CB Power...Battery verses Cig. Power Outlet. When?

It depends on what the cigarette lighter circuit in the vehicle was designed to handle, and how many other things are on that circuit. How big of a radio are we talking about?

 

My guess is that would be safe for most cigarette lighters, probably about 5 amps, somebody correct me if I'm wrong. I think the reason a lot of folks say to run straight off the battery is to reduce interference noise. You'll just have to see how it works for you. If you don't get a lot of noise and aren't blowing the fuse, you're in good shape.

 

Personaly my self, it didnt matter if it was 5 watts or 40 i ran it right off the battery, worked better and had all the power the radio needed to work efectively.

 

OHMS LAW
Volts X watts=amps so a 40 watt radio at 13.8 volts would be 552 amps so a 5 amp circuit want get it. how ever a standard radio out put is 5 watts which means it would need 10 watts input since it is 50 percent efficient by design it would need 138 amps.so there you go. no cigerate lighters would be recomended for good operation. Most radios if run on low voltage will perform bad or possably burn them up.
also you go the other way volts X Amps= Watts

 

usually the reason to run off battery vs. cig. lighter is background noise over power needed. works that way in most vehicles

 

You need to check your formula. I=P/E, where I is current, P is power, and E is voltage. So 40watts/13.8volts=2.9amps. I said 5 amps to be on the safe side of what he should expect a rig like this to actually draw. You should have intuitively known that 552amps or even 138amps couldn't possibly be right, you could do some serious welding with that kind of current. Who said anything about running on low voltage? He's running it off the cigarette lighter, not a solar panel. Please explain what you mean by "burn them up," and what exactly would get damaged.