Low battery voltage
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
Low battery voltage
My battery (dash #'s) registers 10.8 to 11.2 when I turn on the key, 12.8-13.2 once started. If I drive around awhile, sometimes, the voltage drops into the mid 12's. I also get occasional dash light flickering. Starting the car sometimes takes up to 3 tries before she catches and fires all the way.
Is this the alternator or just a battery issue? Battery is old and this car has been in storage for awhile. A new battery is prob on the list anyways but how do know the tell-tale signs of an alternator slowly going?
Is this the alternator or just a battery issue? Battery is old and this car has been in storage for awhile. A new battery is prob on the list anyways but how do know the tell-tale signs of an alternator slowly going?
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
Pro
Joined: Jan 2011
Posts: 580
Likes: 8
From: Clemson SC
Advance Auto and others can check them both out in the car to some extent. However, IMO the tests seem to be more reliable when they are each on the bench separately.
Sounds to me like it may be at least somewhat an alternator issue since it should be charging at the 13+ volts when driving at speed, i.e., at a reasonable rpm above 1000 or so, and the car will run off the alternator voltage until you stop and idle. At night, you might also notice the lights dim significantly at idle because of the low battery voltage, i.e., when the alternator is not charging much.
My philosophy has always been to not take a chance when the battery seems to be going -- it probably is and can make other items look like they are bad. Of course, it can also be a wiring issue. I once had a bad gage fuse (pink with black wire) which will also keep the alternator from properly charging.
Good luck getting to the root of the problem!
Sounds to me like it may be at least somewhat an alternator issue since it should be charging at the 13+ volts when driving at speed, i.e., at a reasonable rpm above 1000 or so, and the car will run off the alternator voltage until you stop and idle. At night, you might also notice the lights dim significantly at idle because of the low battery voltage, i.e., when the alternator is not charging much.
My philosophy has always been to not take a chance when the battery seems to be going -- it probably is and can make other items look like they are bad. Of course, it can also be a wiring issue. I once had a bad gage fuse (pink with black wire) which will also keep the alternator from properly charging.
Good luck getting to the root of the problem!
Le Mans Master
Joined: Feb 2000
Posts: 9,060
Likes: 214
From: Epping NH
You can do a load test on the battery when it's fully charged. Hold the leads of the volt meter to the corresponding battery terminals and watch the volt meter while someone else starts your car. Make a note of how low the battery voltage drops. A normal car battery will drop to 10 or 11 volts. If your battery voltage drops below 10, this is a sign that it needs to be replaced.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
In Florida where is HOT a old battery is 3 years old. If I get past that with any of my cars I feeling lucky but ready for a battery. If you alternator is not charging the battery properly, then your cranking problem may be related to that especially if the battery is old and does not have the full power and snap of a new battery.
But your flickering lights and low charging voltage symptom is probably the voltage regulator (not battery) in the alternator going bad. Test the charging voltage with a external DVM and make a determination with that.
If it looks like the charging is low, either get the alternator rebuilt or get one with a lifetime exchange.
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
In Florida where is HOT a old battery is 3 years old. If I get past that with any of my cars I feeling lucky but ready for a battery. If you alternator is not charging the battery properly, then your cranking problem may be related to that especially if the battery is old and does not have the full power and snap of a new battery.
But your flickering lights and low charging voltage symptom is probably the voltage regulator (not battery) in the alternator going bad. Test the charging voltage with a external DVM and make a determination with that.
If it looks like the charging is low, either get the alternator rebuilt or get one with a lifetime exchange.
What a serious royal PITA to replace the battery. I had to remove the gill panel, loosen the lower rocker panel, and undo the engine shield just to get it out because some genius GM design engineer decided to put it under the Cruise control unit.
It does start right up now! Thanks everyone for the advice!
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Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
My MGB 2-6 volt batteries were inside the car under the rug and plate.
Once you get in your mind how the vette battery comes out, it won't seem a pain in the future.
How is your charging voltage now and are the lights still flickering?
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
I have seen worse. Once saw a battery changed at a parts store where the car had to be jacked up and the front right wheel removed.
My MGB 2-6 volt batteries were inside the car under the rug and plate.
Once you get in your mind how the vette battery comes out, it won't seem a pain in the future.
How is your charging voltage now and are the lights still flickering?
My MGB 2-6 volt batteries were inside the car under the rug and plate.
Once you get in your mind how the vette battery comes out, it won't seem a pain in the future.
How is your charging voltage now and are the lights still flickering?
