I recently purchased a 45ft Californian. The battery charger was original (1988)-Silicon Diode brand. The batteries were all low on water and I refilled them. The boat was then idle - getting engine work with little draw on the batteries except lights, Within 3 weeks the water levels dropped. Apparently there were three circuits hooked directly to the charger. The charger has been replaced and I am thinking of exchanging the 8Ds for 31 series. I know it will take about 3 31s per 8D. I think there is room for them and I'd rather not deal with the heavy 8Ds. The boat has three 8Ds and no battery dedicated to the generator ( which I would like). I'd like some advice - seems most the boaters I know are getting away form the 8Ds. Thanks