Voltage drop on battery when headlights are OFF, fine when they're on

[Androideka]

Here's a weird one for you guys and TLDR: New battery, voltage is 12.5 and radio glitches with headlights OFF and 13.8-14.2 and works OK with headlights ON

2015 Camaro V6 6 speed manual

The car was taking awhile to crank, so a few weeks ago I got my battery tested at AutoZone and they replaced my 3 year old battery under warranty (cool!). It's a Duralast Platinum EFB.

After getting replaced, I now have a problem: When my car is running and headlights are ON, the battery voltage readout on the dash is good - 13.8-14.2 and no issues (for the most part, will get to below)

As soon as I turn my headlights off or it's light out and they auto turn off, the voltage shoots down to 12.5 over a few seconds and the radio glitches out and starts popping through the speakers until I turn the car off, open/close the door and the let the computer kill the power. A few times, the radio has glitched out when the headlights are on at 13.8. I can turn the lights on/off and watch the battery voltage go up-down. When driving with the lights off, the battery will just stay right around 12.5 indefinitely - the battery won't actually die

Is this a bad battery, or did something happen during the battery change that caused some kind of electrical issue? A side note: when bolting on the positive terminal, the socket fell off the ratchet and sparked on the terminal/some kind of metal bracket. Everything else in the car works perfectly except what I described above

 

[dogememe]

Some issue with the computer controlled charging system I'd guess? Turning the headlights on tells the computer there is more electrical load so it increases charging output.

 

[D60]

Charging behavior sounds normal for new cars. They don't always charge but the additional draw of the headlights would trigger it.

I think you have a radio/radio circuit problem.

 

[Vercingetorix]

Smart alternator at work.

 

[Jetronic]

get the schematics out, often times there's a voltage stabilizer in smart charging cars) to keep stuff inside the car seperated from the changing voltages. Is that still working?

 

[SC Maintenance]

The charging behavior seems normal to me also. The new generation of cars will turn the alternator completely off if they feel their isn't enough load to need it.

Did you wire your stereo directly back to the battery? If so you likely bypassed the smart charge current sensor, so the ECU doesn't know you need more power?

If you wired it into the existing wiring system - like a current fuse panel or whatever, then it sounds like your stereo doesn't like a voltage at 12.5V. Might be too small gauge wire and isn't getting enough current or something?

 

[LvR]

Possible that there is a BMS on the vehicle that wasn't told it's got a new battery? (IOW coded the battery properly)

 

[Androideka]

Charging behavior sounds normal for new cars. They don't always charge but the additional draw of the headlights would trigger it.

I think you have a radio/radio circuit problem.

That sounds reasonable, would this show up in an advanced OBD scan? I have a cheapo $20 scan tool for CELs, but I can take it to AZ for a scan

 

[Androideka]

The charging behavior seems normal to me also. The new generation of cars will turn the alternator completely off if they feel their isn't enough load to need it.

Did you wire your stereo directly back to the battery? If so you likely bypassed the smart charge current sensor, so the ECU doesn't know you need more power?

If you wired it into the existing wiring system - like a current fuse panel or whatever, then it sounds like your stereo doesn't like a voltage at 12.5V. Might be too small gauge wire and isn't getting enough current or something?

That makes sense, I have never paid attention to the charging habits/voltage before this unfortunately. The stereo is completely stock - but definitely doesn't like the 12.5v all of a sudden - guaranteed to stop working once it hits 12.5 and won't recover until a full power kill. Any ideas for troubleshooting that portion?

 

[Androideka]

Possible that there is a BMS on the vehicle that wasn't told it's got a new battery? (IOW coded the battery properly)

Interesting, what would cause this, and what would I be able to do to get the sensor to realize the new battery?

 

[D60]

Any time my friends or clients think I know stuff (I know BITOG knows better -- and rightfully so), it's really just that I have a smartphone and the Information Age can be pretty cool:

 

[tcp71]

The radio popping isn't normal, but the charging behavior is normal for a smart battery management system (BMS) most new cars have. You either need to reset the BMS to account for the new battery, or unplug the inductive ring that circles the negative ground wire near the battery for it to charge without the BMS affecting things.

