Leaking AGM starter battery

[marujo.sortudo]

I've had the same starter system since I purchased my boat 2 seasons ago. I haven't burned up more than 70 gallons of diesel, despite sailing quite a bit. Plenty of starts, though, as the engine does get used to charge up the electrical system. My engine is a Westerbeke W33A (4 cyl, 30 hp.) There are two alternators attached with the original one dedicated to charging the starter battery and a separate 100A alternator that charges the house bank. My starter battery seems to be a bit of a surprise to me, being a Concorde Chairman AGM-1248T. At the end of each season, I've noticed corrosion on the one of the posts & lugs (negative, IIRC) and can see a small hole next to the lug. This spring, I took the battery out and hooked it up to the BatteryMinder charger/conditioner that I use for my AGM Lifeline Batteries in the house bank (for which the BatteryMinder is designed.) This charger comes with a temperature sensor that goes on the battery, but despite this some acid came up after just 2 days on the charger (this charger is not necessarily designed for Chairman batteries.) The starter battery still holds a good charge, but I'm worried that it can't sustain this kind of use and/or it isn't the appropriate battery for this application. Thoughts?

 

[Stu Jackson]

Sounds like you're overcharging it. Most starter banks are always full, since you only need a few amp hours to start an engine. Having that separate alternator always charging the start bank is overkill. You could wire both your alternators to the house bank and buy an echo charger to take care of the start bank. Many dual engine catamarans do this.

another option would be to leave the starter alternator connected, but switch off the regulator (do NOT interrupt the alternator output). This will turn off the signal from the regulator to that alternator and it will not produce amperage. Much simpler, too.