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twice now I've inadvertently left my Bolt plugged in while away on a trip…and come back to a 100% dead as a door nail Bolt - jumping the 12 volt battery has "recovered" the beast - but the car is sooooooo dead when in this circumstance that even that is an iffy and time consuming process...

now I know the manual says you're not supposed to leave it plugged in - and other times I've gone away and left it unplugged...

but it seems to me that _IF_ you leave it plugged in for several days you shouldn't be rewarded with a dead car upon returning from your trip.

has this happened to anyone else, any idea why the 12 volt is dying even when the car is plugged into shore power?

the latest event left some Tranmission/Motor fault codes in the car's computer that I'm going to have to visit the dealer to get things cleared up...I'll also discuss with them my experience and see what they say.
 

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I was away for two weeks this winter. It was about 25 degrees during that time. I left my bolt plugged in for two weeks, in case it needed conditioning. Got home, no conditioning, but full batteries and no worries. I think you and the dealer need to talk, this should not happen. Let us know what you find out, that must be extremely frustrating.
 

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If you leave the car for less than 4 weeks, you are supposed to leave it plugged in.

The algorithm (previously) posted on this site says that the firmware in the car checks the battery voltage more often when plugged in. (However, I think that the logic posted is not good enough == too low voltage before charging 12V)

You should *never* have returned to a dead 12V battery (if less than 4 weeks).

If the vehicle is still under warranty, get the battery tested, and get a new battery. (It might have sat for too long at a dealer lot, improperly (or not) charged, and the 12V battery is probably crap at this point.)

I have maintained for quite a while, that a quality "battery maintainer" (1A or less charge) is a great (possibly even "needed") accessory for EV owners. I "maintain" my EV 12V battery twice a month (a full "saturation" charge).
 

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Do you keep the keyfob near the car (within about 15ft, even if on the other side of a wall)?

Many vehicles will not go into standby mode unless the keyfob is NOT detected.

Vampire loads are pretty easy to test by process of elimination, pulling fuses until the parasitic load comes down to a reasonable amount. Might as well have the dealer look at it, but I trust myself to get it done faster and more competently.
 

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I was away for two weeks this winter. It was about 25 degrees during that time. I left my bolt plugged in for two weeks, in case it needed conditioning. Got home, no conditioning, but full batteries and no worries. I think you and the dealer need to talk, this should not happen. Let us know what you find out, that must be extremely frustrating.
Something's wrong. Get the dealer to diagnose. What was the SOC on the main battery when you plugged in, and what was it after you jumped the 12V battery?
Ours has been plugged in every night for two years. Sometimes driven every day, sometimes left for two weeks; zero issues. Something is wrong with your car or your charger or your electrical service.

jack vines
I second, third, fourth all of the above. As I recall, you've had a number of issues with your Bolt EV (including several that are completely unrelated to a 12 V battery dying while on a trip). Maybe you should escalate this to GM corporate so they can do a thorough diagnostic of the entire vehicle, mechanical and software.

Every car model has the potential for a lemon here or there, but the Bolt EV is literally the most reliable EV sold. Your circumstances seem rather unique, and you'd probably be hard pressed finding another Bolt EV owner who has encountered anything similar. It's time to talk to the people who actually designed and built the car.
 

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If the vehicle is still under warranty, get the battery tested, and get a new battery. (It might have sat for too long at a dealer lot, improperly (or not) charged, and the 12V battery is probably crap at this point.)
I second, third, fourth all of the above.
 

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Discussion Starter #11
thanks all - my service appointment is Monday April 22 - I'll update the thread once I have more information

yes - my Bolt has been far less reliable than any of my other cars and my personal experience does not match the overall statistics - it goes to show how much those stats will indicate your personal experience with a. single example for a mass produced product.

I'll be curious to see what they say...

my prediction is they will replace the 12 volt - say they can find nothing else wrong the car, clear the fault codes (which were caused by me jump starting the 12 volt to reanimate the Bolt) and tell me if it happens again to bring it back for more service…

we'll see.
 

