[drdiesel1]

A forum user sent me the portion of the service manual on the 12 V system and its interaction with the HV battery is indeed complex. If the Bolt is off, the system checks the 12 V battery system from time to time and will use the HV system and inverter to recharge the 12 V system. It also runs in a desulfation mode. Too complex to summarize here, but this ain;t your 65 Mustang system for sure. In grad school my Mustang had a low battery and to start it hot didn't work because the compression was too high, so I used to let it cool for 15 min and then it would start! Worked that way for a few months.

On Star sent me the following warning today. "A critical issue with the engine and the transmission has been detected. Please service your vehicle immediately." (Yikes) So other than trying to get it started for a 50 mile ride to the dealer in two days, I am not messing with it.
To be continued.****

I posted this on this forum a while back :nerd:
Charging System Description and Operation
12 V Battery The following information is for the 12 V battery only.
For information about charging the high voltage drive motor batteries, refer to Drive Motor Battery System Description.
Charging System Operation The purpose of the charging system is to maintain the battery charge and vehicle loads. The main difference between a conventional generator charging system and this system is that the generator has been replaced by the 14V Power Module. The 14V Power Module provides the power to charge the battery from the high voltage system. There are 7 modes of operation and they include:

• Battery Sulfation Mode
• Normal Mode
• Fuel Economy Mode
• Headlamp Mode
• Voltage Reduction Mode
• Battery Maintenance Mode
• Plant Assembly Mode

Charging System Components 14 V Power Module
The 14V Power Module provides the power to charge the battery from the high voltage system. The ECM provides a pulse width charge request signal (L Terminal) to the 14V Power Module. The 14V Power Module returns a PWM feedback signal (F Terminal) to the ECM. The 14V Power Module reports status and fault modes as a function of duty cycle. The 14V Power Module charges the battery based on the ECM signal.
Drive Motor/Generators
The drive motor/generators are serviceable components located within the transmission housing. When the rotors are spun, an alternating current (AC) is induced into the stator windings. This AC voltage is then sent to the drive motor generator power inverter module (PIM) where it is converted to high voltage direct current (DC) power. The output of the PIM is converted into low voltage electrical power by the accessory DC power converter module 14V Power Module for use by the vehicle's electrical system to maintain electrical loads and battery charge.
Body Control Module (BCM)
The body control module (BCM) is a GMLAN device. It communicates with the engine control module (ECM) and the instrument panel cluster for electrical power management operation. The BCM determines the desired voltage set point and sends the information to the engine control module (ECM) which sends this information to the 14V Power Module. The BCM monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state of charge.
Battery Current Sensor
The battery current sensor is a serviceable component that is connected to the negative battery cable at the battery. The battery current sensor is a 3-wire hall effect current sensor. The battery current sensor monitors the battery current. It directly inputs to the BCM. It creates a 5 V pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0–100 percent. Normal duty cycle is between 5–95 percent. Between 0–5 percent and 95–100 percent are for diagnostic purposes.
Engine Control Module (ECM)
The ECM receives control decisions based on messages from the BCM as well as the HPCM2
Instrument Panel Cluster
The instrument panel cluster provides a means of customer notification in case of a failure and a voltmeter. There are 2 means of notification, a charge indicator and a driver information center message of SERVICE BATTERY CHARGING SYSTEM.
Hybrid/EV Powertrain Control Module 2 (HPCM2)
The Hybrid/EV Powertrain control module (HPCM2) is a GMLAN device. It communicates with the engine control module (ECM) to control the voltage set point sent to the 14V Power Module during the battery maintenance mode.
Battery Sulfation Mode Battery sulfation mode is used to help maintain the battery life. The charging system will enter a battery sulfation mode which tries to increase the vehicle charging when the charging system voltage is less than 13.2 V for about 30 minutes. Once in this mode, the BCM will set a targeted output voltage between 13.9–15.5 V for about 5 minutes. Following this 5 minutes, the BCM will then determine which mode to enter depending on the system voltage requirements.
Normal Mode The BCM will enter Normal Mode whenever one of the following conditions are met.

