Join Date: Apr 2006
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Re: Charge Controller Conundrum
I think you will find there can be even greater and less obvious differences between PWM and MPPT. Typically, PWM controllers will be traditional 3-stage chargers, especially the cheap ones.
In contrast, a BlueSky MPPT controller will look at the solar panels, then look at the battery, and it will apply the maximum amperage that it can, at a very slightly higher voltage than what the battery is at. Let's say that's maybe 0.3V over what the battery is actually at. (I forget the specifics, would have to go find old notes.) So you may find it is charging a discharged battery at "only" 12.2 volts, instead of the 13.8 that you expected. That's intentional. Once the battery comes up another tenth of a volt, the charging VOLTAGE will be increased as well. Until it finally does get to 12.8 volts, and the controller switches from bulk to acceptance and float modes.
Any of the good MPPT controllers will be way more sophisticated than an old-style 3 stage charger or cheap PWM controller. Each will mumble "proprietary algorithm" and decline to discuss a lot of details, but they ARE using microprocessors to optimize the charging process, way more so than a PWM controller.
It may not make any difference to one user, but to the next one, trying to recover from three days of overcast and cram in every amp you can in just a few hours...these things can add up.