At wits end with 12v Fridge causing voltage spikes during Absorption

Q&A and troubleshooting
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1

Hey all,

I’ve be dealing with voltage spike issues with my lithium set up for ages. Details here:

https://communityarchive.victronenergy.com/questions/193619/voltage-spike-during-absorption-on-multiplus-3000.html

Yesterday I finally captured what I believe to be the culprit. The damn fridge cycling. It’s a Dometic 12v chiller unit. Max draw 15amps.

What I believe what is happening is, when the stars allign and the fridge cycles off during last stages of absorption the field colapse of the 3 phase inverter on the fridge unit backfeeds the rest of the system.

See the video. At 40 second mark I manually disconnect the fridge.

Is there anything safe that can be done to prevent this? I thought about installing a balmar APM on the fridge, or a diode to prevent backflow…but I wanted to ask you all.

I have vsense wired on the multiplus, tried to enable and disable dvcc nothing helps. I’ve confirmed with a multi meter, and if you listen closesly the fan in the backgrouns speeds up as well.

2

Is this a compressor or absorber fridge ?

3

Compressor. It’s this unit: Dometic CU Adler Barbour Unit | Dometic USA

4

Possibly add an SPD

5

Happy to give it a shot. This is outside my current experience. What sorta device would I be looking to add? I.e. any recommendations? Would this go on the fridge unit or somewhere on the bus bar before the shunt to prevent surges back to the battery?