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Thanks for interesting thread. I am soon to leave for 5 weeks and planned to leave my Bolt plugged in. Now I am uncertain if that is a good idea or not. It is garaged and this time of year garage temp is 68º +/- 2º.
If I were to leave it unplugged is there a recommend SOC (I'm usually between 45% & 75%).

When I first got my Bolt I checked the 12v battery voltage frequently, it ranged between 12.9v and 12.4v over the period of 3-4 weeks. I don't put a lot of miles on, I typically charge every 3-4 weeks.
 

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twice now I've inadvertently left my Bolt plugged in while away on a trip…and come back to a 100% dead as a door nail Bolt - jumping the 12 volt battery has "recovered" the beast
The OEM 12 Volt battery is often damaged on arrival due to computer memory loads discharging it at high temperatures while waiting to be sold.

One or two cells go bad.

Ask the dealer for a warranty pre-charged 12V replacement. This solves the true problem.

It happened to me.

Meanwhile, plugging in all the time is harmless and guarantees that the 12V will be charged when necessary.
 

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I found this info on a GM site and posted it eons ago (OK, a few months ago...). Since we're talking about storage, here it is again:


Executive Summary!!

To turn the Transport Mode On/Off
Ø Start the vehicle (as indicated by the green Ready light),​
Ø Activate the hazard flashers,​
Ø Press and hold the brake pedal,​
Ø Then press and hold the Start/Stop button at least 15 seconds.​
Ø The “Transport Mode On/Off” message will appear on the DIC.​
Ø Then turn the hazard flashers off.​
Ø Allow the vehicle to sleep at least 2 minutes prior to restarting.​

The full text of what I found:

I stumbled on this site and thought it might be of value, noting how many discussions there are regarding long-term storage methods for the Bolt:​
Transport Mode
11-08-49-001V: Transport Mode On Message Displayed in Driver Information Center (DIC) and/or Battery Light is Flashing (Follow Procedure as Outlined Below) – 2010-2018 Buick Cadillac Chevrolet GMC​
Condition
Some customers may comment that there is a “Transport Mode On” message displayed in the DIC and/or the red battery light is flashing. The transport mode is intended for use on vehicles being shipped over long distances, and includes vehicles shipped into and outside of the United States and Canada.​
Some products will be shipped from the assembly plant with the Transportation Mode On. The feature reduces the electrical load on the battery when the vehicle is parked, which extends the battery stand time.​
To alert the operator that the mode is on, the red battery telltale will be flashing and if equipped with a DIC, it will display a Transport Mode On message. 24 hours after transport mode is turned on, with the vehicle Off, (with exception of 2015 Full-Size SUVs equipped with RPO AVF, and continuing in later model years without AVF) the key must be used to enter the vehicle, as the following functions will be disabled: Passive Entry, Remote Keyless Entry, Content Theft. For 2015 Full-Size SUVs (Cadillac Escalade models, Chevrolet Suburban, Tahoe, GMC Yukon Models), with RPO AVF, and continuing in later model years without AVF; the Remote Keyless Entry function will remain enabled during transport mode, allowing entry without a key. Exit lighting timers will function but will be reduced.​
Note: For PEPS vehicles in transportation mode, the key fob will operate for the Start/Stop button, as long as the fob is inside the vehicle.​
When the vehicle is running, the only difference in operation will be the DIC Message and Battery Telltale on. The Passive Entry and Remote Keyless Entry functions are restored with the ignition in run.​
The intent of the feature is to prolong battery stand time. The mode SHOULD be left on and it is recommended to leave it on while the vehicle is in dealer inventory. Also a customer may want to use the mode if the vehicle is going to be stored. The method to turn the mode off is the same to turn the mode on.​
Refer to the section below for the method to turn the mode off and on.​
Procedure
Note: Normal Vehicle Diagnostics and Service Procedures Should Not Be Performed when Transport Mode is Active.​
Turn Off Transport Mode Prior to Performing System Checks or Service Procedures.​
When the Transport Mode is on (active), enter the vehicle using the steps below.​
1. Attempt to unlock the vehicle with the FOB.​
2. If the vehicle is not responding to the FOB, press the PEPS door handle switch a few times (if equipped) then attempt to unlock the vehicle with the FOB.​
3. If the vehicle is not responding to the FOB, the key must be used to enter the vehicle.​
4. Turn the Transport Mode on/off using the appropriate procedure below.​
2017-2018 Chevrolet Bolt EV
To turn the Transport Mode On/Off,​
start the vehicle (as indicated by the green Ready light),​
activate the hazard flashers,​
press and hold the brake pedal,​
then press and hold the Start/Stop button at least 15 seconds.​
The “Transport Mode On/Off” message will appear on the DIC.​
Then turn the hazard flashers off.​
Allow the vehicle to sleep at least 2 minutes prior to restarting.​
***​
Hope the above is of some use.​
Rich​
 

