octaviannedelus avatar image
octaviannedelus asked

BMS overvoltage protection , MPPT charges to 16 Volts in absorption mode

5139552d-0a1d-4102-bb31-b9ca52c983b8.pnghi guys! One problem i am facing with my setup and is that my BMS is always disconnecting the charging of my battery due to single cell overvoltage. When this happens my solar charger (victron 100/30 smartsolar) goes to absorption mode and starts increasing the voltage in the sistem ... it reaches 16 volts sometimes.I have it set up to lifepo4 and normally it’s supposed to charge up to 14.2 V in absorption mode.

I don’t understand how it’s supposed to work but i taught that when the battery is full or reaches a certain voltage, the MPPT is going to float mode and keeps it charged without forcing it so that the BMS has to trip.

How do i avoid all this?

MPPT ControllersLithium BatteryBMS
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rickp avatar image rickp commented ·

I am guessing, but to raise the voltage of a battery pack the incoming charge voltage needs to be higher than the current voltage of the pack. You can lower the absorption voltage in the SmartSolar settings, though it may result in your batteries not charging to 100%.

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1 Answer
H.W.Oelofse avatar image
H.W.Oelofse answered ·

I have experienced this with some lifepo4 batteries where when they are brand new the cells take quite a while to balance and this issue can be made more obvious when charging at a high rate sometimes it may be useful to charge the battery for some time at a lower amp rate and give the cell balancing on the bms a chance to equalise the cell voltages. I currently have a 100/30 on a small system charging a lifepo4 battery and regularly put the full rating of the charge controller into the battery without any issues and certainly no over voltages. The over voltage will occur because the mppt has lost the battery reference due to the bms shutting down and the output will overshoot the programmed voltage in this situation.

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