I put the original German Schonestien Gel Batteries (imported from Canada) on my sail boat in the late 1980s with a controller charge rheostat so I could charge the batteries at a much higher rate when needed. This was the main selling point of the Gel's when they first came out. Another was that it did not hurt the battery to discharge it below the 50% level, which we did many times. I Reset the controller for the alternator to 15.3 volts so all normal charging was done to that voltage level. We sold the boat in 1998 with the batteries still installed and operating with no problems. We never experienced a problem with them even though they were installed on their sides beneath the main bunk. I did also equalize the three batteries on an irregular basis, perhaps three times a year, to the 15.3 voltage level. Don't have them on my boat now as I haven't gotten around to it yet, but as the current batteries die, will replace them with AGMs. I swear by them. Ron & Molly Bodeen, 1986 42' Heritage East, MTOA #2950, AGLCA #3464, San Diego, CA