• The wipers are ON for more than 3 seconds.
• GMLAN Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control head. High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to enter the Charge Mode.
• The estimated battery temperature is less than 0°C (32°F).
• Vehicle Speed is greater than 145 km/h (90 mph)
• Current Sensor Fault Exists
• System Voltage was determined to be below 12.56 V
• Tow/Haul Mode is enabled

When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9–15.5 V, depending on the battery state of charge and estimated battery temperature.
Fuel Economy Mode The BCM will enter Fuel Economy Mode when the ambient air temperature is at least 0°C (32°F) but less than or equal to 80°C (176°F), the calculated battery current is greater than −8 A but less than 5 A, and the battery state of charge is greater than or equal to 85 percent. Its targeted 14V Power Module set-point voltage is the open circuit voltage of the battery and can be between 12.6–13.2 V. The BCM will exit this mode and enter Normal Mode when any of the conditions described above are present.
Headlamp Mode The BCM will enter Headlamp Mode whenever the high or low beam headlamps are ON. Voltage will be regulated between 13.9–14.5 V.
Voltage Reduction Mode The BCM will enter Voltage Reduction Mode when the calculated battery temperature is above 0°C (32°F) and the calculated battery current is greater than −7 A but less than 1 A. Its targeted 14V Power Module set-point voltage is 12.9–13.2 V. The BCM will exit this mode once the criteria are met for Normal Mode.
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..

Plant Assembly Mode The BCM will increase charging voltage for the first 500 miles of operation in an effort to ensure that the 12 V battery is fully charged when the vehicle is delivered to the customer.
Electrical Power Management Overview The electrical power management system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems. This electrical power management system primarily utilizes existing on-board computer capability to maximize the effectiveness of the charging system, manage the load, improve battery state of charge and life, and minimize the system's impact on fuel economy. The electrical power management system performs 3 functions:

• It monitors the battery voltage and estimates the battery condition.
• It takes corrective actions by adjusting the regulated voltage.
• It performs diagnostics and driver notification.

The battery condition is estimated during Vehicle OFF and during Vehicle in Service Mode. During Vehicle OFF the state of charge of the battery is determined by measuring the open-circuit voltage. The state of charge is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.
The state of charge can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. During Vehicle ON mode, the algorithm continuously estimates state of charge based on adjusted net amp hours, battery capacity, initial state of charge, and temperature.
While running, the battery degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.
In addition, the electrical power management function is designed to perform regulated voltage control to improve battery state of charge, battery life, and fuel economy. This is accomplished by using knowledge of the battery state of charge and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.
Instrument Panel Cluster Operation Charge Indicator Operation
The instrument panel cluster illuminates the charge indicator and displays a charging system warning message in the driver information center when the one or more of the following occurs:

• The engine control module (ECM) detects system voltage less than 11 V or greater than 16 V. The instrument panel cluster receives a GMLAN message from the ECM requesting illumination.
• The BCM determines that the system voltage is less than 11 V or greater than 16 V.
• The instrument panel cluster receives a GMLAN message from the BCM indicating there is a system voltage range concern.
• The instrument panel cluster performs the displays test at the start of each Vehicle ON cycle. The indicator illuminates for approximately 3 seconds.
• Vehicle ON, with the engine OFF.

Battery Voltage Gauge Operation
The instrument panel cluster displays the system voltage as received from the BCM over the GMLAN serial data circuit. If there is no communication with the BCM then the gauge will indicate minimum.
This vehicle is equipped with a regulated voltage control system. This will cause the voltmeter to fluctuate between 12–14 V, as opposed to non-regulated systems which usually maintain a more consistent reading of 14 V. This fluctuation with the regulated voltage control system is normal system operation and NO repairs should be attempted.
SERVICE BATTERY CHARGING SYSTEM
The BCM and the ECM will send a GMLAN message to the driver information center for the SERVICE BATTERY CHARGING SYSTEM message to be displayed. It is displayed whenever the charge indicator is commanded ON due to a failure.

 

[TotaledJetta]

CAN'T GET NO SATISFACTION
I took it to Fremont Chevrolet today, after putting it on the Charge Point system overnight to ensure that the 12 V system would be charged enough to start the car.

Left at 8:30, travelled 39 miles and arrived at Fremont Chevrolet, at about 9:40, waited until about 10:20 to talk to service advisor Juan, who listened briefly and recorded “Customer states 12 volt batter has drop (sic) to 9 1/2 three times. Check and advise.” He estimated they would need the car over night. So I took BART back to Berkeley and about 2 PM service advisor Matthew Je called to say the battery had been very low on charge, they had charged it an it checked out OK and the car was ready to pick up. They had checked the car and found no problems. When I suggested there must still be a problem, he said their policy did not allow to replace the battery that tested OK. I told him that was unsatisfactory and he said the service manager would call. 5:15 PM, no word yet.

