Bosch charger LED off or battery not charging: work out whether it is the charger, the PowerPack/PowerTube or the bike
ChargerBosch eBike Systems
Bosch chargers are deliberately dumb on the outside (one LED, no fan on the 2A) and smart on the inside: the charger and the battery negotiate before any current flows, so most 'not charging' complaints are a battery that refuses, not a charger that failed. This flow tells you which.
Warning: Bosch batteries have no user-serviceable parts and a Bosch charger only works on Bosch batteries. A generic 42 V charger will not charge a Bosch pack and can damage the charge socket. Do not charge a PowerPack that has been dropped, dented or wet until a dealer has checked it.
What you need
- The Bosch charger: Compact 2A, Standard 4A, Fast 6A, or the 4A Smart System charger (BPC3400); the model is printed on the underside
- The battery, ideally removed from the bike so you can see its LED bar
- A working wall socket (test it with something else)
- For Smart System bikes: the eBike Flow app on your phone, paired with the bike
LED patterns and what they mean
| Charger LED off, plugged into mains, no battery | Normal on the 2A and 4A Classic chargers: they have no standby light. On the 6A and the Smart System 4A the LED should show white or green at standby; if it is dark the charger has no mains or has failed. |
| Charger LED off, battery connected | Charger and battery did not shake hands. The classic chargers show nothing until the battery accepts charge, so a dark LED with a battery attached means the battery is refusing or the plug is not seated. |
| Charger LED steady (green on Classic, white on Smart System) | Charging in progress. The battery's own LED bar animates to show progress. |
| Charger LED off after charging, battery LEDs all lit then off | Charge complete. Classic chargers switch off completely; the battery bar goes out a few minutes after reaching full. |
| Battery LEDs flashing, charger LED on | Battery is outside its charging temperature window (below 0 or above about 40 degrees C). Charging pauses until the pack returns to range. |
| Battery LEDs: only the outer ones flash, or a chase pattern | Battery fault detected by the BMS. Matches error 620 or 640 on the display when fitted to the bike. Dealer diagnosis needed. |
| Smart System charger LED blinking red | Charger-side fault or wrong battery voltage detected. Unplug both ends, wait 30 seconds, reconnect. Persisting blink: charger. |
Step by step
1. Is the wall socket live and the mains lead seated?
Use another appliance in the same socket. Then push the C7 figure-of-eight mains lead firmly into the charger; it is a common half-inserted culprit.
If OK: Go to step 2.
If not: Socket, breaker or lead. Fix that first; it is not a Bosch problem.
Use another appliance in the same socket. Then push the C7 figure-of-eight mains lead firmly into the charger; it is a common half-inserted culprit.
If OK: Go to step 2.
If not: Socket, breaker or lead. Fix that first; it is not a Bosch problem.
2. Charge the battery off the bike
Remove the battery (key, unlock, lift). Plug the charger's round connector into the socket on the battery itself. Press the battery's button and watch the LED bar.
If OK: Battery LEDs animate and the charger LED comes on: charger and battery are fine. The problem is in the bike's charge socket or harness. Verdict: bike.
If not: Nothing happens off the bike either: continue with step 3.
Remove the battery (key, unlock, lift). Plug the charger's round connector into the socket on the battery itself. Press the battery's button and watch the LED bar.
If OK: Battery LEDs animate and the charger LED comes on: charger and battery are fine. The problem is in the bike's charge socket or harness. Verdict: bike.
If not: Nothing happens off the bike either: continue with step 3.
3. Does the battery show any charge level on its own button?
Battery off the charger, press the button once. Count the LEDs.
If OK: At least one LED: pack is above its deep-discharge threshold and should accept charge. Go to step 4.
If not: No LEDs at all: the pack is either deeply discharged (left flat for months) or its BMS has latched off. Leave it on the charger for 30-60 minutes at room temperature, then retry once. Still dead: dealer, verdict battery.
Battery off the charger, press the button once. Count the LEDs.
If OK: At least one LED: pack is above its deep-discharge threshold and should accept charge. Go to step 4.
If not: No LEDs at all: the pack is either deeply discharged (left flat for months) or its BMS has latched off. Leave it on the charger for 30-60 minutes at room temperature, then retry once. Still dead: dealer, verdict battery.
4. Is the battery at a chargeable temperature?
A pack that came in from a frozen garage or was left in a hot car will refuse charge. Feel the case; give it two hours indoors if it is cold or hot.
If OK: Room temperature, still nothing: go to step 5.
If not: Flashing battery LEDs while on the charger confirm the temperature lockout. Wait and retry; nothing is broken.
A pack that came in from a frozen garage or was left in a hot car will refuse charge. Feel the case; give it two hours indoors if it is cold or hot.
If OK: Room temperature, still nothing: go to step 5.
If not: Flashing battery LEDs while on the charger confirm the temperature lockout. Wait and retry; nothing is broken.
5. Inspect both charge connectors
Look into the round socket on the battery and, if used, on the frame. The pins must be straight, dry and free of green corrosion. Look at the charger plug for a cracked shell or a pin pushed back into the housing.
If OK: Clean connectors. Go to step 6.
If not: A bent or corroded pin on the battery side is a dealer repair (the socket is potted into the pack). A damaged charger plug is a new charger.
