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Discussion Starter · #1 · (Edited)
I just got to thinking, I don't remember seeing a post that had any information about the 12 volt battery in the rear of the Volt.

Is it old-fashioned lead-acid, nicad, or is it lithium ion like the big battery?

Because if it isn't one of the newer, longer lasting types, that would be one item that maybe could use an upgrade. It would be cool to have a 12-volt system that is as long lived as the 360-volt one.

I have never had a lead acid battery that lasted much more than 3-4 years, but possibly they are overcharged more than the one in the Volt, which shortens their life.

I think someone posted that the charging voltage on the volt 12 volt system is lower than the average ICE car.

I would really like to find out more about this subject, if anyone has information on it. If it is higher tech, that would be one more place where Volt repair bills may be significantly less than regular ICE cars.
 

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Here's some recent information on the Volt's AGM battery in this month's GM Techlink
http://www.sandyblogs.com/techlink/2011/11/volt-12v-agm-battery-testing-1.html
WOT

[update scottf200]Internet archive/wayback machine
http://www.sandyblogs.com/techlink/2011/11/volt-12v-agm-battery-testing-1.html
Volt 12V AGM Battery TestingBy Blog Post on November 1, 2011 7:05 PM | No Comments

As the 2012 Volt arrives in your dealership, it is important to remember that the 12V battery in the Volt is an Absorbed Glass Mat (AGM) battery. Testing and charging the AGM battery is different from regular lead acid batteries. The AGM battery uses glass mats that absorb electrolytes that are pressed between the plates instead of immersing the plates in electrolytes. This allows for a smaller, lighter battery that is less susceptible to heat but still delivers the same amount of power.

Review #PIC5442 for specific instructions on how to test and charge the 12V battery in the Volt.

When using any battery charger, check that it is set up properly to charge an AGM battery. The preferred charger to use during PDI, calibration updates or any other repairs that requires use of a battery charger is the EL-50313 Midtronics GR8 battery charger/tester.

Make sure to select the proper battery type, AGM, and CCA, 630, during charger set up. Selecting the wrong type of battery and CCA could cause misdiagnosis and/or overcharging of the battery, which could lead to inadvertent battery replacement or battery damage.

TIP: The battery test using the EL-50313 Battery Tester requires correct connections to the battery terminals. A failure to obtain the correct connections during the test may result in a failed test on a good battery.

TIP: Use the Out of Vehicle test for each battery when testing a vehicle with dual batteries.

For information on how to properly maintain the Volt's 12V battery in dealership showrooms, review #PIC5448. There is a common misconception that having the charger plugged in will maintain the 12V battery (either with the stationary 240V or 120V charger).

When plugging in a 240V or 120V charger, the vehicle will charge the 300V battery and will also maintain the 12V battery to power up the modules needed to complete the charge event. When the 300V battery is fully charged, the modules will go to sleep and the vehicle will no longer trickle charge the 12V battery even though the 240V or 120V charger is still plugged in.
[update end]
 

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The NOCO brand battery chargers provide the proper charging profiles to maintain a AGM battery. A quick google search should line up one if needed.
 

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Here's some recent information on the Volt's AGM battery in this month's GM Techlink
http://www.sandyblogs.com/techlink/2011/11/volt-12v-agm-battery-testing-1.html
WOT
Nice post!
... the 12V battery in the Volt is an Absorbed Glass Mat (AGM) battery. Testing and charging the AGM battery is different from regular lead acid batteries. The AGM battery uses glass mats that absorb electrolytes that are pressed between the plates instead of immersing the plates in electrolytes.
This allows for a smaller, lighter battery that is less susceptible to heat but still delivers the same amount of power.
<snip>
For information on how to properly maintain the Volt's 12V battery in dealership showrooms, review #PIC5448. There is a common misconception that having the charger plugged in will maintain the 12V battery (either with the stationary 240V or 120V charger).

When plugging in a 240V or 120V charger, the vehicle will charge the 300V battery and will also maintain the 12V battery to power up the modules needed to complete the charge event. When the 300V battery is fully charged, the modules will go to sleep and the vehicle will no longer trickle charge the 12V battery even though the 240V or 120V charger is still plugged in.
 

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During the early Volt development, the proposal / question of why not a lithium ion 12-volt battery was posed. Cost was one consideration (along with whether most customers would really care about the chemistry of the small battery, and be willing to pay more for it), but the reason against it was primarily risk management. It was decided to focus all the Li-Ion knowledge and resources on the high-voltage battery during development and validation. Perhaps some day there will be a lithium ion 12-volt battery included.
 

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Li batteries are getting a lot of attention for micro-hybridization or "stop-start". Lithium batteries as 12V to be used for a number of restarts during a shorter drive (ie. in a city with stop lights) need not only the normal quick drain "cranking amps" but also higher charge-rates by the onboard generator. So, with mass production of 12V batteries, the costs can come down. What is good too is you don't need to necessarily replace them after 5-years like the Lead-acids.

Problem with Lithium as 12V is cold weather. The Volt needs the 12V to run the computer and some other components even if sub-zero weather. The 12V does not start the engine but rather the primary 360V battery does through the generator. I guess it doesn't need the level of cold cranking amps as in a normal ICE.
 

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While the Volts 12 vot battery is a lead acid battery and all lead acid batteries that I have tested (over 10,000 of all different types and subject to different conditions), none last more than ten years, if abused (over charged, constantly cycled, or left discharged for a month or so) will fail in less than a year.

Lead acid batteries if used with in there specifications and suggested applications should last about six years.

The AGM and Gell cell batteries are both of the Sealed Lead Acid (SLA) type and can last through longer times with out a charge and deeper discharge situations, than the non sealed type, but they do not take over charging as well (this explains the lower charging voltage).

The SLA battery costs more than the flodded type but takes minor common abuses much better.

The extra cost it would take to build and properly tempature controle a seperate 12 volt Lithium battery, is not justified for the application that the 12 volt SLA battery serves in the Volt.

So what if it has to be changed twice as often as the main battery, the cost is retiivetly low and it can be changed by the average do it your selfer.
 

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The lead acid tech is fine and desirable for what GM is using it for here - running fairly conventional 12v accessories designed for the normal lead-acid voltage range.
While the AGM is a little bit different than the usual starting battery, it's only a little bit different. As another poster pointed out, this type and gel cells really don't like overcharging.

I get over 10 years out of fairly crummy tech L-16's in my house PV system, but that takes nursing them. The Rolls-Surrette ones I recently installed (or gee, would that be 5 years ago) are warranted for 25 years - these things can last, with care.

I currently have a call in with GM, however, because the built-in charger for that 12v AGM battery is holding right at 15v with the car on. That's too high for long life there, and perhaps a bit hard on some of the accessories too. I noticed as I put a 1200w inverter on it for emergency power backups and its over-voltage shutdown trips regularly.

Hopefully, there's an adjustment in there. Yeah, I could hook a honking, heatsinked shottky diode in the line to the inverter and solve that (lose half a volt) - but the rest ain't quite right as is, so it should be fixed at the source.

Note, volts at float on almost any battery should change with temperature...I measured this in a balmy 65f.
 

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Thank you for posting the links :
The 12 volt system was on my to do read list.
Looks like we come out way ahead in self-discharge and cold weather power.

Interesting too about using purer lead in the plates. We used old newspaper type lead in science class to make lead h2so4 batteries.

--- now I have to add a volt meter to my Volt -- off to Radio-Shack --
 
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