Chevy Volt recovering from dead battery

2021-11-19

(UPDATED 2022-05-11, a brand new battery died suddenly, and the behavior observed and fixes applied have been updated here for clarity)

This is a very specific topic. I have a 2013 Chevy Volt, and have had it for about ten years. The AC Delco battery recently died (after 9.5 years on the job, which is extraordinary), and I replaced it with a NAPA AGM. However, the new battery wasn’t fully charged, and the Volt only charges it under specific conditions.

This is uh, a full rundown of quite a few hours worth of screwing around.

TLDR

Jump the car (always from under the hood, not the battery itself)
quickly put it in park, engage the parking brake, open the charging port
disconnect jumpers
disconnect the 12v in the back
wait a couple minutes
reconnect the 12v battery
plug the car into a wall outlet (yes, this is required)
jump the car again
when the car acknowledges negotiation with the charger (the charging light on the dash goes green and the car "bleeps"), disconnect jumpers.

The situation

I got into my car, hit the power button, and it took an oddly long time to get off the "initializing" screen, and the cabin lights were dim. All the lights were dim, and dimming fast. When it finished booting, it displayed a raft of warnings (service stabilitrak, power steering, braking, charging system, etc - check engine light, and eventually battery light). The car then slowly dimmed until it died.

This was a dead battery. I bought a new one, replaced it (more on that process later), and that fixed the issue. However, store batteries aren’t fully charged, and after a week or two of not driving, i came back to it, and the new one was empty as well.

(By "dies" i mean it’s at the end of its life and won’t be useful anymore. But "empty" i mean it’s a good battery that just needs charge)

A list of things that don’t work, that you need to have working, without a healthy 12v battery

The button that opens the hatch from the outside
the button that opens the charger port
the parking brake
the shifter

This will become relevant later, but you should know what you’re in for.

When the Volt charges 12v

The Volt has (at least?) two battery systems - the "main battery", which is what directly powers the drivetrain and takes up the bulk of the weight of the car; and the 12v battery; which is identical to any other car battery you’ll ever find. Almost every function of the car that requires power (lights, screens, power steering, brakes, etc) is run by the 12v battery, not the main battery. This is standard with how regular cars work, too.

Except regular cars generally have an alternator - when the engine is running, it charges the battery. The Volt doesn’t do this. (more detail) It has a gas generator, but there is no alternator. The 12v battery is charged from the main battery - but only when you’re driving (read: when the main battery is discharging) or the car is plugged into a wall charger.

What happens when a car battery is empty

When the Volt deals with a nearly-empty battery, it engages Battery Saver and a few other low-power mode settings, in order to extend the life of the car. This is normally a great idea, but unfortunately this failure mode comes at a price - it never gives up on its state. This means that if you hit the power button to start the car, it did go into driving mode (as opposed to being parked). And due to the problems of batteries, it will still try to stay in driving mode when you jump the car. Adding power only serves to make it struggle to retain the state it is currently in. Unfortunately, you cannot charge the car when it’s in driving mode. You also don’t have enough power to switch to parking mode (sometimes literally there isn’t enough to operate the parking brake, but mostly pressing the power button will cause the display to blink before remaining in the current mode).

When the Volt is completely unable to draw 12v power (because you disconnected the battery, or because it’s completely dead), this acts as a sort of "reset". It doesn’t lose any memory, but whatever state your vehicle was in is forgotten. You’re not in driving mode anymore.

How to get at the 12v battery

Fun fact, the hatch requires power to operate, so you’ll need to put the back seats down, crawl in the back with a wrench of some kind (I used an Allen wrench, but whatever it is needs to fit a 7/16ths square hole), remove the small square cover in the center of the door (below the hatch windows), dig around to find a square hole, twist it (so the the square rotates), and the hatch will open. Video about this, which was a lifesaver to me.

Then, with the hatch open, pull up the floor in the back - and by "pull up" i mean fully pull it out, the triangle latches at the "hinge" should be displaced, and you should see a bit square alumnum box in front of you (the APM), along with the molded plastic compartment that usually houses the wall socket charger and air compressor. On each of the four corners there are screws, a 10mm socket wrench fits them fine. Take them out, remove the molded plastic floor, and in front of you is the battery.

The plastic cover over the positive terminal hides the breakout terminals. Remove it by finding the plastic "clamp" on the "front" (towards the front of the car) side of it and flipping it, then wiggling it off (i’m vague here because this one because it’s impossible to screw up - just unclamp anything clamped and pull on it til it comes off).

How to jump the car

Congratulations, none of those steps help you jump the car. I hope you read the whole page before following steps.

Under the hood (which is popped mechanically, thankfully) are two terminals, a big positive lead, and underneath a plastic cover two fused… screws. Yeah literally just screws. Attach positive (red) first - to the screw. Then attach negative to the bolt. Turn on your jump pack or whatever, and now your car has power. If you’re using a jump pack you might need to hit a "boost" button to make it work. Now you’ve got power, cool!

Except it probably didn’t get you anywhere.

I spent so much time writing about drive mode and battery saver for precisely this moment - your car came alive, but not fully. The lights are still dim, and the computer is still screwed up. You can’t turn the car off, and you can’t do much. No matter how many buttons you push, the car will just drain the battery jumping it, and go back to the state it was in.

Instead, you should first disconnect the 12v battery and wait five minutes. This will take the car out of any previous state it was in (battery saver / driving mode etc). Next, plug the car in - we need to do this because at this point the 12v will only charge from a wall outlet, not the main battery itself. Finally, jump the car as described.

Finally, it’s important to note that the Volt requires tons of energy to boot. In my experience, it requires about 30% of a full charge of an 18000mAH jumpkit to be able to usefully do anything. The car seems to prefer to keep lights on instead of prioritizing the functionality of the shifter, brake, charging port, hatch, or other things that you actually need.

This was way too many words

I know.