FoxESS Community - Owners & Installers Forum

Hi. I'm planning to sell the battery modules in my current ECS2900 battery stack. Normally the recommendation is to have Fox ESS battery modules at 50% +/- 5% SoC when adding them to an existing stack. https://fox-ess.tech/battery-expansion- ... n-process/

Does this apply when the battery modules to be added are used batteries rather than new? E.g. if I sold the battery modules at say 90% SoC, could the person buying a module/modules just get their own battery stack to 90% SoC too and then add the battery? Or does the 50% +/- 5% rule also apply when adding used batteries to a stack?

Thanks!

SoC is a virtual construct, the real accuracy comes from measuring battery pack voltage and ensuring the pack it is being added to, each battery is within 0.5V.

Going off SoC alone, when selling used batteries, at a minimum you should ensure that it is above 50% as over time the internal resistance of the battery will gradually reduce it’s charge - obviously you can sell it at a higher SoC but make sure you record the SoC and the date so the new owner can get their pack close (and then they should use the pack voltage to confirm it’s accuracy, otherwise they may end up with many weeks of charge cycling to balance).