Thread: What Fuse 's do I use??

Battery and UHF, probably only a 5A or less, check the specs on the UHF. If its a GME TX3x00 or TX4x00 then a 3A fuse.
Battery and Scanner I would suspect the same, again manual should tell you.
100W Driving lights I'd fit a 25W fuse between the battery and the relay.
For the fridge, check the manual again, I have a 40L Engel with a 20A fuse at the battery, I doubt you would need bigger than 25A.

Originally Posted by amshaw

Ive been using those inline jobs that take the normal size spade fuse....with the rubber body and dust/water cap. At $4ea well worth it I think.

They're great. But...make sure you mount them up the right way. Their water-proof capablities are questionable, and the caps do not have a drainage holes in them. Thus once you get them full they tend to stay that way. Makes for icky corroded terminals.

Easiest way to work this out is to use the normal formulae

watts divide by volts = amps
amps multiplied by volts = watts

Therefore if you know the maximum wattage of your item you diviide by the volts and you end up with a 'normal' current draw - you then add between 30 and 50% and you end up with the fuse size. 30% for passive items like bulbs and 50% for non passive things (motors and the like)

100 watt lamps running on a nominal 12 v

100 / 12 = 8.5 amps plus 30% = 11.5 amps

250 watt fridge on 12v

250 /12 = 20 amps plus 50% = 30 amps

5 watt radio/scanner

5 / 12 = 0.41 amps plus 30% = 0.5 amps

a 5 amp or even 3 on a device that normally draws half an amp or less is too much - but they are often the smallest fuses you can get.