The recently built telescope garage has no power running to it. This is a minor concern because the Corvette will spend the winter in there, and I would like to use the Deltran battery minder that I bought last winter. Also, I would like to recharge the telescope mount power cell, and leave it there, near the telescopes.
However, I do have a 35 watt output (under ideal conditions, of course, so I don't really believe it) solar panel that I bought at Harbor Freight some years ago for some experiments. (Unfortunate discovery: there is really no money available to fund startup work on ways to improve output of photovoltaics.)
With addition of an alligator clip to cigarette lighter plug converters from Radio Shack, I was able to recharge the telescope mount power cell, although I will have to remember to disconnect it when it is fully charged, for risk of overcharging the battery. However, when I tried to use the same approach to feed the battery minder, no luck. I used an inverter originally bought for recharging a video camera while driving to feed the battery minder--and the battery minder would not come on.
I verified that the inverter (originally bought for a 2001 vacation to the East Coast) still works; I was able to take output from the solar panel, run it through the alligator clip to cigarette lighter plug, and then plug a 110 VAC input cell phone charger into the inverter--and it recharged the cell phone.
My guess is that the battery minder has a certain minimum amperage input before it starts working, and the inverter just isn't getting enough wattage from the solar panel to provide that minimum amperage. Any guesses as to how to figure out what that level might be? The temptation is strong to buy another solar panel (or a larger one) to put in the window of the telescope garage so that it can operate the battery minder to keep the Corvette properly charged in winter, and the telescope mount power cell the other three seasons.
I have a vague recollection that if you want to combine multiple photovoltaic panels together, the lowest voltage output panel determines the net output. (Or is it the lowest amperage output panel?) At a minimum, it suggests that if I were to get another PV panel to pair with this, I might as well get another one of comparable voltage and amperage.
UPDATE: Thanks for the suggestions. I just ordered the Deltran Battery Tender Solar Charge Controller from Amazon. It was $21.95 plus shipping--an absolute bargain. It looks like I can use it in the non-snow seasons to keep the telescope mount power cell topped off.