Maybe this belongs in the Done something really stupid thread...except that I got away with the seemingly stupid behavior for a full year before it caught up with me. 
This happened on my current trip to the eastern Sierra (I'm still out there), after I got a hole punched in the side of my camper by a tree branch and after I got my tire sidewall sliced by a sharp rock. Yes, really -- all on the same trip!
A year ago, just before my 2012 October eastern Sierra trip I installed two 120-watt solar panels on the roof of my camper, hooked together in series, and because of the high voltage produced in series -- over 30 volts -- I needed/wanted to use an MPPT controller, and I already had one anyway, a Solar Converters Model PT 12/24 - 10TC, for my free-standing panel. The "10" in the model name means 10 amp output capacity. Well, these two panels each can produce 7 amps at 17 volts (under ideal conditions) and after the MPPT does it's magic the combined amperage could be as high as 20 amps (theoretically under ideal-for-MPPT conditions). So I bought a second MPPT controller like the one I already had, thinking that I could use them in parallel to handle the power.
But when I wired them that way I found that it didn't work.
So I decided to gamble on the fact that the solar panels will never put out their theoretical capacity since they're horizontal and I never camp on the equator at noon. And I figured that the "10 amp" capacity was a conservative rating and that it might handle a little over 10 amps without harm.
Well, it worked fine for the past year (as far as I could tell), even when the output amperage was 11 or 12 amps...until late this morning. It was very sunny and yet cold -- ideal conditions for solar panel power. I happened to look at the charge controller and the "charging" light was not lit AND the "full" light was not lit, and the "watts up" meter downstream showed that it was getting nothing from the controller -- it was dead. But the "corpse" was still warm -- in fact it was very hot...which I figure wasn't a good sign. I checked the connections and they seemed fine, and I stuck the leads of a voltmeter on the wires from the panels and it read about 40 volts (which is about what the "open circuit" voltage should be for the two panels in-series)...so there wasn't a problem upstream from the controller.
I figure that the high power being fed the controller today -- after probably other times like today -- was more than it could stand. R.I.P.
So I guess I'll order a new charge controller -- one rated for a least 20 amps, as I should have done when I put the 240-watt solar system together.
And I think I'll cut my trip short by a few days, start heading home. With 3 gear-incidents in one trip, I think the universe is trying to tell me something.
(even though, technically, all of the incidents were my own fault... )
This happened on my current trip to the eastern Sierra (I'm still out there), after I got a hole punched in the side of my camper by a tree branch and after I got my tire sidewall sliced by a sharp rock. Yes, really -- all on the same trip!
A year ago, just before my 2012 October eastern Sierra trip I installed two 120-watt solar panels on the roof of my camper, hooked together in series, and because of the high voltage produced in series -- over 30 volts -- I needed/wanted to use an MPPT controller, and I already had one anyway, a Solar Converters Model PT 12/24 - 10TC, for my free-standing panel. The "10" in the model name means 10 amp output capacity. Well, these two panels each can produce 7 amps at 17 volts (under ideal conditions) and after the MPPT does it's magic the combined amperage could be as high as 20 amps (theoretically under ideal-for-MPPT conditions). So I bought a second MPPT controller like the one I already had, thinking that I could use them in parallel to handle the power.
But when I wired them that way I found that it didn't work.
So I decided to gamble on the fact that the solar panels will never put out their theoretical capacity since they're horizontal and I never camp on the equator at noon. And I figured that the "10 amp" capacity was a conservative rating and that it might handle a little over 10 amps without harm.
Well, it worked fine for the past year (as far as I could tell), even when the output amperage was 11 or 12 amps...until late this morning. It was very sunny and yet cold -- ideal conditions for solar panel power. I happened to look at the charge controller and the "charging" light was not lit AND the "full" light was not lit, and the "watts up" meter downstream showed that it was getting nothing from the controller -- it was dead. But the "corpse" was still warm -- in fact it was very hot...which I figure wasn't a good sign. I checked the connections and they seemed fine, and I stuck the leads of a voltmeter on the wires from the panels and it read about 40 volts (which is about what the "open circuit" voltage should be for the two panels in-series)...so there wasn't a problem upstream from the controller.
I figure that the high power being fed the controller today -- after probably other times like today -- was more than it could stand. R.I.P.
So I guess I'll order a new charge controller -- one rated for a least 20 amps, as I should have done when I put the 240-watt solar system together.
And I think I'll cut my trip short by a few days, start heading home. With 3 gear-incidents in one trip, I think the universe is trying to tell me something.
(even though, technically, all of the incidents were my own fault...
)
