I am currently developing this device.

It will go on sale in my store approximately in June 2020. The price will be €75, shipping €10.

Functions of the Yamaha battery dongle

  1. A battery hack that let you mount any battery on a Yamaha e-bike, not just a Yamaha battery.
  2. A very accurate battery fuel gauge with the LTC2944, not just simple voltage measuring.
  3. Fuel gauge indication with 5 LEDs.

Yamaha e-bike battery hack with very accurate Fuel Gauge
Yamaha e-bike battery hack with very accurate Fuel Gauge

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Yamaha e-bike battery dongle with very accurate Fuel Gauge
Yamaha e-bike battery dongle with very accurate Fuel Gauge


Take the cable from the battery to the Yamaha motor.
Cut off the connector of the Yamaha battery.
Connect the three wires to the dongle: 

M- Motor - Black
M+ Motor + Red
Data   Grey


Connect the new battery as follows:

B- Battery -
B+ Battery +


Yamaha battery hack

As with other brands, the Yamaha motor blocks if another battery is connected, but this protection can be hacked. The Yamaha does not use encrypted authentication.

Example of use

On my solarbike, the Maxun One, I want to use a Yamaha PW-X2 mid-drive motor. The problem is that the Yamaha battery is not suitable for my solar bike because:

  • The PV panels can charge the battery with a current as high as 8A. Normal Li-ion e-bike batteries can’t stand this high charge current. I need LiFePO4 battery cells.
  • The battery must allow simultaneously charging and discharging, this isn’t possible with the Yamaha battery.

Battery authentication

As with all e-bike motor manufacturers, the motor blocks when another battery is detected than the same brand. Note that this is unallowed product tying, see my article Product tying.

Fuel gauge with the LTC2944

The Yamaha battery has a fuel gauge built in and passed the battery capacity to the mid-drive motor and the display via the data cable.If a battery other than the Yamaha battery is used, the capacity should be measured on another way. A fuel gauge IC, the LTC2944, is used for this.

Fuel gauge LED indication

The dongle can also be used universally as an accurate battery fuel gauge for any battery. The remaining battery capacity is continuously displayed with 5 LEDs. If the battery is switched off or disconnected, the capacity-value must be restored when it is switched on again. The capacity-value in mAh is therefore stored in an EEPROM. 

Dongle during development

Yamaha battery dongle development
Yamaha battery dongle development


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