Old 6V battery - still good?
 

Helping family clean their house I found a 6V 4Ah sealed lead acid battery. Family said they don't need it, so I took it for some projects.

The label states the voltage should be 7.2-7.5V, but at home I checked that it has only 3.2-3.3V. Is this too low? Does voltage this low mean that it was discharged too deep and/or for too long, and the battery will not be useable?

If it can be saved, then do I need a dedicated 6V charger? I don't have one, and not sure I want to invest in one. I doubt I can use the 12V charger for my car battery...

Those little sealed lead acid batteries usually don't last long even in the best of conditions, they're built to be cheap. Not to mention largely obsolete when lithium batteries are cheaper nowadays.

You can try pulse charging it, but they rarely start working again.

If the voltage is that low and it’s been sitting, I’d say it’s done and ready for recycling without further test. If you want to test it charge it up and discharge slowly (say1/2 amp rate) and measure how many amp hours you get before the voltage tanks.