Question: I’ve been thinking about upgrading my boat’s batteries to gel cells because I’ve heard that they can offer really good deep cycle capabilities and if charged correctly will last a long time. My buddy is telling me that the charging regimen for all deep cycle batteries is the same, regardless of battery chemistry or type. What’s the story here?
Answer: This is a question that comes up all the time. All batteries technically have different characteristics in both discharge and recharge modes. In fact among the battery types available to the marine market, gel cells are the most finicky in terms of their recharge needs. But, at least according to one major manufacturer that I’ve talked to (East Penn Manufacturing) the makers of the popular Deka Marine brand of batteries, they say their gel cell batteries outlast their AGM (absorbed glass mat) batteries in a deep cycle application. The caveat to that, though, is that the batteries be connected to a charger that is properly calibrated for gel cell technology.
This matter gets complicated, especially on power boats with standard engine driven alternators. Most OEM engines use alternators with integral voltage regulators that are not properly calibrated for gel cell technology. So, all the while you are motoring along, you are actually damaging your gel cells on a power boat (or sailboat) unless you have a custom external regulator that has been calibrated for gel technology. Gel cells are great, but they are indeed more sensitive to their charge regimen than all other battery types available to us today—with the exception of lithium ion batteries, which are another whole topic unto themselves.