 

[D60]

Interesting, what would cause this, and what would I be able to do to get the sensor to realize the new battery?

On Fords BMS is reset with a higher end scan tool or Forscan. However I'm not sure GM employed such a system in 2015. Maybe. A web search would answer that, too.

It's unlikely AutoZone would install a BMS battery. I know on O'Reilly's site for BMS-Fords it has tech notes full of doom about "PANIC- battery requires professional installation. Sky is falling." @dogememe could maybe speak to this

 

[SC Maintenance]

That makes sense, I have never paid attention to the charging habits/voltage before this unfortunately. The stereo is completely stock - but definitely doesn't like the 12.5v all of a sudden - guaranteed to stop working once it hits 12.5 and won't recover until a full power kill. Any ideas for troubleshooting that portion?

In that case I would say you definitely have something else going on. I can't imagine a OEM stereo having any issues with 12.5V.

 

[Dave9]

Something is going on with the radio or circuit to it. You might measure for voltage drop when the fault occurs, at the fuse (easier) then if good, at the radio. Also check for good (very low resistance to battery) ground. If both are good, radio is probably failing. This assumes you aren't facing a narrow opportunity/unlikely situation where you just happen to be blasting the radio at high volume and this little bit of voltage difference isn't enough for that volume so it is clipping.

 

[Audiman]

Have you checked for corrosion at the battery terminal clamps?

 

[dogememe]

On Fords BMS is reset with a higher end scan tool or Forscan. However I'm not sure GM employed such a system in 2015. Maybe. A web search would answer that, too.

It's unlikely AutoZone would install a BMS battery. I know on O'Reilly's site for BMS-Fords it has tech notes full of doom about "PANIC- battery requires professional installation. Sky is falling." @dogememe could maybe speak to this

It does say that in the system for Fords and certain Euro cars but I can tell you that exactly ZERO customers care and they all just go install their battery and move on with their life. But when it says that we don't usually install the battery. But the customers end up doing it so the only difference is it's their problem vs our problem.

 

[khogle2]

Here's a weird one for you guys and TLDR: New battery, voltage is 12.5 and radio glitches with headlights OFF and 13.8-14.2 and works OK with headlights ON

2015 Camaro V6 6 speed manual

The car was taking awhile to crank, so a few weeks ago I got my battery tested at AutoZone and they replaced my 3 year old battery under warranty (cool!). It's a Duralast Platinum EFB.

After getting replaced, I now have a problem: When my car is running and headlights are ON, the battery voltage readout on the dash is good - 13.8-14.2 and no issues (for the most part, will get to below)

As soon as I turn my headlights off or it's light out and they auto turn off, the voltage shoots down to 12.5 over a few seconds and the radio glitches out and starts popping through the speakers until I turn the car off, open/close the door and the let the computer kill the power. A few times, the radio has glitched out when the headlights are on at 13.8. I can turn the lights on/off and watch the battery voltage go up-down. When driving with the lights off, the battery will just stay right around 12.5 indefinitely - the battery won't actually die

Is this a bad battery, or did something happen during the battery change that caused some kind of electrical issue? A side note: when bolting on the positive terminal, the socket fell off the ratchet and sparked on the terminal/some kind of metal bracket. Everything else in the car works perfectly except what I described above

Regulated voltage control. Doesn’t sound unusual for this system. Normally if it’s working ok you can see the voltsge go way up closed throttle down a grade or when an accessory is loading the battery. May have to diagnose that system to see if it’s causing noise on the LAN.

 

[Androideka]

Any time my friends or clients think I know stuff (I know BITOG knows better -- and rightfully so), it's really just that I have a smartphone and the Information Age can be pretty cool:

Yeah checking the forums and what everyone is saying on here, definitely sounds like a blown stereo unit/electrical issue in the stereo unit. I got my battery replaced again yesterday for free just to rule that out, same issue. To the dealership it goes, I don't want to load up the parts cannon fixing an electrical issue on my own if I don't have to. We'll see what they say

 

[tiger862]

I bet they find a bad ground. Different vehicle, however on a Toyota I found a 3rd break light bulb that had high resistance causing same problem. I used to run into weird problems at dealer.