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# f5al250v fuse: good for 180 watts at 12 volts?

#1
07-13-16, 09:12 PM
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f5al250v fuse: good for 180 watts at 12 volts?

I have a car cig lighter socket with a f5al250v fuse in it. Internet research shows a pretty high 1,250 watt capacity (5 amp x 250 v). Can this thing handle 15 amps at 12 volts? The item description suggests a much lower capacity so I don't know what to think.

#2
07-13-16, 09:27 PM
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The voltage is the maximum voltage that can be run thru the fuse.
The amperage is 5A.

A fuse's protection is expressed in amps.... not watts.

There are 32v fuses that are slightly different than the 250 ones but I've always used the 250v fuses for 12v applications with no problems. The voltage rating of the fuse must be over the voltage it's protecting.

What are you concerned about protecting ?

#3
07-13-16, 10:02 PM
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I've been converting amps and volts to watts to compare it to my system, which is 12 volts. I have a bunch of devices working at anywhere from 1 AMP at 5 V to 6 AMPs at 12 volts. They will all be connected to this one plug, looks like this:

12V 24V Male Car Cigarette Lighter Socket Plug Connector Switch 1 5M E | eBay

The total wattage to be drawn (by taking each device, multiplying amps x volts, and adding those numbers up) equals about 180 watts. The car's 12v socket fuse is 15 amps, which at the 12 volt system equals about 180 watts. It already works without blowing the fuse. I was simply redesigning the system to do away with the "cig lighter" sockets since they are unreliable due to the car's vibration and slip out. So what am I protecting? Basically, just the components of the above mentioned cig lighter plug that will be inserted into the car's 12v power port. I don't want its wires to melt. The rest of the system has already been tested and is protected by the car's own 15A fuse in one of the fuse boxes.

#4
07-13-16, 10:23 PM
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Most car electronic equipment like phone chargers, GPS's, etc. come with cigarette lighter plugs with a fuse enclosed that is sized for that device. It sounds like you want to cut the plugs off and hard wire to one master plug.

If that is your intent then you should install an inline fuse with the proper size for every device. Then you could connect them all to a common cigarette lighter plug although drawing a continuous load of 15A thru a lighter socket and plug is not ideal.

#5
07-13-16, 10:37 PM
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I've been converting amps and volts to watts to compare it to my system, which is 12 volts.
Not really correct. The amps is the important number so long as the voltage rating of the fuse is greater than the applied power. For example in a 12 volt environment a 32v rated 5a fuse will work just the same as a 200v rated 5 amp fuse. But one by the multiplication of volts time amp would be 160 and the other 1000. Using that method the 32v rated fuse would seem to be better but it isn't. They will both blow at 5 amps.

#6
07-14-16, 08:01 PM
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So can I safely replace that 5A fuse with a 15A fuse, or will the wires of the cig lighter burn out?

Another question: can I just put a piece of metal instead of the cig lighter fuse in the cig lighter and just rely on the 15A car fuse to protect from a short-circuit?

#7
07-14-16, 09:17 PM
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So can I safely replace that 5A fuse with a 15A fuse
It depends on the wire size.
can I just put a piece of metal instead of the cig lighter fuse in the cig lighter and just rely on the 15A car fuse to protect from a short-circuit?
That makes no sense. Can you rephrase?

#8
07-14-16, 10:09 PM
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Yes...... the lighter well is protected at 15A by the car's fuse.

He wants to put a 15A fuse in the lighter plug or a piece of metal as a shorting bar.
Instead of a piece of metal just use a larger fuse.

But remember..... I mentioned a continuous high current draw thru a lighter plug is not recommended. I would consider the wire size run to most lighter wells as undersized. As you draw more current the voltage will go down.

#9
07-15-16, 09:11 PM
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Well, it's running consistently quite well at a nominal 180 Watts (using car charger plugs, not the system I wanted to use). However, it's a bit too bulky and I will likely be replacing the system completely with something that uses about half of that power.

#10
07-16-16, 04:26 AM
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Check the wiring within the device expected to carry the full 15 amps.

Calculation 1, overheating: The same rules apply to 12 volts as for 120 or 240 volts for example 14 gauge wire up to 15 amps, 12 gauge wire up to 20 amps.

Calculation 2, voltage drop: Lower voltage circuits are more sensitive to voltage drop because voltage drop in a given piece of wire is a given number of volts and not a percentage of the circuit voltage.

Choose the larger wire size you come up with after doing the two sets of calculations.

Sixteen gauge or smaller wire in your device will limit the current draw to under 15 amps (or well under 180 watts at 12 volts).

#11
07-18-16, 05:55 PM
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I suspect the only reason it's working right now is because the actual voltage being drawn is far less than the nominal voltage.

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