DIY Offgrid Project – Integration Part 2

Lithium Iron Phosphate batteries like all lithium batteries need a battery management system to protect the individual cells from being over charged or over discharged.

This is a Batrium M8 Cellmon.

It connects to a monitoring box that has an embedded computer. In turn there is some software that only runs on a Windows machine that visualises the performance of the battery.

If a cell reaches maximum safe voltage before the others have fully charged the pack will not be fully charged. The red bits are the cellmons that are “by-passing” which means they are attempting to limit the voltage across their cell in an attempt to “balance” the voltages across all the cells. They can do this for about 1 amp which means it will take a while before the battery pack is fully “top balanced”. I can help this process along by discharging a high cell with a load like an incandescent headlight bulb. But during the main part of the charge and discharge cycle the cells are all at much the same voltage so the real imbalance is relatively small.

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