Look into the round socket on the battery and, if used, on the frame. The pins must be straight, dry and free of green corrosion. Look at the charger plug for a cracked shell or a pin pushed back into the housing.
If OK: Clean connectors. Go to step 6.
If not: A bent or corroded pin on the battery side is a dealer repair (the socket is potted into the pack). A damaged charger plug is a new charger.
6. Try a known-good Bosch charger of the same generation
Classic (2A/4A/6A) chargers fit Classic and Active/Performance Line packs 2014-2021; the Smart System 4A charger fits Smart System packs, and Classic chargers also charge Smart System packs but not the other way round for full function. Any dealer will let you test.
If OK: Battery charges on the borrowed charger: yours is dead. Verdict: charger.
If not: Still nothing on a known-good charger: the battery is refusing charge. Verdict: battery, continue to step 7 to read why.
Classic (2A/4A/6A) chargers fit Classic and Active/Performance Line packs 2014-2021; the Smart System 4A charger fits Smart System packs, and Classic chargers also charge Smart System packs but not the other way round for full function. Any dealer will let you test.
If OK: Battery charges on the borrowed charger: yours is dead. Verdict: charger.
If not: Still nothing on a known-good charger: the battery is refusing charge. Verdict: battery, continue to step 7 to read why.
7. Read the error on the display or in the Flow app
Fit the battery to the bike and switch on. A Classic display (Intuvia, Purion, Kiox, Nyon) shows a numeric error; the Flow app shows a plain-text fault for Smart System. Look for 620 (battery communication fault), 640 (internal battery fault) or 602 (battery temperature).
If OK: No error on the bike but no charging: the BMS charge path alone has failed, which a dealer can confirm with DiagnosticTool. Verdict: battery.
If not: Error 620 or 640 confirms the battery has locked itself out. Verdict: battery. Error 602 is temperature; wait it out.
Fit the battery to the bike and switch on. A Classic display (Intuvia, Purion, Kiox, Nyon) shows a numeric error; the Flow app shows a plain-text fault for Smart System. Look for 620 (battery communication fault), 640 (internal battery fault) or 602 (battery temperature).
If OK: No error on the bike but no charging: the BMS charge path alone has failed, which a dealer can confirm with DiagnosticTool. Verdict: battery.
If not: Error 620 or 640 confirms the battery has locked itself out. Verdict: battery. Error 602 is temperature; wait it out.
8. Check the bike's own charge socket if the pack charged off-bike
With the pack fitted, plug the charger into the frame socket. Wiggle the plug gently and watch the battery LEDs. Also check the small harness behind the socket where it plugs into the battery holder.
If OK: Charges through the frame socket now: it was a loose plug. Keep the socket cap closed.
If not: Charges off-bike, not on-bike, plug seated: frame socket or harness. Verdict: bike; dealer replaces the socket assembly.
With the pack fitted, plug the charger into the frame socket. Wiggle the plug gently and watch the battery LEDs. Also check the small harness behind the socket where it plugs into the battery holder.
If OK: Charges through the frame socket now: it was a loose plug. Keep the socket cap closed.
If not: Charges off-bike, not on-bike, plug seated: frame socket or harness. Verdict: bike; dealer replaces the socket assembly.
What you now know for sure
- Charger: Battery charges on a borrowed Bosch charger but not on yours. Classic chargers fail silently because they have no standby LED. → Replace with a Bosch charger of the matching generation. A 4A charger is the sensible default; the 2A Compact is travel-only and the 6A only helps on DualBattery setups.
- Battery refusing charge: Deep discharge, temperature lockout, or a BMS fault (error 620/640). → Deep discharge and temperature resolve with time indoors. A BMS fault is dealer-only: they read cell voltages and fault history with DiagnosticTool and can tell you if the pack is warrantable.
- Bike charge socket or harness: Pack charges off the bike but not through the frame. → Dealer replaces the charge socket or the holder harness. On PowerTube bikes this is often the cheapest fix of the three.
- Nothing wrong, just slow: A 2A Compact on a 750 Wh pack takes over seven hours; a 4A about four hours. Riders switching from a 4A to the travel 2A often think something broke. → Use the 4A charger for daily charging; keep the 2A for travel.
Manuals and video
- Bosch eBike Help Center: official error-code index
- Bosch eBike downloads: quick start guides and battery guide
- Bosch eBike dealer search (DiagnosticTool readout)
Videos found on YouTube and checked automatically; they are other people's work, not ours.
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Frequently asked
My Bosch charger has no light at all when I plug it into the wall. Is it broken?
Not necessarily. The Classic 2A and 4A chargers have no standby LED; the light only comes on once a battery is connected and accepts charge. The 6A and the Smart System 4A do show a standby light. Test with a battery that you know is fine, or with a borrowed charger.
What can the Bosch dealer read that I cannot?
With DiagnosticTool the dealer sees individual cell-group voltages, the number of charge cycles, the temperature history, the fault log with timestamps, and whether the BMS has permanently locked the pack. That decides between a warranty claim, a repairable fault and a new pack.
Does error 620 mean the battery is dead?
620 is a communication fault between battery and drive unit. Sometimes it is only a dirty or wet contact on the battery holder; clean and dry the contacts and retry. If it persists and the pack also refuses to charge, the BMS has logged an internal fault and a dealer needs to read it.
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.