Solar Controllers--Don't be a Sucker! :(

BFL13 wrote:
... but can you confirm that is while pointed or close to, so that it would not go higher based on angles?

I can't tilt my panels and have never made an attempt to measure or improve my solar harvest by "aiming' them... so. no I cannot confirm that.
If convenient, when parking my rig I might try to point south-ish.

...get more AH per day using MPPT than with PWM, even with same max amps at mid-day. How can that be? The sun makes the same curve across the sky so the same angles at the same times either side of high noon.
The hours are the same and the amps the same, so how can you have more AH??

The answer to this question is embodied in the definition of Power which you probably learned back in Electronics 101. Here's a simple description (without taking into consideration battery SOC or efficiency losses);
- Power (W) equals Volts (V) times Amps (A) **
- Solar panels make their most power (W) at a specific voltage (V) and current (A). Manufacturers call this the "Maximum Power Point". In the case of my Grape panels the value is 17.7V and 5.70A, that's the Vmpp and Ampp respectively... So 17.7 x 5.70 = 100.89W
- If a PWM controller is used, then the solar panel's voltage is forced to match the battery voltage (example 13.6V). Again, using my Grape panel as an example... 13.6V x 5.7A = 77.52W. That's a (theoretical) sacrifice of 23 Watts of available power.
- However the DC-DC converter in an MPPT controller allows the solar panel to remain at it's Vmpp while charging the battery at whatever the programmed charge voltage is, and up to the maximum power (W) available or (depending on SOC) what the battery will accept.
- In perfect conditions (cold panels, mid-day sun, low battery SOC, zero efficiency losses) one of my Grape panels could theoretically charge my battery at 13.6V and 7.3A (= 100W). Note that this charge current is 1.6A higher than the current at the panel. Voiá, there's the benefit of MPPT (more Amps)!

Of course that I don't camp in a laboratory, and have never experienced these perfect conditions. However as I said before I do have my panels wired in series (Vmpp~35.4V) which I could not do with my old PWM controller. As a result, I can start charging as soon as the panel voltage exceeds the battery voltage (shortly after sunrise) and continue charging late into the day (more time).

Now, of course, there are losses and inefficiencies and dollars (lots of dollars!). You could make a spreadsheet a mile long trying to calculate where the break even point is... or you could just go camping ;)

I hope this is helpful,
-Mark

** Yes, I know that current should be expressed as"I" and power as "VI". But I am simplifying, so please forgive my breaking with convention.