Questions:
If everything is OK,
Why would the battery be in a low state of charge after driving 40 miles and been hooked to the EVSE.? The service manual says if it is low and the EVSE is connected it will charge it.

Why has it dropped to 9.6 V on three separate occasions and not been able to start the car?

 

[drdiesel1]

CAN'T GET NO SATISFACTION
I took it to Fremont Chevrolet today, after putting it on the Charge Point system overnight to ensure that the 12 V system would be charged enough to start the car.

Left at 8:30, travelled 39 miles and arrived at Fremont Chevrolet, at about 9:40, waited until about 10:20 to talk to service advisor Juan, who listened briefly and recorded “Customer states 12 volt batter has drop (sic) to 9 1/2 three times. Check and advise.” He estimated they would need the car over night. So I took BART back to Berkeley and about 2 PM service advisor Matthew Je called to say the battery had been very low on charge, they had charged it an it checked out OK and the car was ready to pick up. They had checked the car and found no problems. When I suggested there must still be a problem, he said their policy did not allow to replace the battery that tested OK. I told him that was unsatisfactory and he said the service manager would call. 5:15 PM, no word yet.

Questions:
If everything is OK,
Why would the battery be in a low state of charge after driving 40 miles and been hooked to the EVSE.? The service manual says if it is low and the EVSE is connected it will charge it.

Why has it dropped to 9.6 V on three separate occasions and not been able to start the car?

Did you check the battery voltage after you charged it ????? Just because you
charged the car with the EVSE is no indication the 12 volt battery was actually charged.
You would need to test the battery voltage after charging to verify it was actually charged.

It's very possible the car has an amperage draw and they never tested for it.
They charged the low battery and tested it after charging and the battery is good.
Your dealers service advisor is an, idiot, at best.

They need to perform a parasitic load test to find out if/what is draining the 12 volt battery,
or why it's not being charged by the inverter... Electrical issue always seem to escape most
techs and idiot advisors don't help.

 

[TotaledJetta]

Did you check the battery voltage after you charged it ????? Just because you
charged the car with the EVSE is no indication the 12 volt battery was actually charged.
You would need to test the battery voltage after charging to verify it was actually charged.

It's very possible the car has an amperage draw and they never tested for it.
They charged the low battery and tested it after charging and the battery is good.
Your dealers service advisor is an, idiot, at best.

They need to perform a parasitic load test to find out if/what is draining the 12 volt battery,
or why it's not being charged by the inverter... Electrical issue always seem to escape most
techs and idiot advisors don't help.

I agree I should have tested it this morning before leaving and after having it hooked up to the EVSE last night, but
my concern was would it "start" and get to Fremont. If the service manager does call I will ask what tests were
performed on the battery. It certainly could be an inverter issue, however in some of my earlier testing, I saw the
voltage across the battery rise to 15 v after turning the car on. That implied the inverter was charging at least at that time.
Based in the service manual description the computer can use various voltages and routines to keep the battery charged, so
a single measurement doesn't tell the full story. I am thinking the most meaningful measurement is Vbattery when the car has been
sitting and before it is turned on.

Wouldn't you think a 40 mile 1hour plus drive would be enough to charge the battery?
I wonder if it is safe to buy a AGM specific charger and put it on the battery without disconnecting the battery. No way do I
want to disconnect the battery and mess up the computer control system.

At Fremont Chevrolet, I learned they have sold about 500 Bolts (they got 300 early on) and now have zero available. They are a huge dealership,
but only have two techs capable of servicing Bolts. Keep your fingers crossed that your Bolt operates flawlessly.

 

[drdiesel1]

I agree I should have tested it this morning before leaving and after having it hooked up to the EVSE last night, but
my concern was would it "start" and get to Fremont. If the service manager does call I will ask what tests were
performed on the battery. It certainly could be an inverter issue, however in some of my earlier testing, I saw the
voltage across the battery rise to 15 v after turning the car on. That implied the inverter was charging at least at that time.
Based in the service manual description the computer can use various voltages and routines to keep the battery charged, so
a single measurement doesn't tell the full story. I am thinking the most meaningful measurement is Vbattery when the car has been
sitting and before it is turned on.

Wouldn't you think a 40 mile 1hour plus drive would be enough to charge the battery?
I wonder if it is safe to buy a AGM specific charger and put it on the battery without disconnecting the battery. No way do I
want to disconnect the battery and mess up the computer control system.

At Fremont Chevrolet, I learned they have sold about 500 Bolts (they got 300 early on) and now have zero available. They are a huge dealership,
but only have two techs capable of servicing Bolts. Keep your fingers crossed that your Bolt operates flawlessly.

