Input on Solar Charging/Maint sytem

[JonCBrand]

So I have 3 deep cycle batteries in my boat, setup where 2 run all accessories and 1 for engine only, when running there is a solenoid to connect all 3 batts to allow charging. I have an extensive amount of lighting on the boat for night runs, with all lights on the total draw is near 80a. I know the stock charging system wont be able to keep up. I have no access to shore power at my slip so I want to set up a solar system to bring the batts back up when at the dock.

My plan is to have 3-4 20+ watt panels permanently mounted to the boat, then use a charge controller to manage the charging.

My question is I have heard that having the panels connected to the batts while the engine is running will damage the panels by "backfeeding" current.

Any thoughts on this or experience??

[rancherlee]

A charge controller should have, key words, a blocking diode to protect the panels from backfeeding damage. I know my 5 watt panel warns about disconnecting the panel before starting the engine but seeing as the panel can put out over 16v with no load I don't see how the 14.6v my outboard puts out can damage it. I've left mine connected for the past year and it still works just fine. How offen do you use the boat? A single 20 watt panel should charge a pair of batteries in a week. 4 panels in bright sun shine should cranks out a healthy 5-6amp for 8h a day.

[JonCBrand]

Im on the boat every other day, but would only be using the high current lights at night which is maybe 3 times a month.

Maybe Ill start with 2 panels and the controller and see how it does.

[killerkernrich]

I use a small yammie gen set 2000 watt to charge up my 3 batts.