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Discussion Starter · #1 ·
How does the Gen 2 Volt maintain the 12V battery voltage? Does it only charge and maintain the voltage when the vehicle is running?
I monitor the voltage using a device that is plugged into the front cigarette lighter. (there is no voltage when the vehicle is OFF and I understand this is normal). When the vehicle is running, no matter what mode I have it in, the voltage will vary somewhat but usually is between 13-14.5 volts. I suspect this is normal as well. I guess my real question is, can the battery voltage be maintained with the generator is not running? Does the 12V battery receive any charge when the vehicle is off and plugged into a wall outlet?
 

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How does the Gen 2 Volt maintain the 12V battery voltage? Does it only charge and maintain the voltage when the vehicle is running?
I monitor the voltage using a device that is plugged into the front cigarette lighter. (there is no voltage when the vehicle is OFF and I understand this is normal). When the vehicle is running, no matter what mode I have it in, the voltage will vary somewhat but usually is between 13-14.5 volts. I suspect this is normal as well. I guess my real question is, can the battery voltage be maintained with the generator is not running? Does the 12V battery receive any charge when the vehicle is off and plugged into a wall outlet?
When the Volt is powered on there is an auxiliary power module (APM) that serves as a DC to DC voltage converter. The APM powers all of the 12V systems and also charges the 12V battery. This is true whether the Volt is running on the high voltage battery or if the gas engine is running. The Volt does not have a traditional alternator. The APM performs the functions that an alternator would perform. The 12V battery is needed to start the Volt's computers and systems, then the APM takes over after a few seconds.

When the Volt is plugged in and charging the high voltage battery the 12V battery is also being charged. Once the high voltage battery is fully charged the Volt stops charging the 12V battery. If you leave the Volt plugged in, for more than 30 days, the 12V battery can run down even though the Volt is plugged in. In this case GM recommends connecting a 12V battery tender to the 12V battery to be sure the 12V battery remains charged.
 

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When the Volt is powered on there is an auxiliary power module (APM) that serves as a DC to DC voltage converter. The APM powers all of the 12V systems and also charges the 12V battery. This is true whether the Volt is running on the high voltage battery or if the gas engine is running. The Volt does not have a traditional alternator. The APM performs the functions that an alternator would perform. The 12V battery is needed to start the Volt's computers and systems, then the APM takes over after a few seconds.

When the Volt is plugged in and charging the high voltage battery the 12V battery is also being charged. Once the high voltage battery is fully charged the Volt stops charging the 12V battery. If you leave the Volt plugged in, for more than 30 days, the 12V battery can run down even though the Volt is plugged in. In this case GM recommends connecting a 12V battery tender to the 12V battery to be sure the 12V battery remains charged.
Does this mean you should be able to "jump" the 12v by plugging the car into the evse as long as the battery is not full?


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Not to jump start the Volt but plugging the EVSE into the Volt should trickle charge the 12V battery (not like a 10 amp battery charger more like a 1-2 amp trickle charger) so that after enough time has elapsed you might be able to start the Volt using the partially recharged 12V battery. The way to jump start the Volt is to attach jump start battery leads to the Positive (+) and Negative (-) terminals that are located under the hood near the firewall on the driver's side. Alternately, if you can open the hatch, then the jump start leads can be connected to the 12V (+) and (-) battery posts.
 

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In Gen1 only charges when charging the main battery, but I undestand that Gen 2 EVES will monitor 12v battery while being plugged "not charging'' the main battery..I am not sure (my car is a 2014) I see that the cooling of the APM 12 v,battery charger is different in Gen2,..In gen 1 had a fan ducting fresh air, how is in Gen2 ???.
 

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When the Volt is plugged in and charging the high voltage battery the 12V battery is also being charged. Once the high voltage battery is fully charged the Volt stops charging the 12V battery. If you leave the Volt plugged in, for more than 30 days, the 12V battery can run down even though the Volt is plugged in. In this case GM recommends connecting a 12V battery tender to the 12V battery to be sure the 12V battery remains charged.
Not exactly. Sense the 2013 model year, Volts have had a '12 volt battery tender' module. If the Volt is plugged in and completed charging, it periodically checks the 12 volts and keeps it charged.
 

