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Discussion Starter · #1 · (Edited)
I've been doing the occasional look on alibaba for batteries, found another one that is very affordable, well without knowing shipping costs. Would like advice on using these batteries and my analysis. Alibaba is a freaky website, they always want me to download an app, here's a search that got me here on alibaba. "lipefo4 battery 3.7v 135ah oumeida". Here's the link:
3.7v Lithium Ion Battery 3.7v 135ah Rechargeable Battery For Electric Vehicles 3.7v135ah 3.7v Battery - Buy Ternary Lithium Battery 3.7v135ah,3.7v Battery,3.7v Lithium Ion Battery Product on Alibaba.com

Editing my mistakes (milliohm, not microohm)

Specs
  • 3.7v nom, 4.2V cut-off, 4.2V charge voltage, 3C-5C max discharge, 3C charge, 0.4mohm resistance, 20C-60C operating temp
  • dimensions: 50mm x 175mm x 140mm
  • 135ah x 3.7v => 0.5 kWh
  • 2.25kg

The inverter is 480V max, 480V/4.2= 114 batteries. 421V nominal.
114 batteries => 57 kWhr
228 batteries => 114 kWhr
$29 ea at 228 volume, $6,612 plus shipping and plates, etc.

3C discharge for 135ah battery means 3x135=405A. 5C=>675A
Two in parallel gives 810A, the motor looks like 730A peak, 300A continuous.
At peak current, 730A, 365A per string.
365A * (0.4 milliohm) * 114 = 16.7 V drop per string at peak.
(365A^2) * ( 0.4 / 1000) *114*2 = 12 kW generated at peak
(150A^2) * ( 0.4 / 1000) *114*2 = 2 kW generated continuous max

That's a lot of watts!

2.25kg x 228 => 518 kg, 1130lbs.

The temp specs, -20C to 60C, haha, i have eye dr appt in a week because these glasses are way off... :)

What do you suggest for heat/cool? Cold plates inbetween on the 140x175 end? Would plates on the 50x140 surface work or the 175x50 surface?

If these are something I can really make work, it's much more economical than the used tesla batteries I've seen, but also very heavy.

Thanks!
Mark

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Discussion Starter · #6 ·
Those voltages do not look right to me for LFP cells. Isnt the charge voltage generally 3.65, and nominal 3.20 per cell for LiFePO4?

And on your calculation you are dividing milliohms by a million - so your I^2 R calculation is off by 1000. Should be 12000watts at peak, and 2000 watts continuous. Even at 12000 watts, it will take a long time to heat up 1100lbs of batteries. Didnt old-school prismatic batteries like this generally just air-cool the packs?
Doh! What was i thinking? Thanks! I've corrected the original post.

These are old-school? when I'm looking at batteries, what would i look for "new school"? :) Thx!
 

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Discussion Starter · #13 ·
Wow, I'd like to really thank you all for the information, it's great! And you've helped me to avoid some sort of misrepresented battery!

I found an updated chart on lithium battery pricing.
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My initial costs from parts houses ($/kwhr)
Used Tesla: $299
New Leaf (Alibaba): $234
LG Chem Super Cell: $310
CALB 72ah: $603 (super duper high amperage)
These batteries and some from the same vendor: $53-$68 ==> too good to be true

It looks like buying batteries from local houses are a premium. Hybrid and racing batteries, high current, are definitely at a premium.
 

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Discussion Starter · #15 ·

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Discussion Starter · #18 ·
Toshiba has nice modules. They don't sell to individuals, but they're in Mitsubishi EV and apparently Nissan now.

This summer, I'll buy a 2012 Nissan Leaf that gets only 75 miles on a charge. It drives, but the passenger side is crunched in and you cannot use those doors. I'll salvage it eventually, great price.

The 2012 is the 24kWhr battery. Maybe I can get a replacement before i salvage it with one of the higher capacities and then use the batteries for salvage. anyways, discovered MyNissanLeaf.com for more info.
 

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Discussion Starter · #20 ·
75 miles of range is good enough to get you started....the price is right - free.
That’s some sage advice. Battery won’t affect the fun much and provides a learning tool. There will be newer cheaper batteries a few years later.

I could save more cash by using the leaf drive unit. A quick look, I haven’t seen anything about new gears that would get really big gear ratios. With 200lb-ft torque, I’d need some pretty big gear swap to feel happy with it. FYI, the leaf has more performance than the original ICE (100 hp, 173 lbs-ft), but that only went 50 mph.


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Discussion Starter · #23 ·
Thanks. I’m now sufficiently wary of unknown sources.

I really like the idea of seeing what I can do with my old but not too worn leaf cells. This is likely a three year project. I can build a new pack in four years with lower cost.


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