threesixty avatar image
threesixty asked

Victron Mppt 75/15 battery charge current limit does not account for appliance loads

Hey Guys, i have a Victron mppt 75/15 and iam using 3x 100 Watts solar modules with it. they are Connected in Series and gave between 200-250 watts in good conditions. I also use a 72AH battery. Devices like fridge and lightnings are connected to the load Output.

My Problems is: i set the Max battery Charge current to 7A which is the best charge rate dir this battery to Get a Long lifetime. The battery Starts charging with 7A, but every additional cunsumer like a fridge with 10A Drops this current. In the example of the fridge, the battery is discharging with 3 Ampere. Now i change the Max charge current to 15 A and the problem seems Solved. 5A charging the battery and the Rest 10A powering the fridge. But if i Turn off the fridge, logically the battery is charging with 15 A. I think this is a bug in the Management of the current. What do you think? Also also recorded this behavior which german comments:

MPPT Controllers
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1 Answer
ripper avatar image
ripper answered ·

This is correct behaviour. You are indeed only setting the output of the charger. The charger does for now not know what he powers.

One could argue that if all the loads are on the load terminals it could determine the battery amps by simple substraction of the two already known amperages and adjust accordingly.

That would be a new feature that could be requested. It is probably easily done via software und is indeed a good idea.

For now, you would have to spend a couple hundred extra and buy more blue gadgets. The function is called dcxx or something. It looks at the amps going to the battery via the bmv and adjusts the solarcharger accordingly.

That likely does not make a whole lot of sense economically. If the battery is non agm/gel I would just go wide open and keep an eye on the fluid level once a month.

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