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Not exactly. Sense the 2013 model year, Volts have had a '12 volt battery tender' module. If the Volt is plugged in and completed charging, it periodically checks the 12 volts and keeps it charged.
Makes sense. Thanks.
 

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Discussion Starter · #8 ·
That makes better sense. If the vehicle is plugged in, it should always be able to be started.....or in other words, the 12V battery should not be too low to perform its function (unless it is dead for some other reason, such as a bad cell).
 

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Does this mean you should be able to "jump" the 12v by plugging the car into the evse as long as the battery is not full?
If the 12v is dead, there won't be power for the Volt to recognize that you've plugged in the EVSE and it won't signal for power to turn on. Gotta use the jump posts under the hood first, and let the Volt being On charge the 12v for a while (10-15 minutes) before there's enough power it it that you can shut the car off, plug it in, and finish off the charging of both batteries.
 

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If the 12v is dead, there won't be power for the Volt to recognize that you've plugged in the EVSE and it won't signal for power to turn on. Gotta use the jump posts under the hood first, and let the Volt being On charge the 12v for a while (10-15 minutes) before there's enough power it it that you can shut the car off, plug it in, and finish off the charging of both batteries.
Actually, I've heard of people trying to charge with a dead 12V and usually it results in a clicking sound which, from what I've heard it described as, sounds a bit like an ICE car trying to start with a dead 12V because there's a contactor that clicks on and off trying to connect the HV charge system. This probably only happens if the 12V is right on the border of being dead.
 

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Not exactly. Sense the 2013 model year, Volts have had a '12 volt battery tender' module. If the Volt is plugged in and completed charging, it periodically checks the 12 volts and keeps it charged.
******

NOT EXACTLY.... been there, done that.

If you leave your volt plugged in for over 30 days, the 12v battery will drain down. I am talking with experience from a 2017 VOLT built May 2016.

If the High Voltage battery is not being charged, the electronics go to sleep and only the car monitoring system is active. This is enough to drain the 12v battery over time. Mine lasted about 30 days.

To charge that 12v battery, you need a charger that is compatible with with AGM batteries.

The difference is AGM batteries have one way pressure release vents. You cannot add liquid to an AGM battery.
If you use a regular charger, the battery will vent vapour and you cannot replace it.
Charge too many times this way and the battery is toast.

This string also talks about the 12v battery
http://gm-volt.com/forum/showthread.php?258377-Long-Term-Storage
 

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How does the Gen 2 Volt maintain the 12V battery voltage?
A user on another Chevy Bolt forum posted a fairly detailed description of how the Bolt maintains its 12V battery. It's surprising just how complex it is.

It's obviously not the Volt, but I'd be surprised if there weren't at least a few similarities between the two systems. Both have a high voltage battery, auxiliary power modules, a charging subsystem, and were likely designed by many of the same people.
 

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There is conflicting information in this thread from what I have read previously on this forum. From what I understand from previous threads (but cannot find them ATM), the Gen 2 Volt since about 2015 does keep the AGM battery topped-up IF plugged in. This was apparent from someone who actually measured the resting plugged-in voltage on the 12V battery after some days not used, but plugged in.

Any AGM battery will normally be charged at about 14.4VDC if its voltage is low, and will then be float charged at about 13.2-13.5VDC.

Any lead acid/battery that has been sitting for some days NOT charged will have a battery voltage of less than 12.75VDC (which is the standard resting 100% fully-charged voltage.

It would only take a few days and a couple of measurements with a multimeter to confirm whether or not the AGM battery is or is not being charged when plugged in.

Has anyone done this?
 

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There is conflicting information in this thread from what I have read previously on this forum. From what I understand from previous threads (but cannot find them ATM), the Gen 2 Volt since about 2015 does keep the AGM battery topped-up IF plugged in. This was apparent from someone who actually measured the resting plugged-in voltage on the 12V battery after some days not used, but plugged in.

Any AGM battery will normally be charged at about 14.4VDC if its voltage is low, and will then be float charged at about 13.2-13.5VDC.

