diy solar

diy solar

Is Boost battery charging voltage the same as absorption???

My batteries were 70% when I start using them.
Show a pic of the voltages when they are at 70%. Should be around 3.30v

Anything below 3.0v per cell, and you will have fast voltage drop. There isn't much power left at that level 9% SOC on its way down to 0% at 2.50v.

From your earlier post, it looks like Cells 6 and 14 are having problems. Did you top balance? That is what is probably causing your undervoltage cutoff by the BMS to protect the battery.

Do you have a Shunt to measure the actual energy going into and out of your battery? It could be that Cells 6 and/or 14 have an internal problem that is sinking power from the other cells and causing your "self discharge". Do you have a temp sensor on those batteries? Are they running hot?
 
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Show a pic of the voltages when they are at 70%. Should be around 3.30v

Anything below 3.0v per cell, and you will have fast voltage drop. There isn't much power left at that level 9% SOC on its way down to 0% at 2.50v.
IMG_8602.png
This was yesterday, right when I plugged the batteries to the BMS and into the inverter to charge from the sun
 
My inverter is a hybrid one.

My loads work with solar then battery then utility I have it to switch to grid mode at 48v it shouldn’t drain the battery.

My inverter doesn’t discharge the batteries it seems the problem to be the BMS or BMS being wrong due to the field
 
My loads work with solar then battery then utility I have it to switch to grid mode at 48v it shouldn’t drain the battery.
You are at the bottom at that voltage. That is a good setting for a BMS to disconnect but 50 volts is better to switch to grid for an inverter setting.
My inverter doesn’t discharge the batteries it seems the problem to be the BMS or BMS being wrong due to the field
Maybe you are not getting full charge because that one cell is limiting how much you can put in that pack. Also it may be your balance is set for discharge and you are better off having balancing when charging. It should be set to start balancing at 3.4 volts. It may take a few cycles to get them balanced at the top. From the picture above, your BMS should be able to tell you how many Amps are discharging. From that picture it looks like you are charging at 30 Amps. At that rate it should take nine hours from empty to full. Hard to do when effective solar charging will get you 6 to 7 hours on a good day.
 
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