My 13 year old thruster/windlass battery has given out. It is an 8D gel cell. In checking around to get a good price on a replacement (lowest so far is $390 which seems pretty good to me) I'm finding that equivalent size (8D) AGM battery prices, which were once much higher than Gel Cells, have come down quite a bit and are now very competitive with the Gel Cells. The AGM specifications are for a little more capacity (245 ah vs 225 ah) which is not of any great consequence in the application but they also seem to have less internal resistance and thus higher rated MCA ( 1725 vs 1470) which would be good for the high current draw of both the thruster and the windlass. The sticking point in my mind is that I have heard that the AGM does not have the longevity of the Gell cell. The West Marine catalog says a Gell has a life of 1000 cycles while the AGM is only good for 300 cycles. I'm interested in hearing from anyone who would care to comment on the decision making. JULES SIEGEL K42 #188 CARINA

I have AGM group 31 house batteries, West Marine label (made by East Penn Mfg - Deka). I replaced a set of Deka Gels (also good for house banks) with them. They are presently almost eight years old, and work like new. They have far more than 300 cycles on them (more like 1500). I think I read that Deka was being conservative in their estimates when their AGM's were new, and thus the 300 estimate. Seems to me it should have been updated by now. BTW, I have Optima starting batteries (also AGM), same age. They also have many times 300 cycles on them, and work like new. They also make great starters (7 years old) in my diesel truck. Based on my experience and that of a few friends, I would choose only AGM's (Deka, Trojan, Optima, or Odyssey) for a boat. Richard Cook New Moon (Bounty 257) > My 13 year old thruster/windlass battery has given out. It is an 8D gel cell. > In checking around to get a good price on a replacement (lowest so > far is $390 which seems pretty good to me) I'm finding that > equivalent size (8D) AGM battery prices, which were once much higher > than Gel Cells, have come down quite a bit and are now very > competitive with the Gel Cells. The AGM specifications are for a > little more capacity (245 ah vs 225 ah) which is not of any great > consequence in the application but they also seem to have less > internal resistance and thus higher rated MCA ( 1725 vs 1470) which > would be good for the high current draw of both the thruster and the windlass. > The sticking point in my mind is that I have heard that the AGM does > not have the longevity of the Gell cell. The West Marine catalog says > a Gell has a life of 1000 cycles while the AGM is only good for 300 cycles. > I'm interested in hearing from anyone who would care to comment on > the decision making. > > > JULES SIEGEL K42 #188 CARINA