Any lead acid/battery that has been sitting for some days NOT charged will have a battery voltage of less than 12.75VDC (which is the standard resting 100% fully-charged voltage.

It would only take a few days and a couple of measurements with a multimeter to confirm whether or not the AGM battery is or is not being charged when plugged in.

Has anyone done this?
Going off of what Runion said, it sounds like after a certain period of time, the 12V will drain below the float voltage, indicating the battery tender does not always remain on.
 

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Yes, I am well aware of what Runion has said but his findings completely negate what others have described. From all my readings post 2015 anyway the Volt IF PLUGGED IN will maintain the 12V battery with some sort of trickle smart charge. The ONLY way to know this for sure is to either get the info from the horse's mouth or do a voltage test on the battery as I described above.
 

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Discussion Starter · #16 ·
Yes, I am well aware of what Runion has said but his findings completely negate what others have described. From all my readings post 2015 anyway the Volt IF PLUGGED IN will maintain the 12V battery with some sort of trickle smart charge. The ONLY way to know this for sure is to either get the info from the horse's mouth or do a voltage test on the battery as I described above.
I plan to do this voltage test (directly at the battery) with the car plugged in and then not plugged in. My car has been sitting in the garage plugged in for several days and the temps are getting cooler now. I'll post the results after several tests on different days. Should be interesting. I find it a little hard to believe that the car doesn't maintain the 12V battery when plugged in...but we'll see.
 

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I plan to do this voltage test (directly at the battery) with the car plugged in and then not plugged in. My car has been sitting in the garage plugged in for several days and the temps are getting cooler now. I'll post the results after several tests on different days. Should be interesting. I find it a little hard to believe that the car doesn't maintain the 12V battery when plugged in...but we'll see.
My Clipper Creek has a fairly loud audible relay when it connects or disconnects mains power to the car. If the car is fully charged and I remote start it while standing near it, I hear the Clipper Creek relay click on at the same time I hear the car power up. This means that when the car is fully charged, there's no mains power unless the vehicle is remote started. Now, that's not to say it doesn't occasionally connect mains power and then disconnect it again, but I have never observed this happening. The only way to really check would be to have an OBD logger attached continuously logging battery voltage over time for several hours starting right before the vehicle reaches full charge.
 

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Discussion Starter · #18 ·
So I took my first voltage reading a few minutes ago. I measured the voltage on the 12V battery directly off of the battery posts on the battery. 12.4V with the car still plugged into the wall and the car is OFF. It's 40 degrees F in the garage. I now have the car unplugged from the wall and will measure the voltage again tomorrow after it sits overnight. I suspect the 12V battery will drop down
some overnight. Then I will plug the car back into the wall and wait again for a time and take another voltage measurement...hopefully the 12V battery will be back up to 12.4 or above if my theory is correct about the battery being "maintained" when the car is plugged in a charging. (the CAR main battery is fully charged at this point and has been for several days as I leave it plugged in when not driving and I haven't gone anywhere for a few days.
 

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Check for WOTs old posts about 12V battery maintenance and charging. 2013+ does attempt to periodically maintain the 12V, just not clear with how much power. Lots of folks have made these measurements, including myself. My understanding is that Bulk charging only occurs with the car on, by the 14V APM. Float charging occurs periodically by the OBCM, when plugged in.
 

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Discussion Starter · #20 ·
Check for WOTs old posts about 12V battery maintenance and charging. 2013+ does attempt to periodically maintain the 12V, just not clear with how much power. Lots of folks have made these measurements, including myself. My understanding is that Bulk charging only occurs with the car on, by the 14V APM. Float charging occurs periodically by the OBCM, when plugged in.
Ok, I just took some more voltage measurements after letting the car sit unplugged overnight. It's still about 40 degrees in the garage. The voltage was now at 12.3V. So I plugged the car back into the wall and then measured 13.3V at the battery....telling me that the car was charging the battery from the wall. After about an hour I checked again and the voltage was now at 12.6V. This leads me to believe that if you leave the Volt plugged into the wall the 12V battery should not go dead.
 
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