Newbie here, worried about controllers and below freezing temps

System

I am brand new to the world of solar power and have the fortune of having acess to some used solar panels. I plan to use these in my bus conversion and my concern is to find a controller that will handle cold temps. Living in Michigan, my bus will get quite cold when not in use and most controllers seem to be rated only to 32F. Today it's 9F! I have not assembled this system and I am still constructing the coach.

Here is the equipment I have:
(2 for now) Seimans Model SM50-H panels
Max Power 50W
Max Syst. Open Ckt 600V
Current: Rated 3.15A, Open Ckt 19.8V, Rated 15.9V

A special note about these panels, is that they have broken glass (basically shattered) and I will need cover them with plexiglass or other reccomended idea. Point is, they are free to me on a first come first serve basis and I don't know how many I may end up with.

I have a Xantrex/Trace SW4024 inverter that to begin with will be fed from only 2 flooded 8D batteries. (the primary reason for the sizing of this inverter is to run 2 rooftop air conditoners while going down the road. The alternator will supply enough current through these batteries. I will expand the battery bank at a later date. For boondocking, I plan to use very little 110. Most equipment will be 12vdc fed from a Vanner equalizer and propane for heat.)

I also have a 7.5KW genset that will tie into the system.

I know I need to go with a 24V system, and I could end up putting out a good deal of amps depending on how many panels I end up with. What can everyone recomend? Thanks!

Glenn Williams

Solar Guppy

Re: Newbie here, worried about controllers and below freezing temps

You have a zero chance of these panels working for more than a few trips in the bus. With the glass shattered, there is nothing to protect the solar cells from cracking with ANY bump or flexing in your moble application.

As to running AC, your WAY off in what two little solar panels generate in energy compared to what the AC draws, by a factor or 5 to 10x. Panels best case might make 400 watts DAY, your AC pulls 1000 watts every hour as a guess.

Lastly, the Alternator will undercharge the two batterys and the batterys will not last long

System2

Re: Newbie here, worried about controllers and below freezing temps

Hello Solar Guppie,
I must have been unclear. The solar panels will not have anything to do with running the AC units. The air conditioning is only for going down the road or when plugged into a 110 source or running off of the genset. Running those off of battery/inverter is out of the question.

As for the generator (not an alternator in my case), it has an adustable regulator, usually set for 27.5V and can be increased some from there if necessary. This in an MCI 7 Bus and it probably can put out over 300A under load. It use to run two HUGE blower motors for heat and air conditioning.

Thank you for pointing out the problem of structural failure in the panels. I had some thought of cutting 1 inch foam insulation to act as a backer for these and I had not decided whether or not to mount them, or pull them out upon arrival at a destination.

I hope this helps make things clearer! Thanks!

Glenn Williams

crewzer

Re: Newbie here, worried about controllers and below freezing temps

most controllers seem to be rated only to 32F.

Really? Here are some other controllers to consider, along with their published low limit operating temperature specs:

Xantrex XW (MPPT): -20 C (- 4 F)
OutBack MX60 (MPPT): -40 C (-40 F)
Morningstar Prostar (PWM): -40 C (-40 F) controller; -30 C (-22 F) display
Morningstar Tristar (PWM): -40 C (-40 F)

HTH,
Jim / crewzer

rrbv

Re: Newbie here, worried about controllers and below freezing temps

I have personally tested in a temperature chamber the SB3024 MPP charge controller by Blue Sky and it performs well between -40 degrees and +70 degrees C. -40C=-40F.
rrbv