a question about charging batteries

Charles Skinner · January 13, 2015

A dear friend has a travel trailer and has no way to charge his batteries while "boondocking." If they go RVing with us to, for example, in a National Forest campground, could I run some kind of electricity cord from my rig when I am charging my batteries, using my big built in Onan generator, and charge his batteries at the same time I am charging mine? Those you who "know me" know that I KNOW nothing about electricity, and will never be able to learn "doodly squat" about it! This could be a solution to his lack of a way to charge his batteries ---- it it would work for his trailer and for mine. Your thoughts? Don't laugh too much if this is a silly question.

C. S.

wa_desert_rat · January 13, 2015

If your rig, like my motor home, has outside 20-amp receptacles there is no reason you could not plug in a battery charger or even connect him to you if he normally plugs into 20-amp circuits. You probably won't be able to hook him up to 30-amp (or 50-amp) unless your generator has plug-ins for those. But a heavy-duty extension cored (not over about 30-feet) to either his 20-amp input or to a battery charger connected up to his batteries directly should do fine. I think most of us have done that at some time or another.

WDR

Kirk W · January 13, 2015

I would just use a quality extension cord from your outside outlet to his RV and power a battery charger for his 12V battery. Should be no problem at all as long as he limits his power use. I don't see any way for you to power his air conditioner, microwave or any of the 120V-ac loads on his RV from your Onan.

StarDreamers.us · January 13, 2015

He could also buy a small Honda charger (or Harbor Freight charger) and charge his own battery as needed.

Safe Travels!

oldjohnt · January 14, 2015

Charles, not to worry mate, there are no silly questions, just a few silly answers now n then lol

I take it from your post his trailer does NOT have its own built in Converter Charger whereby if he's plugged into 120 VAC Shore Power his house battery is charged right???

If he had such you could just run an extensions cord from one of your 120 VAC outlets to his shore power input cord and when your Onan is running (its likes he's plugged in at a campsite) his built in charger will charge his batteries.

However if he does NOT have his own built in Converter Charger he could carry his own portable 120 VAC charger and again plug it into an extension cord powered by your Onan to charge his batteries. BUTTTTTTTTTT if its not a fairly high amp rated charger (like say a 50 to 100 amp), it could take a longggggggggggg time to charge his batteries and that's a lot of run time from your Onan in a National Forest Camp where its usually fairly quiet and some have limited genny run times. SURE such a set up will work, but a small charger would require a lot of Onan run time and that doesn't sound great to me if I were in that camp.

Other methods are he might consider having two in series 6 volt golf cart type of true Deep Cycle batteries in his trailer versus perhaps a single semi or quasi so called RV Marine Battery. In other words he needs all the help he can get in the form of carrying MORE amp hours of stored energy to get him through a night and day if dry camped. I assume he at least has a charge wire back from his truck which charges his trailer battery while driving???? If not he's not going to have a good experience.

A buddy of mine has two 6 volt true deep cycle series golf cart batteries and packs a fold up portable lightweight 100 Watt Solar Panel Charger so he can charge his batteries during the day when dry camped. That wasn't all that expensive, easy to store set up and use and works well for him TELL YOUR BUDDY TO CONSIDER THAT its better then having to run your noisy Onan for a few hours in my opinion.

SUMMARY sure an extension cord and him plugging up a battery charger (Id use at least a 50 amp or bigger to reduce run time) will work while you run your Onan, but Id sure take a look at him using true deep cycle golf cart batteries (to increase his amp hours of stored energy) plus a fold up portable light weight 100 Watt (or more) Solar Panel charging system with its own built on charge controller. Or sure even more solar capacity such as a panel or two on his roof. Having to run your Onan for long periods wouldnt make you my favorite neighbor in a nice quiet Natl Forest Camp lol BUT HEY YES IT WILL INDEED WORK if you don't mind it YOUR CHOICE. Or he could buy one of those nice QUIET small lightweight Honda or Yamaha portable gensets, that's another good possibility although more expensive then a fold up 100 Watt Solar Panel.

John T

Tex Bigfoot · January 14, 2015

Wow

Good answer John T.

You covered it all

Kirk W · January 14, 2015

This could be a solution to his lack of a way to charge his batteries ---- it it would work for his trailer and for mine. Your thoughts? Don't laugh too much if this is a silly question.

Did you get the problem solved? Keep in mind that if you do use a battery charger that connects to 120V-ac on the side of your RV, the cord does not have to carry as much as the battery charger will put into the batteries, but only a bit more than 10% as much because of the voltage difference. If the charger supplies 50A at 12V-dc to the friend's batteries, that will mean that it is drawing about 5/6A through the 120V extension cord. Most quality cords are rated for about 15A and should be fine. You can tell if the cord is OK by making sure that neither it or the plugs on it are getting more than slightly warm to the touch.