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Old 12-13-15, 01:07 AM   #1
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Default High or low voltage for MPPT

Hi all I have a question about MPPT charge controller. I recently put together a off grid solar system with battery bank. Just in case the power goes out. The Charge Controller is:
Renogy Tracer 4210 40 Amp MPPT Charge Controller, 12/24V 100VDC Input
I currently have 3 150watt panels wired parallel with 18-19 volts coming into six golf cart batteries, wired for 12volts. Would I be better off wiring the solar panels in series for the higher voltage?

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Old 12-14-15, 11:19 AM   #2
oil pan 4
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In the manual there should be a efficiency chart showing PV voltage to battery efficiency.

Since this is a real high end MPPT I would not expect there to much drop in efficiency in "12 volt" configured panels versus "24 volt" panels when charging a 12 volt battery with this charger.

Typically the higher the difference in PV to battery voltage means less efficiency.
Doing this with PWM, efficiency falls off a cliff the higher you go with PV voltage.
With MPPT we might be talking a few % in the difference between 12 vs. 24 volts then a few more % as you go to say "48 volt panel" (actually over 80v at open current) configuration.
But what you want is over all system efficiency.

If you are like me and get lots of sun and have the panels very close to the charge controller just leave them configured for 12v.
But if you have longer runs between the panel to the charger controller, doubling the voltage cuts wire power drop in half. If you have lots of over cast then stacking the panels for higher voltage might be the way to go so that you get at least some charging accomplished.
I also have a collection of different 12 volt panels so I leave everything 12 volt.

I can say that leaving the panels configured for "12 volts" makes my MPPT charge controller run very efficiently. I have caught my genasun MPPT running at 97.5% efficiency and its only rated for 97%.

Put up some pics of your rig. We like the doomsday solar backups.
This is mine:
With mine mobility, portability and flexibility are key.

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