dyi battery build from Lithium Polymer


New Member
Aug 27, 2021
I have about 300 Lithium Polymer batteries that recently fell off a truck. I want to make a 24v battery out of them. All in great shape and not very old.
I do not yet have solar panels. That will come soon.
The plan is to run a high efficiency window AC unit (120 vAC) from noon until dark every day. The batteries charge in the morning, if/when there is enough V/W/A, the unit turns on. Runs until its out of V/W/A.

I will get LiFEPO4 batteries later. This is more of a proof of concept. I'm aware of the limited cycles for LiPoly.

Batt: 3.7840 V 3850 mAh. There are some really new ones that are 4.2v, 4500 mAh. But that is a limited number.

1. I've put some of them in packs of 6. 6x3.7840V=22.7V. Is that enough to run a 24 V inverter? 6x3850mAh=2.3 Ah. Do I use 7 per pack or even 8?
2. Do I need a bms for each pack?
3. I put these in parallel. At 6 per pack: approx 50 packs. 50x2.3 Ah= 115 Ah. Less packs if more per pack. Is my math correct? Will this be enough

I guess I'm at the point were I can start making a bunch of packs and put them on a bus bar. I don't want to make 6 per if I need 7 per.

Outside of the questions above, any suggestions, gotchya's or experience would be appreciated.