98 garage queen. Been sitting in the garage covered up since Sept. Battery Tender on the whole time with a "green" light. (Battery Tender Plus) Nothing in the car left on. Uncovered yesterday...maybe half a crank then ticking. Would not start. Interior lights did come on when I opened the door....as did the key in ignition chime. So...I jumped the car, pulled her outside and let it run like 15-20 minutes while I added air to the tires. Shut her off and went to restart.....nothing but clicking. Really?? After running 20 minutes not enough to turn over? Anyways...jumped it again and put it back in the garage on the tender. The tender had a steady red and flashing green light indicating at least 80% charged. Let it sit overnight and this morning charger had a steady green. Car would not turn over again...only clicking. Battery is a Delco that's about 4-5 yrs old. My question is...why does the tender say good to go? Do I need a new battery or should I check something else? Thanks.

 

I agree with 8VETTE7. Your battery likely has a bad cell. The battery may "look" charged to the charger but it won't have any power to start a car.

Given that you were able to jump start the car, it is a pretty good indicator your battery is shot.

 

The Battery Tender Plus puts out 1.25 A and is not a battery "charger", but is a battery "maintainer" - at that rate it will take DAYS and DAYS to recharge a dead battery. 80% charged means about 12.4 V, and that should be enough to start the car, but the idiot lights on those chargers are gross approximations - it you really want to know what the voltage is, you need a proper voltmeter. It can still read 12.4V at rest but have a very low amp capacity and just cause the starter to click instead of turning over. If you measure it after trying to start the car, it may drop down to 10V or less.
Is your tender clamped on to the battery terminals or did you install the connections permanently underneath the battery bolts? You may not have had a very good connection to start with.
You probably have a dead or dying battery that is not accepting a charge, or the connections to the battery posts may be loose and/or dirty not permitting the proper current to flow. You have to get the battery on a proper charger and get it fully charged first, then get it load tested after it is fully charged. Like 8vette7 said, take it to the local battery store or auto parts place, they will charge it and test it for you for free (because they want to sell you another one).
Also the voltage measurement when you take a battery right off a charger is reading a "surface charge". If you really want to know the voltage, measure it a half hour or more after removing it from the charger so that surface charge dissipates. Get the battery charged and tested - that's probably your problem.

 

Just fork out the $120. bucks for a new battery

 

Thanks Guys. I did pull the battery and had it load tested. Bad cell. AdvanceAuto wanted $221.99 for the Red Top. Ordered it online w/Amazon for $165 total. Perfect fit.....fired right up!

 

Thank you for posting your results... glad your up and running!