FAQ

We look forward to supporting you during the design-in phase with our FAQ, our extensive data package, and personal by phone or e-mail. If you can't find a suitable answer in the following FAQ, you are always welcome to contact our Application Engineer Bernhard Krämer.

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Getting Started

  • When a battery is delivered to the customer, it is in "shipping mode". In this mode, the battery outputs 0 V and does not shows any LEDs. To wake the battery (exit shipping mode), apply maximum charging voltage to the battery. Wait 10 seconds before establishing communication with the smart battery and make sure no other devices are communicating on the bus.

    Keywords: no LED, no light, no voltage, no current, doesn't work, storage

  • We strongly recommend using a smart charger with SMBus communication.

    The smart battery sends information about Charging Voltage and Charging Current. These parameters depend on battery type, temperature, and age of the battery. Without a smart charger, you risk charging the battery wrong, which may lead from increased aging to triggering its internal protective circuits.

    Keyword: I2C

  • RRC smart batteries can be used safely without establishing communication between the battery and the host.

    However, it can be advantageous to exchange status information such as RelativeStateOfCharge(), RunTimeToEmpty() or BatteryStatus().

    Keyword: I2C

Setting Up Communication

  • As listed in the smart battery specification, the smart battery 7-bit address is 0b0001011.

  • I²C and SMBus look very much alike but are not the same. Some differences:

    - Pull up resistors in the range of 10 to 15 kOhm for 3V3 systems and 15 kOhm for 5V systems.
    - Clock speed 10 to 100 kHz
    - Multi-master

    For more details, have a look at:
    - General information: https://pdfserv.maximintegrated.com/en/an/AN476.pdf
    - Physical layer specification: http://smbus.org/specs/smbus110.pdf
    - Protocol layer specification: http://sbs-forum.org/specs/

    Keywords: I2C, pullup, pull-up

  • You can switch off the ChargingCurrent() and ChargingVoltage() broadcasts by writing into register BatteryMode() (address 0x03) and setting flag “ChargerMode” (Bit 14) to 1.

    Equally, you can switch off the AlarmWarning() broadcast by writing into register BatteryMode() (address 0x03) and setting flag "AlarmWarning" (Bit 13) to 1.

    Please note that after the battery is reset (e. g., after waking up from shipping mode or a deep-discharged state), these flags are also reset, and the broadcasts begin anew.

    Keyword: messages

Running System – General Questions

  • The PCM is composed of three independent safety levels:

    • 1st level protection: MOSFETs protect the battery cells against
      • over-voltage,
      • over-current,
      • over-temperature,
      • short circuit and
      • under-voltage.
         
    • 2nd level protection: A fuse is actively triggered
      • if an over-current or over-voltage situation occurs, which has not been interrupted by the 1st level protection.
      • if the 1st level protection fails to switch off the charge or discharge FET.
      • if a voltage imbalance beyond predefined limits is recognized.
         
    • 3rd level, cell-level protection: If both 1st and 2nd level protection failed to trigger and the cell's internal pressure considerably increases, resulting gases escape via an intended breaking point (known as venting) that cuts open the internal electrical path of the cell.

    Keywords: BMS, battery management circuit, emergency, blow

  • The T pin is a thermistor pin used to measure the temperature within the battery. But for smart batteries, instead of a thermistor, there is a fixed 300 Ω resistor. The smart battery only communicates its temperature via SMBus.

    Now, when the battery is in shipping or shutdown mode, it outputs 0 V and does not communicate. The charger checks whether it sees the 300 Ω resistor at the T pin to recognize the battery. It then applies a wake-up charge as defined in the smart battery specification. The battery wakes-up and the charging process starts as normal.

    Keywords: thermistor, resistance, ptc, ntc

  • We do not recommend trying to predict the State of Charge by the battery voltage. The results won't be reliable at all.

    However, the fuel gauge inside a smart battery uses charge counters and a complex algorithm to correctly predict the SOC.

  • Standard batteries have a MaxError() register, which indicates the maximum error to expect from the fuel gauge IC. This register typically shows 1% and increases 0,05% after every 24h or after one full discharge cycle. If MaxError() reaches 5%, the battery requests a calibration cycle to recover its full accuracy. Once the calibration cycle is done, the MaxError() register resets to 1%.

    Most often however, MaxError() resets to 1% automatically by normally charging and discharging the battery.

    This happens if the following conditions are met:

           Battery rests still for at least 5h after charging;

           Battery discharges more than 37% State of Charge;

           Battery rests still for at least 5h after discharging;

           Ambient temperature is between 10°C and 40°C.

    These conditions often naturally happen by normally using the battery, at least once every 2-3 months.

    Thus, a calibration cycle generally is not needed.

    Keywords: conditioning, correct, SOC

  • A calibration cycle is required to restore the accuracy of the FG (e.g. Full charge capacity or SOC).

    The following procedure should be followed if a conditioning cycle is required.

           Fully charge the smart battery

           Stop charging

           Let the smart battery rest still for five hours

           Discharge the smart battery below 10% RSOC with a discharge current lower than 0.5C

           Disconnect the smart battery from the load

           Let the smart battery rest still for five hours. After this, the battery is calibrated and MaxError() register is reset to 1%.

    It is necessary to perform the calibration cycle in at room temperature (approx. 25°C).

