patrick-le-floch avatar image
patrick-le-floch asked

Help please, questions about conflicts between mppt, ac dc charger and alternator engine...


In my boat, I just installed a mppt 75/15 with solar panel 300W (I know the mppt is a little fair but the dealer did not report it but at the same time, I live in Brittany France and as my panels are horizontal, it should do it anyway) on my existing installation (3 batteries 100 AH) which has a 25A charger already a power 25A and a alternator 30 A (connected to a dispatcher argofet 100A).

The other day, I plugged in my dock charger and it had a very bizard behavior. He kept starting and stopping. 5 seconds of operation then 20 seconds of stops and so on ... I have the impression that there is a conflict between the mppt and the dock charger and I am afraid that the charger will eventually be out of use quickly.

I also noticed that the mppt was making a sharp noise. Is this normal?

I also wonder how to do it when I'm going to have to use my engine alternator when the mppt will not be enough to charge my batteries. Let me explain. As the mppt charges at 14.4V and my alternator charges at 14.1V. If I put the 2 to operate simultaneously, is there not a risk that the 'indicator' 14.4V alternator at the battery terminals considers that the batteries are charged and that it does not need to to deliver amperes to the batteries? Should I temporarily cut through the application the load of the mppt when I want to use the alternator or all this little world will complement each other intelligently? If everything works well together, is not there a risk of potential overload? (30 A by the alternator and 15A by the mppt).

You can see, I ask myself a lot of questions :) but as I intend to go on long sailing I prefer to be clear and have no problem to solve at sea. Thank you very much for the help you can give me!

MPPT Controllers
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1 Answer
Paul B avatar image
Paul B answered ·

no you need not worry.

which ever unit has the higher voltage this is the one that will continue to charge.

ie if the batteries are full and say are at 14.2 then the solar will keep charging but the alternator would reduce its charge automatically.

in regards to your shore power charger, this issue would have nothing to do with the solar system,

and it could be that the batteries are full at 14.4 and the shore power charger is set at 14v so its turning off, it does sound strange but you would need to discuss this with your charger supplier

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