mpmattman avatar image
mpmattman asked

12V Marine system help


I will do my best to keep this short:

I have a 26ft. Sailboat on the Ossiachersee in Austria.

Because of weight, I want to switch from Lead Acid to Lithium. Because Lithium is so expensive, I want to switch from PWM to Victron MPPT for max battery protection (and max batt/solar efficiency.)

Unfortunately, due to different solar panel sizes, I can't have the PVs in series (see diagram).

Is my diagram here correct, or do I need less or more components?

Any info is greatly appreciated!




MPPT Controllerscerbo gxMPPT SmartSolardc system
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1 Answer
dazey77 avatar image
dazey77 answered ·

As your mixing panel sizes, I think you want a MPPT for the 100w panels and one for the 50s.

17v solar is low for the MPPT too. I would work on having everything in series.

You indicate a BMV712 but not its shunt!

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mpmattman avatar image mpmattman commented ·

Thanks for the info dazey77! I am a noob when it comes to MPPT. So if I were to use 2 MPPTs, I would just connect each one directly to the battery via a smart shunt rather than a battery protect?

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dazey77 avatar image dazey77 mpmattman commented ·

Yes, logically you connect both MPPT to the battery (in parallel)

The shunt is required if your using the BMV712, it sits between the -ve connection of the battery and the ground point. It monitors all the current going in and out of the battery so that you know the approx battery level. The system logical earth point becomes the shunt connection going to the earth point and NOT the battery terminial.

The battery protect is as you indicate, between the battery +ve and the loads that you want to shed once the battery level gets too low.

You obviously need to add fuses into your drawing.

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