    Keyword: calibrate

Charging - Trouble Shooting

  • The figure below shows that the charging process for Li-ion cells is split into two stages: the constant current phase (CC) and the constant voltage phase (CV). With a fully discharged battery, the CC phase is the first to take place. In this phase, the battery is charged by a constant current. Gradually, the voltage rises until it reaches the maximum charging voltage. Then the CV phase begins, in which the charging occurs at a fixed voltage. The charging current gradually decreases. When the charge current reaches a threshold called the "taper current", the battery is considered fully charged.

     

     

     

     

     

     

     

     

     

    Li-ion Cell Charging Profile

  • A smart charger either "listens" to the battery broadcasts of ChargingCurrent() and ChargingVoltage() parameters, or actively polls these registers. Both parameters are dynamically updated according to the JEITA profile, which optimizes the charging process of Li-ion batteries. The smart charger then applies the requested charging current and voltage to the battery terminals.

  • Yes. All RRC standard smart batteries support JEITA profiles. They serve to adapt ChargingCurrent() and ChargingVoltage() as a function of temperature and battery health.

  • A "Level 2" smart charger acts as an SMBus slave device only. It adjusts its output in direct response to ChargingVoltage() and ChargingCurrent () broadcasts sent by the smart battery. In Level 2 charging, the Smart Battery is completely responsible for initiating the communication and for providing the charging algorithm to the charger.

    In contrast, a "Level 3" smart charger can act as an SMBus master device. Thus, the battery does not necessarily need to broadcast its charging parameters. The Level 3 Smart Battery Charger can also poll the Smart Battery to determine the charging voltage and current the battery desires, and then dynamically adjust its output to meet its charging requirements.

    A Level 3 Smart Battery Charger is free to implement an alternative specialized charging algorithm. It may also interrogate the Smart Battery for any other relevant data, such as time remaining to full charge, battery temperature or other data used to control proper charging or discharge conditioning. For example, a medical device with stricter temperature limits than the Smart Battery's self-contained charging algorithm may use a Level 3 Smart Battery Charger that factors the battery's reported temperature into its charging algorithm.

  • Packet Error Check (PEC) is an additional byte in the SMBus protocols used to check for an SMBus transmission error. Thus, it improves the communication reliability and robustness between the smart battery and the host/charger. If a charger level 2 is used paired with a battery that uses PEC in its broadcast, the charger must be PEC compliant.

    The smart batteries which use PEC are: RRC2020; RRC2024; RRC2040; RRC 2040-2; RRC2054; RRC2057.

Coupling Multiple Smart Batteries

  • As listed in the smart battery specification, the smart battery 7-bit address is 0b0001011. This is valid for all smart batteries. If you consider using more than one battery in your system, view question 5.2.

    Keywords: communicate, communication, several, parallel, serial, series, two, 2

  • Since all smart batteries have the same SMBus address, it is necessary to use a 1-to-2 DEMUX (e.g., PCA9544A) to ensure independent communication with only one battery.

    Keywords: communicate, several, parallel, serial, series

Smart Battery Qualification

  • RRC batteries have a shelf life of 12 months under the following conditions:

    • The battery is in shipping mode
    • Ambient temperature is 25°C
    • Initial SOC is 30% at 25°C.

    To prevent the batteries from becoming deeply discharged, the user must recharge them to 30% SOC at least every 12 months. If the temperature is higher than 25°C, it may be necessary to recharge more often.

    Keyword: storage

  • One cycle count corresponds to an accumulated discharge of 90% of design capacity.

  • Please refer to the respective smart battery specification or the battery label to access the list of certificates that each smart battery has. This table shows the correspondence between the certificates and the countries in which they are valid.

     

    Country:

    Certificate: 

    Country:

    Certificate:

    International

    CB

    China

    CQC

    Europa

    CE

    India

    BIS

    Russia

    GOST-R

    Thailand

    TISI

    Belarus /Kazakhstan / Kyrgyzstan

    EAC

    South Korea

    KC

    USA / Canada

    c UR us 

    Taiwan

    BSMI

    Australia /New Zealand

    RCM            

    Japan

    PSE

    Keyword: certification

  • To access the certification documents, please ask your RRC sales representative. To acknowledge RRC smart batteries certificates in combination with your target application, you just need to present these documents to the certification authorities.

  • RRC smart battery certificates are updated on a regular basis. Any new certificate introduced in the world market will be analysed. RRC is constantly paying close attention to this topic. In case there is any question regarding upcoming certificates, please contact your sales representative.

    Keywords: obsolete, old

  • RRC Power Solutions designs, develops and manufactures its products based on the quality management systems ISO9001, ISO14001 and ISO13485.

    Keyword: certificate

End of Development

  • When storing or shipping batteries, make sure to set them in the so-called "shipping mode". In this mode, the battery circuitry shuts down to eliminate the parasitic current draw.

    To set the battery into shipping mode, use the Write word protocol and send the shipping mode command (0x0010) over the ManufacturerAccess register (address 0x00) twice within 4 seconds. In some cases, the battery may require 30 seconds before entering into this mode. Verify the following conditions:

           Send two shipping mode commands within 4 seconds.

           Send no further commands in-between the two shipping mode commands.

    There are three different ways to confirm the battery entered shipping mode:

    • Press the push button on the battery pack and verify that no LED light up;
    • Verify that the battery does not establish SMBus communication (NACK when addressed);
    • Verify that the battery output voltage is 0 V.