I foolishly believed what the diagnostic code on my battery charger told me and bought a new battery. Charged it up, drove about 30 miles that day and then parked it for a week. Started real slow next attempt, so without thinking much, I figured I didn't charge the new battery enough. Charged it up and it started OK. Sat another couple of weeks and it wouldn't crank enough to start. A few weak turns and then click-click like an old solenoid gone bad.

Put the charger on it again and it read the code for "bad cell". So now I'm thinking my original battery was likely OK and maybe the starter windings are just old and weak or it's something else.

Any thoughts from real mechanics? (Instead of this old backyard tinkerer from back in the day when you could climb in the engine compartment to do lots of the work?)
TIA,
Steve

 

You could have a parasitic draw. Each time you've had starting issues you said you've let the car sit for a couple weeks. What you need to do is test the voltage after the battery is fully charged and then test it after it's sat a couple weeks. You should be registering above 12.5v. A fully charged battery should read between 12.7-12.9v.

 

Below is my write up on checking for a drain. Let us know how it goes.

Also:

A fully charged battery should be 12.6v or more.

It's not 12 volts it's 12.6 because each cell is 2.1 volts.

If the battery is

12.5 = 85% charged
12.4 = 65%
12.3 = 50%
12.2 = 35%
12.1 = drained



Parasitic Drain Testing:

Suggest you remove the hood light bulb first so it does not provide a drain.

For measuring battery drain I would hook up an ammeter to the negative side of the battery by removing the negative cable and measure between the cable and the negative battery post.

When you connect the ammeter the car should draw several amps until it goes into "sleep" mode which can take several minutes. Normal sleep mode drain should be 30 milliamps or less by GM standards. You will need an ammeter that can transition from whatever the drain is down into the sleep mode. If you have a drain I suggest the following:

Once you determine you have a drain with an ammeter what I recommend first is to listen to each fuse box and see if you hear any relays operating. If not, then place your hand on each relay to see if any of them feel hot. That can be the start if you find something like that is happening.

If nothing shows up you can hear or feel then I recommend you separate the two fuse boxes from each other. This is easy and done by removing the Red cable from the engine fuse box that feeds the passenger fuse box. It is on the right rear side of the engine fuse box. There is a stud there where the large Red wire from the battery connects. Just remove the nut and disconnect the large Red wire feeding the passenger fuse box and reattach the Red battery cable. NOTE: I would recommend disconnecting the negative ammeter hookup when working on the positive side doing this.

What you will be doing is measuring the drain with an ammeter to see if disconnecting the passenger fuse box causes the drain to go away or not. By depowering the passenger fuse box you will depower the BCM which controls the sleep mode so do not expect the sleep mode to happen.

If removing the feed to the passenger fuse box you then see you have eliminated the drain then you know it is something related to those circuits. If it does not reduce the drain then you know it is related to the engine fuse box. It could be a rare case where you have some drain via both fuse boxes and we can deal with that if you think it is the case.
Just so you know, even though it may appear to be a problem in the engine or interior area the fuse boxes do feed circuits to each other that are not affected by separating the boxes. So, separating the fuses boxes can tell you how to narrow down your search but still not where the issue may be. That is where the schematics come into play to track down the “real” culprit. Hope that makes sense.

Once you basically know where it is then you can remove fuses and relays to see where the drain is coming from.
PS: There are cases where the alternator causes a drain so it can be disconnected and see if the drain drops.

 

An ace mechanic (friend of my brother) looked it over and thought it was the same type of thing you guys noted. Strangely enough, the new battery (Deka) also had a bad cell. Replaced it again and it seems fine. Will advise if anything changes, but looks good so far.
Thanks very much for the info.
Steve