Solar learning

[ProGeek]

I've picked up a few bits of info about solar in the past week that I'd like to pass on. If there are experts, please correct me, because I'm not one.

It's bad to mix panels of different wattage.  The lower power panel will drag down the higher power panel when wired in series.

Don't mix panels when using a MPPT charge controller. The controller tries to optimize the panels and won't work right with panels that are not the same wattage or age. Panels degrade over time, so the old panels will drag down the newer ones.

A 12V panel rated at 100W is roughly equal to a 200W 24V panel in as far as power. The 24V panel is not twice as powerful.

The summer heat has a significant effect on power generation. Just as an example, a 260 watt panel when it is 95F and the panel is 131F in direct sun, it outputs around 39 watts less or 221 watts.

[RWS]

A 12V panel rated at 100W is roughly equal to a 200W 24V panel in as far as power. The 24V panel is not twice as powerful.
---------------------------------------------------------------------------------------------------------------------------------
So we have a 12 VDC panel that yeilds 8.333 Amp    Power = E x I  so 12 X 8.333 is 99.996 Watts.  That I agree with.
Now we have a 24VDC panel that yeilds the same 8.333 Amps.  P=ExI   24 x 8.333 = 199.992.  So as far as power goes the 24V panel is aprox twice as powerful as the 12V panel.  Indeed they are marked 100W which is power and 200W which is power.  Since this thread is titled solar learning.  Each solar panel or series string of solar panels must have a fuse.  10Amp is almost too small as the 80% rule comes into play for the continuous load current.
RWS

[ProGeek]

Thanks my math is off. Maybe you could help with my math. Assuming 2 of the below panels wired in series, 30A MPPT controller, four 12V deep cycle 120 AmpHr batteries, and 4.5 hours of sun per day. How much can I run a 8.5A 115V pump per day and not discharge my batteries? My figures say the panels will generate 2295W and the pump uses 990W per hour. So accounting for all the loss in the system, I can run it for 1.5 hours per day, but not continuously. Is that correct?

Pmax       255W
imp        8.5A
vmp         30V
Short Isc   9.09A
Short Voc   37.4

[RWS]

You will be lucky to get 2 hours run time intermittently.

[ProGeek]

I figured max 90 minutes of run time in 30 minute intervals, when we have good sun. Maybe 60 minutes on partly cloudy days.