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Discussion Starter · #2 ·
As soon as I jump start the 12volt battery all the messages go away and the car "starts".
Taking back to Chevy dealer near me to doag but they had it last year and spent around 1k and it was never really fixed. They did software update and replaced the high voltage coolant tank
Any help is appreciated.
Peace. Sgw
 

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No other ideas, with what you have posted, it's 99% a dead, failing, or faulty 12V battery.
You didn't say WHY the car was in the shop last year, could it be related ??????
 

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OpenEVSE home charger, 2013 Volt base, added tow hitch, K&N filters, 3d printed interior mods, etc
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Failing DC/DC converter not charging the battery? Put a multimeter on the terminals before start and when the car is on, what's the V do?
 

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Discussion Starter · #8 ·
Ok took the 12v battery out what a pita. Took it to auto zone. Charged it for 2 hours. Good news is battery is holding a charge. Bad news is tech thinks something in the car is draining the battery. How do I find that drain?
Any clues?
I read that Bluetooth left on can drain battery but idk.
 

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Ok took the 12v battery out what a pita. Took it to auto zone. Charged it for 2 hours. Good news is battery is holding a charge. Bad news is tech thinks something in the car is draining the battery. How do I find that drain?
Any clues?
I read that Bluetooth left on can drain battery but idk.
It could be a LOT of things. All the way down to "leaving your keys hanging too close to the car" in terms of dumb causes. (Yes, the Volt will not properly snooze if your RKE fob is within 10-15 feet of the vehicle. You can hear a relay tick on if you walk up to the properly-snoozing car with a fob in your pocket when it notices the key.)
 

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OpenEVSE home charger, 2013 Volt base, added tow hitch, K&N filters, 3d printed interior mods, etc
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What should the battery do if it's good vs bad?
This is my opinion from observation, not referencing a tech manual. If someone has tighter specs with more authority behind them, please chime in.

Battery resting no load / no charge / open circuit after 24 hours at room temp: 12.8 +/- .2V

Battery installed in car, everything off, should be the same V, maybe one or two tenths lower at most.

Once car is on and DC/DC converter is on, you should see 13.8-14.5V roughly across the terminals. It may move up and down a bit within that range, preferably smoothly without too many big jumps, but no big excursions out of that range. Adding loads may cause a V change but again it should be small (<.5V maybe), smoothish, and pretty consistently in that range. Converter may decide to turn off completely after some period of time also (if it thinks the 12v battery is fully charged), so battery would go back down to resting-ish voltage if that happens. But the converter should kick on again within maybe 5-10 minutes, depending on loads on the 12V systems on the car.

Before my last 12v battery change, with the DC/DC on, I was seeing lots of jumpy transients within 2-5 seconds to as low as 13V and straight up to just shy of 16V. After change, voltage values and changes were smaller and smoother.

A failing DC/DC might not raise the voltage the 1+V necessary to actually force current through the battery, or shoot up way high in voltage or be all over the place (bad regulation). Adding loads like headlights on, climate fans, etc should make the "bad behavior" from a failing DC/DC worse.

Again, this is not an official diagnostic test or anything, just my observations.

The phantom drain issue also seems plausible. Nothing left plugged into your OBD2, right?
 

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Discussion Starter · #12 ·
This is my opinion from observation, not referencing a tech manual. If someone has tighter specs with more authority behind them, please chime in.

Battery resting no load / no charge / open circuit after 24 hours at room temp: 12.8 +/- .2V

Battery installed in car, everything off, should be the same V, maybe one or two tenths lower at most.

Once car is on and DC/DC converter is on, you should see 13.8-14.5V roughly across the terminals. It may move up and down a bit within that range, preferably smoothly without too many big jumps, but no big excursions out of that range. Adding loads may cause a V change but again it should be small (<.5V maybe), smoothish, and pretty consistently in that range. Converter may decide to turn off completely after some period of time also (if it thinks the 12v battery is fully charged), so battery would go back down to resting-ish voltage if that happens. But the converter should kick on again within maybe 5-10 minutes, depending on loads on the 12V systems on the car.

Before my last 12v battery change, with the DC/DC on, I was seeing lots of jumpy transients within 2-5 seconds to as low as 13V and straight up to just shy of 16V. After change, voltage values and changes were smaller and smoother.

A failing DC/DC might not raise the voltage the 1+V necessary to actually force current through the battery, or shoot up way high in voltage or be all over the place (bad regulation). Adding loads like headlights on, climate fans, etc should make the "bad behavior" from a failing DC/DC worse.

Again, this is not an official diagnostic test or anything, just my observations.

The phantom drain issue also seems plausible. Nothing left plugged into your OBD2, right?
i did leave the fixd reader in the obd2, now that you mention it.
I will be putting the 12volt back in the 2012 volt tonight and load test it.
making sure nothing is in obd2 and no bluetooth as well.
wish me luck
'
 

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Discussion Starter · #13 ·
This is my opinion from observation, not referencing a tech manual. If someone has tighter specs with more authority behind them, please chime in.

Battery resting no load / no charge / open circuit after 24 hours at room temp: 12.8 +/- .2V

Battery installed in car, everything off, should be the same V, maybe one or two tenths lower at most.

Once car is on and DC/DC converter is on, you should see 13.8-14.5V roughly across the terminals. It may move up and down a bit within that range, preferably smoothly without too many big jumps, but no big excursions out of that range. Adding loads may cause a V change but again it should be small (<.5V maybe), smoothish, and pretty consistently in that range. Converter may decide to turn off completely after some period of time also (if it thinks the 12v battery is fully charged), so battery would go back down to resting-ish voltage if that happens. But the converter should kick on again within maybe 5-10 minutes, depending on loads on the 12V systems on the car.

Before my last 12v battery change, with the DC/DC on, I was seeing lots of jumpy transients within 2-5 seconds to as low as 13V and straight up to just shy of 16V. After change, voltage values and changes were smaller and smoother.

A failing DC/DC might not raise the voltage the 1+V necessary to actually force current through the battery, or shoot up way high in voltage or be all over the place (bad regulation). Adding loads like headlights on, climate fans, etc should make the "bad behavior" from a failing DC/DC worse.

Again, this is not an official diagnostic test or anything, just my observations.

The phantom drain issue also seems plausible. Nothing left plugged into your OBD2, right?
Put the known good battery back in. Voltage all reads good with loads and without loads. Still getting a check tire pressure warning. High voltage charges and car starts and can be driven. Going to charge it up and take it back to Chevy to run a diagnostic on it AGAIN. Wish me luck.
 

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Put the known good battery back in. Voltage all reads good with loads and without loads. Still getting a check tire pressure warning. High voltage charges and car starts and can be driven. Going to charge it up and take it back to Chevy to run a diagnostic on it AGAIN. Wish me luck.
The tire pressure warning simply means that one or more of your TPMS sensors have died. They only last about 10 years. Totally unrelated problem.
 
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