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Discussion Starter #1
I bought my Gen 2 Volt in Jan. 2016. Gently driven only on Sundays (hah), so just under 30,000 miles, of mixed highway/surface road travel, 80% electric. In our location, we get winter lows in the 30's, summer highs in the 100's. Only one visit for service in nearly 4 years for a "shift to park" replacement.

I've read about the nightmares when the 12 V battery fails. This happened with my wife's Prius, fortunately just before pulling out of our garage. I have one of those little volt meters plugged into the 12 V outlet. Immediately after turning engine "off", it reads 12.6. So, should I get a new 12 V battery? Can the local auto parts store check the 12 V in the Volt?

Many thanks.
 

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The Volt charges the battery from the main battery when it is on. The battery may hold a charge just after the car is turned off but may still be bad. To get a better idea it is better to check after the car is off a few days to allow the battery to drain gown if it is going to. Not sure about checking at power outlets (they may get turned off after a while). Best to do it from battery posts to get most accurate.
 

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Discussion Starter #3
The Volt charges the battery from the main battery when it is on. The battery may hold a charge just after the car is turned off but may still be bad. To get a better idea it is better to check after the car is off a few days to allow the battery to drain gown if it is going to. Not sure about checking at power outlets (they may get turned off after a while). Best to do it from battery posts to get most accurate.
I'm not very savvy about electricity. Can I test this myself using a multi-meter, across the 12 v battery terminals?
 

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Since you already have a DC voltmeter plugged into the Volt's accessory port it can provide some useful information re the Volt's charging system and the 12V AGM battery.

When the Volt is powered on you will see anywhere from 15.4V down to 12.4V being provided by the Volt's 12V Accessory Power Module (the Volt does not have a conventional alternator as with an ICE vehicle.)

After you power off the Volt, before you open the driver's door, the Volt will maintain power to certain 12V systems for 10 minutes or until you open the driver's door. The 12V accessory ports, USB ports, entertainment system, exterior lights and interior lights will remain powered. You should see perhaps 12.6V to 13.0V when the Volt is first powered off, over the 10 minutes the the 12V battery is powering these accessories the voltage will drop; if it stays above 12.0 - 12.2V then everything is probably OK with the 12V battery. The 12V battery is suspect if the voltage reading falls under 12.0V. A fully charged 12V AGM type battery would read 12.8 - 12.9V; in general use you will see 12.3V - 12.6V and everything is probably fine with the 12V battery.

If you want to test the voltage of the 12V battery with a multi-meter tester, after the Volt has been sitting, not being charged, you can access the 12V jump starter terminals under the hood, on the driver's side. The (+) terminal is under a protective plastic cap that is stamped (+.) The negative or ground terminal is an elongated hexagonal nut/bolt that is connected directly to the vehicle chassis by the firewall (also on the driver's side.) You can, of course, also access the 12V battery terminals directly (there is a plastic fuse holder attached to the battery that makes it a bit difficult to gain access to the (+) battery terminal. (Note: the jump starter terminals located under the hood are fused, only to be used for jump starting the Volt not jump starting another vehicle using the Volt as a 12V power source.)

If you plug in the Volt to charge the main battery the 12V battery will also periodically be charged to maintain the 12V battery.

In all probability your 12V battery is probably still good. I like to replace my 12V battery at the 3 to 4 year mark based on my experience with multiple vehicles and both AGM type and conventional 12V batteries. I would rather pay the cost of a new battery at 3 - 4 years than be inconvenienced by a dead 12V battery in winter, or being unable to unlock or start the vehicle parked at the airport when returning from a trip.

One useful accessory you may want to get is a small portable lithium battery jump starter. These are generally available for less than $50, can jump start the Volt's 12V systems. Since you are not trying to turn a 12V starter motor to crank an engine even the smallest capacity jump starter pack should be able to boot up the Volt's 12V systems. One exception would be if the 12V AGM battery had an internally shorted cell (the 12V battery voltage would read less than 11.0V, perhaps as low as 9.0V.) In that case you would need to disconnect the negative terminal from the 12V AGM battery before a small jump starter would be able to power up the Volt.
 

