What size battery fuse.

Place for all of the tips, hints, and facts around the electrical and electronic stuff found around Trailer Sailers, Trailers, and associated vehicles.
Post Reply
User avatar
Even Keel
CompetentCrew
Posts: 50
Joined: Feb 14th, '19, 11:34
Has thanked: 0
Been thanked: 5 times

What size battery fuse.

Post by Even Keel » Feb 13th, '21, 20:34

I've got an 18ah lithium battery, 50 watt solar panel and controller.
I have 10 amp fuses on radio, light and cig. socket, and a 15amp fuse about 150mm away from positive battery terminal. It all works ok BUT I keep on blowing 15 amp battery fuse. I think wiring is 6 gauge. Does 15 amp battery fuse sound about right? I hope it's not a stupid question.

User avatar
bachus
Yachtmaster
Posts: 3816
Joined: Jan 24th, '13, 20:43
Location: Bayside, Melbourne
Has thanked: 53 times
Been thanked: 143 times

Re: What size battery fuse.

Post by bachus » Feb 13th, '21, 21:56

First the fuse size. The fuse close to the battery is to protect the wiring from the battery. 6AG wiring will take 30amp and over say 5meter will result in approx 0.2volt drop . . the point being is that the 15amp fuse is underrated and a higher value fuse would be ok to protected the wiring.
The 18AH lithium battery will have a rated maximum continuous discharge current - likely to be 10amp - and peak instantaneous current in the order of 30amp. I would pitch the fuse to blow below the peak current of the battery - protecting the battery and the wiring from it. For example a 25amp fuse if the peak current is indeed 30amp.

But what is even drawing 15amp to blow the 15amp fuse. Your list of devices attached to the battery seem pretty innocent for want of a word.

The radio or light or cig. socket 10amp fuses are not blowing so none of these devices individually are the cause. But combined the three could achieve 15amp. I am ignoring the 50 watt panel - it will not generate enough current to blow it. The cig. socket what is it being used for?

I would look for something loose - an intermittent short . . .
Jim
Castle 650 #96. Mystic.
Towing with Ford Territory SZII TX AWD

User avatar
Even Keel
CompetentCrew
Posts: 50
Joined: Feb 14th, '19, 11:34
Has thanked: 0
Been thanked: 5 times

Re: What size battery fuse.

Post by Even Keel » Feb 14th, '21, 08:07

Thank you for explaining this so well Jim. Cig. Socket is only used to charge phones. You were spot on with peak battery discharge current, so I will go with 25 amp fuse. I was thinking it was a surge from solar controller but you have put this idea to rest. I will try and find a loose connection.

Post Reply

Return to “ELECTRICKERY (Electrical and Electronic Stuff)”