The battery I got is a 700 CCA, much improved over the 525 Everlast (Walmart) I had in there that tested 390 CCA today at Advanced when tested under load with their machine. They could not test the alternator as their machine was broke. I'll see how it behaves tomorrow. I still think the alternator may need replaced but the current battery certainly needed to go.
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
I would tend to agree. You're in that suspicious area where it is not a flat 12 volts but should be about 14.5-14.7 in the morning when first started. It should drop down some as it charges to about 14 volts. These are approximate numbers and only ranges for alternators vary as do read outs on the dash car to car.
But it seems that it is charging but somewhat low and definitely warrants looking into.
But it seems that it is charging but somewhat low and definitely warrants looking into.
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
I would tend to agree. You're in that suspicious area where it is not a flat 12 volts but should be about 14.5-14.7 in the morning when first started. It should drop down some as it charges to about 14 volts. These are approximate numbers and only ranges for alternators vary as do read outs on the dash car to car.
But it seems that it is charging but somewhat low and definitely warrants looking into.
But it seems that it is charging but somewhat low and definitely warrants looking into.
Instructor
Joined: Jun 2002
Posts: 154
Likes: 3
From: San Diego CA
A blown diode in the alternator will also give you a weak charge. (Jump starting someone else's vehicle can cause this.)
If you do need an alternator, I would recommend finding a shop in town to rebuild the one you have. They tend to be better quality than over the counter rebuilds. You can also have them upgrade it to put out more amperage, IF you need it. (upgraded lights, amps, speakers, etc)
If you do need an alternator, I would recommend finding a shop in town to rebuild the one you have. They tend to be better quality than over the counter rebuilds. You can also have them upgrade it to put out more amperage, IF you need it. (upgraded lights, amps, speakers, etc)
Pro
Joined: Dec 2009
Posts: 502
Likes: 0
A blown diode in the alternator will also give you a weak charge. (Jump starting someone else's vehicle can cause this.)
If you do need an alternator, I would recommend finding a shop in town to rebuild the one you have. They tend to be better quality than over the counter rebuilds. You can also have them upgrade it to put out more amperage, IF you need it. (upgraded lights, amps, speakers, etc)
If you do need an alternator, I would recommend finding a shop in town to rebuild the one you have. They tend to be better quality than over the counter rebuilds. You can also have them upgrade it to put out more amperage, IF you need it. (upgraded lights, amps, speakers, etc)
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
I would tend to agree. You're in that suspicious area where it is not a flat 12 volts but should be about 14.5-14.7 in the morning when first started. It should drop down some as it charges to about 14 volts. These are approximate numbers and only ranges for alternators vary as do read outs on the dash car to car.
But it seems that it is charging but somewhat low and definitely warrants looking into.
But it seems that it is charging but somewhat low and definitely warrants looking into.
Battery hangs in the 13.0-13.4 range when driving.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Alternator output cold is 14.7 volts and the dash voltmeter will always read 0.3 volts lower due to voltage drop across the ignition switch contacts. The alternator is designed to reduce its output voltage with increasing temperature and your dash voltmeter should read 13.3 volts approximately when the alternator gets to its operating temperature.
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
Alternator output cold is 14.7 volts and the dash voltmeter will always read 0.3 volts lower due to voltage drop across the ignition switch contacts. The alternator is designed to reduce its output voltage with increasing temperature and your dash voltmeter should read 13.3 volts approximately when the alternator gets to its operating temperature.
Thanks for the replies everyone!
Instructor
Joined: May 2011
Posts: 102
Likes: 0
From: SE SD
Replaced the battery with an Autocraft Gold from AdvancedAutoParts. Used my $50 off over $100 coupon so got it for $55.
What a serious royal PITA to replace the battery. I had to remove the gill panel, loosen the lower rocker panel, and undo the engine shield just to get it out because some genius GM design engineer decided to put it under the Cruise control unit.
It does start right up now! Thanks everyone for the advice!
What a serious royal PITA to replace the battery. I had to remove the gill panel, loosen the lower rocker panel, and undo the engine shield just to get it out because some genius GM design engineer decided to put it under the Cruise control unit.
It does start right up now! Thanks everyone for the advice!
Thread Starter
Racer
Joined: Apr 2011
Posts: 296
Likes: 1
From: Tipp City Ohio
I took the old Everstart back to Walmart today and got a replacement battery. Since I already bought one, won't need it but nice to have as a backup. They wouldn't give me store credit or refund, only replacement so why not.