Thunder Sky Lipo's Any Good

It's rather expensive to get thundersky batteries into the U.S. as the shipping is a killer and there's no U.S. distributor. http://electricmotorsport.com/ can get thundersky LiFePO4 batteries, and if you yahoogle for "Lightning Lithium" (or is it Lithium Lightning?) you'll find some postings about a motorcycle built by Todd @ electricmotorsport.com using those thundersky batteries. I happened to touch that bike yesterday while helping its owner load it on the truck.

- David Herron, http://davidherron.com/

I have 14 50 Ah LCP cells in an e-max, but have no experience of the LFP cells. Be aware that LFP are quite different from the LCP cells that have been around for a few years. LFP is the newest chemistry by TS, so you won't find many with hands-on experience from them.

The information I have gathered about LFP is that they temporarily can deliver higher currents, up to 10C, than the LCP series. They are also cheaper. On the other hand, capacity as measured in Ah is lower for the same weight, and the output voltage is lower - even though the maximum charge voltage is the same. This is a serious drawback, because in many applications the voltage is limited by the controller and auxiliary systems (and possibly the charger and BMS). But this voltage will not be used in operation, because the output voltage is lower.

Example. Let's say you have a maximum system voltage of 60 V. You choose to build a pack of 14 LCP cells. If you charge them to maximum 4.25 V you will be at 59.5 V. When using the vehicle, voltage will stay around or little below 3.6 V/cell, or 50.4 V. If you choose LFP cells, you can't add more than 14 cells, because maximum voltage when charging will still be 4.25 V/cell or 59.5 V. But normal voltage in use will be around 3 V per cell, or only 42 V. For many applications there will be a big difference in performance.

The LFP cells are supposed to have a longer lifetime, in number of charge cycles, under certain conditions. Though already the LCPs are specified to 1000 cycles, and that is a lot in any EV. The rest of the parts on my e-max will most likely be scrap after 1000 complete cycles. Aging of the cells is more likely to set the limit, but we don't know much about how the LFP series will age. For LCP we do know that internal resistance increases gradually over the years, so they become unsuitable for EV use after 3 to 7 years. (It depends on a number of factors.)

My conclusion of this small investigation was: if you need high current, LFPs should outperform LCPs. If not, LCPs will give you superior range and output voltage (=speed, in many applications).

My LCP cells behave as expected, so far. I will post an update in a while.

Regards,
Rolf

Did you get to measure the impedance of those cells or whole pack ?
What did you paid for them ? , how fast do you charge them up ?
Could you post a picture of them ?
Are you using a BMS and whose is it ?
Any peak current measurement ?
what about range ?
Have 2 Lepton with Nickel-Zinc been thinking about LifePO4 . concerned about their price .