jack burniston

Battery tests 12.5 volts. yesterday went to start, dead. Jumped and drove into town, parked. Returned 3 hours, not enough battery to start. frustrated
thanks Jack

843de

to the forum Jack!

I see you're driving a 2009, while that's a tad young for the OEM Delco to poop out, it's not impossible.

You say that the battery had 12.5 volts, was that a static voltage, or did you have it load tested?

If is hasn't been load tested, that's your first step, batteries can show an adequate voltage with no load...but hit them with the draw from the starter and pffft!

Once you've either eliminated the battery as the weak link(which is my bet that it is), then it would be time to look for parasitic voltage drains like a stuck door switch not killing the dome/map lights.

blacky

Test voltage with car running. Jump start if necessary. If 13.5 - 14.5 V, then charging system ok.

Run engine for 10 or 15 minutes then shut down. Put volt meter across from jump post under hood to good ground and crank engine. If voltage drops excessively, say to 10.5 - 11V from 12.5 - 12.8 V, then most likely it won't crank, suggesting internal resistance in battery (meaning battery shot); or possibly contact resistance, probably at battery terminal(s). Volt meter between top of battery post and clamp during cranking should read essentially 0 V, else contact resistance (meaning remove clamp and clean up post and clamp with wire brush).

Testing fluid with hydrometer is a good idea, but a battery with too much internal resistance can still charge up and test ok with a hydrometer.

If car cranks ok immediately after shut down, then disconnect battery for a 3hours. Reconnect battery, and if it cranks ok, then run for a few minutes and shut down with battery connected for 3 hours (simulating your trip to town), and see what happens.

You can test directly for excessive drain by disconnecting one side of the battery and inserting amp meter in series, but you have to make sure no lights or anything else normally off are on.

Running down a starting battery to dead shortens its life. If that battery is already 5 years old, then even if something else is at fault, such as the charging system, I would replace battery.

donbrew

I had a problem with my former (2008 HHR) like that. I think that I had a bad wire at the alternator. The connector is susceptible to water infiltration, and the wires are thinner than you'd think with a sharp bend in them. I sold the car before I got it "officially" diagnosed.

IgottaWoody

Bad cell...while it will show 12.5 under no load...once a load is put on it will drop like a rock....

jack burniston

thanks for the input. I now have more information. Battery under load 12.5volts. After 3 hours battery is down to 10.5 volts at the terminal. The post in front next to fuse box shows 8 volts. Draw is somewhere between. I checked to red post closer to the firewall next to the fuse box. lower voltage.
What is in between? I am going to clean the battery posts right now. Thanks

whopper

Just replace the battery.

blacky

Did you check charging voltage first? You can do that in many locations, the most obvious is across battery terminals. Look for something around 14.5 V. If you replace the battery but the charging system was at fault, you're not going to like it, because the same symptom will reappear shortly. Regardless of what the real trouble is, the battery does not like what it is going through, and I would definitely replace it, but only intelligently once you figure out what is wrong.

12.5 V: what was the load?

10.5 V: load or no load, was battery disconnected for the previous 3 h?

8 V: load or no load. Where were the two meter probes? What was ground?

Lower voltage: Stay out of there.

With no load, there is no current, and voltage does not change along a wire.

Sidecardog1

I agree with 843de 100%. A "load" is with a testing machine, not the car running with lights/radio/ac on. A battery will show normal voltage but will have no capacity when it goes south, it can drive you crazy. If your car was running fine when you jump started it, then your alternator circuit is fine. If when you take your car to a place to have it load tested and the battery passes, THEN start looking elsewhere, NOT BEFORE.

db/sb

This▲▲▲▲▲ A good load tester, like the one I have will not only test the battery but also the charging system, eliminating the need for the 'rocket science' mentioned above..........