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Opinion: Bosch E Bike tech

I have ridden e bikes, commuter and mountain but I have never serviced them. Brian came in to drop some knowledge. He’s the tech rep for Bosch USA e bikes, so knows a thing or two.

Drive units (motors)

Bosch e bike
Left: Lower torque motor (50Nm). Right: high torque(75Nm), and below the on bar control units.
Exploded diagram of a Bosch Active Line Drive Unit

In my mind I was ready to be disassembling gearboxes, ringdrives, motors and seals. Turns out the whole transmission (motor assembly) is crazy good German engineered and is designed not to be serviced and have a 7+ year life!

Close up of the drive unit aka motor. this is where the pedal arms attach, but you can see this thing is rugged and over engineered. the unit weight about 9lbs.

The drive units or motors sit where the bottom bracket would be. Bosch have a few kinds, some designed more for commuting and some with higher torque for mountain biking.

There are two mechanical things to think about. The drive and the crank arms. Because of the mechanical nature of Power Assist, the spider and chainring is separate from the crank arms.

Standard interfaces for the crank arms ISIS and Mini ISIS (found on lower torque models). In the picture above the smaller cylinder with internal threads is the ISIS interface for the crank arm. Note: Bosch do not use standard crank arm bolts they use special M15 and M12 bolts.

The separate chain ring / spider attaches with a special reverse threaded lockring (made by Bosch) like a track cog lockring. You can see this in the photo above being the larger threaded cylinder is where the drive ring / chainring spider would sit.

E Bike Diagnostics

Most of the problems in e bikes come from battery issues or bad wires. Which now makes sense in service items because it’s more about the electronic system and electronic monitoring.
Bad wires are from pinched internal wires from incorrect assembly of the bicycle. Its a big deal because the wires use two way communication between components.
Bad batteries are due to malfunctioning control electronics on board the battery or bad cells within the battery.

The Service answer is – Rely on the on board computers!

Plug it in, run the Bosch diagnostics on the PC and let the computer tell you what needs servicing or replacing. Perfect! No if’s or but’s just objective computer feedback. There is a strong analogy here. Like a car system, a set of components, each with brains and no central unit, It all works together and communicates plug and play, then when needed, specific components can be replaced or serviced.

Bosch E Bike Computers
Part of the system – Handlebar mounted computers that control the pedal assist and measure speed and battery info.

A few interesting e bike tips that I didn’t know.

1) Not using your e bike for a while? (maybe over the winter) Make sure the battery is between 40 and 80% charge- not full and not empty. This is the best case for battery health

2) Batteries work better in normal conditions. If your garage freezes or is tropical in the summer. Bring your battery in the house.

3) When transporting your bike on a vehicle, remove battery and computer but make sure the contacts are covered from dirt or rain. Dirty or oxidised contacts can cause problems in the system.

4) Make sure you stop in and get your e bike serviced. Just like tires and chains on regular bikes the parts wear out and your dealer will give you a computer diagnostics report. No quibbling.

5) If your e bike doesn’t have them, Add lights to your e bike! Yes it’s plug and play, requires some mechanic ing but you can add computer controlled lights that run off the battery no problem.

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