Briggs and Stratton instart - Battery imbalance repair

Introduction

If the green and red LEDs on the charger flash alternately there is a high probability of a battery imbalance. This usually occurs when the battery has not been charged for a long time and the individual cells have discharged differently. The charger cannot compensate for this imbalance. These instructions describe how the cells can be brought back to the same voltage.

What you need

Step 1 Check charger LED

Briggs and Stratton instart - Battery imbalance repair, Check charger LED: step 1, image 1 of 1

Plug the battery into the charger and check if the green and red LEDs on the charger flash alternately. If yes, there is a high probability of a battery imbalance and the following steps might solve the issue

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Step 2 Open the battery pack

Briggs and Stratton instart - Battery imbalance repair, Open the battery pack: step 2, image 1 of 1

Open the battery by removing all 4 TR10 screws
The cover can be removed without much effort

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Step 3 Measure cell voltage

Briggs and Stratton instart - Battery imbalance repair, Measure cell voltage: step 3, image 1 of 1

Measure the voltage of all 3 individual battery cells
Cell1: BV+ - BV2
Cell2: BV2 - BV1
Cell3: BV1 - BN
If cells have different voltage (>0.1V) this indicates a battery imbalance

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Step 4 Charge cells to same voltage

Briggs and Stratton instart - Battery imbalance repair, Charge cells to same voltage: step 4, image 1 of 1

Charge each cell to the highest individual cell voltage (no need to fully charge all of them)
Set power supply to 4.1V and limit current to 750mA. 750mA is the standard charging current for a LGDAHB21865 cell. If the battery has different cell type, the datasheet needs to be checked first.
Important: Do not exceed cell type rated charging voltage or current. Refer datasheet.
Connect the power supply to the terminals of the individual cell and charge until terminal voltage reached. Make sure polarity is correct (positive to positive and negative to negative). Observe the charging procedure at all time.
Important: Individual cells are not protected against reversed polarity. Wrong polarity will kill the cell.
Note: If battery cell is not charging the cell might be dead. Don't continue charging and consider replacing the cells or recycle the battery.
At the end of the charging procedure verify each cell has same voltage using the multimeter (+/- 0.01V). Note that cell voltage provided on the power supply unit might not be the same when measured with the multimeter.

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Step 5 Reassemble and charge battery

Briggs and Stratton instart - Battery imbalance repair, Reassemble and charge battery: step 5, image 1 of 1

Reassemble the battery and charge it using the original charger
Battery is charging normally until fully charged
Note: If the issue occurs again during the charging process this would mean that the individual cell were charged at different rates. The cells aged differently and the internal resistance is not at a similar level anymore. Only replacing the cells would solve this issue. Consider contacting a re-cell service.