Bosch Gen5 - Still flashing at 100%

[rooftiler1]

Hi, I'm not sure if this is a common trait, but I thought I'd ask. On my eMTB, when I charge the battery while it's still in the bike, the display shows '100% Charging', and the top bar on the Bosch crossbar display continues to flash. I usually unplug the charger once it shows 100%, but if I were to leave it connected, how long (if ever) would it take for the display to indicate that it's fully charged?

 

[Bear-uk]

Hi, I'm not sure if this is a common trait, but I thought I'd ask. On my eMTB, when I charge the battery while it's still in the bike, the display shows '100% Charging', and the top bar on the Bosch crossbar display continues to flash. I usually unplug the charger once it shows 100%, but if I were to leave it connected, how long (if ever) would it take for the display to indicate that it's fully charged?

I don't have a Gen 5 but the Gen 4 charger keeps on adding a small charge to fully top out the battery after the 100% shows up.
Remember just because it says 100% doesn't mean it's absolutely full.
I reckon the Gen 5 will be the same.
Any reason why you haven't left it on charge?
I sometimes forget mine and leave it on all night. Once it's full the BMS board stops it overcharging.
Unlike the cheap batteries that set on fire and are giving decent bikes a bad name.

 

[Joecrow]

On both my Gen 4 and Gen 5 bikes, 750W and 800W batteries resp. the last led stops flashing when fully charged and all leds stay lit while still connected to the charger.

 

[Anders]

Mine (gen4) is the same. I guess its the BMS that does a balancing, i.e. makes sure the cells all have the maximum charge.

 

[AlfreDoss]

Mine (gen5) flashes at 100% for a while, then finally shuts off.

 

[Shark58]

Mine (gen4) is the same. I guess its the BMS that does a balancing, i.e. makes sure the cells all have the maximum charge.

@rooftiler1

That is the correct answer. After the total charge reaches 100% the BMS starts a cell balancing process to even out the voltage of each individual cell.

This needs to be done on a regular basis to prevent premature degradation of the battery.
So don't unplug the charger before all lights stop flashing. This won't take long after 100% is reached.

For technical details on cell balancing see Battery Balancing.

 

[rooftiler1]

Ok cheers for the replies, i guess I needed to leave it on a bit longer then.

 

[JP-NZ]

My gen 4 still flashes even when its 100%. When its fully charged it switches the bike off. I would presume Gen 5 is the same.

 

[irie]

It switches off after completing cell balancing.

 

[Doomanic]

What do you guys think about the advice of charging it to 80% rather than 100% to preserve the battery (charging to 100% only when you really need the range) and charging to 60% if the bike is not going to be used for a prolonged period of time? Is that woo woo or sound advice?

That is sound advice but how do you know if you're going to need 80% or 100%?

 

[AlfreDoss]

The Flow app will show 100% but the battery continues to charge with LED flashing for awhile until it completes and shuts off. What do you guys think about the advice of charging it to 80% rather than 100% to preserve the battery (charging to 100% only when you really need the range) and charging to 60% if the bike is not going to be used for a prolonged period of time? Is that woo woo or sound advice?

I used to do this way with my former ebike and after 6 years battery health was still at 100%, even if I can't assure if two things are related

 

[rooftiler1]

As a conclusion to this thread, I've confirmed the battery completes its charging cycle correctly. The process from a 50% state of charge is as follows:

• Main Charge (50% to 100%): Takes approximately 2 hours.
• Balancing/Absorption Phase (at 100%): Continues for about 1 more hour before the charger powers down.

So, the extended time at the end appears to be a normal cell-balancing phase.

 

[KuRi]

As a conclusion to this thread, I've confirmed the battery completes its charging cycle correctly. The process from a 50% state of charge is as follows:

• Main Charge (50% to 100%): Takes approximately 2 hours.
• Balancing/Absorption Phase (at 100%): Continues for about 1 more hour before the charger powers down.

So, the extended time at the end appears to be a normal cell-balancing phase.

I have the exact same issue, and I thought it was a battery defect. Mine keeps charging almost 1 hour more after 100% is reached. Thanks for your insights, it looks normal then, but weird.

P.D: Bosch 750wh battery on new battery wild 2026 with cx gen5.