Number54

I have a feeling I ruined my battery by letting it decharge completely in the cold a few times. The car wouldn't start if I left it for ~2 weeks.

So I bought a new battery and everything is fine, except...

Since I'm unsure about how functional my old battery is, I decided to just keep it as spare - charge it up and have it ready.

I put it on charge and when it finished, I went to disconnect it and heard some buzzing. I thought it was electric noise from the charger. But after disconnecting the charger, if I put my ear to the battery it sounds like it is bubbling. Very soft bubbling like what you'd hear from the top of a foamy beer, not like a soda.

Any idea what this is?

Thanks.

*edit*: Note that both batteries are stock Moll ones from the Porsche dealership.

2K4GT3

For flooded or lead-acid batteries, some bubbling is normal during (or just post) a charge. Depending on charge rate the amount of bubbling can range from undetectable to pronounced. It's best, if possible, to charge at a lower amperage or slow rate (perhaps 2 amps) over a longer period of time. More often than not charges are time critical and we charge at rates between 10-20 amps or more. It's common to get the sounds you experienced as a result of these higher charge rates. Additionally, gas often accumulates under the plate banks and sometimes you can hear it bubble up if the battery is tilted after being charged. As for the condition of your battery, you might try a load tester on it. If you don't have access to one, a service station can probably perform this test for you. A volt meter may tell you the current battery voltage but that can sometimes be misleading, using a load tested will give you reliable results.

Number54

Interesting, thanks. I was charging at 3A on a flat surface.

jpeytonii

Don't know if this is a factor, but discharged batteries will freeze in cold weather. Trying to charge them in a frozen state is a big no-no. What type of battery charger do you have? One of the newer "smart" chargers that will automatically vary voltage and amperage based on battery condition and state of charge or a fixed voltage "trickle" charger? I saw your post re 3A but don't want to make assumptions.

Cheers

996FLT6

Don't put your face to nething that doesn't sound normal.
Look what that guy in "Aliens" did- DT in the worse way possible!!! Mike

DAB+

Try striking a match near the battery vents when it bubbles

Number54

It was inside, warm temps. I don't think the charger is smart - it has 3, 9, or 12A fixed options.

Number54

Heh! I didn't know what it was, the sound led me to the battery. I didn't do it again!