This has been an interesting thread to watch. I don't pretend to be an expert in AGM batteries as they might be used by a trawler owner, but we do have several hundred of them in our equipment at work. The reason we buy them rather than conventional batteries is that AGM batteries are cheaper in the long run than conventional batteries when used in the manner that we use them. Some seem to think that avoiding Hydrogen explosions is a major reason to weigh the battery decision analysis in favor of the AGM batteries. That is interesting, but it never entered our minds when we were considering which batteries to buy. Don't get me wrong. A hydrogen explosion is a serious potential problem. They can blow the whole front end of a heavy truck apart. Our safety films show pictures of people who have been seriously disfigured by them. The few battery explosions that I've seen could have been just as bad. Fortunately, they are very rare; and even better, can be made all the more extremely rare with proper battery handling procedures.