Synergy S3 Electric Bicycle

An Old Electric Bicycle

When people asked me what I would do when I retired, I mentioned building a solar bicycle as one of the projects. However, it was just a pipe dream – I never purchased anything toward the actual project. That is, until Valentine’s Day this year, when I saw this bike at an estate sale for $300. This will be the beginning of the project.

When I got the bike, there were a few small problems:
1) Front brake pads missing. No problem. I had some on hand.
2) Owner lost the charger. For the initial charge, I opened up the battery pack and charged the 12V batteries individually from a 2 amp auto battery charger. I later got a charger on eBay for $11.25
3) The XLR charger port was not working. I repaired a loose wire inside the battery pack.
4) The batteries did not hold much charge. Got new ones. $20 at Halted Electronics.
5) Various cables were loose around the bike. Secured with tie-wraps.

Synergy S3 Electric Bicycle
This is a first-generation electric bike. It will serve for this project, and the price was right.
Battery Pack
This is the battery pack. Inside are two 12-volt, 12-amp-hour sealed lead-acid batteries in series. No Lithium-Ion here!  There is an on/off switch with green, yellow, and red LED bars to the right, indicating the state of charge. The 3-pin XLR jack connects directly to the batteries, and is where the charger plugs in.
Handlebars are very much like an ordinary mountain bike, except for the little paddle near the right grip, which turns on the motor.  There is no continuous throttle like modern bikes – the motor is either on or off.  Rotating the left grip shifts the chain to any of 7 speeds.  Handlebar brakes are conventional, except that there are additional cables that cut the power from the motor whenever the brakes are activated. That round thing near the left grip is a bell.
Rear Wheel
There is an external chain drive motor, as opposed to the hub motor found on many newer bikes.  Note that for the pedal drive, there is only the rear derailleur, no front.  Perhaps the designers thought that wide gear ratios would be unnecessary on an electric bike.
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