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Discussion Starter #1
Hey all, I'm not all techy involving electrical, so hoping someone can point me in the right direction..

Installing a blue seas fuse block, and have the following that's going to be added to it...

1) heated grips
2) heated vest
3) cigarette lighter
4) cigarette lighter

Was wondering what size fuse to use in each of the above? I also have a voltmeter going it, but I presume that goes right to the battery, not the fuse block.

Thanks!
 

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Not an easy answer. Depends on the wattage of the equipment and wire sizes.

You can use these charts for easy reference to wire and max amps. Also has a wattage column. Scroll down to the bottom.

Wire Gauge Tables

Typically:

Heated grips: 3 to 5 amps
Heated Vest: 5 to 7.5 depending on the wattage of your vest
Cig. Plugs: Normally rated higher than you need. Will depend on the wire size you run to the battery and what you plug in. For a GPS a 3 amp will be plenty. If you run a compressor, then a 10 would work with a 16 ga wire (in case you want to go bigger at some point).

If you know the wattage of the equipment, just divide the wattage by 12 and add 20%. Then choose the next size fuse up. Just make sure your wire is large enough to handle the load (see chart). Example: Heated Grips at 35Watts: 35/12*1.2=3.5..use a 5 amp. I just run everything with 16 gauge and it covers me for most applications.
 

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FORUM GODFATHER.....R.I.P. PAT
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You want fuses big enough to handle 20% more than the load requires and small enough not to let the wire overheat if something goes wrong. To start with, you need to know the sizes of the loads you are putting into the cigarette lighter sockets. You can put a voltmeter on the fuse block. If you run it to the battery, it will be on when the ignition is off.
 

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Keep in mind that the purpose of a fuse or circuit breaker is to protect the wire from excessive current which causes overheating. The capacity of the fuse depends on the ampacity of the wire, and sometimes on the device you're powering. As GW says, first decide on what you'll plug into the cig lighter sockets, buy sockets that will more than handle the load, then wire that more than handles it, and suitable fuses. Loads like GPS, cell phone charger, etc. are miniscule. Heated gear is higher. Aftermarket horn is high. Some lights are high load. Check the label on an air compressor.

Sometimes the load is listed in watts rather than amps. Watts are the unit of electrical power. Amps are the rate of flow of the electrons. Voltage is the force of the electricity.
Watts = volts x amps
Amps = watts ÷ volts; for example 120 watts on a 12 volt system draws 10 amps, so you'd want a circuit with at least 12 amp capability (20% excess rule).

You want the voltmeter on a switched circuit, i. e., a circuit that is on only when the key is turned on. The voltmeter uses a very small amount of power, and eventually it could draw down your battery.
 

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Discussion Starter #5
Awesome, thanks guys!

Will put the voltmeter right onto the block, and work out the fuses ...

What gauge wire would people recommend, as an all around size? Looking at the chart, looks like 18 would be enough for all but the most power drawing things, but I was going to go with 14 all around?
 

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FORUM GODFATHER.....R.I.P. PAT
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14ga is a very large wire. I use 12ga from battery to fuse or grounding blocks, 14ga to a Stebel horn, 16ga to heated gear and 18ga to just about everything else. If it doesn't have a motor (including a large horn diaphragm) or make heat (possibly a byproduct of light), 18ga is probably plenty.
 

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Discussion Starter #7
14ga is a very large wire. I use 12ga from battery to fuse or grounding blocks, 14ga to a Stebel horn, 16ga to heated gear and 18ga to just about everything else. If it doesn't have a motor (including a large horn diaphragm) or make heat (possibly a byproduct of light), 18ga is probably plenty.
Thanks GW!
 
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