The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Lucas, Ignition, Charging, Electrical => Topic started by: Topdad on 14.07. 2023 09:28
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after using an old inline fuse for 10myrs I went modern and fitted a new one but it keep blowing so basically what size fuse should I use I'm on12v with low wattage rear bulb everything else standard .
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I've got a 12v system and using a 10A fuse. Also i use a 7.5A for the reg/rec and a 15A for the ignition coil.
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Depends on what your total wattage is. This is my rule of thumb:-
Add it all up and divide it by your battery voltage and that will give you the total amps you'll be using when everything gets switched on. Double that and use a fuse rated nearest to it.
Examples:
12v: If total is 60w divided by 12v = 5 Ah x 2 = minimum 10 Amp rated fuse.
6v: If total is 60w divided by 6v = 10Ah x 2 = minimum 20 Amp rated fuse.
I have a sidecar fitted, Quartz Halogen 35/35W headlight on bike, indicators on bike and sidecar, indicator warning light and buzzer, two stop lights and sidecar front light - all LEDs except the headlight and I use a 15 amp blade fuse at battery terminal.
Pilot light doesn't need to be added because it's not on at same time as headlight and in my case only two indicators will be working at a time. But I will have two stop lights on at the same time. The stop lights alone if they were incandescent bulbs would be 42w. These sort of things need to be taken into consideration.
Rog.