Rather than start a new thread I thought I'd add to this one. I've had a Can Tire 100W (8A I recall) solar panel sitting around for a year or so, so finally picked up a cheap $20 30A chinese PWM controller. Although Glenn laid out some good points on PWM vs MPPT, for my use PWM makes more sense and it will also be used in the PWM sweet spot of under 170W. Glenn is correct that MPPT will get a net gain of tens of percent, but that's over the course of a longer period of variable light under cooler temperatures. However for low-light hot weather harvesting, my panel was still putting out 16 volts almost an hour after sundown in the shade (which is a benefit of monocrystalline cells) and thus my el-cheapo PWM was still charging it just fine.
The biggest kicker of all of this is that for my casual use I can buy 10 of these controllers for the price of a decent MPPT controller in case one dies.
I tested this on our big RV (not my offroad trailer), so I wasn't running a fridge, but for 3 days we were using a 4.4A water pump for toilet for 4 people, plus doing dishes 3x / day, misc washing of hands, cooking etc, plus a few incandescent trailer lights inside. The 12V deep cycle was almost full the entire weekend.
Next test will be to see how well it performs keeping my ARB fridge running in George Bailey.
The biggest kicker of all of this is that for my casual use I can buy 10 of these controllers for the price of a decent MPPT controller in case one dies.
I tested this on our big RV (not my offroad trailer), so I wasn't running a fridge, but for 3 days we were using a 4.4A water pump for toilet for 4 people, plus doing dishes 3x / day, misc washing of hands, cooking etc, plus a few incandescent trailer lights inside. The 12V deep cycle was almost full the entire weekend.
Next test will be to see how well it performs keeping my ARB fridge running in George Bailey.
