question

jasonsele avatar image

Multiplus ignores AC input when battery is too low

I have two multiplus 24/3000/70-50 and two MPPT 250/60 with 300amps of 24v lithium batteries and a color control . It's a 50amp RV with a each multiplus connected on L1 and L2. I have an issue that only happens when I am connected to shore power and run the batteries too low.

A few times I've overloaded the AC input by running too many appliances including air conditioners and that trips the shore power breaker. This usually happens when I am on 30amp shore power, even if I set the input current limit to 30amp max. Because the system works so well it switches over to my batteries and I sometimes don't notice. It eventually drains the batteries and shuts off the system with the low power alarms. Once this happens I can't get the shore power to charge the batteries any more. I reset the breaker so that there is power AC in 1 but the multiplus won't accept the power input. At this point usually the multiplus is off and the switch for "on/off/charger only" won't do anything. I have to use a jumper cable on the terminals of the multiplus to power it back on. Once it is on it still does not accept the AC shore power input to charge the batteries and I have to wait until the solar panels charges them enough that it will allow AC in again. Even with both multiplus on, resetting the switches, and seeing main on, the color control still shows AC input at 0 and state is off. However, the solar input works fine and once the batteries get recharged to a certain level it accepts the AC input again.

I assume that the batteries have to be restored enough for the system to return to normal but why would it accept solar in and not shore power in to charge them? Obviously this creates a problem when it happens at night because I have to wait until the sun comes up in the morning to charge the batteries. Shore power, generator or any input on AC in 1 will not work until the batteries recover.

So two things I'd love to fix. 1. How can I get the multiplus to stay on when I have shore power but batteries are low? Why would I need to jump it? 2. How can I get the multiplus to accept AC input when the batteries are dead? Shouldn't AC input work all the time?

MultiPlus Quattro Inverter ChargerGeneratorlow battery warning
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1 Answer
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @jasonsele

what kind of batteries are you using? (brand / type / bms?)

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I have 6 X Battle Born 24v 50amp batteries with BMS

Hi @jasonsele

If you have AC on both inverters, do they start up?

(just a hunch, when batteries are at 0V due to BMS disconnecting, a multi-phase system might not be able wake up on a single phase input)

I am assuming a bit here: is it a split-phase system?
and what do you mean by: 'I have to use a jumper cable on the terminals of the multiplus to power it back on '

jasonsele avatar image jasonsele Daniël Boekel (Victron Energy Staff) ♦♦ ·

It's a split-phase. When the batteries are too low I actually put 12v on the multiplus terminals where the battery input comes in and that is enough to fire up the multiplus and feed the color control so I can get to the menu. What I don't understand is why the multiplus would not function with AC input still active. Should the AC on both inverters keep them running?

Hi @jasonsele

is there AC input on both inverters? or just one?

I think you need input on both inverters on a battery that is at 0 volt (due to BMS disconnected)...

jasonsele avatar image jasonsele Daniël Boekel (Victron Energy Staff) ♦♦ ·

I'll check. I believe it is.