New Bimini Solar Project

[PhilDuhs]

When you have multiple controllers - eg. if I went down the individual SS-MPPT-15L controller per panel route - do you get any conflicts as each controller goes through its "bulk, absorption, float" cycles? How do all the controllers sync their cycle times/voltages or does this not matter?

[LeaseOnLife]

I guess these worries are depending on how sensitive you think your batteries are. With gels I would worry, flooded cells not so much.

Going from bulk to absorption is only voltage dependent, all parallel controllers will see the same battery voltage and will reduce current to avoid exceeding the setpoint. I have not seen any hunting/fighting between the controllers.

Going to float is a funtion of time, if you really have 3h in absorbtion with your 840Ah bank, they all 'should' go into float. One controller may keep the absorbtion phase longer than the others but will also finally switch to float voltage.

You could set 3 out of 4 controllers to a lower voltage setting and only have one set to the max for your battery type. But I call this overthinking it.

Dirk

[ChuckSK]

If the battery can accept the output from all the controllers, each controller does the best it can. If the battery cannot accept the total output, then it does not matter if the controllers are synched. If the battery is fully charged, then the last controller to go into float will determine battery voltage.

[PhilDuhs]

Thanks to everyone for the input and advice. I've updated my design (see attached) to make it much simpler and used a separate, lower spec charge controller per panel (Morningstar SS-MPPT-15).

Just one more question: when calculating the wire sizes (using an online calculator) should I double the run length to allow for both + and - cables or just use the actual distance the cables will run?

Should be ordering the solar panels this week - then it's just the small matter of getting them to the boat in Northern Cyprus!

Phil