On that front, prices were looking depressingly high (like starting around $500 for 650 Wh assembled, or $5-$6 each for cells to assemble) until I stumbled across some links here and elsewhere pointing to sources of cheap cells. Here's a summary of the options I'm considering:
- 14s3p made of Orbtronic 5.75-Ah 26650s...894 Wh for $419.58 (most expensive option here, but the lowest cell count...cells support 15A discharge)
- 14s5p made of Samsung INR18650-30Q cells...777 Wh for $349.30
- 14s10p made of Lishen LR1865LA cells...1036 Wh for $174.99
- 14s7p made of Sanyo UR18650A cells...798 Wh for $132.30
- 16s3p made of Fullriver LiFePO4 32700 cells...829 Wh for $71.99 (cheapest option here; cells support 9.9A discharge)
Also, with the LiFePO4 pack: while I have found a 16s BMS labeled as supporting this chemistry, is there anything different about the charger? I've used CR123 Li-ion and LiFePO4 cells in flashlights before, and they needed separate chargers (presumably to handle the voltage difference). 16s LiFePO4 puts out 51.2V nominal, which is just a little bit shy of the 51.8V you'd get from the usual 14s string. That difference, divided across 16 cells, is only 37.5 mV. Would a standard 52V charger be safe to use with a 16s LiFePO4 pack?
Addendum: After posting, I found this, which suggests that the little bit of overvoltage involved here likely wouldn't bring harm to a LiFePO4 battery pack. A "52V" charger would put out 58.8V; divided across 16 cells, you get 3.675V each, which is only 25 mV above LiFePO4's 3.65V full-charge level. Additionally, LiFePO4 appears to be much more tolerant of overcharging (700 mV per cell vs. 100 mV for other Li-ion chemistries).
All that said, this is my first time out with this stuff, so I just want to make sure I'm not missing something glaringly obvious to the more experienced.