is no activity bad?

NO!

If there is bubbling in a cell or all of the cells, the battery is overcharging. If only one cell is bubbling, then it is a bad cell.

The true condition of the battery is measured in specific gravity and takes a hydrometer. Most people don't have them, as it is somewhat hazardous to extract battery electrolyte from the battery. Better to use a volt meter.

Here's the deal----

Disconnect the battery charger and turn on the headlights for about 2 minutes. Then turn them off, and allow the battery to be at rest for about 10 minutes.

Using a DIGITAL (as opposed to an analogue) volt meter, check the battery voltage.

Full Charge > 12.5 V.

3/4 Charge > 12.3 V

1/2 Charge > 12.2 V

1/4 Charge > 12.1 V

Discharged < 12.0 V

The above is a pretty good measurement of the condition of the battery.

But it is NOT a judgment concerning the available current the battery may be able to supply. The voltage can be well above the 3/4 charge rate, and be so calcified that there is no available amperage, and the battery must be replaced.

NOTE------->

The reason that the DIGITAL meter is required is that the analogue meters are not accurate enough to show the minute differences between full charge and even dead, never mind between 1/2 and 3/4 charge.

Good Luck

is it gaining a charge ? dont worry.