Multiplus Compact 12/1600 mal function at high currents

DIY
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1

I am using a Multiplus 12/1600 within my Caravan. together with a 280ah Lipefo4.

Last week during my vacation I had a pitch with an external powersupply limited to 6a hence I limited the Input to 6a.

While using the airconditioner or the heater the multiplus went reproduceable into mal function.

Even though the airconditioning was working well during the First night.

The malfunktion starts with a beep and a couple of sek/min no DC/DC converter function.

At the Same time all 12 Volt consumers are working proper means are supplied with Power.

At Home I tested the system with the heater, while Not beeing conneted to external 230 v Power supply.

Power consumtion according to Multiplus approx. 960 w.

Power consumtion according to Batterie BSM approx. 1300 W.

The heating was working fine for several minutes, but after approx. 10-20 min the same issue.

The Multiplus is reporting a low Batterie while the other 12 v consumers are working quite well.

What are potential root causes?

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2

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As you are operating at the maximum power fro 25C ambient, then there will be some significant warming.
Also, if there is any high resistance in the battery cables / fuses/ connections in the dc supply to the multi, that will cause this type of fault. Make sure your battery cables are up to the job by measuring the dc input voltage to the multiplus with the load on.

3

So basically you say I should use a bigger multiplus for that use case? Am I right?

I confused about the error Message indicating a low battery.

In mean the replacement would be acceptable to me as I am operation at the edge of the boundary conditions. On the other hand I don’t want to replace it and facing the root cause was not the multiplus but the battery or something else..

4

First, test the system under load by measuring the terminal voltage inside the multiplus.
IF you have a big drop between either the bat positive and the multiplus positive in terminal, or similar on the negative side, then you have a wiring fault.
if you measure the battery terminals as low voltage on load, then the battery is the problem,
If the voltage into the Multi is good (>12.5V) on load, but you still get the low voltage error, then the multi has an internal fault.

5

Root cause identified. The screw inside the multiplus clamping the negativ wire was loose.

Many thanks for your guidance!

@victron: How can that happen? Seema something went wrong during your assembly process?

6

Cables can easily work loose due to temperature cycling, vibration etc.