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Yellow wire on Sram E-matic battery charger?

johnscura

🧲 New user
Joined
Oct 2, 2025
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Westerndigital!
I have a 2014 Electra Townie Go! that rides nice but is missing a battery charger. Battery is now at 75% charge so I am afraid to ride bike until I find a way to charge the battery. This Sram made battery requires 3 wires to charge (red/black/yellow). No idea what the 3rd yellow wire does so I don't know how to mod a typical 2 wire 36V charger to be able to charge. One person noted the battery has a power switch on it. You can charge with battery on bike or off bike. Maybe the yellow wire prevents charging if the battery is turned on and/or turned on and on bike. With the battery removed from the bike you can measure voltage at the battery's output connector. Probing the battery's 3 charge port inputs with a VOM shows zero combination can deliver and current/voltage with the battery turned on or off. If anyone has a charger I would love to hear what comes out/goes into yellow wire (voltage to open/close relay, thermistor, etc.).
 
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