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Discussion Starter #5
Many thanks. It sounds like you recommend getting a new battery, since I am now closing in on 4 years. I will do the tests that you suggested during the day today, and report back. If I don't fry myself trying.
 

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I'm not very savvy about electricity. Can I test this myself using a multi-meter, across the 12 v battery terminals?
Yes. Just be sure the setting is on the 20V (or equivalent) DC range. Not AC. Not Ohm. Not Amp which are the other possible settings on most multi meters.
 

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Many thanks. It sounds like you recommend getting a new battery, since I am now closing in on 4 years. I will do the tests that you suggested during the day today, and report back. If I don't fry myself trying.
I would start shopping, looking for a sale price for the correct Group 47 AGM battery. Will the battery make it through this winter? Probably but there is no way to know for certain. Will you be unduly inconvenienced if your Volt does not unlock, cannot be started one day when you need to use the vehicle? Only you know your threshold for being inconvenienced. If you carry a jump starter battery pack in the Volt you need to learn how to access the hidden key slot in the door handle of the driver's door, how to jump start the vehicle if the 12V battery is not holding a charge. (Note: you won't be able to open the hatch if the 12V battery is discharged; you would need to climb into the hatch from the rear seat and remove a small access panel and use a screwdriver to manually operate the hatch release mechanism. If you need to jump start the Volt it is much easier to access the jump starter terminals located under the hood, as previously noted.
 

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I'm still running with the OE 12v battery after more than 8.5 years in my 2011 Volt here in warm Arizona. I don't understand why anyone would replace a perfectly good battery if it hasn't caused any problems. The battery lives in the passenger compartment which is a pretty nice place for the battery to live, otherwise you would be uncomfortable as well. The 12v doesn't have much of a job to perform: monitor the remote keyless entry system when the car is off, provide enough power to bring the Volt electronics to life when needed are about it.

The "little volt meter plugged into the 12v outlet" won't tell you anything about the state of the battery, because the outlet is turned off a few minutes after the Volt is powered down. The only time it will give you an indication of the state of the battery is when the battery is too low to power up the car and turn on the 12v outlet - too late to do any good.

Measuring the voltage from under the hood is a fine idea, but when you open the door to pop the hood the Volt's 12v system will be effectively ON. So open the hood then leave the Volt alone for some time (6-8 hrs) without charging. At that time you will get a reasonable reading of the voltage.

The most effective health check of the 12v battery is a load test that most auto parts stores can do. Usually, the battery is removed from the car and tested on a load bench to examine the response/recovery the battery exhibits. Be warned that the auto parts store is in the business of selling batteries and the report may not be accurate.

VIN # B0985
 

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The interior lighting will only stay on for ~30 minutes if you leave the door open. Letting the 12V battery sit, unplugged and not charging for some hours can get you a better indication of the nominal battery voltage.

A load test is of little value when testing a hybrid vehicle 12V battery; the battery never has to perform under the load conditions of a conventional battery where it must deliver 150 amps for perhaps 10 seconds while cranking a starter motor.

Batteries succumb due to age, environmental temperature, vibration and duty cycle. An unintentional deep discharge of a non-deep cycle battery will permanently affect the battery's ability to operate at full capacity.

There is no certain way to determine when a battery may be at the end of it's useful life. Unless a cell within the battery is dead; then the battery will read less than 11V.
 

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Here's another discussion of this topic.
You'll see that my battery failed well before the "average" life span (well, someone's has to, or it wouldn't be an average, right? You're welcome). Now I have a new battery and am on the lookout for a super deal on one of those lithium jump-starters that jcanoe mentioned. But, I've got time, right? Sure, I do....
 

