Wrong. This logic applies to NiCad batteries and consumer dry cells not lead acid. A fully charged healthy battery-out of a car- should read 11.9 to 12.5 volts. Most car batteries have six cells, each aproximatley 2 volts. Installed in a properly operating car, the voltage should be 13.5 to 14.5 volts. The higher voltage is generated by the alternator and this higher reading is an indication that the battery is charging and that the charging system is operating properly. Accessories that draw large amounts of current will pull the voltage down. Any reading less than 12V indicates that the alternator is not charging the battery and the system is 'drawing' power from the battery.

To the OP's question/ problem:

1. Have someone check for high resistance grounds. Connecting an ohm meter from the neg battery terminal to the alternator body will reveal if the ground connection has high resistance. A good reading should be very close to zero.

2. Pull fuses on accessories one at a time to see if one or several are at fault for excessive draw.

3. Check all electrical connections at battery and alternator and ensure they are tight. Any missing ground straps?

 

Any resolution to this or updates?

I fear I may be in the same boat and do not want to replace the alternator if it is not necessary. My battery is less than a year old too (Interstate mtp-91) ???

Had it charged twice in the last 3 days and ran it for over 20 minutes, but then after 2 short stints it would not start the car (just clicking) ????

 

Get the car started and check the voltage reading in your battery...should read >14 volts.

Or you can use a Durametric and read real time voltage. I'm in Southern CA if you need my Durametric....

 

New battery installed and within 1 minute, volts dropped from 14ish to 12ish...

Taking it to my mechanic tonight for new alternator. This better fix it!!

thanks for the help and offer

 

I thought we had already cleared this up. It is normal for the readout to read 14 volts initially (when it's charging) and then drop to around 12.5. You should only be concerned if your batery voltage drops below 12 V.

Flash, it sounds like you might just have a bad battery. When you had it charged did they check to see if any cells were bad?

 

I did replace the battery (after the tester read that it was bad and needed replacing) and then the voltage dropped from 14 to BELOW 12 within a couple minutes on running with the new battery.....

It's getting a new alternator as I type this. That should do the trick..... it better!