Actually, I would recommend that two 12 volt panels be put in series, rather than parallel for a 12 volt bank.
The Midnite engineers have found that in some systems with 12 volt panels and 12 volt battery, a switch from a PWM to a Midnite MPPT controller has caused decreased or inadequate charging. This only occurs when the panels are hot, and with batteries that need (relatively) high absorb voltages.
It occurs because the MPPT controllers need a volt or two more headroom than the PWM controllers, and there may not be enough headroom between Vinput and Voutput when the panels are hot. If the controller is going to sweep and find the max power point, it needs a few volts to sweep through.
That all said, I tend to agree with you on over all system design... I was just being picky about your use of the word "optimal".
--mapmaker
The Midnite engineers have found that in some systems with 12 volt panels and 12 volt battery, a switch from a PWM to a Midnite MPPT controller has caused decreased or inadequate charging. This only occurs when the panels are hot, and with batteries that need (relatively) high absorb voltages.
It occurs because the MPPT controllers need a volt or two more headroom than the PWM controllers, and there may not be enough headroom between Vinput and Voutput when the panels are hot. If the controller is going to sweep and find the max power point, it needs a few volts to sweep through.
That all said, I tend to agree with you on over all system design... I was just being picky about your use of the word "optimal".
--mapmaker
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