RV Battery Charging From Trucks Alternator

[JAG1]

If camper batteries are way down is it hard on the Alternator?

[Mopar1973Man]

No. It will not draw more that the fuse will alway typically like for my RV its got a 40 Amp fuse for the trailer plug so its below 40 amps because it never blows the fuse.

[JAG1]

So what if you run big cables? Or is there any situation in which the Amp draw would be hard on the trucks electrical system?

 

I ask since I had an alternator go out on me.  I was charging up two dead batteries on my camper running down the highway and it kicked the bucket.

Edited April 15, 2016 by JAG1

[Mopar1973Man]

Typically you should have a fuse or something limiting the charge or current flow to that circuit so to protect from over loading. I wouldn't use much more that 10-14 AWG wire for charging the RV batteries. Like even the Dodge trailer plug is only a 10 AWG cable and again limited to 40 Amps on the trailer plug. Even my RV with nearly dead batteries never draws hard on the system because of cable and fuse limits.

[moostang]

How do you charge the RV batteries from the truck?  Do you have to wire it specifically to do that or is it already set up? 

[AH64ID]

The 7 pin plug is setup to charge. 

 

My OEM fuse is 30A; however, due to the size of the wiring the most I have ever seen going into the camper batteries is about 15A. 

 

That's not nearly as hard on the alternator as the grid heaters. 

 

I li do know that some folks will run larger wiring to their campers/trailers for faster charging but I have never seen the need with my use. 

[Mopar1973Man]

47 minutes ago, AH64ID said:

I li do know that some folks will run larger wiring to their campers/trailers for faster charging but I have never seen the need with my use. 

 

Bingo... Batteries are better off slow charged anyways. Rapid charging batteries is hard on both the alternator and the battery. Even after couple hours of driving the batteries on the RV are typically back up within 80-90% of charge. At least speaking for 2nd gen trailer sockets its wired hot constant so even after the truck is shut down the main two batteries will continue to balance with the RV's two batteries.

[JAG1]

I have number 8 wire to charge my camper batteries but still only get 13.6  when the trucks' at 14 volts. Is that the fuses limiting the current?

  Like I said, it's not hooked up right now cause it seemed to take forever... just charge with the generator because even all days driving would not do a whole lot.

[Mopar1973Man]

No. That's voltage drop over distance. The longer the run the less voltage will travel the distance. Like my solar panels in the front yard to keep the voltage high I had to run 2/0 cable. In your case the distance from the hook up point to your RV battery there is amount of loss for the distance of feet.

 

http://www.calculator.net/voltage-drop-calculator.html

 

 

Edited April 15, 2016 by Mopar1973Man

[AH64ID]

2 hours ago, JAG1 said:

I have number 8 wire to charge my camper batteries but still only get 13.6  when the trucks' at 14 volts. Is that the fuses limiting the current?

  Like I said, it's not hooked up right now cause it seemed to take forever... just charge with the generator because even all days driving would not do a whole lot.

 

As Michael said it's the distance. Did you increase the size of the ground too?

 

There is probably 30', if not more, of cable between the alternator and the camper batteries. At a 30A charge rate and a 14V supply the voltage at the camper batteries will be 12.87V. To get to the a better charge voltage the wire needs to be at least 6 or the current drop to under 20A. 

 

It's a slow charge, but all day driving would charge most setups even at 15A max. 

 

My truck won't charge my batteries from 50% SOC in a 2-3 hour drive and I don't even think they get up to 75%. Then again I have a 300AH battery bank. 

 

 

 

 

Edited April 15, 2016 by AH64ID

[IBMobile]

                                      wire size chart      

    https://www.tessco.com/yts/industry/products/itm/automotive/get_wired.html

[JAG1]

yep its the wire size then. Think I'll just hook it all back up again and get what I can out of it. I do have a manual switch to control the charging. Letting the grids do their thing first, charge the truck battery up awhile then switch it to the on position of charging.

 

Yes I have no. 8 grounding as well. I think it all grounds thru the camper tie downs but I ran a ground wire anyway.

[JAG1]

Next, I would like to know what sized solar roof panels do I need for my 2 group 31 batteries was thinking looking on Craigslist for some.