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Discussion Starter #11
Here are results from testing today:

Voltmeter plugged into 12v outlet: Volt turned "on": 12.9v; driving: 12.7v; Volt turned "off", sitting for 8 min., radio on: 12.1v

Multi-meter testing across "jump start terminals" under hood: Volt turned "off" for 8 hrs., opened driver side door, popped hood latch, closed door, opened hood, interior lights out for 2 hours: 12.45 v

A little background: I'm in my 70's. This is the best car I've owned since my Porsche 911S back in the 1980s. Both share a problem: hard to get in and out. I have mobility issues due to back, spine, hip problems. Crawling around under the car, or from the passenger compartment to the trunk to access the 12v battery are out of the question. I would have to depend on AAA if the 12 v fails.

So, what's the verdict: get a new battery, or just get a Lithium battery jump starter and keep fingers crossed?

Thanks to all for your input.
 

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The readings you have for the 12V indicate the battery is currently OK but are not conclusive. The lithium battery jump starters are good insurance against getting stranded. Check on Amazon for any number of small, inexpensive (~$40.00) examples of jump starters.

Since you already know how to access the jump starter terminals here is a link to a YouTube video that demonstrates how to remove the door handle cover to access the key slot and how to remove the emergency key from the key fob to open the driver's door should you find your key fob battery has died or your 12V battery has become discharged.

Unlocking a 2016 Volt with a dead key fob or dead 12V.

Regarding those jump starter packs:

1) Never cross the streams. (Seriously, the current generation of jump starters have built in protection against shorting the clamps or confusing positive and negative when connecting to the 12V battery.)

2) Never charge a lithium battery if the battery temperature is below 32F. This will permanently damage the battery cell(s). Wait until the battery has warmed to room temperature before charging.

3) Don't expose the lithium battery pack to high summer temperatures such as inside a vehicle during the summer months. Although the manufacturers may claim that it is OK to expose the jump starter to temperatures as high as 120F or 130F it is probably not a good idea. Electronics don't like excessive heat, this is also true for batteries.

4) In very cold weather you may have to warm the jump starter pack for perhaps 30 minutes by placing it indoors or inside your coat before the battery can deliver the rated power and start your vehicle.
 

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Question:

Since our AGM Volt batteries do not start the engine, 'traditionally', do the CCA of the battery matter, as much?

Would it be possible to just physically measure the dimensions, and use another type( group) as long as it fitted

Are BOTH the front and rear 12V batteries identical?? ( both group 47)
 

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Question:

Since our AGM Volt batteries do not start the engine, 'traditionally', do the CCA of the battery matter, as much?

Would it be possible to just physically measure the dimensions, and use another type( group) as long as it fitted

Are BOTH the front and rear 12V batteries identical?? ( both group 47)
Group 47 is a common size so I don't know why you'd want a different type. CCA isn't important as the 12V isn't doing a lot of heavy lifting. Going to a bigger battery will empty your wallet more than do you any good.

There is no front and rear 12V batteries. The battery sits under the rear cargo deck accessible after undoing a few retaining nuts. You may be confused by the extension leads under the hood that go back to the battery in the rear.
 

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Question:

Since our AGM Volt batteries do not start the engine, 'traditionally', do the CCA of the battery matter, as much?

Would it be possible to just physically measure the dimensions, and use another type( group) as long as it fitted

Are BOTH the front and rear 12V batteries identical?? ( both group 47)
There is only one 12V battery in your Volt, it is in the rear under the hatch floor. Group 47 (also known as spec H5) is the correct size and has the correct terminal orientation for connecting the battery terminals. You should only replace the OE Group 47 AGM battery with another Group 47 AGM battery. Conventional, i.e. non-AGM batteries have different charging requirements; your Volt is programmed to charge and maintain an AGM battery. If you were stranded, another 12V battery could get you going but then you would need to install the correct battery as soon as you could.

You are correct that CCA is not critical in the Volt application but does provide some indication of the overall capacity and capability of the battery.

Some manufacturers do not offer an exact match for the dimensions of the Group 47 battery. Optima, the one of the companies that pioneered the AGM type battery, does not offer an exact match for the Group 47 (the Optima battery is too tall for the space where the battery needs to be installed in the Volt.)

More on the Group 47 battery can be found here.
 

