The other day I was checking my tire pressure and filling the tires using one of those cheap inflators when I noticed it was running slowly. So I turned on my handy-dandy X50 and switched it to the voltage mode, and it showed around 10-11 volts. Not good.
Then I checked the fluid level in the battery (which I have never done because it's a PITA to remove the bracket to get to the covers), and it was low. I topped them off with filtered tap water (I know you're supposed to use distilled water, but I didn't have any). Afterward, the X50 read 12.2 or so volts, which was better.
Although the car has been starting no problem (though it's hard to tell if it's cranking slowly since it usually starts right up), the voltage still seemed low when the car isn't running. After driving into work this morning, I used the X50 to check the voltage again with the engine off, and it was between 11.5-12.2 volts, depending on if I had the lights or wipers on or not.
Just now, I went out to the car, after it's been off for 30 minutes or so, and used the X50 to check the voltage again. It read between 11.7-12 volts with the engine off. With the headlights on (high beams or low) it dropped to around 11.3 volts.
With the engine running I get between 14-15 volts, so AFAIK the charging system is working fine.
I know I should test at the battery with a digital voltmeter, but I don't have access to one at the moment. But based on what I've posted so far, should I get a new battery? The battery in there is about 4 years old, so it's probably getting close to the time for a new one, especially with winter around the corner.