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Solar panel with charge controller. #5081053
04/20/19 06:38 PM
04/20/19 06:38 PM
Joined: May 2010
Posts: 10,093
out there
spasm3 Offline OP
spasm3  Offline OP

Joined: May 2010
Posts: 10,093
out there
I have talked about this before, a few years ago. I have a new travel trailer that comes with a solar charge port. Its a 10 amp port with a 7.5 amp fuse. This seems to go right into the battery circuit with no charge controller, so a simple solar panel would not be isolated at night. So what would be a good panel and charger controller. I keep my trailer in a shed some 100 feet from the house. the shed is in full sun. I think a 50w panel would be enough at 3-4 amps to keep the battery charged.

Any suggestions? The shed is a metal shed 24ft wide by 41 feet open on each end so the charge controller would need to be water proof.

I can get a plug to fit the port on my camper. it looks like this. Anyone else run a solar panel to keep the battery charged?

[Linked Image]

[Linked Image]


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Re: Solar panel with charge controller. [Re: spasm3] #5081072
04/20/19 06:55 PM
04/20/19 06:55 PM
Joined: May 2014
Posts: 1,607
Minnesota
philipp10 Offline
philipp10  Offline

Joined: May 2014
Posts: 1,607
Minnesota
on a continual basis it shouldn't take anywhere near 3-4 amp to keep a battery charged....should it?

Re: Solar panel with charge controller. [Re: spasm3] #5081116
04/20/19 07:37 PM
04/20/19 07:37 PM
Joined: Dec 2016
Posts: 8,459
Waco, TX
Linctex Offline
Linctex  Offline

Joined: Dec 2016
Posts: 8,459
Waco, TX
A 10 to 25 watt panel will easily keep your RV battery topped off - as long as there's no continual draw.

If the fridge is left on all the time - 300 or more watts will be needed.

For just keeping the battery topped off, I think something like this would be great for you:

https://www.amazon.com/Morningstar-Guard-4-5A-solar-controller/dp/B0012N4SZW/ref=sxin_2_ac_d_pm


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Solar panel with charge controller. [Re: spasm3] #5081117
04/20/19 07:39 PM
04/20/19 07:39 PM
Joined: Dec 2016
Posts: 8,459
Waco, TX
Linctex Offline
Linctex  Offline

Joined: Dec 2016
Posts: 8,459
Waco, TX


"The evidence demands a verdict".
(Re:VOA)"it's nearly impossible to actually know the particular additives that are in there at what concentrations."
Re: Solar panel with charge controller. [Re: spasm3] #5081156
04/20/19 08:26 PM
04/20/19 08:26 PM
Joined: Oct 2010
Posts: 1,881
california
wrcsixeight Offline
wrcsixeight  Offline

Joined: Oct 2010
Posts: 1,881
california
I have the controller linked above.

Avoid. The wire entry screws are basically one time use. I.stripped.mine with jewellers screwdriver.

The interface is clunky. Ridiculous. . It will limit voltage. But choosing
/changing this voltage is nightmare.

The USB ports.overload above 0.62Amps.

It will simply seek one voltage and hold it there. 14.4v from mid morning all day long every day will overcharge.


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Re: Solar panel with charge controller. [Re: spasm3] #5081500
04/21/19 09:04 AM
04/21/19 09:04 AM
Joined: Jun 2011
Posts: 1,381
Texas
wag123 Offline
wag123  Offline

Joined: Jun 2011
Posts: 1,381
Texas
You just need a simple PWM charge controller. It should be rated at at least double the amps that you will need because 99% of them are manufactured in China and many products coming from there have inaccurate/overrated specs. A 10 amp controller would be appropriate if using a 50 watt solar panel. Also, if the controller will be outside in the elements it will need to be waterproof, like this one... https://www.amazon.com/dp/B07315CF47. FYI, MOST charge controllers are NOT waterproof.
A 50 watt panel would be appropriate for this application. You should not go lower because it will not often produce the full 50 watts. The system with controller is only about 85-90% efficient (at best, in full mid-day sun), and lower on long wire runs. Also, the solar panel output will diminish over time. Monocrystalline solar panels degrade less than polycrystalline solar panels over time (they are also more efficient).
One other piece of advice, don't cheap-out on the wire. You are going to need a fairly large gauge wire if there will be any appreciable distance between the solar components and the trailer, think 12 gauge copper at 50-75 feet (larger gauge if using copper clad aluminum wire). Smaller gauge wire will carry the 4 amp load, but the higher resistance causes a rather large voltage drop in DC current systems.

