blown fuse on battery charger + lead to battery

Hi all,
To preface, my boat is still on the hard at this time.
I have a three bank 40 Amp Xantrex battery charger for my two engines and generator. I have two group 27 in parallel for each diesel and a group 31 for my genny.
Yesterday, I hooked up my shore power cord to my Honda 2000 generator, turned on my AC power, turned on the battery charger breaker and almost instantly, one of the indicator lights went out. I dropped into the engine room after shutting off the battery charger breaker. I looked at each fuse in the + wire from the charger to the battery banks and found that one of the fuses blew
The wires and contacts were extremely hot.
These are a 50 amp fuses.
What gives? I have never had an issue like this before. I was running the Honda Generator though my normal shore power inlet, which also goes through a double pole breaker and Isolation Transformer. I have attached a pic of the inline fuse
.

How's the wiring to that battery? Whats the voltage at the battery in question? Could the battery shorted it self?

If it was me, I would replace the fuse and use that charging bank on other battery just to make sure its not the charger. Thats after I thought the battery bank in question was good.

Check the fuse holder itself for any looseness and/or oxidation at the contacts and grippers. Check the actual wires for any sign of corrosion including inside any crimps.

All create resistance which will heat and blow a fuse even if there is nothing else wrong.

THis will be more likely if the circuit is carrying close to the fuses rating.

However, it oxidation is bad enough it can happen. The fact that the wiring itself was hot would suggest this.

Of course do a load test on the batteries to be sure they are not on the way out.

I would use the charger for a bit on the other 2 banks to make sure they are operating correctly. Leave the fuse that blew out for the test. Then if the other 2 banks work ok start checking the things mentioned above.

IWould not suggest using Amazon grade electriclal components

CMS said:

IWould not suggest using Amazon grade electriclal components

Click to expand...

Did not know amazon manufactured electrical components.

I just make sure it is name brand like Blue Seas products. Where I live Amazon delivery makes it very convenient.

Soo-Valley said:

Did not know amazon manufactured electrical components.

Click to expand...

They do not.

For a fuse to suddenly and decisively blow like that, something has either just broken, or been changed to create a short.


While hauled out has there been work done on the electrical system? If so, I would look closely at how it might have created a problem.


Next I would look at the generator hookup. I'm wondering if some sort of reverse polarity issue might be at play. One test would be leave the output disconnected, then turn the charger on and measure the voltage between the output and ground. That will tell you if the charger is doing something crazy.



Be careful running the charger with the primary output disconnected. Most of the multi-output chargers are really single output with a couple of tag-along low power taps. The charger's control is completely regulated based on the primary output, and the other outputs just follow along for the ride. So with a primary output disconnected, you might not get sensible output from the secondaries. It will all depend on the exact design of the charger, but just be aware that it might not be as expected.