are mixed.


I'd say no problem.



First, *cells in parallel*:
(Increasing pack capacity, keeping voltage the same)

If the cells are of same type and approx same capacity, they have similar internal resistance and share current quite well. The one that tries to sag less in voltage, drives more current.

Even when there is some difference in current sharing, they balance each other automatically when in parallel.

Connecting li-ion cells in parallel is an old practice and AFAIK, has never caused problems, even when the process tolerances cause the cells to differ from each other. LiFePO4 cells do not change much in a few years use, either, and it can be seen that the cells even between different manufacturers are quite similar.

For extreme constant discharge applications, I would only suggest paralleling very similar cells, same manufacturing date, same batch. But this is when the full combined power of all parallel cells is needed.

But, simply put, if one cell of x Ah is enough for the specific purpose alone, adding another one cannot make things worse, even if they didn't share the current well. They will balance each other in "normal" use.

Hence, power applications (hybrids with small packs, racing) are very different from energy applications (normal battery EV with usable range with normal driving habits)

An example: If 1000A is needed from 4 parallel cells and every one is specified to 250A max, they need to be very similar so that they share the current so that no one will overheat. But if only 250A is needed anyway, overcurrent cannot appear.

Absolutely no difference in BMS. BMS cell module is connected normally to parallel cells.


Or, *cells in series*:
(Increasing pack voltage, keeping capacity the same; now the motor controller will take less current from the pack. Same effect on total energy = range.)

Adding new cells to existing strings has been done numerous times with no problems. This is possible with li-ion because of 100% charge efficiency (no peukert effect) -- in a string, it is guaranteed that every cell sees the same current, and seeing the same current, every cell receives and gives the same charge as the others.

As always,
- Sum of all internal resistances define performance and efficiency
- Smallest capacity cell defines the total pack capacity. (Unless redistributive BMS is used.)
- If some of the cells has a lot worse IR (e.g., defective cell, bad connection), it may affect performance and overheat, but this is out of scope here and affects all kind of packs.

Absolutely no difference in BMS here, either. Of course more BMS cell modules are needed.


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## PStechPaul (May 1, 2012)

I searched for low cost LiFePO4 cells and the best I could come up with was about $0.60/Wh from this company:
http://www.ebay.com/itm/4-Pcs-18650...m-battery-Blue-Flat-Top-LiFePo4-/400373810881

In 4 piece quantity they are actually $0.73/Wh and the largest quantity they list is 24:
http://www.ebay.com/itm/24-Pcs-1865...m-battery-Blue-Flat-Top-LiFePo4-/380543065868

Maybe in quantity of 100 it might get down to $0.40/Wh so I would have a 576 Wh 320V pack for $230 or 1152 Wh for $460. I might order the pack of four so I will have something to work with for my BMS and charger, and it will at least make a nice little 12.8V supply for automotive accessories.

I don't know why strings of cells in a tube would not be sufficient. At least for the AA and C cell form factor they seem to be made for that and it works well enough in flashlights if there is a strong spring to hold tension and the mating contacts are clean. 

From what I see of the flat top 18650 cells they might have the plastic sleeve extend over the ends so that some sort of connector disc would be needed between each cell. I'm not sure if spot welding would be safe, and you would need to weld tabs on each end and then connect them externally which might create a tighter fit in a tube. But a BMS would need to access each contact in any case, so maybe a disc with a soft conductive coating on the surfaces could be used. Maybe conductive epoxy? 

You bring up some good points. I think there was another thread about using 18650 cells, and I should find that and get more information. For right now I'm just doing research and plan some testing, but for the OP you are probably spot on about the LiFePO4 being the only sensible option. And I suppose that it could be considered an investment and most likely a lightly used battery pack could be resold here or on eBay for at least 50-75% of purchase cost if the conversion was unsuccessful or suffered damage that did not compromise the cells. 

BTW, I found a long thread on 18650s: http://www.diyelectriccar.com/forums/showthread.php?t=75941&highlight=18650

And another which shows some results for the "UltraFire" brand showing 50% rated capacity: http://www.diyelectriccar.com/forums/showthread.php?t=80358&highlight=18650


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## Siwastaja (Aug 1, 2012)

PStechPaul said:


> I searched for low cost LiFePO4 cells and the best I could come up with was about $0.60/Wh from this company:
> http://www.ebay.com/itm/4-Pcs-18650...m-battery-Blue-Flat-Top-LiFePo4-/400373810881


Sorry -- I forgot you were making a very small pack. Indeed $/Wh is higher for small LiFePO4 cells. Take a look at RC LIPOs, like Turnigy 20C models at Hobbyking, and you are back at about $0.45/Wh. But it's probably not worth the shorter lifetime. Unless you really need a lot of current from a small pack. Edit: For example: http://www.hobbyking.com/hobbyking/store/__18558__Turnigy_2200mAh_1S_20C_Lipoly_Single_Cell_.html



> I don't know why strings of cells in a tube would not be sufficient. At least for the AA and C cell form factor they seem to be made for that and it works well enough in flashlights if there is a strong spring to hold tension and the mating contacts are clean.


