How to Tell If a Bluetooth Lithium Battery Is Bad and How to Test Bluetooth Lithium Batteries？

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How to Tell If a Bluetooth Lithium Battery Is Bad and How to Test Bluetooth Lithium Batteries?

By Renogy Tech Support Team July 25th 2023

This troubleshooting guide applies to the following products:

Bluetooth Lithium Battery Issues

Common problems of Bluetooth lithium batteries are:

How to Tell If a Bluetooth Lithium Battery Is Bad?

For most common problems with Bluetooth lithium batteries, we can usually determine the health of the battery by measuring its voltage, checking the SOC, cell voltage data, and inspecting the wiring. Please refer to the troubleshooting steps corresponding to each specific problem for more details.

How to Troubleshoot Bluetooth Lithium Batteries?

The following are common issues and corresponding troubleshooting methods for Bluetooth lithium batteries.

Battery not holding charge

Troubleshooting steps:

  1. First, it is necessary to confirm whether the battery has been over-discharged during use and has not been activated for charging for a long period of time;

  2. Use a multimeter to measure the open-circuit voltage of the battery and check whether the battery is in undervoltage protection mode (if the open-circuit voltage of the battery is below 10V, it means that the battery is in undervoltage protection mode). If the battery is in undervoltage protection mode, remove all connection wires from the battery and use a charger that matches the battery parameters and has lithium battery activation function. Activate and continuously charge the battery when the ambient temperature is above 41℉. After the voltage at the battery terminal rises to 12.4V or above, the battery can enter the normal charging state;

  3. Check the battery information on the DC Home APP to see if there is any prompt for protection (such as low temperature, overcurrent, etc.). The battery cannot be charged under these protection states;

  4. Check whether the charging parameters of the charger are consistent with the battery parameters (as shown in the figure below). If they are inconsistent, there may be a problem with charging the battery. You can also cross-validate the battery or charger to confirm whether there is a problem with the charger or battery;

  5. If the above steps still cannot confirm whether the battery is faulty, please contact Renogy for assistance and provide the above troubleshooting results and relevant videos for further confirmation. You can refer to the example video when submitting a case.

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Battery cannot be fully charged

Troubleshooting steps:

  1. First, check the battery cell voltages through the DC Home app. If there is a significant difference in voltage between the battery cells, it may be due to one cell reaching the overvoltage threshold first, causing the battery to stop charging and not fully charge. In this case, refer to the troubleshooting steps for "Unbalanced cell voltages".

  2. Confirm if the battery has been excessively discharged and not activated for a long period of time during use. It is also recommended to not exceed 80% depth of discharge (DOD).

  3. During the battery charging process, check the battery information page in the DC Home app for any related protection prompts (such as low temperature or overcurrent). The battery will not fully charge while in these protection states.

  4. Verify that the charging parameters of the charger match the battery parameters (as shown in the figure below). If they do not match, it may cause issues with charging the battery. Cross-checking the battery or charger can also help confirm if there are any issues.

  5. If the above steps still cannot confirm whether the battery is faulty, please contact Renogy and provide the system wiring diagram (including load model and power), as well as the above troubleshooting steps and results for further confirmation.

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The battery cannot maintain its charge

Troubleshooting steps:

  1. First, use a charger that matches the charging parameters of the battery (as shown in the figure below) to fully charge the battery. When the battery is fully charged, its voltage should be 14.4V. Disconnect all the wiring from the battery, and let it sit for at least half an hour. Then measure the open-circuit voltage of the battery. If it is above 13.4V, the battery is fully charged. Then leave the battery unused overnight (without any wiring attached, and in an environment with no significant temperature changes), and measure the open-circuit voltage again. If there is a significant drop in the open-circuit voltage, it indicates a battery failure.

  2. If there is no significant change in the battery voltage after being left unused, connect a resistive load (such as an electric water heater) to the battery and discharge it continuously until the battery reaches low-voltage protection. Record the discharge time and calculate the battery's capacity based on the load power and discharge time. Compare the calculated capacity with the rated capacity.

The State of Charge (SOC) of the battery is inaccurate

Detailed description of the problem: The SOC of the battery does not correspond to the battery voltage. Specifically, the battery SOC is high, but the cell voltage is low (basically out of power), as shown in Figure 1 below; the battery SOC is low, but the cell voltage is high (basically fully charged), as shown in Figure 2 below.

For the relationship between SOC and voltage of lithium batteries, please refer to the "Lithium Battery State of Charge Chart" in the appendix.

