A general idea for off road lights and batteries

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A general idea for off road lights and batteries

Postby jethro » Wed Feb 08, 2017 11:12 pm

I have mounted several overhead off road lights up top as well as 2 backward lights to illuminate the bed.
I am only running 1 battery. (1 big one)
Was thinking of maybe adding a small car type battery just to power the lights. Want the gen to charge that battery too and also have its current available for starting. BUT--- I don't want the lights to be able to run down the main (big) battery.

Idea is to wire up little battery in parallel as normal. (for engine) Wire the new lights to small battery only.
Put in a couple of relays so that whenever I hit the switch to turn on the aux lights- that current passes through the coil of another relay (have to split the current with a resistor some how) which unhooks the little battery from the big one.
Idea is to not let the lights suck out of the big battery- only the small one. Once shut off - the alt charges both.
Would I want to try to make the alt. charge the little batt while the lights are running ? Would that need an additional high current diode to isolate the big battery / ( I may have to draw a picture to think it though....)

Anyone tried something like this ?

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Re: A general idea for off road lights and batteries

Postby CumminsPower59 » Thu Feb 09, 2017 12:05 pm

If you are dead set on running two different sizes of batteries, I'd recommend a battery isolator.

It may be easier to just upgrade to the factory dual battery mounts, and then run your lights off them.

Or, upgrade to a pair of large AG M deep cycles and put them in a side box/tool box.

Unless you are pulling massive amps while the engine is off, you should not have any issues. In the fleet of utility trucks I maintain, we can power all of our lighting for quite some time with the engines shut down. We do install low voltage disconnects, so when the battery voltage dips below 11.1V, all non LED lighting trips off. We have run several tests on our upgraded lighting, I let one truck sit overnight with the work lighting on and they were still on when I came in 12 hours later.

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