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Went to start up and initially the radio and systems came up. Never got going. The Battery Saver Active message came up. Under the battery symbol it shows a wrench. I checked the battery voltage which read 9.39 V and dropping. In a half hour it read 8.55 Volts. The car won't shutdown, at least the start light looks on. Called the dealership, but couldn't get anyone to talk with me. At least it is parked at home. Suggestions?
 

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Went to start up and initially the radio and systems came up. Never got going. The Battery Saver Active message came up. Under the battery symbol it shows a wrench. I checked the battery voltage which read 9.39 V and dropping. In a half hour it read 8.55 Volts. The car won't shutdown, at least the start light looks on. Called the dealership, but couldn't get anyone to talk with me. At least it is parked at home. Suggestions?
Throw a charger on it, or temporarily connect a battery long enough to put the car in ready mode, which should charge the existing battery. If the traction battery can take a charge, then plugging in will also charge the 12v.

Dealerships are notorious for allowing batteries to die. Doors left open, lights left on, radios turned on for long periods while the car is off, etc.

If the Bolt is like the Prius, then it consumes more power if the fob is left within about 10ft of the car. Another thing to be aware of. I wouldn't be surprised if the manual mentions something about fob storage.
 

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The solution was simple, but I sure didn't find it in the Bolt manual. I did try putting my last century, garage sale, charger on and it charged at above 8 amps for a while and then the charger started acting in some on off mode. The I called Chevy Roadside Assistance and a guy with a portable battery showed up. After connecting it for about 10 minutes the battery voltage recovered and the Bolt came to life without further problems. So, it is similar to an ICE system, except when you jump an ICE and start the engine, the alternator can keep it going until the battery recharges. I suspect with the Bolt the 12 V battery needs to be charged to maintain 12 V. Just guessing though.

Point 2. The root cause must have been cockpit error by me for not shutting down properly yesterday. Live and learn, then repeat.

Is there a good explanation of how and when the Bolt recharges its 12 V battery?:)
Throw a charger on it, or temporarily connect a battery long enough to put the car in ready mode, which should charge the existing battery. If the traction battery can take a charge, then plugging in will also charge the 12v.

Dealerships are notorious for allowing batteries to die. Doors left open, lights left on, radios turned on for long periods while the car is off, etc.

If the Bolt is like the Prius, then it consumes more power if the fob is left within about 10ft of the car. Another thing to be aware of. I wouldn't be surprised if the manual mentions something about fob storage.
 

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It's charging whenever the car is "on". In a discussion with a tech someone asked what would happen if they connected an inverter to the 12v battery if the traction battery would continually provide power to maintain the 12v system, creating a 60kWh UPS. He said it's not recommended but yes, the high v system will continually charge the 12v system to make up for the load. Don't know what the max load the 12v charging system can sustain but I'm guessing it's probably 80a+.

Now i'd have to assume that it is also charging when the car is off so that the car's battery conditioning systems and on star etc. can stay alive for extended periods but don't know for sure. Maybe the system relies entirely on the capacity of the 12v battery for that.

Lots of words, just realized I didn't really answer your question. Sorry!
 

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As you say, the 12v battery is charged whenever the car is "on", fed from the traction battery through an AC > DC converter. I haven't seen anyone answer the question of how many amps the converter can handle, but your guess of 80+ is probably close.

The 12v battery also charges when the traction battery is charged. It does not charge when the car is off and the traction battery is not charging.
 

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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.
 

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As you say, the 12v battery is charged whenever the car is "on", fed from the traction battery through an AC > DC converter. I haven't seen anyone answer the question of how many amps the converter can handle, but your guess of 80+ is probably close.

The 12v battery also charges when the traction battery is charged. It does not charge when the car is off and the traction battery is not charging.
Sorry for being pedantic but I think you meant DC > DC converter. The only thing AC in the car is the output from the motor speed controller.... and maybe the A/C compressor.
 

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Holy copy and paste Batman!

drdiesel, what resource are you pulling that info from?

On a semi related note, I got excited for a moment when I saw tow/haul mode, but then I saw "system on engine off" or something to that effect so I figure those items are missed remnants from ICE days.
 
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