Adding Solar to an RV

[Minnesota Dan]

I have recently bought a 20 foot Cherokee Grey Wolf and it came with a 50 watt solar panel. I would like to feel comfortable that I could dry camp for 3-4 days and I don't think that 50 watts is enough to run my DC refrigerator, fan, and water pump usage for that amount of time. From my previous tent camping days, I have a 100 watt solar panel, and a 'solar generator' kit that includes a charge controller and a 1,000 watt inverter.

My question is, can I just attach my 100 watt solar panel's charge controller to the trailer batter to supplement the 50 watt panel? To my mind, there should not be an issue with this. However, I want to be certain that doing this would not overload the 50 watt panel's charge controller system.

Eventually, I do plan to upgrade the trailer's solar system overall, but that is not in this year's budget.

Thanks!

 

[TonyL]

Does your 100 watt panel have a controller or were you thinking of connecting direct from the panel to the battery?

 

[creativepart]

My question is, can I just attach my 100 watt solar panel's charge controller to the trailer batter to supplement the 50 watt panel?

Yes, you can simply attach your charge controller directly to your battery bank. This is assuming your 100w kit has a 12v charge controller - which it likely does.

And you are correct that the 50-amp panel won't do a lot,

If you only have one battery - the best thing for your plans would be to replace it with two Group 31 Deep Cycle batteries (such as 2-100ah AGMs) OR 2-220ah 6v Golf Cart batteries. Most small compressor fridges will demand about 50ahs a typical 24-hour period. Most TT come from the dealer with one smaller Group 24 or Group 27 Marine/Deep Cycle which is not a true Deep Cycle battery.

Smaller batteries have smaller amp hours of storage - so a Group 24 may have 60ah and a Group 27 may have 80ah while a Group 31 typically has 100ah. Wired in Parallel two of those will give you 200ah of storage. But keep in mind for longevity you want to limit the number of times you discharge the batteries below 50%. So, that means you'd have 100ah usable from the two batteries.

Two 6v Golf Cart batteries wired in Series will give you 12v and they generally provide ~200 to 220ah of deep cycle storage. But still you want to limit the draw to about 50% of total capacity.

Golf Cart batteries will give you the most bang for the buck, but require regular maintenance that some people are not all that good at doing.

One more thing - even with more batteries and more solar you should plan on having a generator as a back up. Depending on the time spent on your trip you should not expect to get by without some means of recharging your batteries.

 

[Kevin Means]

Yes, you can add your 100 watt panel to your setup. Just use a simple (cheap) PWM controller and wire it directly to your house battery bank through a fuse.

You said you wanted to be able to run your "DC" fridge while boondocking. DC powered RV fridges consume a LOT of power, and adding a 100 watt panel to your solar setup won't make much of a difference at all. Did you mean to say that you wanted to be able to run your RV's fridge on propane? The control boards in LP fridges use a small amount of DC power when the fridge is running on propane. Adding a 100 watt panel will help offset that draw and help keep your battery charged.

Kev

 

[Mark_K5LXP]

keep in mind for longevity you want to limit the number of times you discharge the batteries below 50%

How many times? What's the definition of "longevity"?

Mark B.
Albuquerque, NM

 

[Minnesota Dan]

Thanks all for the comments, these help a great deal.

To answer some of the questions above:

* Yes, my extra 100w solar panel is hooked up to a charge controller.

* The Fridge, unfortunately, is DC/AC only. It looks like manufacturers are moving away from a propane option on refrigerators.

 

[Mark_K5LXP]

Generally with two controllers feeding one battery the panels will both contribute up to their inherent capacity in bulk charge mode. From there though you can't be assured the absorption and float mode setpoints of the controllers will match so one controller may cut back sooner than the other. Generally the batteries are at a point where they won't accept any more power than that anyway so it's a don't care, but just something to be aware of. The elephant in the room here isn't two disparate panels and controllers, it's the disparity of the source capacity and load. Adding a 100W panel is certainly going to help but it still may not be enough to keep up with what you want to run. You'll need some measured data of what your panels can supply and how many Ah your loads are pulling to see if you can recover enough. It may turn out you're still in deficit mode every day but if you can gain enough to make it your 3-4 day goal before the batteries are flat then I would say it's a workable option.

Mark B.
Albuquerque, NM