Figure 1

Figure 2

Troubleshooting steps:

  1. If there is only one battery in the battery pack:

a. The battery's SOC can be calibrated by following these steps: Set the Boost Voltage of the charging equipment to 14.6V according to the battery charging parameters shown in the figure below. Then charge the battery until the terminal voltage of the battery is above 14.4V and the battery's SOC displayed on the DC Home APP shows 100%, which indicates that the battery's SOC has been calibrated.

b. After the battery's SOC has been calibrated, it is recommended to change the charging voltage (Boost Voltage) back to 14.4V.

c. When the battery is not in use, it is also recommended to disconnect the connection between the battery and the system to prevent parasitic loads in the system from causing deviations in the battery's SOC.

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2. If there are multiple batteries in the battery pack:

a. The maximum number of Bluetooth lithium batteries that can be connected in parallel is eight. Before parallel connection, each battery should be fully charged, and the voltage difference between the batteries should be less than 0.1V. Then the batteries can be connected in parallel according to the wiring method shown in the diagram, and the cable specifications and lengths between the batteries should be consistent to ensure a tight connection.

b. If the SOC is still inaccurate after following the above requirements, it is necessary to calibrate the SOC of each battery separately according to Step 1.

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Unbalanced charging and discharging current

Troubleshooting steps:

  1. The maximum number of Bluetooth lithium batteries that can be connected in parallel is 8. Before parallel connection, each battery should be fully charged, and the voltage difference between the batteries should be less than 0.1V. Then the batteries can be connected in parallel according to the wiring method shown in the diagram, and the cable specifications and lengths between the batteries should be consistent to ensure a tight connection. It is recommended to let the battery pack sit idle for 12-24 hours after completing the parallel connection between batteries.
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2. Due to the differences in internal resistance between different batteries, the charging and discharging currents of paralleled batteries will be slightly different, especially when the battery pack is charged or discharged with a small current. Therefore, it is normal for different batteries to have different charging and discharging currents under low-current charging and discharging conditions.

3. If there is a significant difference in the charging and discharging currents of paralleled batteries under high-current charging and discharging conditions, you need to check whether the paralleling of the batteries meets the requirements of unbalanced charging and discharging current - troubleshooting Step 1. If it meets the requirements, please provide Renogy with the actual wiring diagram of the batteries and screenshots of all battery details displayed in the DC Home APP, including the battery cell voltage, as shown in the figure below, in order to further analyze the problem.

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Unbalanced cell voltages

Detailed description of the fault: The individual cell voltage is low or high, as shown in the following figure.

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Troubleshooting steps:

Check cell voltage via DC Home APP.

  1. When the cell voltage is around 3.2V, if the voltage difference between a particular cell and the other cells is more than 0.2V and this difference persists for more than 10 minutes, the cell is faulty.
  2. When the battery is at the end of charging (fully charged), if the voltage difference between the cells is more than 0.4V and this difference persists for more than 10 minutes, the cell is faulty.

Bluetooth cannot connect to the DC Home APP

  1. First, you need to rule out the possibility that the Bluetooth is already connected to DC Home APP on another phone. In this case, Bluetooth cannot be connected. You need to disconnect the Bluetooth from the other phone, then update DC Home APP to the latest version, and add the device in DC Home APP. Select "HUB Mode" to search for Bluetooth, as shown in the figure below. 
    DC home HUB MODE
  2. If Bluetooth is not connected to another phone, disconnect all connections to the battery and use a multimeter to measure the battery's open circuit voltage. If it is below 10V, the battery is in undervoltage protection mode, and its built-in Bluetooth is also turned off. In this case, you need to use a charger with lithium battery activation function to fully charge the battery and then reconnect Bluetooth in DC Home APP. If the battery is not in undervoltage protection mode, give the battery a charging or discharging current greater than 1A to activate the battery and then reconnect Bluetooth in DC Home APP.
  3. The effective connection distance of the Bluetooth built into the battery is 3m-5m. Please ensure that you are not too far away from the battery when connecting Bluetooth.
  4. Ensure that there are no electromagnetic interference devices around the battery, as electromagnetic interference can cause Bluetooth communication failure.
  5. If you still cannot connect Bluetooth and DC Home APP after checking the above steps, please provide the above troubleshooting steps and results, as well as a video to Renogy for further analysis. You can refer to the example video when submitting a case.

Appendix I Lithium Battery State of Charge Chart (77℉)

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The table above is for reference only because slight variations in battery voltage may occur among different batteries. 

Troubleshooting Video

Alternatively, you can check the video below for troubleshooting details about the following:

  • Charge failure
  • Full-charge failure
  • Capacity degradation
  • Communication issue
  • Unbalanced charging and discharging currents
  • Inconsistent cell voltages
  • Temperature abnormality
  • SOC inaccuracies
 
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