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RVing message boards => Trailers & Fifthwheels => Topic started by: DOUGRV on August 15, 2017, 04:28:05 PM

Title: Battery Charging with truck
Post by: DOUGRV on August 15, 2017, 04:28:05 PM
I do not own a generator and I usually do not camp at a power site so when I am at a site for some time my battery runs low. I know my trailer battery charges when I am towing so I thought what if I had a second battery to put in my truck bed, plug it into the trailer socket and charge a battery while I am doing that tourist thing. My problem is that I do not know if this would work and if it is doable what I would need to do it. Further, how do I ensure that I am not overcharging the battery? Do I need to ground the battery?
As you can see electrical is not my thing.
Title: Re: Battery Charging with truck
Post by: lone_star_dsl on August 15, 2017, 04:39:00 PM
I think your best bet would be to put a spare battery on a solar powered charger ( http://products.batterytender.com/Solar/5-Watt-Solar-Tender-Charger-With-Built-in-Controller.html ) and swap them out as necessary.

I'm not sure how quickly a solar unit could bring a dead battery back to life though.
Title: Re: Battery Charging with truck
Post by: blw2 on August 16, 2017, 07:41:43 AM
a couple comments
that power feed to the bargman trailer connector in some trucks is switched to the ignition
Other trucks it's always on
Plugging into this will drain your truck's engine battery when the alternator is not operating
and my last thought is that those small battery minder type solar panels are as far as i know only good as maintainers...and they may not ever bring a discharged battery back up.  I think you'd need a fairly large solar panel for that.

I think the best answer depends on the length of time you are talking...and what your power demands are.
I'd guess the best bet for most folks would be just increase the on-board battery bank in the RV....i.e add another battery or convert to true deep cycle batteries with bigger capacity
and then only if you are talking extended periods of time or huge demands would it make sense to start adding big solar panels
Title: Re: Battery Charging with truck
Post by: Gary RV_Wizard on August 16, 2017, 08:07:16 AM
The 12v power feed from the truck is probably not all that great at charging, but it's better than nothing. For decent charging, the voltage needs to be upwards of 13.0v and 5-10 amps, and it's still going top take many hours if the target battery is low, so 40-50% discharged. So yes, it works. How well depends on several of variables.

Nor do you have to use the trailer plug. A set of jumper cables and a connection to the truck's own battery will probably work faster & better, at least while the engine is running. Many modern vehicles have designated terminals under the hood for use in jump-starting. Those same points will work for charging an alternate battery while the engine is running. I suggest disconnecting from them when not running, however.
Title: Re: Battery Charging with truck
Post by: Telemark46 on August 16, 2017, 04:33:21 PM
If you have not already switched to LED lights, doing so will stretch your battery noticeably. 

Ever since a kind and well-prepared RVer saved our bacon with a portable jump-start battery, we have carried one on trips.  You can hook the built-in jumper cables to your RV battery and partially recharge it.  I don't leave it hooked up full time, but I suppose you could.  They can be recharged from your tow vehicle if you are making side trips, although ours did not come with the necessary wire.   They come in a huge range of capacities (and prices) so you can make an educated guess how much you will need for the length of your trips.  I haven't looked into the specs or value of the ones in this link, but it might be a starting place to see what is available.

http://bestreviews.com/best-jump-starters
Title: Re: Battery Charging with truck
Post by: jesseo715 on August 17, 2017, 09:00:57 AM
I'll second both the LED lights and dual batteries hooked up to the trailer.  We comfortably did 5 days dry with our setup.  Battery power never went below 60%.