[Mopar1973Man]

Remember if they are mounted to the roof the RV MUST be park in direct sunlight always! If free standing then the RV can be parked in the shade and the panels can be moved out to the sun. Just remember I'm powering a entire 2 story house with only 400w of solar. The RV is a mere 45w of solar and does well. So a single 265w panel would be more than enough.

 

http://www.homedepot.com/p/Grape-Solar-265-Watt-Polycrystalline-Solar-Panel-GS-P60-265-Fab2/206365796

 

 

[JAG1]

So what about the less expensive panel called Amorphous type? they tend to be less wattage but better in shade since they won't disconnect sections of the panel with some shade cast on it?

 

I like the lower cost and the flexible panel.

[Mopar1973Man]

What your looking at is Charging Amps. Typically around the 13.2 V. So 265W / 13.2V = 20 Amp charge rate. What I've got is the Amorphous type from Harbor Freight. As for the 45w I'm just about 3 Amps a charging Amps.

 

 

Quote

 

Exaggerated claims of shading tolerance

The simple fact of the matter is, no panel is shade tolerant to any great degree and it just doesn’t make sense to install an expensive solar power system in an area that experiences a great deal of shade as the system’s performance will be extremely low.

 

 

[IBMobile]

Check out this site and use the side arrows for other articles on solar.

http://www.truckcampermagazine.com/camper-tech/systems/installing-a-solar-panel-system-part-1/

[Mopar1973Man]

The reason I mention the freestanding and warn about roof mounting is like everyone here I've talked too. They done the roof mounted panels and suffer during the summer time because the need to park the RV in full sunlight make the panels work efficiently. Like most of us that boondock look for shade to tuck the RV in so the living area is comfortable because there is no A/C. So if the RV is in shade the solar is worthless. Typical summer temperature for me is between 105-110*F so I normally hunt for as much shade as possible.

 

So if my panels where over the bedroom area (forward) then my solar is worthless. Free standing I can chase patch of sunlight really easy. Still keep the interior of the RV very comfortable for the evening without having to park in direct sunlight.

Edited April 17, 2016 by Mopar1973Man

[JAG1]

So yours aren't the multi crystalline type mike? If so I'm very interested about that.

 

I want mine on the roof even though I'm a shade type guy also. At least they'll work while parked for shopping/ eating and on route.

 

IBM, I like Michael Nelson answers.... He is an electrical engineer and that's terrific that he takes time for us around here.

[Mopar1973Man]

1 hour ago, JAG1 said:

So yours aren't the multi crystalline type mike?

 

For the house its multi crystalline (400w) . For the RV its Amorphous type. (45w)

 

1 hour ago, JAG1 said:

I want mine on the roof even though I'm a shade type guy also.

 

My Barber did exactly what you did put them on the roof and now carries a generator because parking the RV under the shade of the trees while camping the batteries are always dead. So back to carrying gasoline and gasoline generator. The reason I converted to solar is that amount of gasoline and run time required for the generator to catch up the batteries. I hated listening to that engine run even if it was on the other side of the pickup on a cord.

 

Solar is completely quiet as long as the panels are exposed to full sunlight. Just partial coverage can degrade the charging 50% or more. Kind of like why I never stuck the solar panels on the roof of the house. Because in the dead of winter they would become worthless covered with snow, more shade where the house sits vs pole in the yard. The only reason I'm considering the solar upgrade on the house is the sole fact winter time direct sun is very limited so I need to increase amperage to get a better recharge in the winter time. Like like now either RV or the house can operate solely on the panels with no issues. Then again it about location of the panels.

 

Consider this... Current outside temperature.

 

Here is the house panels. No shade.

 

RV in the shade of the tree like if I was camping.

 

Now the temperature inside the RV. That 21*F reduction of heat. Even though the outside temp is 71*F at the time of shooting the pictures. It will stay much cooler in the RV all day long.

 

So now the panels where on the roof there would be little to ZERO production. At least the interior of the RV is already air conditioned cool. For me small 3 amp charge with shade would kill it off to ZERO. Even my 400w array on the pole just a passing cloud shadow will kill off over 75% of the charge rate.

 

So are you willing to be uncomfortable in the RV being hot in the summer for free power?

 

I would say store them in a clip on the roof but make them removable and standalone so you can park in the shade, place the panels in the sun but store them on the roof when traveling.