Converter blowing fuse

Hello all,

I have a 2007 Hi-Lo 25C. This last week boon docking I went to charge the batteries for the second time with the genny and about 10-15 minutes into charge there was a pop noise the wife heard and then no more charge. I found a blown 30A fuse. Replaced it and pop again. The batteries were fully topped off when we left (from converter) and had been charged once while up on the mountain from the genny as explained.


We went to town for more fuses and all they had were 40A. I put one in and it would last about 10 minutes before blowing.

Troubleshooting I disconnected all batteries (I have 3). Converter produced power without blowing fuse, 13.3V.
Charge all 3 batteries with car charger then let settle. Turn on lights and identify 11.5V on each battery individually with lights on.
Connect battery 1 only and charge 15 min. No blown fuse
Connect battery 2 only and charge 15 min, no blown fuse.
Connect battery 3 only and charge 15 min, no blown fuse.
Connect battery 1 and 2 only, charge 15 min, no blown fuse.
Connect battery 1 and 3 only, charge 15 min, no blown fuse.
Connect battery 2 and 3 only, charge 15 min, no blown fuse.
Connect battery 1, 2 and 3 and pop, blown fuse within 10 min.

What gives?

The converter may not be able to handle the three batteries at the same time. You probably have no more than a 45 amp output converter.

Just guessing bad, loose connection on the converter or at the battery on the charge wire or ground.

RichR said:

The converter may not be able to handle the three batteries at the same time. You probably have no more than a 45 amp output converter.

Click to expand...

I thought of that but the converter has been charging these 3 batteries for 3 years now. I do wonder if as they age they are drawing more amps then they use to?

garyk52 said:

Just guessing bad, loose connection on the converter or at the battery on the charge wire or ground.

Click to expand...

Checked all grounds and they are tight. What is weird is if one did have a loose connection, would it not blow the fuse when hooked up single or double, not jus do it when all 3 are connected?

Try unhooking the batteries and leave them sit idle for a day then check the voltage on them. See if one or more has had a significant drop. Better yet take them and have them tested.

Check the state of charge chart on this excellent webpage:
The 12volt Side of Life (Part 1)

RichR said:

Try unhooking the batteries and leave them sit idle for a day then check the voltage on them. See if one or more has had a significant drop. Better yet take them and have them tested.

Check the state of charge chart on this excellent webpage:
The 12volt Side of Life (Part 1)

Click to expand...

Great article, thanks!

wolfster101 said:

Great article, thanks!

Click to expand...

You should also get part two:The 12volt Side of Life Part 2

The info in both of these articles is somewhat dated but for the most part is excellent.

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