The Problem

This winter, my deep cycle batteries froze when the heating system failed. You can see the bulged sides in the photo. A straight edge across the worst battery has a 1/4" gap on either side across the 6" side- they have curved sides now. I have 16 batteries, each is a deep cycle battery, Rolls Surette S460, cabled in four groups of four batteries per group for a 24 volt system. The batteries cannot be fully charged, so it is expensive to have the generator charge them. It is like paying for a full tank of gas, but only getting half the milage out of that fillup.

So I have tried to restore the charge by taking the eight worst to town, and putting then in pairs of 2 on an iota charger to equalize them. I've tried cleaning them out, putting in new battery acid, and equalizing them. One out of four improved with cleaning. The specific gravity readings on each cell were taken over several days. The four best batteries were returned, and have been running the house over the summer. Now I have to figure out what to do. Which batteries do I use? How should they be cabled together? Can I do more to bring any battery back to full charge?

I need to calculate my electrical demand. The heating system is the hardest to figure. One box says it has 40 amps on startup. That can't be true! I hope. I'll see if the library can lend me their watt measuring gizmo. Electrical demand in the summer is almost nothing, as the heating system is not on, the mechanical ventilation system is off, and lights are used very little. I have been practicing not using the electric fridge. Milk needs refrigeration unless it is added to viili, like yogurt. Need the fridge, but with the house running on 4 batteries, it is off now. With winter coming, either the heating system gets turned on, or the water blown out of the pipes and I heat with wood. Can this new configuration of batteries handle the load?

Each battery weighs 125 lbs. The battery room is upstairs in the heated garage. It is really a two person job to get those batteries out of there and into town, and hard to find another person in the middle of the wilderness. I'd rather leave them there. In fact, the Trace 4024 power panel seems to have done a better job of restoring the batteries than taking them to town and putting them on the iota charger did.

Solar panels charge these batteries without generator backup completely in the summer. In November and December, the sun rarely shines. The generator is propane; the price of propane has gone from $0.80 to $2.90 per gallon since I started construction eight years ago. The house could run off the generator, but the cost would not be reasonable, and it is not good for the planet. The batteries can't freeze again; what is there can run a washer, dryer, dish washer, garbage disposal, garage door openers, and 220v well pump in the summer, without the generator. It is a structural insulated panel house (SIP), so is so tight that it has to have a ventilation system running in the winter. Without it, the windows frost over, melt, and rot the window frame. Winter demands more from the batteries and generator. How much more depends on the ability of the generator to fully charge the batteries. When do I say it is time to just not use these batteries anymore? How many batteries do I have now that I want to use? How will I cable them together?