Solar design help please

[Majja13]

Ok this spring I want to assemble my solar for my TT. I figure I do not need huge amounts but do want a little buffer. TO make it a little easier I am figuring about 200 W (so 2X 100 W panels)

A system kind of like this one 200 W system

How ever I think I want to use a MPPT controller instead of a PWM controller. Can anyone give me some advice on the charge controllers and opinions on why you like that one. I would like to be able to just add a panel or two down the road if I ever have to. Also I am not mounting this to my TT but rather make it kind of like a portable unit as there are places we go that the roof does not get much sun form the trees.

As of now my entire TT is on LED's and I have no inverters. I am looking at putting in a 12V TV/DVD combo. But that is down the road. So All i need is the ability to top up after using lights and when I go late in the year to top up after having to run the heater quiet a bit.

Thank you
Matt

[westend]

Majja13 wrote:
Will i need to add a cutoff switch for when I am on Shore power to protect the Charge controller?

No, the charge controller and converter will play along nice with each other. Sometimes, depending on variables, the device that delivers the most power will do most of the heavy lifting and the other charger will sulk along in a corner, taking a time-out. Sometimes, both chargers will be additive delivering more charge than either single device.

I'd suggest to use a manual circuit breaker between the solar panels and the charger. It is a handy way to turn off the solar charge if you wish to do some work on the system. I use this CB manual breaker. I think I've interrupted power just a couple of times to do some battery upgrades.

[Majja13]

Will i need to add a cutoff switch for when I am on Shore power to protect the Charge controller?

[Golden_HVAC]

For the cost of laptops these days (in the $300 range) you might consider a 15" laptop and charge that with a small 100 - 200 watt inverter that plugs into a cigarette lighter receptacle. You can play a DVD on the laptop.

Your RV will use about 35 AH daily to run just the CO meter, propane detector and refrigerator. Lights and everything else is on top of that.

100 watts will make between 28 and 35 AH daily, depending on conditions, and full sun. You will not have very much reserve. But you do not require the battery to be full daily, just not as low as the day before. It will recharge the day after you stop camping. . .

If I had $200 to spend, I would rather buy a $13 PWM controller and a 100 watt panel, than to spend it on a MPPT controller, and no solar panel expansion kit.

The link above is a wonderful price on panels. You might want to check this link too, compare shipping costs, ect.

SunElec.com

SolarOnSale.com

Good luck,

Fred.

[scrubjaysnest]

The break even point for MPPT is 400 watts of solar. Rule of thumb: 100 watts of solar per 100aH of battery and that will probably be low. Do an energy audit even though it's a pita. There is a spread sheet here on the forums; it will get you closer but still tends to be a little low.
As for the amps out of the panels a typical 100 watt panel will be 5 to 5 1/5 amps under ideal sun at 77 deg. Panel ratings Vmp times Imp @ 77 deg = wattage.

[KD4UPL]

Morningstar and Blue Sky would be my picks for a small MPPT controller. However, with 200 watts you've already got a potential for nearly 20 amps. Depending on how much you want to add a 60 amp controller might not be a bad idea. The Outback FM60 or Conext XWMPPT60-150 would be great choices. MidNite solar makes some nice ones too but I don't have any personal experience installing any of theirs. We always go with Outback or Conext since they also make inverters. I like to have all the equipment in an off grid system match so it can communicate on the same control bus.

[westend]

I use a single 235W panel and a Morningstar MPPT-15 controller. The controller puts me at just about the maximum for that module. If you are just going to use the two modules on an intermittent basis, there are less expensive PMW controllers that will work just as well. The nice thing about the Morningstar controller is that it is fully programmable through the software interface and has temp compensation functionality. I would look for those two features no matter which type or brand of controller chosen.

Tip: before you embark on a portable system, I'd suggest to take a module in hand and try positioning it. They are not that heavy but are larger in dimension than some anticipate. I wouldn't want to schlep one in and out of my trailer, let alone two. It may behoove you to mount one and then have a good connection system to a portable. That will give you some more option and functionality. When you are driving, at least a single module will be charging. The same would be true for storage.