LOL! I'm a Bolt tech at a Chevy dealer :nerd:

I already told you, they charged your 12 volt battery and tested it.
It passed and that's all they did. Your SA is an idiot, IMO!

You shouldn't need to charge your 12 volt battery with a regular battery charger.
The car should handle all that itself. Like I've said 3 times now, you might have
an amperage draw/parasitic load that's draining your 12 volt battery. You need
to test the input to the 12 volt battery when the car is charging and when the
car is in run mode to verify if the battery is being charged during these times.

A parasitic load test can be done to find out if the car is draining your 12 volt battery.
When you pick up the car, ask them for a copy of the charging/battery test results.

 

[TotaledJetta]

When I picked it up, we went through the test data on the battery. They charged it up, did a load test and there were no problems. Before picking it up, I had them check to battery voltage and it was 12.6 Volts, after about 24 hours. So it seems unlikely that the battery caused this. So how the battery got discharged is still a mystery. How much and how fast the Bolt recharges the 12 V on the road is an open question. One tech said it is more like a trickle charger on these cars, unlike the ICE cars where the alternator charges at fairly high currents. These 12 V batteries have significantly less cranking power than for an ICE car.
Other thoughts for what they are worth.
1. Always turn the car ON before messing with the parking brake.
2 Always set the parking brake, before turning the car off.
(The parking brake has some kind of electric motor activator, which draws significant current to operate.)
3. Don't leave the key fob in the vicinity of the car, or the car might wake up.

I think I will buy a AGM charger, so if the battery goes low, I have a quick solution. Thinking about the BatteryMinder 2012 AGM.

So, at some level the experiment continues.:nerd:

Thanks for all the input and suggestions.

 

[drdiesel1]

When I picked it up, we went through the test data on the battery. They charged it up, did a load test and there were no problems. Before picking it up, I had them check to battery voltage and it was 12.6 Volts, after about 24 hours. So it seems unlikely that the battery caused this. So how the battery got discharged is still a mystery. How much and how fast the Bolt recharges the 12 V on the road is an open question. One tech said it is more like a trickle charger on these cars, unlike the ICE cars where the alternator charges at fairly high currents. These 12 V batteries have significantly less cranking power than for an ICE car.
Other thoughts for what they are worth.
1. Always turn the car ON before messing with the parking brake.
2 Always set the parking brake, before turning the car off.
(The parking brake has some kind of electric motor activator, which draws significant current to operate.)
3. Don't leave the key fob in the vicinity of the car, or the car might wake up.

I think I will buy a AGM charger, so if the battery goes low, I have a quick solution. Thinking about the BatteryMinder 2012 AGM.

So, at some level the experiment continues.:nerd:

Thanks for all the input and suggestions.

I guess they decided to let you be your own guinea pig then

I wouldn't start charging the battery until you know if this issue remains an issue
You obviously missed most of what I tried to tell you. GOOD LUCK!

 

[malkaven]

@drdiesel1 thanks for the information on the 12v battery. Is there a way to tell when the battery is in maintenance mode? Hopefully I didn't miss that in the documentation. Also, when is maintenance mode does the car reduce its capabilities(ie not let you drive) until its complete? Assume the car is off/not plugged in when it enters maintenance mode and then turned on at some point before its complete.

 

[TotaledJetta]

I guess they decided to let you be your own guinea pig then

I wouldn't start charging the battery until you know if this issue remains an issue
You obviously missed most of what I tried to tell you. GOOD LUCK!

It has been about 3 weeks since they charged the 12 V battery and I took the car back. Recently I checked the battery voltage and it was about 55 F outside, I first opened the hood, waited awhile and approached with no key fob, so it would be in a resting state. Battery read 12.45 V, which is not a full charge, but close. So the battery seems to be holding its own. I am careful when I start to 1. Push the ON button, 2. Release the emergency brake, 3. Shift for Drive or Reverse. When I end the trip I : 1 Shift to park, 2. Set the emergency brake, 3. Push the button for OFF. That way it puts almost zero stress on the 12 V system, since when the car is "on" the traction battery is dealing with the 12 V system. I am guessing operating the emergency brake, when the car is OFF, takes some charge from the 12 V system.

I purchased an AGM 12 V battery charger, but haven't needed it.

My working theory, is through pilot error, I seriously discharged the 12 V system, and the sophisticated battery management system of the Bolt did not manage to recharge it properly.

