DC DC starter battery charger on Amel 55 fuse sizes

Billy Newport

My generator wouldn't start last weekend so on poking around, the starter was weak. I could start the engine and then I could start the generator. On checking why the starter was weak, the DC-DC charger output side (#3 under the nav seat) was blown. It's a 15A fuse. So, no charger, dead battery, gen won't start. Ok.

Looking at the Victron manuals for an Orion 24/12/25 DC DC charger. It has a normal bulk output current of 25A with a peak output of 35A. Why have Amel installed a 15A fuse, it's even labeled 15A.

So, I left the boat this week and when I came back today, the 15A fuse I replaced is blown again. I discussed with BillR and for now, I've replaced both fuses with a 20A and a 40A (don't have a 35A). Now, given what I can figure out, I don't know how this ever worked but clearly the boat is 4 years old and has 20k nm on it. I've sent an email to Denis, the old owner asking what gives.

Do the alternators on the gen OR engine charge the starter battery? Is it just the DC-DC charging it?

The cables are 10 gauge wire. I can't see how long they are. 24V @ 20A is no problem for 10 awg. 12V at 25A is good at 10 feet long with 1% V drop.

Amel 55#56

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