hey guys try not to get mad if im posting these questions on the wrong website but its for my diesel truck. i have bought 2 28 volt 600 watt airplane landing lights for my truck for off road use obviously but what im not sure is how to make 28 volts to run them. I love wiring but kinda stumped on how to get the power to these guys

 

if you take 2 matching 12 volt batteries and you connect the positive of one battery to the negitive of the other and then hook the lights up to the negitive of one battery and the positive of the other you will get 24 volts

 

you can use a 3p2t switch or relay to switch the batteries between series and parallel. the attached schematic shows how to wire it up so as to charge the batteries when the lights are off and power the lights when the switch is on

keep in mind that the switch or relay needs to be able to at least handle the current of the two lights.

600 watts x 2 = 1200 watts. 1200 watts/24 volts = 50 amps

a 12 volt relay will be easier to find with this rating

 

This setup would be a lot easier if you had a milspec truck, since it'd already be set up correctly to do this.

Be really careful with your relay setup if you are going to try to make a battery go back and forth between series and parallel with the other, if your relays don't work correctly you could short the battery with itself. It's not cheaper but I think I'd rather either convert the truck to 24 volt for starting (24 volt starter and alternator) and just run all the 12 volt stuff off the first battery. An alternative would be a 3rd battery. You could tie it in series with your other two for your 24 volts for you lights. Charging could either use an inverter and charger or a second alternator (of if you aren't using them too long at a time just run it down and charge later).


If you want to use your second battery for 12 volt starting and as the second battery for 24 volt, I'd suggest trying to find a heavy relay that will let you do everything with one switch. They do make them, just a matter of finding them.

Also, they do make 12 volt airplane landing lights...



You could also look into a DC transformer to step up your 12 volts to 24 volts. That would be the easiest solution, I don't know how expensive a 1200 watt one would be though.

 

I would go this route personally. Make sure you fuse all power connections.