Alternator size and auxiliary lights

My truck has a 100 A alternator. I just ordered an N-Fab light bar and 4x55W Warn lights. That's about 18 A with all four running.

Does anyone see any issues with running the four new lights at the same time as factory headlights and fog lights?

 

I've got 2 PIAA's up front and they're 85W/ea, so not quite as much as yours but no issues with them at all. They're always running with high beams only. You should be fine, make sure all your wiring, relays and switches are heavy enough to handle the load.

Just a suggestion, but with 4 auxiliary lights, why would you need the fogs on? Seems like unnecessary strain on the electrical system running 2 extra lights that aren't really doing much.

 

Thanks for the reply there Pugga.

You raise a good question about the extra lights. I was just looking at the worst case with all lights running. Two of the lights are driving lights and would only be used off-road. But if all the lights can work at the same time then no worries.

As a point of interest, how much is drawn from the alternator under normal factory conditions?

 

Thanks Chris. Even at 40 A there is plenty of reserve in the alternator.

 

You're not just running 4 lights, headlights and fogs. You're also running the tail lights and parking lights (probably negligible draw, being a lot of LEDs). Add on the A/C, radio and whatever electronics you add (CB, bigger radio system, etc) and it may add up quick!

I've run 2 55W and 2 85W before with no problem. I also have 2 55w lights in back that haven't seemed to drain, granted they're reverse lights so they don't go on for long. And I also have the tow pack - 400A alternator, if I recall.

 

w/tow package..120amp.

 

I agree with what you say. Would the factory lights/ac/radio etc. be included in the 35-40A that Chris suggested?

I have fog lights (2x55W or 9.2A), reverse lights (2x55W or 9.2A), CB radio (less than 1A) and the four new lights (4x55W or 18.3A). That puts me at about 37A with aftermarket lights.

And I think I read 130A for the tow package alternator.

 

Thanks for the tip