Dead battery- what could it be?

[KevinH1990]

The common wisdom is that AGM (absorbent glass mat) batteries withstand periods of limited use better than traditional lead acid batteries. I don't drive my Boxster every day. Some weeks I might drive it 3 times and other weeks as much as 5 times.

I installed an AGM battery in my Boxster two years ago and one in my Mercedes C230 in April 2018. So far, both have been reliable. The battery in my Mercedes is older, but I usually drive that car more often than the Boxster.

[MikeMcMo]

Originally Posted by KevinH1990

The common wisdom is that AGM (absorbent glass mat) batteries withstand periods of limited use better than traditional lead acid batteries. I don't drive my Boxster every day. Some weeks I might drive it 3 times and other weeks as much as 5 times.

Thanks for that, good to know! But I heard you can't use a regular charger to bring an AGM battery back to life...

[MikeMcMo]

Okay, new information for anybody still following…

I'm pretty sure I'm on the trail of what drained the battery so quickly.

I used a friend's charger and topped off the battery, and I just put it in this afternoon. I immediately heard a clicking sound like a relay going on and off every two or three seconds.

Sitting in the driver's seat, it sounded like it was coming from the passenger door. I go around to the passenger side and it sounds like it's coming from the space under the dash above the passenger footwell, but I couldn't get in there to see any more because of the way it was parked in the garage, and then I ran out of time. Are there some relays up there?

Any idea what my next troubleshooting move should be? Thanks once again!

[MikeMcMo]

Originally Posted by KevinH1990

The common wisdom is that AGM (absorbent glass mat) batteries withstand periods of limited use better than traditional lead acid batteries.

Thanks, good to know. For now I have revived the old battery with a friend's charger and it seems good. But I do sometimes go 5-6 days between drives so I wonder if I should look into an AGM for my next battery. But I heard that that kind of battery can't be recharged with a standard charger and you would only somehow cook it. Know anything about that? TIA.

[JFP in PA]

Originally Posted by MikeMcMo

Thanks, good to know. For now I have revived the old battery with a friend's charger and it seems good. But I do sometimes go 5-6 days between drives so I wonder if I should look into an AGM for my next battery. But I heard that that kind of battery can't be recharged with a standard charger and you would only somehow cook it. Know anything about that? TIA.

Most modern chargers/maintainers have a specific profile for AGM batteries as they finish at a slightly higher voltage than a conventional flooded cell battery. Again, most modern chargers have "float" profiles built in to prevent overcharging, which was common with older, non-electronic chargers.

[Gilles]

A month ago I parked my car at a friends house as I needed the space to work on a different vehicle and noticed that the battery struggled a bit to start the engine (2016CS with original battery..), the car was parked at her house for about two weeks but left the hood latch covered with a towel just in case.

Afterwards, I installed a new AGM battery and it ran great (starts the engine with much more power), however yesterday I plugged the Durametric to reset the oil service message and I noticed that I had a P1559 code on the engine module..

Could the P1559 code caused by the weak battery, and just needed to be cleared? Thank you!