If anything new occurs I will update this thread.:nerd:

 

[TotaledJetta]

[/B]

LOL! I'm a Bolt tech at a Chevy dealer :nerd:

I already told you, they charged your 12 volt battery and tested it.
It passed and that's all they did. Your SA is an idiot, IMO!

You shouldn't need to charge your 12 volt battery with a regular battery charger.
The car should handle all that itself. Like I've said 3 times now, you might have
an amperage draw/parasitic load that's draining your 12 volt battery. You need
to test the input to the 12 volt battery when the car is charging and when the
car is in run mode to verify if the battery is being charged during these times.

A parasitic load test can be done to find out if the car is draining your 12 volt battery.
When you pick up the car, ask them for a copy of the charging/battery test results.

I agree with you that recharging the 12 V system should not be necessary. It is still a mystery to me, why even after is was
run down, perhaps by pilot error, the Bolt system did not recharge it properly during the 40 mile trip down there. In my earlier testing
I saw that the traction battery was charging the 12 V when the car was ON, but stationary. The voltage was up to 15 V and then dropped
to about 13.3V. The techs did a load test on the battery. They also measured it after sitting 24 hours and it was reading 12.6 V.
For all I know, it is a bad line of code, in a millions lines of code. Anyway, I have had no further issues as described below.
Thanks for commenting. I don't think too much of the whole "Service Advisior" approach to car problems, I would rather talk
to the tech.

 

[rgmichel]

so I put a battery charger on it and monitored the voltage

Did you use an AGM battery charger or a regular car battery charger? AGM batteries limit the charging voltage and a have specific charging cycle.

 

[TotaledJetta]

Did you use an AGM battery charger or a regular car battery charger? AGM batteries limit the charging voltage and a have specific charging cycle.

It was a regular car battery charger. Since then there is another chapter of the story. See below.

 

[TotaledJetta]

BOLT 12V system troubles continue.

Today, Nov 14, the low 12 V battery problem reoccurred, much like the previous events described above. Got in the car, turned it on the red Battery symbol came up. Checked and Vb was 9.63 Volts. I have an new AGM charger and tried that. It went into desulfating mode and Vb continued to drop. At Vb 9.28 V tried a standard charger than does about 8 amps. Voltage came up a little, but this charger can't do 8 amps for too long. So called Chevrolet Roadside Service. Same guy arrived with his monster portable battery. After about 5 min, the Vb jumped to 13 V, the car "started" most of the error messages cleared. I took it for a 10 min 40 minute drive and after turning OFF, Vb read 12.52. Hooked up EVSE and Vb with to 13.4 for short time then to 12.59 V. The EVSE will start charging the traction battery at 11 PM.

In the morning, it is a 40 mile drive to the dealer, if it starts. Hopefully, they will take this more seriously than the last time, when they just charged the battery and wouldn't do anything else.

I checked the history of these problems, and the time between EVSE charges of the traction battery are 10 days, 7 days, and 9 days. In between the car has typically been run on fairly short trips. That seems like a clue.

Doesn't explain why after after an hour trip (40 miles) to the dealer two weeks ago, the tech said the battery was "discharged".

Could be a fault of the battery charging system. During the latest incident "Service Battery Charging System" message came up. So, that would be my learned guess.
Your input is welcome.

I am not happy with the Fremont Chevrolet service department, but the Concord Chevrolet service department said that the earliest appointment would be two weeks. Ah, GM, now I remember after having a crap 1984, Oldsmobile, I sworn that I would never own another GM car.

 

[rgmichel]

BOLT 12V system troubles continue.

Well, the logical thing for the dealer to do is to replace the battery with a new one. AGM batteries are not inexpensive, so best let the dealer replace it, just in case you can claim it on the warranty. If the problems persist, then its another electrical fault. Whatever happened, you might have ended up damaging the battery with a regular charger, but even so I would not have expected it to go so quickly. I recently ran my Bolt EV battery down to zero volts by using its wireless network for 5-6 hours in service mode. My AGM battery charger would not work to recharge, because it won't charge below 4 volts. So, I plugged in a regular charger for 5 minutes to bring the battery voltage up above 4 volts, then swapped in my AGM battery charger and charged the battery for 24 hrs. The charging voltage stayed at about 12.6 volts for about 3 hrs than gradually dropped for another three hrs, then trickle charged for 24 hrs. I have had no problems since.

