Inverter HI voltage cutout

sjvicker

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Joined
Feb 1, 2022
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I think I have something wrong in my system and I can't figure out what it is. I've had my inverter cut out and restart a few times a day due to a high voltage condition. Here's the specs on my system.

24V system
SanTan Solar T Series 250W panels in a 3x3 series/parallel configuration: should be 112.8V and 26.55A https://store.santansolar.com/product/santan-solar-t-series-250w/
EPEVER 40A BN Series SCC
2 Enjoybot 100AH 12v batteries.
Giandel 24v 3000w pure sign inverter
High voltage cutout only happens with the SCC connected and mid-day.

I reduced the max voltage through the EPEVER controller (29.2v) and still had the inverter cut out due to high voltage. Through searching it seems that the EPEVER controller can sometimes have issues with sun hitting panels as clouds move away and cause an overvoltage so the recommendation there was to move to a Victron.

I took the recommendation and swapped the EPEVER SCC for a Victron smart solar 150/45 and the inverter still had an overvoltage condition of 32.93V (verified thanks to Victron's data logging). I know I'm way over paneled but I'm still within the Voltage specs of both SCC's ability to handle it. I'm in the PNW so planning for the grey days is a must.

What am I missing?
 

sunshine_eggo

Happy Breffast!
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I'll have to pull those this weekend. The only setting in the Victron I changed was to select the LI battery option.

That tells me enough.

EDIT: Missed the 24V bit. @mikefitz is correct. The individual 12V need to be fully charged individually and in parallel before being put in series for 24V.

The Enjoybot batteries are likely imbalanced and triggering a BMS over voltage protection event, which instantaneously prevents charging. The MPPT may briefly spike in response to the loss of load.
 

mikefitz

Photon Sorcerer
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My guess is that the battery BMS is opening the charge path due to cell over volts, the controller cannot respond to this quickly enough and the volts rise. A charge volts of 29.2 is excessive, reduce to a lower voltage, say 28 volts.

I assume the batteries were at the same state ofcharge before connecting in series .

Mike
 

sjvicker

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Feb 1, 2022
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I assumed but never verified they were the same state of charge. Thanks for the feedback. I'll charge them individually and see if that fixes the issue.
 

sunshine_eggo

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I assumed but never verified they were the same state of charge. Thanks for the feedback. I'll charge them individually and see if that fixes the issue.

LFP batteries tend to ship in the 30-50% SoC range. For hazmat purposes, I think it's supposed to be <30%. At those lower states of charge, it's almost impossible that two 12V will be exactly the same mAh from full. Even a 0.1% difference in cell SoC can trigger HVD when pushing total voltages of 3.65V/cell.
 

sjvicker

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Feb 1, 2022
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4
Following up on this:

last weekend I hooked each battery up to the SCC and let it charge to full (Float light on on the SCC, 0amps to the battery according to the app). .3V difference between the batteries according to the multimeter. So far I haven't had any high voltage cutouts.

Thanks everyone!
 
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