question

dfr avatar image
dfr asked

Adsorption voltage throttles over battery bms cutoff

Battery: LiTime 24v 100ah

Charger: vicrton 150/35 mppt

Bulk /adsorb voltage 28.4v

Adsorb Time: Fixed 2hr with 2a tail current

Float voltage 27v

BMS overvolt cutoff 30v


Battery charges just fine in bulk. When bulk finishes and switches to adsorb, I know everything drops out for a second and regathers the mppt. When it's ramping back up the voltage goes to 30-32v which triggers the internal bms overvolt disconnect. Then, after voltage drops back to 28.4v, which is also my adsorb, the bms connects again. Repeat about 4 times. Then float kicks in which typically is at 0a unless I have a load, then a small current at 27v.

My adsorption is set to fixed with a 2hr max but a 2a tail. I assumed it would stop adsorb at either 2hr or 2a, which ever came first. Maybe it has to be in adaptive mode

Why is it throttling voltage over 30-32v? I was thinking of dropping charging voltage to 27.6v and float to 26.8v. My thinking is maybe the battery wont be full and allow the charger to actually go into adsorb.

Was also thinking I could turn off adsorb and let float push a little but I'm not sure I should

MPPT Controllers
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1 Answer
klim8skeptic avatar image
klim8skeptic answered ·

It sounds like the BMS in your battery is disconnecting due to a cell over volt protection (cell imbalance). When the BMS disconnects from the mppt there is a brief voltage spike.

Try reducing the battery bulk/absorp voltage to 28v. A few charge cycles should sort out any cell imbalance.

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dfr avatar image dfr commented ·
That seems to have made a difference. lowered to 27.6v adsorb and 26.8v float and it ran better, no spikes.
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