 

[TotaledJetta]

Looks like they fixed it this time. Took it to Fremont Chevrolet. This time a different service advisor took the time to listen to what I had observed and wrote it down for the technician to read. Suggested, they might be able to fix it in 4 hours, so I stuck around to see. One of the symptoms I mentioned was the Service Transmission warning on the DIC (Driver Information Center). Anyway the tech found a number of problem codes (DTC) (diagnostic trouble codes), which start with a p anyway, associated with the transmission module. Searched the Bulletins and found a document related to this. Checked the computer module for the transmission, updated the software and afterwards none of the problem codes reappeared. Apparently when the car was on the road the charging system was in "Ignition ON/Vehicle in Service Mode and therefore not charging the 12 V battery properly. So hopefully that solves it.

I makes sense because after driving it 40 miles down there two weeks ago, the tech said the battery was depleted. Too bad he didn't investigate why. The above description is shortened and written in simpler terms, as I understand it.

A few questions unanswered. Why didn't they find it last time? If it is a known software glitch, why isn't Chevrolet more proactive? But for the moment, I am relieved that this problem is behind me. Not shocked that it was software though.

BOLT 12V system troubles continue.

Today, Nov 14, the low 12 V battery problem reoccurred, much like the previous events described above. Got in the car, turned it on the red Battery symbol came up. Checked and Vb was 9.63 Volts. I have an new AGM charger and tried that. It went into desulfating mode and Vb continued to drop. At Vb 9.28 V tried a standard charger than does about 8 amps. Voltage came up a little, but this charger can't do 8 amps for too long. So called Chevrolet Roadside Service. Same guy arrived with his monster portable battery. After about 5 min, the Vb jumped to 13 V, the car "started" most of the error messages cleared. I took it for a 10 min 40 minute drive and after turning OFF, Vb read 12.52. Hooked up EVSE and Vb with to 13.4 for short time then to 12.59 V. The EVSE will start charging the traction battery at 11 PM.

In the morning, it is a 40 mile drive to the dealer, if it starts. Hopefully, they will take this more seriously than the last time, when they just charged the battery and wouldn't do anything else.

I checked the history of these problems, and the time between EVSE charges of the traction battery are 10 days, 7 days, and 9 days. In between the car has typically been run on fairly short trips. That seems like a clue.

Doesn't explain why after after an hour trip (40 miles) to the dealer two weeks ago, the tech said the battery was "discharged".

Could be a fault of the battery charging system. During the latest incident "Service Battery Charging System" message came up. So, that would be my learned guess.
Your input is welcome.

I am not happy with the Fremont Chevrolet service department, but the Concord Chevrolet service department said that the earliest appointment would be two weeks. Ah, GM, now I remember after having a crap 1984, Oldsmobile, I sworn that I would never own another GM car.

 

[Sean Nelson]

Looks like they fixed it this time.

Glad to hear it! Thanks for taking the time to post all the details here - it will come in very handy if someone else runs into the same issue.

 

[rgmichel]

Congratulations. We are glad its solved.

Looks like they fixed it this time. ... updated the software and afterwards none of the problem codes reappeared. Apparently when the car was on the road the charging system was in "Ignition ON/Vehicle in Service Mode and therefore not charging the 12 V battery properly. .

What a relief! Only software. You must have been pretty stressed out. Now you can return to just pure enjoyment of the wonderful Bolt EV. Congratulations!!!!

It ironical that I told you my story of deliberately putting mine into service mode to use the wireless network, and had the same 12v battery discharge problem. It certainly sounded like what I experienced. Fancy the car putting itself into service mode while you were driving. Very strange.

 

[quirkySquirt]

Very useful experience, thank you for taking one for the team!

 

[borkbork]

Looks like they fixed it this time.

is there any TSB or other associated number on your work order/receipt? could be useful in the future.

 

[TotaledJetta]

is there any TSB or other associated number on your work order/receipt? could be useful in the future.

The following is part of the report. "Inspected for Bulletins and Doc ID's found Doc Id # 4339170, Ignition ON/Vehicle in Service Mode." I guess that is a TSB, Technical Service Bulletin. I am definitely learning too many acronyms.

I am surprised I am the only one responding on this forum with this problem. I picked up my Bolt Jan 13, 2017 (Friday the 13th) so maybe I was unlucky, but there must be more bad code out there somewhere. Before taking it in the first time On Star sent me an email, saying Service Needed on the transmission. So maybe they knew more than Fremont Chevrolet. At least this time, the car came back with the tires pumped up to the correct pressure.

Hmm, thinking fondly of the simplicity of my 1965 Mustang, that I kept for 41 years. When the drive shaft feel off, it was obvious what the problem was.:nerd: