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Victron centaur battery charger overcharging, please help diagnose and repair

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New Member
Hi there,

I have a Victron Centaur battery charger, 12v 200 amp output. It's a monster!

On inspection it's actually two identical 100a chargers in the same case, connected in parallel. Other than a tiny 3 wire cable whose purpose I'm not sure of, there is nothing connecting the two chargers other than the battery cables and the mains cable.

The problem is, as the battery gets full, the voltage goes up, and up, and up, to 15.4v! It should max out at 14.4v. This is very damaging to my 900Ah bank of AGM batteries which are being overcharged.

So, first step was to isolate the problem by disconnecting mains power from each charger module separately. It turns out that the front module (with the new fans) charges at 15.4v when the batteries are fully charged.

The back module alone charges up to a relatively modest 14.9v. T

There are DIP switches to select the charge mode (AGM, Lead Acid or Gel). There are no other documented settings but there is a row of jumpers and a potentiometer on each module. Victron support were very unhelpful and refused to tell me the purpose of these so I have not touched them. They said all I can do is send it off to a Victron dealer and hope they fix it, which could be very expensive and they'll probably just try to sell me a new one.

It's possible the previous owner did find a way to calibrate it for some special purpose requiring a higher voltage and I just need to return it to normal.

This charger cost thousands of pounds new, has a huge capacity and accepts an unusually big range of input voltage so I'm very keen to get both modules working properly.

It's currently installed in a very inaccessible place so it might be while before I can respond to any tests requiring access inside but please give me your suggestions of what to try. Also, has anyone seen a similar fault before and what was the cause? Is it economically repairable?

Thanks very much for your help.
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Well-Known Member
Most Helpful Member
Welcome to ETO, syohana!

The Victron Centaur battery charger is, essentially, a switched mode power supply, per the victron manual, page 6., "Description". Two of them in parallel, as you noted.

What that means, in your case, is that it is a pretty sophisticated device (as opposed to most, simpler battery chargers). And as such, without a schematic (I also found nothing online), I'm afraid that diagnosing your problems, as well as repairing them, will be a daunting task.

That said, it is possible that some highly detailed, sharply focused pictures of the PCBs (top and underside) might reveal some damage (or some possible calobration opportunities) that could lead to some repair suggestions.


New Member
Thanks Bob, I feared that was the case.

I'll post photos when I have time to get the charger out as it's rather hard to access.

Meanwhile I wonder if anyone has encountered a Centaur or similar switch mode type charger/PSU with the same symptoms who could point me in the right direction for the fault?

Many thanks,
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