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mlsadler avatar image
mlsadler asked

BMS managed solar system

Am puzzled, I use WECO lithium batteries 5K3 I managed to set up my system and its controlled by the battery BMS through the color control gx, what have noticed once the batteries get fully charged at SOC 100% the BMS turns off the MPPT and the batteries start discharging to cater for the loads and when the SOC is back to 98% they then start charging again, I would have rather expected that the BMS only cuts off its charging and lets the MPPT provide solar for the loads keeping the batteries at 100% SOC, how can I achieve this ?

BMS
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shaneyake avatar image shaneyake commented ·

That is typically how these systems work, go to 100% and hold. Is the battery connected via CAN? Can you see in VRM what the BMS charge voltage and charge currents go to? Will be in the advanced tab, under battery monitor widget. It might be that the BMS is completely disabling charge.

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mlsadler avatar image mlsadler shaneyake commented ·
Yes the battery is connected via CAN, yes the BMS completely disables charging coz the voltage stays constant at 53.2V while charge current is 0. What i expected was atleast allowing a pass through current for running loads instead of discharging the batteries
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shaneyake avatar image shaneyake mlsadler commented ·
For safety if the battery is commanding 0A the system will go to 0.

All my installs with CAN batteries the batteries will keep the charge current high even when fully charged only if there is a problem, temperature, imbalance will the system reduce the charge current. My systems just change the voltage to control charge.

Has this been like this from day 1 or has this only been happening recently? Can you tell if there is any cell imbalance? You could try lower the voltage in DVCC to 52V, see if the batteries still get to 100% but they shouldn't turn off the current.

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mlsadler avatar image mlsadler shaneyake commented ·
Yes the system has been like this right from the start, the minute the batteries get to 100% the MPPT charge current is cut off to 0 and the batteries start discharging upto 98% then the MPPT will start charging them again this goes on like that until the sun sets
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shaneyake avatar image shaneyake mlsadler commented ·
Yeah, That means your battery is causing the problem. I would try lower the charge voltage. It might fix this problem.
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wjf avatar image wjf mlsadler commented ·
@mlsadler Did you ever sort this? And if so how?
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stephenv avatar image stephenv shaneyake commented ·
Yes best to set the max charge voltage, we have stopped it fully charging at 100%, it runs at 99% charged which prevents the MPPT turning off
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1 Answer
Paul B avatar image
Paul B answered ·

answered via comments above

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