the battery is on the charger and the meter is right in the middle. Would that be the problem?
The gauge that you were referring to is an indication of how much work the charger is having to do to get it back up to 12-13 volts.
When the car is running, check the voltage of the battery. It should be between 13-16 Volts DC. If it is, that will tell you that your alternator is working. The alternator uses this elevated voltage level to keep the battery charge topped off. (Lead Acid batteries are charged by voltage and Nicads are charged by amperage)
If you decided to get your battery checked at a parts store, be sure to fully charge it!!!!! If not, the tester will kill a weak battery.
Most batteries go "dead" over time due to tiny flakes that come from the plates in the cells. When the level of debris reaches the bottom of the plates, it causes the plates in that cell to short!
Long life batteries have deeper cavities for this debris to collect in!
One last thing! Only add water to a fully charged battery! I worked in a battery shop for Raytheon Aircraft, and added water to the batteries before they charged. a couple of hours later I had a mess on my hands when they overflowed!