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Discussion Starter · #1 ·
Purchased my 2019 V3 a few months ago with 3000 miles. Car had been sitting on the lot for 2-3 months prior. In the next few weeks the car acted like it didn’t want to start a few times and it didn’t start on one attempt. The onstar diagnostic report also told me my battery was low. So I asked the dealer to replace the battery under warranty. They kept my car 3 days but said the battery tested good so they just charged it. My question is what battery voltage should I be getting on the dash? It almost always reads 12.4-12.5 when I’m driving and sometimes it gets as high as 13.6. Is 12.4 ok for this car? Seems kinda low to me. After they charged the battery it was in the 13s and 14s for a few days but now it’s back to 12.4-12.5 which is what it was before they charged it. Should I be concerned? I’m assuming the alternator is good since car has less than 4000 miles. Thanks.
 

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With car running a you should see at least 13.5 to around 14 volts. If the battery is back down to 12.5 volts, it's not fully charging. Sounds like it should be replaced. They should also have tested the alternator output. Also, 3 days to check a battery, that's another issue.
 

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Discussion Starter · #3 ·
With car running a you should see at least 13.5 to around 14 volts. If the battery is back down to 12.5 volts, it's not fully charging. Sounds like it should be replaced. They should also have tested the alternator output. Also, 3 days to check a battery, that's another issue.

So you’re saying on your V3 the battery voltage shown on the dash never drops below 13.5? So on my way home from work this evening the voltage actually read 13.8. But when I went to work it read 12.4-12.5 all the way there. I also got a “service steering column lock” message pop up when I left from work which I’m guessing may be related to a low battery also? The car also failed to remote start at that time. I agree they should have also tested the alternator.
 

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A good battery with engine off should read 12.5vdc. Your charging system (DIC) when running should read about 14.2vdc.
 

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Discussion Starter · #7 ·
So a reading of 12.4-12.5 during normal driving is a cause for concern? So no other v3 owners get a reading that low on the DIC? I read somewhere that voltage is sometimes reduced by the computer on purpose to limit alternator usage and save a small amount of gas. Any truth to that does anyone know?
 

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Just checked mine. After sitting for several days, bat showed 13.1v at startup. Normal highway driving showed avg 14.4v. If you're seeing 12.5 while driving that would be low..
 

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This has been covered many times already, and is the same for all GM vehicles. You can no longer rely on engine running voltage since fuel economy is #1.

These cars have variable charging voltage systems. Plenty of threads on this for vettes and camaros. Battery display voltage can be anything from 12.3-15.0 and be considered normal even for a new battery. It will generally stay in the 12.x with the engine running until it decides something needs extra juice: headlights, full throttle fuel pump, or the battery needs charging.
 

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I see 12.5 while cruising and no issues with the car. I don't have voltage on the screen all the time to see if it varies. Again, no issues with the car or starting, etc.
 

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Battery voltage under 12.6 is not 100%. Once the bat is fully charged the regulator will reduce charging enough to maintain bat voltage, if draw increases, so does the regulator. Search battery charging. Or go to a local auto parts dealer, they can easily do a load test to show the bat state.

151441
 

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thats no load voltage, ie car off for several hours. Also, those readings are different for flooded lead vs AGM, and vary based on temperature. AGM 100% is usually higher V than flooded.

Here are my readings from a while ago when I was concerned about the battery. All readings when car off were taken from battery terminals in trunk from a multimeter. The multimeter battery readings match the car display reading during idle, so I assume the car display is correct battery voltage.

Readings on my 2Yr old AGM battery kept on battery tender:

24hr after unplugging temperature compensating tender: 12.85V
Immediately after startup: around 12.0V, then increase to 14.8-15.0 within a minute before slowly dropping back to 12s
Cruise control 100miles 70F day: 12.3V (might pop to 14.7 occasionally, then return to 12.3V)
Idle in garage after drive: 12.3V
immediately after Shutoff car: 12.7V (yes voltage goes UP after turning off car)
24hr after car off, no battery tender: 12.85V
 

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Discussion Starter · #13 ·
This has been covered many times already, and is the same for all GM vehicles. You can no longer rely on engine running voltage since fuel economy is #1.

These cars have variable charging voltage systems. Plenty of threads on this for vettes and camaros. Battery display voltage can be anything from 12.3-15.0 and be considered normal even for a new battery. It will generally stay in the 12.x with the engine running until it decides something needs extra juice: headlights, full throttle fuel pump, or the battery needs charging.
Thanks for that info I just read through the manual and it does state that as well. It says that is normal and if there’s a problem with the charging system an indicator light will pop up on the DIC. So I won’t worry about it for now. But I wonder why the car did not start that one time. It did start on the second attempt though.
 

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hot starts? Try this. I added an extra 1ga ground just like in this thread, and it worked wonders for hot start. Before the extra ground, the car sometimes struggled hard enough to pop a "service stabilitrak" and "check rear axle" light.

 

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Discussion Starter · #15 ·
hot starts? Try this. I added an extra 1ga ground just like in this thread, and it worked wonders for hot start. Before the extra ground, the car sometimes struggled hard enough to pop a "service stabilitrak" and "check rear axle" light.

Thanks for the link I never knew there was an issue with hot starts on these cars.
 

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My car was having a hard time starting, just replaced the battery 2 days ago. Starts perfectly fine now and when driving sits around 12.5, and when at WOT goes up to about 13.8-14.0

ACDELCO batteries have a 3 year warranty so make sure you look into that
 
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