Re: Solar panel with charge controller. [Re: spasm3] #5082532
04/22/19 09:12 AM
04/22/19 09:12 AM
Joined: Feb 2007
Posts: 3,859
Southeast
meep Offline
meep  Offline

Joined: Feb 2007
Posts: 3,859
Southeast
If you're using a small panel, like a 10 watt panel, no charge controller is needed, just a blocking diode. A 10 watt panel won't produce enough overcharge to stress a battery. That's a maintainer. If you want something that can allow you to to occasionally run lights and accessories without ever plugging it in, you'll need a fullsize panel and the controller.


2018 F150
2015 crv (wifey!)
Re: Solar panel with charge controller. [Re: spasm3] #5082774
04/22/19 01:41 PM
04/22/19 01:41 PM
Joined: Oct 2010
Posts: 1,881
california
wrcsixeight Offline
wrcsixeight  Offline

Joined: Oct 2010
Posts: 1,881
california
10 watts of.solar panel can easily overcharge some batteries. The no charge charge controller advice might or.might not be valid depending on the battery., Capability of hot solar panel through glass. And parasitic loads. As well as the state of charge of the battery when solar panelstarts producing.

Lots off dried up failed batteries out there because.of.unregulated.small solar panels whose.owners were.told no controller was needed. It's just not true in All cases. Too many variables.


LA 318 Roller Cam
Pennzoil Platinum 10w-30 HM
Fram ultra XG8A
Fram Ultra XG16 on remote transmission filter mount
Re: Solar panel with charge controller. [Re: wrcsixeight] #5082977
04/22/19 05:06 PM
04/22/19 05:06 PM
Joined: Feb 2007
Posts: 1,231
Perris, CA
Anduril Offline
Anduril  Offline

Joined: Feb 2007
Posts: 1,231
Perris, CA
Originally Posted by wrcsixeight
I have the controller linked above.

Avoid. The wire entry screws are basically one time use. I.stripped.mine with jewellers screwdriver.

The interface is clunky. Ridiculous. . It will limit voltage. But choosing
/changing this voltage is nightmare.

The USB ports.overload above 0.62Amps.

It will simply seek one voltage and hold it there. 14.4v from mid morning all day long every day will overcharge.

I had one of those that was defective from the get-go. Voltage went above 15 and never dropped.


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Re: Solar panel with charge controller. [Re: wrcsixeight] #5083499
04/23/19 08:14 AM
04/23/19 08:14 AM
Joined: Feb 2007
Posts: 3,859
Southeast
meep Offline
meep  Offline

Joined: Feb 2007
Posts: 3,859
Southeast
Originally Posted by wrcsixeight
10 watts of.solar panel can easily overcharge some batteries. The no charge charge controller advice might or.might not be valid depending on the battery., Capability of hot solar panel through glass. And parasitic loads. As well as the state of charge of the battery when solar panelstarts producing.

Lots off dried up failed batteries out there because.of.unregulated.small solar panels whose.owners were.told no controller was needed. It's just not true in All cases. Too many variables.


can't argue with that- though in my experience a 10W panel doesn't truly output 10 Watts at 12V. Open circuit they'll put out 18-20V, and at a short circuit they'll put out 0.75-1 amps, and into a 12V load they'll put out maybe half an amp. Into a 14V battery and a through a blocking diode (0.7V loss, so it looks like a 14.7V battery or 3.3V difference), the current quickly tapers to a quarter amp or less. For that reason I won't even bother with something that small.

On our travel trailer I installed a 150W 2'x4' panel with a 15amp (?) charge controller. the weak spot for so many of the controllers is that the SCRs/xFETs used aren't properly cooled. In mine they "hope" that once the back plate is screwed on that the angle of the devices press their backs to the aluminum back plate for thermal transfer. Short of installing heat sinks and a different rear casing, I re-bent mine and liberally applied a gooey silicone thermal grease (not paste like CPU coolers use, the grease flows easier). It's been working now for 3-4 years, with a daily load, as the controller also turns on the porch light at sundown nightly for a few hours. For rough math, that 150W panel seems to be good for about maybe 4-5 amps tops into 12V during peak sun.


So all in all, the wattage rating has been a little misleading for PV in my experience.


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