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Old 06-11-2009, 06:27 AM   #1
Keith
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Vessel Name: Anastasia III
Vessel Model: Krogen 42
Join Date: Oct 2007
Posts: 2,716
AGM batteries, charger on or off?

My bow thruster is powered by AGM batteries. The only charging source is a three stage smart charger, no charging off the engines. Since I only use them occasionally, I normally don't leave the charger on. Just turn it on the day before I'm going to use them to top them off, then recharge them afterwards. There are no other loads on them.

The batteries are showing "weak" on a load tester (toaster as Arild calls it) after about 6 years. I've put my desulphator on them and expect it'll bring them back over time, but I'm wondering if it would be better to leave the charger on all the time?

The last time I used them, I charged them up then turned the charger off. After about a month they were reading about 12.3 volts. Overnight charging brought them up to 13.3 or so. They dropped to about 10v on the load tester.
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