Battery Charger Fuse

[Billy Blue]

I just spotted that the fuse from my battery charger to the service batteries has seriously overheated. The plastic holder is all melted inside, slightly distorted and slight overheating on the cable plastic at each end of the holder.
The fuse has not blown.
The battery charger is a Sterling Pro Charge Ultra 40 amps and charges 3 separate battery banks. 1-the single starter battery 2- single stern thruster battery and 3- the 4 service batteries totalling 400 Ah.
The fuse holder is a Sterling one and I had a Sterling 50 amp fuse in it. Sterling recommend max amp plus 20% for the fuse. Was this right for each bank?
So what could have caused this to overheat and what should I do about it?
Obviously, I'll change the fuse holder.
Thanks
Paul

 

[Croftie]

First thought what cable size and length between charger and service battery, also what type of connector to the fuse holder

 

[Billy Blue]

The distance is less than 1 metre so I used the recommended size for that. I don't have the handbook with me but would 40mm2 sound right?
The fuse holder was Sterling Power single AUE Fuse Holder GFH-168

 

[Croftie]

"40mm2 sound right" - probably less, from the Sterling site I suspect 10mm2

I am sure someone will add but to me I don't like the look of that fuse/fuse holder. First it seems like the old style glass fuse holder that means you have 4 points of possible failure/heat buildup. where the cable enters/exits and both ends of the fuse. Also the wires are gripped with a grub screw like the old "choc block". Personally I would replace with a Midi fuse box like
Strip / MIDI fuse holder
Midi Fuses
then you can use properly crimped cable terminals.

 

[Richard10002]

I was warned off that type of grub screw fuse holder a couple of years ago, either by someone here, or on the canalworld forums.

Seems like good advice

 

[Assassin]

I was warned off that type of grub screw fuse holder a couple of years ago, either by someone here, or on the canalworld forums.

Seems like good advice

Not ideal in a marine environment due to high levels of corrosion and high resistances they can create, and high resistances mean excessive heat.

 

[Billy Blue]

"40mm2 sound right" - probably less, from the Sterling site I suspect 10mm2

I am sure someone will add but to me I don't like the look of that fuse/fuse holder. First it seems like the old style glass fuse holder that means you have 4 points of possible failure/heat buildup. where the cable enters/exits and both ends of the fuse. Also the wires are gripped with a grub screw like the old "choc block". Personally I would replace with a Midi fuse box like
Strip / MIDI fuse holder
Midi Fuses
then you can use properly crimped cable terminals.

Okay, many thanks for the advice.

 

[dpb]

I have a similar charger arrangement (same rating, different make) on my boat. The protection, as installed by the manufacturer is provided by a 50 amp trip switch on the 12v panel. maybe that is a route you could take.