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Dead Bolt

I had the same problem. The car was plugged in for a month without being driven or turned on. When I went to turn on the car it was totally dead. I measured the 12 volt battery and it was at 4 volts. After charging up the battery back to 12 volts then the car came back to life. The "Chevy Service Specialist" which takes phone calls and is not a mechanic said the 12 volt DC charger that takes the high voltage DC battery and lowers it down to 12 volt DC to charge the small battery does not come on unless the car is turned on. I don't know why this charger can not come on when the 12 volt battery voltage drops down to a predetermined level even when the car is turned off. Doesn't the battery temperature conditioning come on anytime whether or not the car is turned on?
I tried to talk to a real Chevy representative from Chevy's website. I don't know if it did any good or not or if they were just giving me lip service. They claim they were going to address my request. But I haven't heard from them.
My two request were.
1 - On one of our displays. We need to be able to read the 12 volt battery voltage before turning on the car's 12 volt DC charger. If we can't monitor the 12 volt battery. We all will eventually hop into a dead car with no warning that your battery is slowly dying. Unlike an ICE car, when turning over your engine to start it, you can tell if your battery is going dead or not.
2 - On your settings you need to have an option to activate or not a feature when your in regenerative braking. To when the car is not rolling the brake lights stay on. This way you do not need to put your foot on the break to make the break lights come on.
I would like feedback from everyone. Thanks
 

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I recommend disconnecting the 12V battery if you will be gone more than a couple of weeks. Or, you could use a smart "trickle charger".


Because, well, the "keep the 12V battery charged" logic just plain sucks.
 

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Well, based on OP's experience, no. The logic on keeping the 12V battery charged up sucks.
I don't get it. You posted the link to the logic, thanks I couldn't find it, but you say "it sucks" It looks just fine to me, what am I missing?

"Battery Maintenance Mode That battery maintenance mode is designed to ensure the 12V battery has a good state of charge. It accomplishes this by checking the voltage of the 12V battery and providing a charge if needed.

When the vehicle cord is plugged in The Hybrid/EV Powertrain control module (HPCM2) will check the 12V battery every 6 hours if the ignition is off. If the voltage is below a temperature dependent threshold ranging from 12.1 (cold) to 12.4 (warm)V, the Hybrid/EV Powertrain control module (HPCM2) will send the voltage set point to the engine control module (ECM). The engine control module (ECM) will send this to the 14V Power Module. Battery maintenance mode will charge the battery for 2-3 hours. If the Ignition is ON, the APM will cycle on as needed to maintain the 12V SOC.

When the vehicle cord is not plugged in
The Hybrid/EV Powertrain control module (HPCM2) will check the 12V battery every 4 days (2.5 to 3 days) and if the voltage is below a threshold of 12.0 may activate battery maintenance. If the high voltage battery state of charge is greater than 40% and the propulsion system is not active, Hybrid/EV Powertrain control module (HPCM2) will send the voltage set point to the engine control module (ECM). The engine control module (ECM) will send this to the 14V Power Module. Battery maintenance mode will charge the battery for 45-90 minutes.."


I think the simple explanation is the OP has a bad battery. I have left my Bolt parked while traveling for 10 days to 2 weeks and never had an issue. I took no particular precaution.
 
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