Sorry, but most flashlights I have seen do not work very well just for this reason! Also, they typically use 0.5 to 1A at most. You would be using a bit more than that, I think. Remember, I^2R. If your tractor would use 5 kW peak at 360V, it would be 13A. BTW, won't happen with AA NiMH cells. And won't happen in "series in tube" construction no matter how good the cells are. From real experience on connecting AA cells in series without spot welding, I would say 2-3 A absolute maximum. Yes, have done it numerous times, with clean contacts and pretty high spring force. It does not work. Believe me.



> I'm not sure if spot welding would be safe


Of course it is. It is the way battery packs are always constructed from single small cylindrical cells. Take apart a laptop battery pack (or Tesla Roadster ) to see it.




> and you would need to weld tabs on each end and then connect them externally which might create a tighter fit in a tube.


Don't put them on a tube, but side by side. 
Edit: putting "battery pack" on Google image search, the third result shows the construction: http://www.asia.ru/images/target/img/product/11/47/00/11470014.jpg



> Maybe conductive epoxy?


Are you serious!? How much current do you think you can pass through a "conductive epoxy"?


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## Ziggythewiz (May 16, 2010)

PStechPaul said:


> I searched for low cost LiFePO4 cells and the best I could come up with was about $0.60/Wh


How small of a pack do you need? My 40AH CALBs were under $0.40/Wh


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## Ziggythewiz (May 16, 2010)

adeyo said:


> Balqon.com then click products tab.


Maybe we're looking at different Balqon.coms. The one I see doesn't have a products tab, just a store link. I don't see a 12V lithium battery in the size you mentioned, and the ones I do see are not fit for EV traction packs.


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## Sunking (Aug 10, 2009)

adeyo said:


> Also, did you notice the Trojan t-105 RE model? Would those work like normal or does the 'renewable energy' model also change things?


I am very familiar with them. The RE series is a true deep cycle battery, meaning they have thicker heavier plates that last longer than the standard hybrid design of the T-105. That is why they are 5 pounds heavier, they have more lead in them. 


The downside it means they have higher internal resistance and cannot deliver the same high current without voltage sag. So no they are not a good choice for EV's.


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## PStechPaul (May 1, 2012)

Siwastaja said:


> Are you serious!? How much current do you think you can pass through a "conductive epoxy"?


I found some conductive silver-filled epoxy with a resistivity of 0.001 Ohm-cm. http://www.masterbond.com/tds/ep77m-f

For a bond between two AA cells, using a diameter of 0.5 cm, and a thickness of 0.2 mm (0.08"), I get a resistance of 0.001 Ohms, so even at 10 amps it would drop only 10 mV and power dissipation would be minimal.

I found a similar product available from:
http://www.mouser.com/ProductDetail/MG-Chemicals/8331-14G/?qs=sGAEpiMZZMvJqaFk9BIiv6jhjM0Pk6JzHea7mFx9BnQ%3d
It is not quite as good, with 0.017 Ohm-cm, but still that would be only 17 mOhms and 170 mV drop at 10 amps:
http://www.mgchemicals.com/products/adhesives/electrically-conductive/silver-conductive-epoxy-8331/

It is rather expensive, though, and spot welding would be superior and less expensive for a commercial product, and maybe even for a DIY project.

The reason stacks of cells in flashlights fail is probably because (1) the contact is usually only a few points on the mating surfaces, (2) the contact pressure is insufficient to deform the metal enough to increase the surface area, and (3) oxidation, contaminants, and surface wear degrade the connection. Using conductive epoxy (especially if it is somewhat flexible) creates a much larger area of contact, and also tends to keep out contaminants and reduce surface wear from shock and vibration. Stronger springs and high quality end contacts can also improve the performance. But you cannot achieve anywhere near the contact force of a bolted connection because that would damage the cells.

After reading some of the threads on 18650 cells, I think even the cheap Li-Ion cells (such as UltraFire) may be viable as long as a good BMS and other protection means are employed, and even if they turn out to be half their rated capacity they will still be less than $0.40/Wh. Comparable size LiFePO4 cells seem to be closer to $1/Wh. If the cells are confined in separate tubes, I think the risk of thermal runaway involving the entire pack is practically eliminated. And these cells have tabs already so they would only need to be connected in series with an extra wire for the BMS, which may even be attached to each cell if my individual cell BMS system works out.


