question

goodsellrod avatar image
goodsellrod asked

over voltage

I am a new solar user with a new system, I am getting a high voltage alarm from the cerbo and the batteries confirm there are multiple high voltage protects enabled, 191 times. the problem is occurring when the batteries are at 100%. the system starts doing a push pull effect on the batteries, every couple seconds it changes from charge to discharge and then ends up in a overcharge. I have 2200 watts of solar peak. it's pushing 200 volts to the MPPT 250/60 which is charging two 48v SOK server rack batteries. the batteries are connected to a MultiPlus-ll 48-3000-35.right now I am having disconnect the pv input when the batteries are full to stop the overcharge. help please:-)


charge current limit
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3 Answers
jessiejim1 avatar image
jessiejim1 answered ·

You can adjust the charging settings on your MPPT 250/60, so that it does not push as much voltage to the batteries when they are already at 100%. You could also consider adding additional batteries to your system, which would allow for more energy storage capacity and help prevent overcharging.

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goodsellrod avatar image goodsellrod commented ·
what setting would adjust the charge current when it reaches 100%. I don't understand the modulating back and forth from charge to discharge when the batteries are full and there is AC current being inverted. if I am using 6 or 700 watts of AC shouldn't the pv be able to provide that and just leave the batteries at 100%?
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kevgermany avatar image
kevgermany answered ·

What are your MPPT battery settings? Are these the same as the battery maker values? Are these lithium batteries?

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goodsellrod avatar image goodsellrod commented ·
yes it appears that the MPPT voltage settings are correct and yes the batteries are lithium. battery charge setting set @60 amps, battery mfr recommends 63 amps, absorption voltage @57.6, float voltage @55.2 as recommended
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kevgermany avatar image kevgermany ♦♦ goodsellrod commented ·
Guessing

Probably the BMS in the battery is cutting the charge by disconnecting the battery.

Could be due to imbalance in the battery, in which case it should resolve over time. Try reducing the charge current to a trickle, leave the system charging for a day or two and don't use the system.

Then set back to normal values.


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derrick thomas avatar image
derrick thomas answered ·

You might look into node red. You could create a flow to pull back on the maximum allowed charging current as you get near the abs voltage. You could do it in steps.

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