Solar Panel Charging

[Plymouth Sailor]

Dear Sailors,

I have a solar panel connected directly to my #1 battery and have a #2 battery as well. I also have the typical red master battery switch which provides options 1, 2 and both. Question: if both batteries are linked together, does that mean that both batteries are being charged by the solar panel?

 

[BarryL]

YES.

If both batteries are connected then the solar panel will charge both batteries

 

[dlochner]

While the answer is yes, there is an important caveat.

When 2 batteries are placed in parallel, the battery with a higher SOC will discharge into the the less charged battery until the voltages in the batteries are equal. At that point the solar panel will supply current to both batteries at roughly the same level.

The problem with charging in the manner you describe is a dying battery will suck the life out of a healthy battery if the switch is left in the both position and charging stops due to nightfall or a big cloud.

Presumably, what you would like to happen is the current from the PV goes to the battery that needs it the most and less current goes to the battery that needs it the least, the more well charged battery. To make that happen the batteries need to be isolated from each other. One popular method is to use a Blue Sea ACR and do not leave the switch on Both.

 

[Mike Culik]

Get a "Dual" charge controller.
It will charge both batteries independently off of one panel.

 

[jviss]

The OP doesn't say if there's a solar controller involved. There should be!

 

[leo310]

What I use is a ARGOFET

from Victron for 2 battery banks (house/starter) with no problems.