LiFePo4 "upgrade" in progess.

[rickst29]

One measures around 105Ah, and the other measures 121Ah (but I stopping the test at 12.00 Volts, with about 9% of capacity remaining unused by the load test).

In each battery, I use a 100A BMS (programmable) with some customized parameters to avoid excessive overcharge and discharge. The battery monitors (bluetooth) run on the cellphone. Both battery packs are compressed, using 4x spring-loaded rods and steel plates to spread the sprung force evenly on the faces of the 4 cells. The compressive force varies between 280 and 420 pounds (due to spring compression), increasing when the cells swell larger. The steel plates, unfortunately, consume most of the weight advantage of LFP batteries - each of these packs is about 50 pounds.

This compression is used to increase the number of charge/discharge cycles. With no compression, the number of cycles (lifespan) is typically around 2500. With compression, you can nearly double that figure. Compression prevents the cell from becoming distorted at higher levels of charge, and prevents lateral stresses within the anode. Both CATL and EVE recommend compression, and I feel that it's correct to assume that all other rectangular cells have similar benefits from being used in this way.

No pre-built rectangular batteries in plastic are capable of containing this feature. A few, battery packs, such as those from BattleBorn, are built with cylindrical cells: In those batteries, the anode rods are not stressed by expansion, because the force is even all around. But batteries which are pre-built using 'prismatic' rectangular cells are, in my new opinion, all inherently defective in lacking this feature. They should only be warrantied for 2000 charge/discharge cycles, and they won't last more than about 2500 cycles.

I will not be recommending any pre-built rectangular battery pack in the future, except from BattleBorn. I now recommend build-your-own. The first photo is my second home-built (121Ah) before adding the heating pads, taping the BMS in place, and adding the wood case. The second photo is my first home-built (finished), with the pad and partial wooden case installed.