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sek avatar image
sek asked

Can I use MPPT output to charge/float battery?

Hi there,

I have a MPPT 75/15 in a boat charging a dedicated house battery and I would like to know if I can connect the output to keep the other 2 cranking batteries charged while boat is stored.

Thanks

MPPT SmartSolar
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1 Answer
kevgermany avatar image
kevgermany answered ·

If the batteries are all the same chemistry/voltage and your wiring is OK, yes. You might find the boat is already wired for this with a switch that connects start and house for boost when starter batteries are low.

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sek avatar image sek commented ·
Hi Kev,

Thanks for replying.

All batteries are light-deep cycles lead acid.

I have done the wiring for the solar and house batteries, I've got a two-way switch which is there only to isolate as I've added a combiner to allow charging of both batteries once the load is available.

there's an Anderson on the end of the load cable that I can connect to the batteries but I'm not sure what voltage to go for as usually they will be nearly full battery just needing topping up and floating....

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klim8skeptic avatar image klim8skeptic ♦ sek commented ·
@Sek There is a risk that when starting the engines, high current can flow from the house batteries to the start batteries.

A risk of blowing fuses in the mppt/wiring that is only rated to 20a.


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sek avatar image sek klim8skeptic ♦ commented ·

The charger would only be connected to cranking batteries while the boat is parked.

I'm unsure if I have to set the load output of the charger to a certain voltage similar to the floating phase.

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