Since I am leaving the Virgin Islands and will not be back in US waters for some time and my batteries were getting near the end (I already lost one last year), I chose to pull the trigger and replace them. Before you think chew my ear off about getting everything I can out of the batteries before I give them up, you might want to know that they were eight years old. That is right eight years when everyone says you should only get 3-5 years. My 900 amp hour bank was down to 600 since one battery failed, but even then I was not getting 600 amp hours anymore. I think the batteries efficiency was down so much that I was really only getting 300 or so. Granted this was enough for me to run the boat on a daily basis and the solar panels did a good job of topping them off each day, but if I had tow cloudy days in a row I was starting to get into trouble. 🙂
So what did I go with? To be honest I replaced them with the exact same thing I had….six 6-volt, 300 amp hour, AGM Lifeline Batteries that I hooked up together to make three 12-volt, 300 amp hour batteries. The reason I use 6-volt batteries instead of 12-volt is simply because my battery locker is maxed out length and width, but not height and the 6-volts are the same footprint but taller than the 12-volt counterpart. I feel having a larger bank is important, which is why I have 900 amp hours. Of course, if you assume 900 is the peak in laboratory conditions and take away 20% for “real life” this gives you 720 amp hours total. But we are not done, you can only use half the battery bank or risk killing the batteries. Therefore, we are now to 360 amp hours of usable power, which is a great number to have in addition to the solar panels I have.
I really do think AGM is the way to go instead of wet cell, because you have to maintain them and you do not get as much power as the AGM. The other option is lithium ion batteries, but I do not think they have been around long enough to work all the kinks out yet and they are very expensive. Speaking of price, I contacted Lifeline direct and they found which warehouse had them available and shipped them to Crowley who in turn shipped them from Miami to St Thomas ($250ish) and all said and done I had the new batteries for less than $2900.
Putting them in was simple, but given that they weight a hundred pounds or so it was not easy. Haha. Once I had the old one out and on the dock I put the new ones in, cleaned all the cable ends, and wired everything back the way it was. The best news is that the guy next to me offered to take all six of the old batteries for $240…..SCORE!!!!!