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## dtbaker (Jan 5, 2008)

PStechPaul said:


> For a bond between two AA cells, using a diameter of 0.5 cm, and a thickness of 0.2 mm (0.08"), I get a resistance of 0.001 Ohms, so even at 10 amps it would drop only 10 mV and power dissipation would be minimal.



I thought we were talking about battery options for a TRUCK and up to 1000 amps with vibration-proof connections, not a 10 amp flashlight?!

small-cell packs for the average DIY are simply asking for trouble with so many more connections, no affordable cell-level balancing/bms. Best bang for the buck that will be dependable is the prismatic LiFePO4 cells for non-racers.

Lead is dead, NiMH is heavy, dangerous, and toxic. hundreds, or thousands, of small cells are not practical for the average DIY to fabricate.


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## dtbaker (Jan 5, 2008)

Ziggythewiz said:


> How small of a pack do you need? My 40AH CALBs were under $0.40/Wh



thats the thing... the OP needs 120v or 144v of at least 100ah to get the range he needs in hilly country. The reality is it MIGHT be possible to do with high-quality 6v lead, but that would cost about $2k and only last 500-700 cycles at very best. The original thread got lost in wildly impractical suggestions for alternate chemistry and small cells.

Given the goal of the OP, I don't think there IS a good alternative to prismatic LiFePO4, and a nice set of 100ah Winstons for $6k or so will be the lowest cost over the life of the build, best resale value, etc.


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## adeyo (Jun 6, 2012)

Ziggythewiz said:


> Maybe we're looking at different Balqon.coms. The one I see doesn't have a products tab, just a store link. I don't see a 12V lithium battery in the size you mentioned, and the ones I do see are not fit for EV traction packs.


balqon.com/store.php#!/~/category/id=2736690&offset=0&sort=priceAsc

Edit: just noticed that I was looking at 'store' the -> 12 volt lithium batteries section.... 60ah rating.... 24 would give 120ah 144v.... But would these not work? It looks like they mention EV's eventhough it isn't unset the EV category.... What would be the downside?


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## adeyo (Jun 6, 2012)

Winston are from Balqon? 

24 X 12v 60ah (120ah tot) = $6,336

Or 

45 X 3.2v 100ah = $4,950 

Are the 12v ok for EV use? In the future I could add another 12pack in parallel for 180ah


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## adeyo (Jun 6, 2012)

On a side note, there is a Chevy Volt at auction. It was in a flood. I assume all of the electrical components would be completely shorted out. However, is it at all possible that the lithium ion batteries would still be salvageable?


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## dtbaker (Jan 5, 2008)

adeyo said:


> balqon.com/store.php#!/~/category/id=2736690&offset=0&sort=priceAsc
> 
> Edit: just noticed that I was looking at 'store' the -> 12 volt lithium batteries section.... 60ah rating.... 24 would give 120ah 144v.... But would these not work? It looks like they mention EV's eventhough it isn't unset the EV category.... What would be the downside?



you are going to need close to 15kWhr on board to get your 30 miles. fewer connections and larger ah cells means less chance for mistakes, easier balancing.... so rather than parallel smaller cells to get to 120ah, then series those to get to 144v.... I really think you'd be better w/ 144v x 100ah (14.4 kWhr) , or 120v x 160ah (19.2kWhr) which would give you a little more range, but a little less 'zip'. Depends on how much range you REALLY need, and being a little conservative with the estimates since a couple other s-10s I've seen don't seem very efficient... You are probably safer to go with the 120v x 160ah and have the better range, the batteries will last longer too.


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## Ziggythewiz (May 16, 2010)

adeyo said:


> balqon.com/store.php#!/~/category/id=2736690&offset=0&sort=priceAsc
> 
> Edit: just noticed that I was looking at 'store' the -> 12 volt lithium batteries section.... 60ah rating.... 24 would give 120ah 144v.... But would these not work? It looks like they mention EV's eventhough it isn't unset the EV category.... What would be the downside?


The 12V batteries they have are somehow inferior cells. They list them as MAX < 1C while the others they say are good to 3C. These are suitable for use as EV AUX batts, but not traction batts. For traction you need at least the 3C cells.


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## adeyo (Jun 6, 2012)

dtbaker said:


> ... You are probably safer to go with the 120v x 160ah and have the better range, the batteries will last longer too.


I bought a unfinished project... Was formerly a kit for a 144 volt system. Would this be a problem? In assuming I can lower my voltage with no problems, but need some advice.


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