A bad battery that holds a charge?

Can a 'bad' battery hold a charge?
My 2004 Tacoma recently started having trouble when I went out to Texas. It's really struggling to turn over so while it's started every time I have tried recently, I can really hear it working to turn over and it sounds like it's barely making it. I was dealing with acid buildup last year, so I noticed a little acid buildup again when I looked at my battery. It didn't look like nearly enough to give my truck trouble, but I cleaned the terminals and sure enough, it still struggles to turn over. That makes me think either alternator or battery.

I go to Autozone & ask the fella to test it. He showed me the reading, and it said "Bad Battery - 100%". Kinda dumb looking back on it, but I completely spaced on the voltage reading. I changed the distilled water in it within the last year too, so while I didn't check the water levels, I guess I assumed that wouldn't be the root of the issue. Should I get a new battery or could there be more to this that I'm just not considering because a bad battery that holds a charge? How does that work... I'm no battery specialist I know the basics & that's about it but I'm just trying to understand if that's really the root of the issue. Autozone told me this could be caused by temperature variations but who knows if he actually knew what he was talking about.

Thanks in advance

 

A "bad" battery can still show fully charged (100%) at 12.6 volts. What makes it "bad" is the cranking amps. If the battery is only capable of say 250 cranking amps, but it is supposed to put out 800, then it will be "bad" and slowly crank the engine, while still showing 12 volts.

 

X2
If it's original, replace it. You got your moneys worth.

 

Thanks for the replies, folks. A couple more details: Today it's cranking but won't start. Pulled the battery, cleaning it up & suppose I will be getting it replaced tomorrow morning. It was manufactured in 09. Bought my taco about 2-3 years ago. Since have added an amp with sub and headunit so it's drawing more power than it used to. Suppose it's still had a pretty good life, at 5 years, but I'm concerned it still might not be the battery for some reason, I just don't have enough knowledge as a whole.

 

You battery is partially sulfated. Depending on the temperature and condition of the engine, 250 amps might not be enough to start your engine. As it gets colder, you will need more amps to crank your engine and the battery's performance is reduced. For more information on sulfation, see Section 16 in the Car and Deep Cycle Battery FAQ on www.batteryfaq.org.