Solar charge controller

[booboo]

I have a pop up camper with two Trojan T-145 batteries and a Xantrex Freedom HFS 2055 inverter/charger. I use the Xantrex to charge the batteries by plugging in at home and with a generator when dry camping.

I would like to add a few solar panels on the roof of the camper to limit the amouont of time I need to run the generator and to maintain a charge on the batteries when not in use. I am planning on mounting 3 120 watt flexible panels in the roof of the camper. My question is what would be a good charge controller to use with this setup?

We don't use the camper in the winter for several months. Would it be a good idea to leave the charger on all the time to keep the batteries fully charged? Also would like the ability to add a 4th panel if needed.

[ewarnerusa]

Are these panels 12V nominal? Or a higher voltage? If a higher voltage, you should absolutely be using MPPT. For 12V nominal panels, you can go with a cheaper PWM controller although an MPPT can be used and theoretically you'd have access to the max capacity of the panels (PWM wastes some of the harvest). But from what I've read is that in actual usage while camping, especially in a flexible panel scenario where you probably won't be tilting the panels to harness max sunlight when your batteries are at their lowest SOC early in the day, you won't really be seeing much more harvest by going the MPPT route. But I don't have MPPT so no personal experience with it. I don't have much advice as far as brands other than you get what you pay for so be wary of the cheap stuff. Plan your install around having 4 panels if you stick with that concept, so get a large enough controller and wiring to minimize voltage losses that you install once instead of having to upgrade later. Look for controllers with temperature correction and adjustable charging parameters. I like my Morningstar Tristar 45 PWM, cost around $200. I didn't get the add on display panel.

For winter storage, absolutely leave the solar connected and you won't have a need to plug it in. If the panels are covered in snow they won't be providing any charge, so keep that in mind for winter storage.

[PNjunction]

I would like to add a few solar panels on the roof of the camper to limit the amouont of time I need to run the generator and to maintain a charge on the batteries when not in use. I am planning on mounting 3 120 watt flexible panels in the roof of the camper. My question is what would be a good charge controller to use with this setup?

This kind of depends - IF you are always going to bulk charge with the generator, to say 80% SOC, and then let solar finish it off and maintain, then an mppt controller is not strictly necessary, as you are already in the high end of the mppt efficiency curve anyway. "mppt" controllers ALSO use pwm for voltage control, so it's not like you are missing anything.

My pick here would be the Morningstar TS-45 Tri-Star 45A pwm controller, provided you stick to bulk charging with the genny up to about 80% SOC. Also include the optional temperature probe to help do it right.

Note that unless you angle those panels towards the sun, you can count on about HALF of the rated current output when they are flat on top of the camper. In addition, you need to watch out for partial shading (overhead branches, wires, camper-top protrusions and the like) which will reduce it further, so perhaps 4 panels would be the better idea from the outset.

For general topping off and maintenance, this would work. Would it be the best? Perhaps not - there are variations like using high voltage grid-tie panels, along with a more expensive mppt controller, but again, you are already in the high end of the efficiency curve, and your cable runs are likely to be short from the camper top to the controller.

Anything other than this, such as deep discharge, many days of autonomy, long cable runs and the like deserve a second look at grid-tie panels, mppt controllers, etc.

[littleharbor]

I've done a number of solar installs on pop up campers. Usually you can locate the sleeve in the canvas where the wires that power the overhead lights run. This is a perfect way to run the wire from the panels to the controller. I would be careful when drilling through the roof , if you do, be careful for the wires that go to said overhead lights.

Also when stored keep in mind that your batteries may be micro cycling due to o2 sensors, etc. best to check electrolyte levels in your batteries when storing and maybe every couple months after. Nothing worse than opening up your batteries to find out you have exposed lead. This is usually found after your first trip out for the season and an abnormally performing battery bank. The damage has been done by that point and you can expect a reduced life for that set of batteries.

[booboo]

My goal is not to use the solar panels to charge the batteries when they get low. It is to keep them from getting low. Right now we usually run the generator everyday for a couple hours to top off the batteries. I am hoping the solar will keep me from having to run the generator every day or maybe at all.

[Mike90250]

Not going to do what you are asking, until you spend a lot of $ on panels
That 55A charger in the inverter, in 2 hours, will pump 1,430 watts into the batteries. 300w of roof mounted panels (flat mounted, parked in full sun) are only going to give you about 60% of their nameplate rating, so expect no more than 500w total, Over a 5 hour solar day in summer you could get 2,500w into the batteries,
3 panels, full sun, charge controller, combiner box and always parking in full sun.

[ewarnerusa]

I'm not sure why the previous poster says your plan won't work, it seems solid to me. We have less wattage and battery capacity than you're proposing (280 watts of 12V nominal panels mounted fixed and flat on the roof with a PWM controller), 2x6V Costco GC batteries (~200 Ah rating), furnace always set fairly warm so the fam doesn't get cold at night, and use an inverter to watch videos on the TV for the kids. I do make sure to park the TT in sun. We've never run low on batteries with this setup during long weekends, even camped in our favorite canyon which makes for late sunrises and early sunsets. I don't even bring the generator most of the time any more. Convert all your interior bulbs to LED to cut down on lighting loads.

While I have no experience with the flexible panels, I have read that they don't perform as well as regular rigid ones. Is there a reason you're focused on the flexible ones?

[booboo]

I am thinking flexible for mounting purposes. like this. 1348515.jpg

[ewarnerusa]

That does look pretty clean and slick.
Here's a thread with many different RV solar installations to get some other ideas for mounting. The key things are to avoid any shadows from antennas, air conditioners, or vent covers.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28427857/srt/pa/pging/1/page/1.cfm