Solar-Panel to Controller Loss

BFL13 wrote:
Much has been made of the lower losses on the panel to controller path with MPPT because the amps are less.

Hmmmm .... as stated ... I wonder if that's the case. In other words, what has a PWM or MPPT controller got to do with any difference in loss of power between the paths used to feed the two controller types? Do PWM controllers run that much hotter than MPPT controllers?

However, could it be that "most" RV PWM solar setups use ~12 volt panels, while "most" RV MPPT solar setups use ~24V, or ~36V, or ~48V panels. If so, then it's the higher voltage starting at the panel (when using an MPPT controller) versus the lower voltage starting at the panel (when using a PWM controller) that is causing the lower line path losses (though slightly more heating of the wires in the path between the panel and the controller).

Remember the basics - to keep path losses low, use high voltages at the beginning of the path and/or keep the path as fat as possible - ideally, do both. Paying attention to both issues will keep current flow from dissipating energy through heating within the path wires.

By the way, to measure losses in the line you don't need a long wire to your voltmeter. Just use the voltmeter (as is comes, stock) on a low range setting and measure panel output voltage at the panel and then measure controller input voltage at the controller. Use a pencil and paper to subtract the two readings. The difference is of course the voltage "drop" in the path between the panel and the controller. This voltage drop - percentage wise - will be less if the current in the path is less or if the resistance in the path is less. Increasing the panel output voltage to 24V, or 36V, or 48V will decrease this voltage drop - percentage wise - for any size wires you might use.