Post #10044

LFP batteries.... These are the most common battery used in solar systems these days. Unlike other lithium chemistry they do not catch fire. Well, they can but they can't sustain the burn. Other lithium batteries like 18650s and NMC bring their own oxidizers and burn fiercely. LFP does not do this. Now, when we talk about a battery, we are talking about a collection of cells. 48v LFP batteries are made of 16 LFP "cells". Cells are always 3.2v and range from 100ah to 628ah (amp hours). So 16 in series makes votlages add, and thats 16 x 3.2 = 51.2v. The amp hours can be multiplied by the voltage to get watthours or kWh. So a collection of 16 314ah cells makes 51.2v x 314 = 16,076wh or 16kwh. Now we are the point that I'm writing about today.... some chinese companies are offering batteries that exceed 16kwh. If they do it with "MB56" 628ah cells, that's wonderful. But most of them are doubling the number of cells. Since they have to have groups of 16 cells, what they do is put additional groups of 16 cells in parallel. The problem with this is if one cell was to short out, the other one(s) in parallel with it would dump power into that bad cell. They should fuse them in this configuration but they don't. If things went really sideways you could have a fire from the heat of the shorted battery discharging.... but not from the chemicals in the LFP cell! So if you are going to get a battery larger than 16kwh make sure it is the MB56 628ah cells and not two 314ah cells in parallel. Models that I cannot recommend because of the parallel issue are Docan Dolphin series with 32 and 48kwh.