If too many modules shutdown, the overall DC voltage will rise when the MultiPlus tries to feed in additional current, and it will eventually stop charging altogether this way. If for some reason one modual becomes imbalanced, and one of the 7 cells does reach the 4.2v cutoff, the BMS will shutdown that module, preventing the MultiPlus from charging it further. To avoid any issues (and also prolong the battery life), my MultiPlus is set with a max absorb voltage of 28.6, divide that by 7, and you will find that the individual cells cease being charged when they reach around 4.1V. For example, my battery is 7S NMC, each cell has a maximum recommended charging voltage of 4.2v, multiply that by 7, and you now have the maximum "pack" voltage, which is 29.4. If you are using "incompatible" lithium batteries as I am, you should take care to ensure that the "absorption voltage" is set lower than the sum of the max cell voltages of your pack. The purpose of a lithium battery "assistant" is so the MultiPlus can communicate with the Battery Management System on your battery pack, if in the event that one individual cell in the pack goes over voltage, the idea is the BMS would then be able to tell the MultiPlus to stop charging. Do leave the "lithium batteries" box checked, this alters the charging curve slightly. As soon as you start customizing the options, the "battery type" is automatically set to "no default" which is still just fine for Lithium batteries. Here is how I have my charger profile configured, as you can see, I do not currently have a specific "battery type" selected, what I did was start by selecting the LifePO4 Lithium option, which did tell me I need an assistant installed (for communicating with the BMS, which I ignored), then I just customized the voltages for my particular battery. You do however at least need some basic knowledge about the battery you are planning on using, such as the chemistry, and number of cells. I am using 12x 960Wh DIY lithium battery modules built from 18650 cells, which works beautifully with my split-phase ESS, without a "Lithium Battery Assistant" installed on any Multi in my setup. You do not need "tested" lithium batteries, or a special assistant.
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