The original battery box in the lazarette was only big enough for two group 27 batteries that were used for the house bank. The battery for starting the engine was located in a plastic battery box in the lazarette as well. The original two group 27 (this is the size of our 12 volt batteries) batteries only had about 150 amp hours total, of which only 1/2 is considered usable. With our 12 volt refrigeration, reading lights, anchor light (when used), water pump just to name a few, we were using about 100 to 120 amp hours a day. That meant we would have had to run the engine once or twice daily to keep up the electrical needs.

After calculating our daily amp hour requirements, along with a conservative estimate of what would be replenished by the solar panel and wind generator, we determined that a bank of about 600 amp hours would meet our needs. We ended up purchasing six Lifeline AGM 6vdc batteries, and hooked them up in series for 12 volts, then parallel for one bank. This provided us with 660 amp hours, of which 330 is considered useable (remember, you don’t want to discharge your batteries more than 50%).

Now that we had our batteries, we needed to figure out a place to put them. The lazarette was out of the question, there just wasn’t enough room. We considered putting them under the port sette, as it was close to the centerline of the boat, but our fluxgate compasses were mounted there (I didn’t want to relocate them), and the storage space was pretty convenient for other things. In the end, it was decided to locate them under the aft cabin berth. There was plenty of room, battery cable runs would be kept to a minimum, and besides, it was really the only other place left on the boat.

A half day was spent relocating the few things we had stored under the berth and for cleaning really good. Marine grade plywood was measured and cut for a base platform, stringers were fiberglassed under the base, then the base glassed into place. The sides were secured using screws to hold them until they were fiberglassed into place. Before the batteries were placed into the compartment, two coats of paint were applied and spacers screwed into the base to keep about an inch between the batteries. The box was designed so that it would accept our six 6 volt batteries, but also to accept two 8D batteries in the future if needed (I wanted some diversity in battery options).

The batteries were placed into the box, and fit nicely. Our neighbor and good friend Dan made the tops to the box. The sides of the box were made high enough so that with the lids on we could store small items on top of the box with out them sliding off. Currently this is where we store our charts and chart kits. Because of the weight of the batteries, almost 350 pounds, ballast in the form of a flexible water tank was added under the pullman berth to keep the boat balanced and from listing to starboard. The temporary water tank will be replaced with spare parts and chain when we go cruising, no chance of them leaking water.

All in all, it took about 4 days from start to finish. The battery capacity is now sufficient to meet our daily electrical needs. With the Fourwinds wind generator and the 120w solar panel we now find the need to charge our batteries by running the engine about once a week. Much better than daily with our previous set up.

Updated 06/22/04
Though the batteries were secured using standard battery straps, I wanted to ensure that there was a stronger, more reliable method of keeping the batteries from moving during heavy seas or a knock down. So I installed two stainless steel bars across the batteries. They were secured using some extra bimini fittings I had along with 1” stainless steel tubing. Removing two screws per bar is all that is required to remove the batteries. Even though I feel confident with this ‘lock down’ system, I did leave the battery straps in place for redundancy.