Rock Lights as back up lights??

[Justafordguy]

Yes that's low, a decent truck battery usually has at least 75 amp-hours.

 

[Steve83]

Any ideas on a set of small led flood lights that can be mounted from there side and not the bottom?

The list is almost endless. Search eBay for "white LED work" (you can add terms like 12V or 18W to narrow the results), and scroll through a few pages. I prefer this shape because it's convenient & unobtrusive in most locations. At worst, it would take a couple of easy brackets to change the way the LED mounts.

...a 300mA draw. I think this is 1/3 of an amp.

It's 0.300 Amps; 1/3A would be 0.33333333333333...

So how long could they be on with engine not (edit) running before I have a issue with a good battery

That depends how good your battery is, and how much current the truck needs for cranking, which depends on how good the starter is, and the carb, and the ignition system, and any other electrical draws that are on during cranking.

But a quick & dirty way to gauge it is: a typical (new) Gr.65 battery stores ~70~90 Amp-hours. That means it could (theoretically) supply 0.3A for (70/0.3)=233.3333333333 hours (almost 10 days) before it was DEAD. It could supply 2 of those for 1/2 as long.

...can't figure out how much they draw off battery...

Watts=Volts*Amps, so A=W/V and 27W/12V(engine/alternator off)=2.25A . Two would draw 4.5A, which I'd expect to kill a fully-charged Gr.65 battery in 15-20 hours.

5 amps...is that pretty low???

Depends what you're comparing it to. It's about the same as a single high-beam halogen headlight; it's ~1/40 what the starter draws; it's ~8x what those other LEDs use; it's ~40x what it would take to interrupt your heartbeat (if it passed DIRECTLY through your heart muscle - not from your skin).

 

[Broncobowsher]

By dead battery, we mean DEAD. Not just a bit low. But the dead to the point it can't recover completely. And not a chance if it doing anything productive for the last half of that life.

Think of it this way. Headlight bulbs are about 35W each. Leave your lights on and you are drawing 70W of headlight, lets say 14W of marker lights being a bit conservative and easy math. So 84W at 12V is 7A of draw. How long can you leave the headlights on, drawing that 7 Amps, and still start the engine?

 

[D.R.Y.]

I picked up a pair of LED lamps from the local farm store, price was right and they are dupable.