I recently bought 2 12V lead acid batteries (AGM type) for my mobile music needs where I need 24V, so I discharge them in series.
At the moment I charge both batteries separately, which is a bit annoying. So I would like to charge them in series, but I am not yet sure if this is a good idea.
When charging them separately I use a bench power supply with current and voltage control set to 14.1V. So, when charging them in series I would set my power supply to 28.2V, but then one of the batteries starts gassing and when measuring the individual batteries I see a voltage difference of about 0.3V.
So, am I doing something wrong here, is it just a bad measurement and nothing to worry about or is it generally a bad idea to charge batteries in series?