Car battery dies

njbaseball14 · 09-30-2007, 08:22 PM

Any idea why my car battery would die all throughout the day. New alternator and I disconnected the positive cable while it was running and it did not turn off so I assuming the alternator is good. Not sure what I should check next.
Thanks.

**Midnight Tech** · 09-30-2007, 08:28 PM

What kind of car is it?
On late model cars it's not good to disconnect any cables while it's running...it creates a surge that can take out all your electronics.

njbaseball14 · 09-30-2007, 08:31 PM

Thanks...I did not know that about the surges. It is a 1980 corvette. When I jump it, it runs great. I turn it off and come back later in the day and it is dead again.

**qldit** · 10-01-2007, 07:15 PM

Good Morning njbaseball14, that symptom often is present when the alternator diodes have been damaged.
The battery is usually completely discharged, dead flat.

Charging the battery and restarting appears normal.

What commonly happens is that there has been a mishap using jumper leads and although the system appears to operate normally, when the alternator is hot after running for a while the diodes break down and a discharge path then exists through the alternator windings.

With the battery disconnected, disconnect and insulate the large feed wire at the alternator, charge the battery properly and reconnect it, see how the vehicle operation is for a day (running entirely off the battery power leaving the alternator discon) or so with limited accessory use (no head lights etc) and if the problem has cleared consider replacing the alternator.

Always be extremely careful with jumper leads, a microsecond mishap is too much!

Others will have different ideas.

Cheers, qldit.

09-30-2007, 08:22 PM	#1 (permalink)
njbaseball14 Registered User Join Date: Sep 2007 Posts: 2 OS: win 98	Car battery dies Any idea why my car battery would die all throughout the day. New alternator and I disconnected the positive cable while it was running and it did not turn off so I assuming the alternator is good. Not sure what I should check next. Thanks.

09-30-2007, 08:28 PM	#2 (permalink)
Midnight Tech Admin/Head GreaseMonkey/Igor's alter ego/Grand Exalted PoohBah Join Date: Dec 2001 Location: SC Posts: 2,920 OS: Windows XP Home/Pro SP3/Windows 98SE/Fedora Core 6/RH 7.2 with Autopoint/TAMS II	Re: Car battery dies What kind of car is it? On late model cars it's not good to disconnect any cables while it's running...it creates a surge that can take out all your electronics. __________________ Please post all questions in the appropriate forum. Questions sent by email or PM will not be answered. Sharing my life...with my Imzadi! Interested in Trek gaming? Check out the Dynaverse! Proud supporter of the Carolinas Aviation Museum. If we have helped you in any way, please donate to keep TSF up and running!

09-30-2007, 08:31 PM	#3 (permalink)
njbaseball14 Registered User Join Date: Sep 2007 Posts: 2 OS: win 98	Re: Car battery dies Thanks...I did not know that about the surges. It is a 1980 corvette. When I jump it, it runs great. I turn it off and come back later in the day and it is dead again.

10-01-2007, 07:15 PM	#4 (permalink)
qldit TSF Gearhead Join Date: Mar 2007 Location: Brisbane Australia. Posts: 592 OS: All Systems, mainly Linux	Re: Car battery dies Good Morning njbaseball14, that symptom often is present when the alternator diodes have been damaged. The battery is usually completely discharged, dead flat. Charging the battery and restarting appears normal. What commonly happens is that there has been a mishap using jumper leads and although the system appears to operate normally, when the alternator is hot after running for a while the diodes break down and a discharge path then exists through the alternator windings. With the battery disconnected, disconnect and insulate the large feed wire at the alternator, charge the battery properly and reconnect it, see how the vehicle operation is for a day (running entirely off the battery power leaving the alternator discon) or so with limited accessory use (no head lights etc) and if the problem has cleared consider replacing the alternator. Always be extremely careful with jumper leads, a microsecond mishap is too much! Others will have different ideas. Cheers, qldit.