Basic Solar Charging Questions?

[PaulRainbow]

The MPP (maximum power point) is a property of the solar panel. It will vary with the luminance, temperature etc, but it has nothing to do with the battery voltage. Tracking this voltage (the T in MPPT) is just modifying the input voltage so the solar panel maintains the MPP. Once again this has nothing to do with the battery voltage. The controller does not have to decide which battery voltage to use, because the battery voltage does not alter the solar panels MPP.

A dual output MPPT controller could be manufactured, but it would be complex because the voltage conversion and voltage monitoring would need to be doubled. The controller (ideally) needs to alter both output voltages based on the needs of each battery. This would make the unit expensive and increase the self consumption, reducing efficiency .

Nonsense. I can't be bothered to re-invent the wheel, so i suggest you and LW have a read up on how MPPT controllers work.

It is unlikely it would be a commercial success as a simpler VSR would be a better solution for most installations.

I already said that several times, starting way back in post #8

 

[noelex]

This is a simple example. The photo shows a particular solar panel’s I/V curve under STC conditions.

You can see the MPP in this case occurs at a solar panel voltage of about 33v. There is no mention of battery voltage because this does not effect the MPP.

If the brightness and/or temperature changes, the graph will alter and there will be a new MPP and this will occur at a different voltage.

An MPPT controller will adjust (or track) its input voltage so it always matches the voltage where the solar panel produces the most power. The input voltage for this circumstance would be 33v.

The controller will also adjust the output voltage so the battery is correctly charged. For a true dual battery controller the output voltage would be different for the two batteries, but no matter how many batteries you connect to the controller or even if there is no battery at all, the ideal input voltage (or the voltage where the MPP of the solar occurs) will not change unless the conditions (brightness temperature) alter.

The battery voltage does not effect the MPP voltage of the panel.