Battery bank question

[Jon Elliott]

I use my new AGM battery exclusively for the windlass and starting.

Great information and thank you. My alerts didn’t notify me of any replies so I’m a bit late responding. My boat will be on shore power which begs another question. Do I allow the shore power charger to charge the batteries and shut the solar panel charger down or let both chargers run? I am by the way going with deep cycle AGMs. Thank you again for the response.

To fully understand your system, please explain. It appears that you have just 2 batteries. What kind of selector switch do you have? I'd assume that you have the ubiquitous 1+2+B switch. If that is the case, do you switch between 1 & 2 for starting and house bank use respectively? This kind of operation makes no sense since the output for starting and house bank is on a common output post. To get the most efficient use of your batteries, you are better off cabling them in parallel to double the capacity for house loads and don't bother with a separate start battery - your engine will start just fine on the house bank. The best thing you can do is double your house bank capacity and if you need an auxiliary, get a 3rd battery and just consider it auxiliary (not start).

If you really want a dedicated start battery, then we're talking a whole nuther system that actually makes some sense if you want to go that route.

Yes, I have the 1/2 both or off selector. I’m thinking of adding a battery disconnect to the solar charger while on shore power. I had been starting the engine on 1 since I got the boat a year ago but recently (as they began to weaken) switched to starting on both. While sailing though, I tend to isolate them just in case

 

[Scott T-Bird]

It's really difficult to provide any rational answers when we don't how you use your boat. Do you just go out for day sails or do you anchor overnight for a day or 2? It sounds like you are on shore power ... how do you charge your batteries? Do you have a charger? What is it? Do you rely on your alternator? What alternator do you have? How much do you motor? Do you just motor out for a short distance before sailing?

You have 2 batteries ... how are they used? You used to start just with Batt 1 or was Batt 1 used for all purposes? If you have been chronically undercharging, it is probably near end of life. What do you do with Batt 2? Do you ever use it for anything or is it just a spare? How old are your batteries? It looks like Sept. 2015 is the date of purchase, correct? Is Batt 1 weakening while Batt 2 is still going strong? What is your typical routine with the selector switch? Using just a single Grp 27 battery for normal use seems like a very small capacity to me for a cruising sailboat ... but we don't know how you use your battery banks. What are your basic needs?

Finally, why do you want solar charging?