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diy solar

Second MPPT?

SkipperJer

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Joined
Jul 3, 2022
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Just finished installing solar on our boat. Can I add a second MPPT controller to charge the start lead acid battery? The input to the second MPPT would be the same as the first MPPT. That is the MPPT controllers would share the panels output.
 
That is the MPPT controllers would share the panels output.
No each MPPT must have its own array. They would compete with each other as they try to find optimum voltage / amperage ratio.

How about a trickle charger from main solar charged bank to starter battery?
 
No each MPPT must have its own array. They would compete with each other as they try to find optimum voltage / amperage ratio.

How about a trickle charger from main solar charged bank to starter battery?
Are you suggesting that the second MPPT input be connected to the solar charged bank? The solar charged bank (house battery ) is lithium and fully charge is around 13.4 volts. The start battery is 12 volts. Don't know if that is enough voltage difference for a MPPT to work. Maybe a simple diode and current limiting resistor between the house bank and the start battery would work.
 
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Something like this Dc to Dc charger could be tied to the first setup as an input, and the output would charge the starter battery:


The one I looked at cold bring the charge current as low as 4 amps.

DC to DC chargers or converters are the only practical method I’ve found to charge a second battery off the same panels.
 
I've used one of these for about 13 years now. Works great. I have not seen it since 2010 as its under the Sprinter passenger seat pedestal. Completely carefree.

 
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