MPPT solar charge controller recommendation?

rjxj wrote:
This is from Bogart Engineering:

As you know, the Bogart Engineering SC-2030 Solar charger uses PWM technology, not MPPT.

The "good" for PWM:
It is simpler and lower cost technology.

Under some circumstances--it can actually deliver more amps to the battery. That would be when:
[...]
PWM is actually more "power efficient" than MPPT--which means less total power loss in the controller itself. So heat sinks in the design can be smaller (and less expensive). Missing in most analysis of MPPT is that there is always a conversion loss with MPPT, which tends to be higher the greater the voltage difference between battery and panels. That's why PWM can actually beat MPPT under circumstances described above.

[...]
The only REALLY BAD part of MPPT, is all the hype surrounding it--for example one manufacturer advertises "UP TO 30% OR MORE" power harvested from you panels. If you are using solar panels properly matched to the batteries, 30% ain't gonna happen unless it's EXTREMELY cold. And your batteries have to be abnormally low in charging voltage--which tends not to happen when it's cold (unless you assume the battery is still discharging while solar is happening). Virtually all the analyses I've seen touting MPPT on the Internet ignore the conversion loss, assume really cold temperatures, assume unreasonably low charging voltages, assume no voltage drop in the wires from panels to batteries, and in some cases assume panels not voltage matched to the batteries, and use STC conditions for the panels (that the marketing types prefer) rather than more realistic NOCT conditions.

The other thing that is misleading about MPPT, is that some manufacturers make meters that show both the solar current and the battery current. In almost all cases the battery current will be greater. The engineers making these know better, but it is implied (by marketing types?) that if you were NOT using MPPT you would be charging your batteries with only the SOLAR current that you read on their meters. That's not true, because the PWM BATTERY current should always be higher than the MPPT SOLAR current. It is the nature of the MPPT that maximum power occurs when the current is lower than the maximum, so they must operate there to get the maximum power. So to properly compare the two you need to compare MPPT with an actual PWM controller in the same circumstances.

Finally, the reason we went to PWM is that I was anticipating that panel prices were going to drop (which they certainly have over the last 5-10 years!) and that the small advantage of MPPT (under conditions where the correct panels are used for the batteries) would not justify their additional cost and complexity. So my thinking, for more total benefit per $, put your money in an extra panel rather than a more expensive and complex technology.

It's unsurprising that a purveyor of PWM controllers extolls their supposed superiority.

If you're interested in an impartial, quantitative analysis, check out this easy to read article:

Victron Energy: Which solar charge controller?

PWM advocates conveniently ignore many of the advantages of an MPPT system beyond the controller itself: the ability to run panels in serial for higher voltage from the PV array (extremely helpful in hot environments) and subsequently lower line losses, better performance in shaded conditions, etc.