Cigarette lighter

[quinten]

Does somebody now if you can put a 12v cigarette lighter in a 24v circuit?

 

[snaggletto]

Robust 12V DC/DC converter, wide input range (13.5 to 34VDC)12 volts output, 15 watts continuous

Or something similar...

 

[quinten]

You cann't just put an original 12v lighter for a fj40 in a 24v socket from a bj40?

 

[73FJ40]

You cann't just put an original 12v lighter for a fj40 in a 24v socket from a bj40?

I assume that the 12V lighter insert will fit in a 24V socket; It's just that the first attempt to use it may catch the truck on fire.

Assume that the 12V lighter insert draws 10 amps. Ohm's law states that for a given 'resistance' (the 12V lighter insert) voltage is proportional to current. So, if you double the voltage (from 12V to 24V), you get double the amperage (from 10 amps to now 20 amps) FOR the SAME RESISTANCE. (Remember, you plugged the 12V lighter into the 24V socket.)

Now the exciting part. You blew the lighter circuit fuse when you first tried out your new lighter, so you changed it from 15 amp rating to 30 amp rating (or wrapped the blown fuse in tin foil.) Now when you plug it in, the fuse won't blow. Oops.

However, Power output is amps squared times resistance. Since the resistance is the same (the 12V insert) power consumption goes from 10 amps x 10 amps x R = 100R to 20 amps x 20 amps x R = 400R. Power increases 400%. That's a lot of heat, really fast!

This is why 12V bulbs burn up at 24V, and 24V bulbs in a 12V circuit are very dim.

 

[rkymtnflyfisher]

 

[DeadguyLLC]

I had a 24 volt M38A1 (military Jeep). I installed a cigarette lighter and just hooked it up to one of the two inline batteries

 

[FF LC FREAK]

I had a 24 volt M38A1 (military Jeep). I installed a cigarette lighter and just hooked it up to one of the two inline batteries

Exactly. For a low amp draw circuit like a cigarette lighter, drawing off only one battery is fine. For a larger draw or to run multiple 12 volt accessories, use a converter like the one linked above. When I had my 24 volt BJ42, I put in a converter and wired in a switched fuse panel that was only 12 volts. Then I could run all my 12 volt accessories from that fuse panel. The problem with running a lot of 12 volt accessories off of just one battery is that you will kill the batteries quickly. With a dual battery setup like this (in series), they do not like having uneven voltage/amp draw.