[2017EX-L]

I have a 21 year old sports car that I seldom drive. It has 30,023 miles on the clock.

Just before Covid hit I put a brand new Group 48 Bosch AGM (760 CCA) battery.

I left the battery in the car but left the terminal connections disconnected.

I connected a trickle charger,......Two years went by.

Today I connected the charged battery to the car, as soon as I made the connection, (within about five to ten seconds) there was clearly an audible "Gurgling" sound coming from the battery.

I understand that batteries are simply chemical reactions and what I am undoubtedly hearing is electrolytes boiling off inside the battery. (Producing hydrogen in the process.)

I'm heading back to where the car is kept to formally test the battery.

I may have to buy a new battery, which I deserve.

Has anyone else dealt with something like this?

 

[Tacoma'03Pilot]

Sounds like you've diagnosed the problem correctly.

Some trickle chargers don't "throttle down" when the battery is charged, and can overheat it. My BatteryTender Junior stays connected to another car all the time, with the desired results. I bought that brand based on reviews (and cautions) here and elsewhere.

 

[cintocrunch]

Yea this is why I spent the money on a decent battery trickle charger/maintainer for my Optimum Red Top. It's been performing very well for over 5 years in my '61 Impala.