Winterizing off grid solar for summer cabin.

[littleharbor]

For your next set of batteries you might consider AGM . They have much lower self discharge rates. They can be left fully charged, and disconnected, for many months with little SOC loss, especially when cold. You could also hang a solar panel vertically connected to a small controller to "maintain" your batteries if you feel the need.

[citabria]

IS it possible for you to just haul the batteries back with you when you winterize the cabin? Set the batteries in a garage with a trickle charger for the winter?

[Basketcase]

What causes a battery to BBQ (from EQ) is that the controller forces a full BULK and ABSORB cycle. THEN it starts the EQ. EQ can only start after Absorb.. But the BBQ part comes along when the sun sets in the winter, and the EQ has not completed (from not enough sun hours in winter days) - So it tries all over again the next day. And the next. All the cycles bubble some electrolyte away daily and pretty soon you need to water the batteries, but you are not there, and so water level falls further and the the exposed plates dry and are ruined. Maybe there will be a couple sunny days and the EQ can finish., and start counting the next 30 day cycle.
So for winter, when you are not cycling the batteries, set absorb = Standby Float voltage and no EQ

That makes perfect sense. Thanks. That's pretty much what I figured.

[Basketcase]

For your next set of batteries you might consider AGM . They have much lower self discharge rates. They can be left fully charged, and disconnected, for many months with little SOC loss, especially when cold. You could also hang a solar panel vertically connected to a small controller to "maintain" your batteries if you feel the need.

What I read about AGM, actually steered me away from them. Higher price, lower life span. I thought the major advantage of AGM was higher charge rate in cases where you need to take advantage of a shorter harvest time? I'm just going off fuzzy memory of when I looked into this months ago. Am I confusing AGM with something else?

[Basketcase]

IS it possible for you to just haul the batteries back with you when you winterize the cabin? Set the batteries in a garage with a trickle charger for the winter?

Possible, but not practical. Its on an island in a bay in Rhode Island. No easy way to get them to mainland. Honestly, for the price of these batteries, I'll be happy with the 6 years I got on the old 12v ones. From the research I've done, I should get more. I wont cry if I dont, but I'd like to do what ever is reasonable for me to do that will extend their life.

[littleharbor]

What I read about AGM, actually steered me away from them. Higher price, lower life span. I thought the major advantage of AGM was higher charge rate in cases where you need to take advantage of a shorter harvest time? I'm just going off fuzzy memory of when I looked into this months ago. Am I confusing AGM with something else?

+Just a suggestion. AGM aren't for everybody and you need to weigh their benefits and drawbacks. I personally feel they are the right battery for my situation. As my off grid system has to sit unattended through three months of Summertime Baja heat. Your situation is different but still you may benefit from very low discharge, complete system shutdown and not having to maintain electrolyte levels.

[Basketcase]

Just to give an update, I opened the house this weekend and everything was perfect. Batteries were charged up and had lost very little water. Plates very much still covered. To fill all cells, I used maybe 1 cup of distilled water. (2, 6v batteries) . I set the charge controller back over to the regular setting for the summer. Thanks for the advice everyone. I think we have a system now.