I have the opportunity to buy either 4x 40ah CALB lifepo4 cells or a 12v module built from original a123 26650 lithium cells at 15ah. My amp draw will be about 400 amps for 10 seconds. There will be ample charge time between discharge and no long term discharge. Which module could you guys see working best for my application? Cost is roughly the same. The guy who builds the a123 module said it will have no problem discharging 400 amps for no more than 10 seconds. And same story goes for the calb cells. I know they are 10c for 10 seconds. Thoughts?
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A123 26650 12v module compared to calb cells
- Thread starter Ktraughb
- Start date
wb9k
10 kW
That's about a 26C discharge rate for the A123 pack, which is no problem at all if you have good solid connections to the cells and between the pack and the load. I can't speak to the CALB cells from direct experience, but I have a friend who changed his motorcycle over from CALB to A123 pouch cells and this gave him roughly a 10% improvement in top speed and range. I would expect the A123's to last longer under the duress, but I could be wrong. The A123 pack will certainly be smaller and lighter.
So the a123 were that good, huh? Here is the listing. I actually had no luck finding this. I inquired about another thing he had for sale and he pointed me in this direction as an option. Only thing is, I don't want to spend $150 on a proper bms for this module, nor the $100 to properly charge it. Is this module worth the maintenance? I know that 4 calb cells in series would be much less maintenance on the basis ill be using them.
http://m.ebay.com/itm/261787643826?nav=WATCHING_ACTIVE
http://m.ebay.com/itm/261787643826?nav=WATCHING_ACTIVE
wb9k
10 kW
OK, I'm pretty sure I know who the sellers are. Those batteries are Hymotion modules, and would be perfect for the use you are talking about. Brand new, they are 25 Ah, so I'm not sure where you're getting the 15 Ah number from. I would go for a fresher set than that...maybe you're thinking get a weaker pack to save some money. The cells may still do the job for you, though they will not perform as well as a pack with more life left in it. I'm also not sure where you get the idea that the CALB cells would require less maintenance. Care and feeding requirements should be near identical, except that you can charge the A123's faster if you need to. What is your application?
Full disclosure...I work for A123, and have had no direct personal experience with CALB cells. You should get other opinions on how these cells will stack up.
Full disclosure...I work for A123, and have had no direct personal experience with CALB cells. You should get other opinions on how these cells will stack up.
granolaboy
100 W
I've been shopping myself for a 12v lifepo4 40ah battery to boost my scooter. I need 100A continuous, 200A peak.
After much research, I'm going to order 8 20ah A123 pouch cells from OSN Power and their assembly kit. 4s2p.
I'll post how that goes...
After much research, I'm going to order 8 20ah A123 pouch cells from OSN Power and their assembly kit. 4s2p.
I'll post how that goes...
arkmundi
10 MW
You'll be happy with that. One thing about that kit is its a bit weak in the plastic unit-to-unit connection. You'll see it when you get it. The "unit" is a plastic bar that takes the tab for one pouch cell and clamps down with a metal bar. Any size battery pack can be made up lego style by snapping together these units side by side. Unfortunately, though the design is ok, its engineering was a bit off as the plastic can break at various weak spots. I used some epoxy to strengthen those joins.granolaboy said:
Other thing is the AMP20 prismatic pouch cells are designed to be housed under compression. Lot's of banter about that on this forum. I cut aluminium plate to size and used duct tape. Puts the whole pack under compression, provides an impermeable case, and yet allows for disassembly when needed. As for cell replacement when the pack nears its useful lifetime.
The only reason I say it is less maintenance is because I can very easily charge 4 cells individually if I use the calb. With the a 123 module, the only way to charge this pack is as it sits in series parallel. The safe way without a special built bms and charger, is a 1 amp charge that is estimated to take about a week. And I only said 15ah because that's what he stated. It looks like the one in his pic shows 16.9 ah. I believe the ad says they're all between 70% and 90% life left, and they won't verify better ones when picking to ship.wb9k said:
dnmun
1 PW
if the A123 cells were used without a BMS during their charge and discharge cycles then you should be concerned about their health. just one time to over discharge land and they never perform again so if you are buying used then keep that in mind.
they are used, but i am not worried about their past use. the seller is very descriptive with their health etc. its what im going to do with them that worries me. lol. ill be honest, im looking for a much lighter option than agm sla batteries at this point, with as little maintenance as possible. maybe for that reason a simple pack of 4 calb cells is what i should be looking at. not some complicated bms with a complicated charging system.
dnmun
1 PW
i would never trust anyone who built and sold a battery with no BMS. it demonstrates a lack of concern or care about the quality of his work in building the battery and is evidence of how he is just out to make a buck by selling something he can make for the cheapest. but he may have gotten the A123 in a third deal and know nothing about them because they came to him used in that format.
sounds like the old 12V motorcycle battery replacement kinda pack.
sounds like the old 12V motorcycle battery replacement kinda pack.
wb9k
10 kW
A123 cells can be discharged to as low as 0.5 Volts indefinitely and recovered with no problem.