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Discussion Starter #16
There is only one 12V battery in your Volt, it is in the rear under the hatch floor. Group 47 (also known as spec H5) is the correct size and has the correct terminal orientation for connecting the battery terminals. You should only replace the OE Group 47 AGM battery with another Group 47 AGM battery. Conventional, i.e. non-AGM batteries have different charging requirements; your Volt is programmed to charge and maintain an AGM battery. If you were stranded, another 12V battery could get you going but then you would need to install the correct battery as soon as you could.

You are correct that CCA is not critical in the Volt application but does provide some indication of the overall capacity and capability of the battery.

Some manufacturers do not offer an exact match for the dimensions of the Group 47 battery. Optima, the one of the companies that pioneered the AGM type battery, does not offer an exact match for the Group 47 (the Optima battery is too tall for the space where the battery needs to be installed in the Volt.)

More on the Group 47 battery can be found here.
I followed the link to the article on Group 47 AGM batteries, then followed the AC Delco link. The result, on Amazon, showed this battery is not compatible with the 2016 Volt, and that there were no compatible batteries. Is this the specific battery for the 2016 Volt: "ACDelco EREV AGM Battery"? If so, I'm having trouble finding it on line at the Delco web site.
 

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Forum users have reported good prices for Group 47 AGM batteries at Sam's Club and Costco. Try the 2017 Volt; not sure why the 2016 is not listed except that the 2016 was only sold in 7 CARB compliant states and only for part of the year before the 2017 Volt replaced the 2016 model year. The 2016 - 2019 all use the same BCI Group 47 AGM battery, even the Gen 1 Volt (2011 - 2015) use this same battery.

There is a single vent tube connection on the OE battery that GM was required to vent outside the cabin. Note: AGM batteries do not normally vent any gases (hydrogen or oxygen); the vent is connected to a pressure relief valve that is designed to open only if the battery case was about to explode due to a severe over pressure condition such as extreme overcharging or in a fire. Bottom line, you don't need to worry about connecting the vent tube, just don't plug any vent(s) that the replacement battery may have. If you prefer, your dealer can install the exact GM Delco replacement battery in your Volt for more $; that one will have the connection for the vent tube.
 

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Discussion Starter #18
Forum users have reported good prices for Group 47 AGM batteries at Sam's Club and Costco. Try the 2017 Volt; not sure why the 2016 is not listed except that the 2016 was only sold in 7 CARB compliant states and only for part of the year before the 2017 Volt replaced the 2016 model year. The 2016 - 2019 all use the same BCI Group 47 AGM battery, even the Gen 1 Volt (2011 - 2015) use this same battery.
I checked a couple days ago with Costco; they don't carry it. No emergency, so I'll shop around. Seems like some may not be an exact dimension fit. Then there's always the dealer, right?

Any specific recommendation for a lithium jump starter, or specs I need to find?

Thanks again to all.
 

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There a literally dozens of brands of jump starters; they probably all come out the same handful of factories in China. I have a DBPower jump starter. There is also Red Fuel / Schumacher, and many many others. No need to spend over $50 as you are not looking for a jump starter that will jump start a V8 engine or a diesel engine.

Something in the 8000 mAH capacity (that is only 8 amp hours) should do the job. You can get larger capacity jump starters but they will be a bit larger, heavier and cost more. In the Volt the jump starter needs to provide perhaps 400 or 500 watts of power (works out to 30 to 40 amps at 12.6 Volts) for perhaps 4 - 6 seconds before the Volt connects power from the high voltage battery and the accessory power module takes over providing all 12V power.

(It would be an interesting experiment to see if 8 D cell batteries wired in series (for a total of 12.48V) would be able to boot up the Volt. I think they probably could.)
 

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Thanks for all your replies, yes...I was thinking there were TWO batteries, since I have seen mentioned Jump from Rear, Jump To the Front...didn't realize it was just the same battery, plus 'extension' leads !!

Was more concerned with saving a little money, should the need arise, by purchasing a slightly smaller (rated) CCA AGM battery, and yes, having used both Optima in the motorcycles and Red/Yellow Top in the car, was just wondering if those AGM's, of a similar 'physical size'.....and pole orientation, could be substituted !!
 
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