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piet-hein-van-asselen asked

Voltage drop under medium load


I have multipluss 12/3000 connected to 2 x 230 Ah victron super cycle in parallel.

System is 3 weeks old. I suddenly noticed a voltage drop 2 weeks ago when someone was testing a vacuümcleaner on inverter. "Only" around 80 amps were drawn for few minutes and the voltage droppen until 11,89 Volts under load. Multipmus gave a short warning by red led status

Batteries were fully charged.

Totday again, batteries fully charged, a small test with watercooker and voltage droppen until 12,2 while taken 109 amps.

Is this normal? Batteries recover immediately after load stops.

Thanks in advance.

Please check date on image.

MultiPlus Quattro Inverter Chargervoltagebattery system voltage
2 |3000

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1 Answer
Alexandra avatar image
Alexandra answered ·

@Piet Hein van Asselen

Yes voltage drop is normal under load. I cannot comment as to the Victron super cycle batteries from personal experience. But I have seen sag on agm batteries high enough to switch off the inverter.

Even on lithiums on a small system you see sag.

But you may be exceeding the battery designed discharge rate a bit there. 109amps is quite high for two gel or agm batteries.

There can be some improvements you can make to help with sag such a shorter runs of cable to the inverter and user larger than recommended cables. And make sure your battery links are also nice and beefy. And of course adding more batteries.

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2 |3000

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piet-hein-van-asselen avatar image piet-hein-van-asselen commented ·

Dear Alexandra,

Thank you for your reply and excuse my late reply.

I have seen the discharge current is above limits indeed.

For the battery capacity (460)is whitin the specs of what is suggested in the manual, (400-1200Ah) i dont understand wich batteries i should use instead.

For now the system is working well. Battery cable length is short enough and connections are proper.

I will keep an eye open.

Thank you for your tips

Best regards, Piet

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