In a pinch (generator, solar, goes south), what's the best/safest way to charge 1 or 2 RV batteries with a truck's alternator? Simply parallel the RV batteries with the truck's battery with a pair of jumper cables? Or, disconnect the truck's battery and give full charge current to the RV batteries?How much charge current can a typical truck alternator produce?Thanks!

We had to use jumper cables for a week , it got us through. The easiest efficient way would be to take the battery out of the truck and replace it with the RV battery. That way the truck would not reduce charging due to the trucks battery not being low.Long ago I would have started the truck, hooked up the cables and disconnect one of the truck battery cables but that truck had no electronics like newer trucks so I'm not so sure it would be a good idea.The last possibility would be to hook up the cables and let everything sit for a few minutes. You would have to be careful if the rigs battery was too low as the two batteries will try to equalize but done right, the trucks battery should be pulled down a bit so that you would get better charging on the rig battery.

Don't disconnect the truck batteries. They consume almost no current unless they too are discharged (also they will not limit current to the RV battery) and you run a chance of seriously damaging the trucks charging system. Simply using jumper cables will work but the amount of current delivered is strongly related to how good the connection is.Also, make the jumper connections BEFORE you start the vehicle. The spark from connecting it afterward can kill electronic systems in the truck. (Same for jumping another vehicle)

I would go with HD jump cables with #4 or better copper wire.Still going to need a solid three hours to get a decent charge into a super low battery.

Your truck may have a space for a 2nd battery, many do, under the hood. If it does place a battery there. When you drive to the store, etc. it'll charge.

Using the jumper cables is a great plan B but you will be violating RULE #1 as to NEVER MESS with your truck start battery system as this is your only way to get home.A better solution is to install a SECOND DEEP CYCLE BATTERY to your truck battery system using one of these smart relays. This way you will always have a second battery available to use with the trucks stand-alone activities and not do harm to your truck alternator system. This second battery will only be normally charged whenever the truck battery is being charged and is switched away from your truck start battery when being used. This keeps from running down your truck start battery. This battery than can be switched into your RV Trailer needs or swapped out. Read up on these two brands of SMART RELAYS Your truck Alternator DC OUTPUT can range from 110AMPS to 250AMPs depending on what model alternator you are using... The 140AMP model is what most newer trucks are using today. The problem with using the standard alternator is when you connect in a second battery using jumper cables the alternator may only sense the close-by truck start battery and adjust its charging output current accordingly. There will be too much loss in the jumper cable due to the long lengths involved.Also playing around with the truck start battery system will most likely end up really getting you stranded. Something I always want to steer clear of...My 2KW Generator sitting secured in the tailgate corner of my covered truck bed is my main PLAN B backup source of power. I carry a portable VEC1093DBD 40AMP smart mode battery charger to charge my battery bank if needed. usually somewhere on the campground is a 120VAC source in a localized bath room, rangers office, etc.. I always note where these places when going into my off-road camping sites. Never know when you may need to drive back and re-charge some batteries if need be. We are always running out of ice and fresh water on these trips too.Roy Ken

Charging RV batteries with TV | Good Sam Community

time2roll
Nomad
Oct 14, 2014
I would go with HD jump cables with #4 or better copper wire.
Still going to need a solid three hours to get a decent charge into a super low battery.
ScottG
Nomad
Oct 14, 2014
Don't disconnect the truck batteries. They consume almost no current unless they too are discharged (also they will not limit current to the RV battery) and you run a chance of seriously damaging the trucks charging system.
Simply using jumper cables will work but the amount of current delivered is strongly related to how good the connection is.
Also, make the jumper connections BEFORE you start the vehicle. The spark from connecting it afterward can kill electronic systems in the truck. (Same for jumping another vehicle)
JiminDenver
Explorer II
Oct 14, 2014
We had to use jumper cables for a week , it got us through. The easiest efficient way would be to take the battery out of the truck and replace it with the RV battery. That way the truck would not reduce charging due to the trucks battery not being low.

Long ago I would have started the truck, hooked up the cables and disconnect one of the truck battery cables but that truck had no electronics like newer trucks so I'm not so sure it would be a good idea.

The last possibility would be to hook up the cables and let everything sit for a few minutes. You would have to be careful if the rigs battery was too low as the two batteries will try to equalize but done right, the trucks battery should be pulled down a bit so that you would get better charging on the rig battery.

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