LiFeMnPO4 40AH cells on sale - thoughts?

JaxPilot

I have been chasing down info on on Lithium packs, as most are probably aware. I have recently been looking closer at the LiFePo4 packs, based on information gleaned from BobBoyce and cgtech, among others.

I came across a link today, it's to an authorized dealer of elite power solutions. While I think their 100AH and 200AH packs are desirable, they are a bit out of my price range. Electric Vehicle Enterprises currently has a sale on their LiFeMnPO4 40AH cells for $37 each. That means I could buy 32 of them to create an 80ah / 51.2v nominal (16s2p) battery pack. The cells themselves would come out to $1184.

It seems to me that that's a pretty decent cost for new LiFePO4 cells, which seem to have a safer failure mode should anything untoward ever happen. It would be a 117 lb pack, roughly 20"w x 14"d x 8.2" tall. Should easily fit. I would have to figure out what I want to do for a BMS, but does anyone see a drawback to these cells at this cost?

BGW

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cgtech

If it's these guys, that's what I originally used. Looks like the configuration you are talking about. They worked fine. Now days I'm using the 100ah cells.

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agpfl

So that would put you at about 4100Wh just for the cells. Did you check out the packs made with Chevy Volt cells? http://evbatterycenter.com/HAC4/inde...bms&Itemid=680

JaxPilot

Actually, impaper, I did. I think I asked if anyone knew about or had experience with them, but don't recall getting any definitive answers. Do you know how they compare to the Leaf batteries, or to the LiFePO4 ones? I don't see any information on their chemistry either. Strike that, they are Lithium-ion - LiMn2O4/LiNiO2

Would there be concerns about the age of these cells, and reduced lifespan? They don't say how old they are, or if they are new or used.

JaxPilot

cgtech, I see that you have only 16 balancers, so am I correct that it looks like you paralleled 2 cells to create 16, 3.2v 80AH modules? Are you using just the balance boards, or did you buy the whole CPU driven EMS?

I'd rather the 100AH cells, but 16 of those run, as a retail buyer, $2480. I could buy 48 of the 40 AH to create a 120AH pack for $1776, but am trying to reduce my costs for lithium as much as possible. I'm hoping that the 80AH setup will give me what I want for range, and the higher voltage will give me the torque and speed I am after.

Volt_Ampere

Parallel cells balance themselves so you only need a 16 cell BMS / balancer. 80AH is ok but I went for 120 with 14 Leaf modules. Each module is two cells in series rated at 60AH each.

JaxPilot

Talked to the president of that company, Bill S. just a few minutes ago. Turns out those 40AH cells are all sold out, and have been, they just haven't updated the web site. They were "lightly used" returns that an OEM used for a while and then returned. Not new.

Back to the drawing board.

BobBoyce

Oh well, such is life. Thank you for letting us know. I'm still saving for the pack that I want to get for my project.