Does Victron MPPT (say 150|70) require more solar output in order to “wake up” for 24V output vs 12V output? I have 840Wp panels so will I get the same Wh per day if I change other system (battery, inverter) from 12V to 24V?
So long as the PV input voltage is 7 volts or thereabout higher than the voltage you seek to charge then yes, you’ll get the same power output. If you go from a 12V to 24V battery bank, you can actually reduce the size of the MPPT since it is rated by output current. If you double the voltage, you halve the current, and hence can use a smaller MPPT. Or, for a given MPPT you can effectively double the amount of power the MPPT can handle.
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Hi The start voltage for an MPPT is PV voltage = battery voltage plus 5V. Thereafter it can charge down to the PV being only 1V above the battery voltage. It works better though if your PV voltage is at least double the battery voltage.
With 840W you would need a 70A MPPT, with 24V only 35A which would be cheaper. It should also be no trouble arranging your string(s) to give 100 - 150V open circuit voltage.
This means less loss in the PV cables. Also, the start voltage is achieved slightly earlier in the morning, so slightly more charge is generated.
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Thank you for the answers. I would be interested in a calculator (or estimate), how much solar energy I will lose when start PV voltage rises with 24V system. Panel Voc is 37.4 and they are in series so 74.8 total. If it’s <0.5Wh per day it doesnt matter. I’m getting now max 5Wh per day because of some shade.
You probably mean kWh.
My guess for your los…not worth thinking about.
Yes, kWh 