Do pv chargers work well in cloudy weather? Here in Michigan we usually get dull, overcast days in January. I'm planning on buying a charger that can run off my generator (Costco has a 10 A unit for $29) but that may not be enough. I'm planning on running about six amps out of a storage battery, say six hours each night). Could a pv source provide 36 amp-hours over the course of a gloomy day?

Any recommendations on specific units, preferably ones that are distributed nationally?

-- Gary S. (garys_2k@yahoo.com), December 15, 1999

Answers

Gary, Call Don Sheets in DeWitt, just outside of Lansing. He builds and sells very reasonably-priced systems of all sizes, from flashlight battery chargers to whole-house systems. (I'm not affiliated in any way.) His number is (517) 372-0347. He has some systems which are specifically made for cloudier areas.

-- Ann M. (hismckids@aol.com), December 16, 1999.

36ah on a gloomy day? Yes, but the array would be huge and pricey.

Here at "Camp Chaos" I'll routinely use about that much power (more during CD production crunches). My system includes PV panels, an AIR403 Windplant and a 12vdc generator (Honda 5hp engine driving an automotive alternator). You should be thinking "hybrid" system here with multiple charging sources. If you try to size the PV array to fill your year round energy needs it will be way too costly. Many folks with PVs use gennys to cover their energy needs when the sun doesn't shine. Being off-grid I'm very conscious of my energy "flows". On a partly cloudy day I may run the gas genny for 20-30 minutes in the morning to get my batts to 85-90% full and hope the sun is enough to top them up fully. I do this for efficency as the "topping" charge should not be at a rate exceeding C/10 (Batt. ah capacity divided by 10) and it's not energy efficient to run the gas genny at those low charge rates.

There's a PDF of one of our most popular articles in the download section of our website called MARK8.PDF that details engine-alternator systems (and homebrewing one).

http://www.homepower.com Home Power Magazine

-- Don Kulha (dkulha@vom.com), December 16, 1999.