The pack in question is 26650 cells in 4S11P. 11 cells in parallel is going to act just like one big cell. There are sense leads to each measurement point in the pack, so you can charge the separate cells groups individually if you want to (though you can only put an amp or two through the interior sense lines) or you can bulk charge. There should be no difference whatsoever in maintaining charge and balance between this and a 4S1P CALB pack other than the current limits on the sense lines. If you wanted to, you could also install heavier lines to the cell goups very easily and charge the cell groups individually at higher current.
The attached file gives technical details about these modules. You can ignore the info about Sybesma's here (though they are the source of the modules in the ebay listing you linked to). Hope that helps clarify what you're looking at.
The pack in question is 26650 cells in 4S11P. 11 cells in parallel is going to act just like one big cell. There are sense leads to each measurement point in the pack, so you can charge the separate cells groups individually if you want to (though you can only put an amp or two through the interior sense lines) or you can bulk charge. There should be no difference whatsoever in maintaining charge and balance between this and a 4S1P CALB pack other than the current limits on the sense lines. If you wanted to, you could also install heavier lines to the cell goups very easily and charge the cell groups individually at higher current.
The attached file gives technical details about these modules. You can ignore the info about Sybesma's here (though they are the source of the modules in the ebay listing you linked to). Hope that helps clarify what you're looking at.
he says he acquired them in the bankruptcy of the company. he may not have actually produced these. not sure. he did say he could build a bms for it for $200 and it will supposedly be good enough for a standard 12v automotive charger. Of course with shipping im at $500 at that point. Which isnt bad for what Im getting, I understand that. Im just trying to be cost effective, and get the easiest maintenance option.dnmun said:
wb9k
10 kW
The story of the bankruptcy is true. These modules were built by A123 for Hymotion packs. I have two Priuses with these packs in them myself. Construction and design quality is in a league most users here have only dreamt of. You can put any old 4S or 8S BMS for LFP on these things and they will run just fine.
wb9k said:
so youre saying theyre good, huh? worth the bms and $? Even though theyre a couple years old? Put it this way, I will never fully discharge these things (so i hope) and the discharging i do will occur a maximum of probably 100 times this year. so basically a 400 amp draw for ten seconds, at most 100 times in the next 9 months. probably on overestimate. i may use them again next year, all depends on their success.
wb9k
10 kW
In my opinion, they are perfect for the duty cycle you describe. I still don't know what your application is though....
arkmundi
10 MW
And I'd like to see a side-by-side technical comparison of A123 and Calb. Throw EIG into that too. I believe that automotive class batteries are a better fit with eBikes and other LEV's. Rather than what a lot of ES'ers do and use hobbyist grade Lipo. An overview and analysis of automotive batteries would be a great addition to the sphere.
wb9k said:
I do something called dB Drag racing. Basically car stereo competition measured in sound pressure level. You may have heard of it seen/it. My system consists of an 8kw amplifier. In reality the starting rate is usually about 6kw, and dependent on voltage drop and impedance rise the amplifier will actually see--it drops in kw rating from there. The hope is around 6kw for 10 seconds. The run consists of a 30 second time period, but with fusing rules etc you usually only get one chance before your fusing blows (aka about 10 seconds. The term-lab meter only takes about 3 seconds to register your peak score.)
wb9k
10 kW
I used to work for Harman's automotive arm; I know exactly what you're talking about. I would think A123 cells should be among your first choices for that application. I use a Hymotion module to drive my better audio system's power amps and the same cells to drive the preamps--though that's not a terribly loud system. Big bursts of current is something A123 really excels at.
not sure how, but i totally skipped this post. That is so awesome you have a pdf of the original data on these batteries. That is very handy. Definitely food for thought toward making my decision. Also, it appears the sense lines have been removed or were never installed in these packs. If I add lines to each pack, should I simply charge them one pack at a time? And what amperage? Or is it okay to parallel these lines to a 12v charge and do them all at once? And again, if so what amperage is okay for such? One reason I am hesitant to available bms is because I fear many will provide protection before I get desired results. Then again, maybe not. I am not trying to discharge the cells to a low voltage, obviously. But I am definitely demanding a lot of amperage , and fear some bms cant handle such.wb9k said:
granolaboy
100 W
arkmundi said:
First off, thanks for all your help arkmundi. It's so nice when you reach out to someone you've never met on a board and actually get help. You rule.
