E-bike: Things that went right and wrong

Things that went North

This page is a link from Conversion to eBike.

  • Using microswitches for both brake handles for brake lights and engine stop turned out to be a very rigid solution.
  • The batterypack construction, with EPDM isolation and aluminium housing is easy to make and rigid.
  • The Sunkko 787A Hack created possibilities to make a 13s6p pack and actually works.
  • 1500 W is really fun, and a must for hills, 10% slope without pedalling is not overkill.

Things that went South

And what I will do different next time.

During my projects many things did not go according to plan. Most things went very well fortunately. I will describe the bummers here for reference and education.

Not enough time

This may sound strange, but it was – and is – a real problem. The lack of time caused the project to have a timespan of more than a year. If I knew that before, I would have made it all less technically complex. Look in the mirror and ask yourself if you can spend enough time.

Unused new battery destroyed

After building two packs with greatest care, one was dropping in Voltage and I could not charge to full voltage (13 * 4.2 V = 54.6 V). I was thinking: “Just shut down the main switch for the coming time and dive in the problem later”. That was wrong, the BMS turned out to be faulty and despite shutting off the main switch, the balance wires slowly drained the brand new expensive cells to 0 V. If I knew then, I would have pulled out the plug of the balance wires. So take appropriate actions in case of problems with charging and voltage. https://vanderworp.org/en/battery-management-system-bms/ is of value here.

Wrong choice of cabling

I standardized on 1 mm2 wires in multiple colours with PVS LiY shielding. They are over dimensioned and not flexible enough. Cables from steer to frame are overdone.

See 48V Wiring for a wire table and considerations.

Old brakes are not reliable

My 7 year old brake cylinders were not reliable any more. Considering the much higher working load: Replaced them all.

Brake disc is warped

Bad luck, probably bend during transport.

Weight distribution

With the batteries in the back, all weight is concentrated there. Next time: between the tubes of the triangular frame.

More power is not always a good choice

Pedal Assistance on a flat road in level 5 is uncomfortable. Worse is that you may make your bike unnecessary expensive because of the extra battery cells you need to feed the engine. On the other hand, 1500 W “lift off” is fun and when there are hills you definite want 1500 W at least.

Choosing tyres is important

Tyres like balloons are no fun, you loose your feeling with the road. Stiffer tyres are better.

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