Battery gallery: Call for Real-life reports

[martinko]

My first prototyp (motor 36V/250W) has Lead Batteries, 36Vx7.2Ah, something like 7.5kg, feels like a real big stone :-(
And, at least according to its specs, at 0.5-1C (this is the area where I usually work in) it just supplies 60% of its capacity, so I really have something like 4.5Ah, at best, or 160Wh, or 20Wh/kg. The only advantage seems to be the price, ~0.35€/Wh.

Looking ahead, I have found a vendor for LiMn Batteries. They sell for 0.85€/Wh, the specific weight is exceptional with 180Wh/kg (means 1.8kg for 40V/8Ah). Data sheet promises only 300 full cycles, which means (at 10Wh/km) about 2.5€/100km extra cost, just for the batteries. LiMn is promised to be reasonably fire save.

LiFePO4 sells for 1.2€/Wh, 1.000 full cycles (makes only ~1€/100km), but 90Wh/kg (which means 3.6kg for 320Wh), OTOH full-blown fire-save (which seems nice, but not so important for me). And, I there seems to be something like 2 months (?) waiting time for actual availability.

A possible way to go for me seems to be LiMn now, and FiFePo later when the LiMn has given up life (I am driving a lot.).

I would be glad for any real-life reports on the different battery types (especially the Li*-variants), but also comments on prices, weight etc, because my wisdom here is from datasheets only.

Cheers,
Martin

 



 

[OneEye]

Numbers you are reading off the datasheets meshes fairly well with the user experiences reported over at the Endless Sphere forums.  They have a larger user base, and have folks riding on Lead, Li-Poly, newer LiMn and LiCo formulations, and LiFePO₄ from high-end (A123 and Phostech) to low-end (a few e-bay sellers who wrap their battery packs in duct tape instead of shrink wrap).  High-end LiFePO₄ prices seem to be moving up currently, while the low end is becoming commoditized.  None of the riders has enough cycles on their bikes to get close to the 1000 or 2000 that is hoped for from the chemistry, so it will still be some time before we get user testimonials matching up with the marketing hype and general speculation.

Personally, it seems like a good time to just keep riding on the Lead battery you bought initially, and wait for things to shake out.  By then maybe you will find out if commodity grade LiFePO₄ will deliver on the hoped-for 1000 cycles.