But yah I've been reading the long long threads about the cells and the kits. Epoxying the bits together is a great idea. I was also thinking of adding the center screws to the metal plates as I saw another guy do, as he noticed the metal plates warped slightly causing a sketchy connection:
http://d9nip7cbts6f3.cloudfront.net/forum/13591-vectrix-lithium-conversion-a123-20ah-packs
I'm thinking i'll drill holes in metal plates and some pilot holes for these screws right off the bat so I don't have to be doing it after it's assembled.
As for the compression, i'm thinking of just putting it snug into a box while discharged, then when it charges up, it gets the compression it needs.
jimw1960
10 kW
wb9k said:
Perhaps you missed the first post where he says he needs to draw 400 amps out of them. It will be hard to find a BMS rated at 400 amps for a cheap price. I would just pull current directly from the terminals and add balance leads to charge with a balance charger. Given the infrequent use, couldn't he do all this a hell of a lot easier with some cheap hobby king lipo?
arkmundi
10 MW
You don't want to under-build the compression. It needs to be orthogonal, meaning equal pressure at every point. Begs for some serious thought & execution of a design that'll work. See http://endless-sphere.com/forums/viewtopic.php?f=14&t=52244&hilit=+a123+compression. As far as drilling the metal plate, that's over-building and a waste of time. The plate bolts are on the outside of the tabs, so don't need to penetrate. You do what you're thinking about and you'll also have to drill the tabs. Your suggestion is not something I have observed or believe is physically likely.granolaboy said:
granolaboy
100 W
Sorry to hijack this thread...If I should move this somewhere else, let me know 
I plan on getting some very rigid light material, like a cutting board, then build the box, heat-shrink it, then band it if I'm feeling paranoid. I don't plan on under-building it, but I think using 1/2" steel plates and a machine to compress it to tonnes of force is overkill for my application. Maybe it isn't...what do I know. I was going off of the doctor's suggestion:
I don't know anything first-hand with this kit; I'm just going off of that thread, where he noticed the plates didn't sit flat:
So he added screws in the middle of the metal plates to get a better connection:
It's not something I want to do, but it seems to me it would be easier to drill the holes before assembling the pack if I was going to do such a thing.
arkmundi said:
I plan on getting some very rigid light material, like a cutting board, then build the box, heat-shrink it, then band it if I'm feeling paranoid. I don't plan on under-building it, but I think using 1/2" steel plates and a machine to compress it to tonnes of force is overkill for my application. Maybe it isn't...what do I know. I was going off of the doctor's suggestion:
Doctorbass said:
arkmundi said:
I don't know anything first-hand with this kit; I'm just going off of that thread, where he noticed the plates didn't sit flat:
So he added screws in the middle of the metal plates to get a better connection:
It's not something I want to do, but it seems to me it would be easier to drill the holes before assembling the pack if I was going to do such a thing.
wb9k
10 kW
jimw1960 said:
I probably take too much for granted here. There is no reason a BMS must use FETs to control current--contactors work quite well too. That said, the starter batteries we make at work use FETs, and they can handle well over 500 Amps of current, so I don't really see 400 Amps through a bank of FET's for less than a minute as any kind of big deal. My fabulous junk box has spoiled me, no doubt about that.
I do agree with you...I would pull directly from the pack, no BMS in the way. Do fuse, of course, but if this has to be cheap (but still perform well), here's what I would do:
Use a decent hobby charger like a Cell Pro 8 to charge and balance the pack. Given the duty involved, this will be light work for the charger. (You'll need a DC power supply along with that, of course.)If you can establish that balance remains good at very low SOC, let the audio amplifier take care of LVC (which will likely never be encountered in the first place, let's remember). If that can't work, use a cell log and a contactor with a FET board in between to control LVC if you must have it. (PM me if you need any lightly used contactors rated for 400 Amps--cheap.) You can do all that for a few hundred bucks, and can use all of it on other items as well. Spend the bulk of the budget on decent cells that will perform well under the demands required for the job. That's where bang for the buck lies in this scenario, IMO.
(Edit): As for cheap HK lipo, I suppose that's an option. I'm not a fan of lipo for safety reasons, but those could also be easily overcome in this application with a fireproof box. It may not have the same versatility and will not have the same level of safety as the A123 pack though. Maybe that does not matter to the OP, but it would to me.
