Lithium-ion batteries used in power tools can fail due to cell degradation, corrosion, or deep discharge. In this project, we repair a completely dead Bosch 18V 2.0Ah battery and upgrade its capacity to 3.4Ah.
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| Bosch 18V 2.0Ah Battery Replacement |
Initial Symptoms
- The battery shows no response when the battery level button is pressed. No LEDs turn on, indicating a possible internal failure.
Battery level indicator shows no light when pressed. - When connected to the charger, the green LED remains static and does not blink. This usually means the charger cannot detect the battery pack.
Battery connected to charger with static green light. - Voltage reading = 0V.
Multimeter probes on the main battery terminals..
This indicates full battery pack failure.
Disassembly Process
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Remove 8 screws from the battery housing.
Removing the 8 screws from the battery housing. -
Pry open top cover carefully.
Prying open the top battery cover. Remove battery level cover (2 screws).
Battery level indicator cover. Remove left and right side panels.
Side covers removed.
Troubleshooting
- Remove insulation tape, nickel strips and PCB.
Insulation tape and nickel strip removed from battery pack. - Inspection revealed the battery cells show heavy corrosion and leakage, which explains the failure.
Severely corroded and leaked battery cells. - Each cell is tested individually using a multimeter. All cells show 0V, confirming full cell failure.
Checking voltage on individual 18650 cells.
Battery Replacement
- Old cells were removed from the compartment (required gentle hammer tapping).
Removing stuck battery cells from the compartment. - New NCR18650B 3400mAh lithium-ion cells are installed. This upgrades the battery from 2.0Ah to 3.4Ah capacity.
New NCR18650B 3400mAh cells installed.
PCB Repair
- Battery leakage caused corrosion on the PCB.
Corrosion on the PCB. - The board is cleaned using isopropyl alcohol, and solder joints are reheated to restore connections.
Solder joints are reheated to restore connections.
Reassembly
- After cleaning and inspection, the PCB is reinstalled carefully into its original position.
PCB installed back into battery housing. - New nickel strips are cut to match the original dimensions.
Nickel strip cut to original length. - The nickel strips are spot-welded in the same configuration as the original battery pack.
Spot welding nickel strips to new cells. - Insulation tape is reapplied to prevent short circuits and improve safety.
Battery pack insulated with protective tape. - All covers are installed back in reverse order, and screws are tightened securely.
Battery housing reassembled and secured
Final Testing
✅ Test 1 – Battery Indicator
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| Battery level indicator working normally. |
✔ Battery level indicator lights up correctly when the button is pressed.
✔ Confirms PCB and indicator circuit are functioning properly.
✅ Test 2 – Charging Test
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| Battery charging with blinking green LED. |
✔ Battery detected by the charger.
✔ Charger green LED blinking, indicating normal charging process.
✅ Test 3 – Load Test
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| Bosch blower powered by the repaired battery. |
✔ Battery tested under load using a Bosch blower.
✔ Tool runs smoothly without power drop.
✔ Runtime is noticeably longer compared to the original 2.0Ah battery.
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