Does a Reefer trailer help power the truck battery's while truck is off?

No..........

 

Jumper Cables

 

Listenin to truckers at the Petro diner counter is a VERY bad habit.

 

You know... if you are pulling reefer it would be wise and beneficial to learn about them... how they work, how to pretrip a reefer, general maintenance, how to set them, etc, etc.... without that basic understanding it is possible that an entire load could be ruined and rejected at the shippers...

If your company doesnt have any information for you.. you can find it online...

 

It doesn't provide power to the batteries on a constant basis like you think. But, you can run jumper cables from the reefer to the track to jump it. If you're lucky, you might even have battery posts behind the sleeper for this exact reason, my T680 has them.

 

In the pre-ABS days, it was often done with jumper cables, or a long piece of decent gauge wire, if the truck had an alternator failure. Nowadays I suppose you could just jump to the ABS hot wire and accomplish the same thing. It's not the best idea to have two alternators going at the same time, unless they are both regulated by the same voltage regulator, so any connection needs to be temporary or switched.

 

you can run a wire from the reefer to your truck batteries and that will charge your truck batteries.
I once had a truck alternator go bad and I ran a wire from my reefer to my truck to keep running,

 

I have jumped my truck with the reefer unit years ago, and only 1 time used a 10 gauge wire from the unit to my truck batteries for a short distance because my alternator belt went bad and it was getting dark. Today many companies frown upon doing anything to the trucks except getting a jump, and even then some companies frown upon doing that.