Is it possible to fry your AGM battery using one of these Ctek battery maintainers (aka ‘smart chargers’ I believe)?
I bought this guy over 15 years ago, shortly after buying the Boxster, since I knew I’d not be driving the car in winter weather. It has performed flawlessly—attach the leads, plug it in, choose the mode setting. It’s been used on the original battery (don’t recall what that was, probably whatever was in the car when bought new by the original owner), and on the first battery I’ve purchased for the car. That was a DieHard, which I picked up in 2014 and lasted like 9 years.
Jump ahead to Mar 2023. Replaced the DieHard with an Everstart Platinum H6 AGM. Car was kept in winter storage for a few more weeks, with the Ctek in place. Then, winter ’23-’24 car was again stored, Ctek in place (on the AGM) for the entire 4 months or so. So then, come fall 2024, I again repeated the procedure, same as always. I checked the car recently (it’s actually at the home of a friend, who goes to Florida for the winter and rents me garage space each winter) and noticed the Ctek, red Error light illuminated as shown above. On the Step 1-8 charging process, it made it to Step 5 (‘Analyze’). Per the Ctek manual, with a charging process that’s been interrupted at Step 5 it’s indicating a battery that “cannot keep charge and may need to be replaced.” I disconnected the Ctek and hooked up the multimeter; getting a reading of 3.25 V. Of course, no headlights, etc.
Last night, got to talking to my son who admitted he’d fried a battery himself. Told me that, even with the Ctek, you need to take steps to avoid overcharging. I’ve always had the thing set at the ‘Snowflake’ setting, which the manual describes as the “Cold weather program. Use for charging at low temperatures and for power AGM batteries like Optima and Odyssey.” It’s winter, it’s Ohio, it’s cold, so that seemed to be the correct choice. It’s always worked for me over the past 15-16 years. What happened this year? I thought these battery maintainers were supposed to be a ‘set it and forget it’ kind of deal? The battery’s only 2 years old, and has a 4 year free replacement warranty, but I’m not sure what I’ll be asked about as far as driving the car, charger usage, etc.