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Yamaha dongle to use 3rd party batteries

Published: 03 August 2019
Last updated: 24 November 2023


This device has two uses: 

See also

Sale on Tindie

The dongles are for sale on Tindie

Yamaha battery dongles for sale

Yamaha battery hack / Wireless battery Fuel Gauge / Watt meter


Please post your questions about the Yamaha dongle on this Endless Sphere discussion topic.

Hacking the Yamaha battery

As with other brands, the Yamaha PW series motor doesn't allow to use any 3e party battery. But with the use of the dongle described here, the Yamaha ebike will be hacked so that you can use any battery instead of the original expensive Yamaha battery.

At electric bicycles, only a battery of the own brand can be used, that is product tying and is prohibited, see my article HERE. If the same existed for cars, the 12V battery could not be replaced by any other battery, which is of course very undesirable. As with other brands, the Yamaha motor blocks also if another battery is used. But a Yamaha ebike can easily be hacked because Yamaha doesn't use any encrypted authentication. 

To develop a hack, GamerPaddy re-engineered the Yamaha mid-drive motor at the Pedelec-Forum. The battery dongle described here is based on the hack from GamerPaddy, but has several improvements such as the fuel gauge with the LTC2944.

Battery authentication, how does it work

As with all e-bike motor manufacturers, the motor blocks when detected that is not the same brand. Note that this is unallowed product tying, see my article Product tying.

The data line is a so-called open collector system that allows the battery to send data to the motor. The 4.7kOhm pull-up resistor to 5V is located inside the motor. Both the motor and the Yamaha battery have an open collector output by which they send the data. After power on, the motor makes the data 5V for a few seconds. The motor is now waiting for a correct data signal from the battery. If no correct data is received after two seconds or so, the motor makes the data 0V and the system is turned off.

If something doesn't work you can check if the data is 5V for a few seconds after power on.

Fuel gauge with the LTC2944

The Yamaha battery has a fuel gauge built in and the battery capacity is sent to the display via a data cable. If a battery other than the Yamaha battery is used, the capacity should be measured externally.
Therefore, the dongle also measures the battery capacity which will be displayed on the Yamaha display and the 6 dongle LEDs.

Characteristics of the Yamaha battery dongle

  1. You can use any battery on your Yamaha ebike instead of an expensive original Yamaha battery.
  2. It is suitable for all kind of batteries from 24V up to 48V, provided that the maximum voltage never exceeds 60V.
  3. The battery capacity is measured very accurately with an LTC2944 fuel gauge IC, not just simple voltage measuring.
  4. Fuel gauge indication also on the dongle, with 6 LEDs.
  5. To save power, the dongle turns off automatically when the Yamaha ebike is turned off.
  6. The battery capacity is stored in an EEPROM so that it is not lost when switched off.
  7. The data signal output has a short circuit protection.
  8. The dongle can be programmed directly via USB.
  9. A NRF24L01 wireless module can be soldered for use as a battery monitor / fuel gauge / Wattmeter.
  10. The dongle is protected against reverse connection of the battery voltage.
  11. The dongle turns on only when the Yamaha motor is connected and turned on.

All Yamaha drive units X2 ST TE CE X2-45

Here are all Yamaha drive units as of April 2021.

All Yamaha motors drive units X2 ST TE CE X2-45

Giant Syncdrive motor

The Syncdrive motor from Giant is just a Yamaha motor under a different name. However, it uses another communication system than Yamaha, namely the CAN-bus. This means that the dongle can’t be used here.

AMASS connectors

The connection cables must be soldered directly to the PCB. However, there is a possibility to use AMASS connectors. You have to purchase these yourself at for instance Amazon or AliExpress.
For use as yamaha dongle it is best to use these:

  • Motor connector J3: AMASS XT60IPW male. The female cable part is the AMASS XT60I.  There is an extra pin for the data.
  • Battery connector J2: AMASS XT60PW-M male. The female cable part is the AMASS XT60-F.


For use as Bluetooth Watt meter dongle use these:

  • Connector J2 and J3: AMASS XT60PW-M male. The female cable part is the AMASS XT60-F.  

Optional AMASS XT60PW-M connectors

Please note that the + indication on this connector is incorrect, it is the battery - connection:

The Amass + indication is wrong here

Dongle installation

You must have technical insight and be able to use a multimeter otherwise I can't help you if something doesn't work. 

  • You must be able to solder accurately and neatly.
  • The most logical place for the dongle is within the battery.
  • Make sure you don't accidentally short circuit the data line with the 36V. The yamaha motor then breaks down (see: Protected data output circuit).
  • The connection cables have to be soldered directly to the PCB. 
  • Make sure that the dongle is protected from water. You can electrically insulate the dongle with for instance plastic spray and heat shrink tubing. Make sure you keep the connectors free of spray. 
  • Please note that the program in the microcontroller chip may be erased if the chip comes into contact with water or your fingers during use.
  • See also: Troubleshooting.

Attention: In case of wiring errors or reversed battery voltage, the Yamaha system will break. So double check the wiring with a multimeter before plugging in the battery.

 Simple protection


  • Use a soldering iron for electronics applications with a large tip.
  • Use electrical solder with an integrated rosin core, preferably Sn60Pb40.
  • The wiring should look EXACTLY like the photos below.
  • Work very neatly, don't make a mess or you won't be able to return the dongle.
  • Be careful not to short-circuit the data pad to the M+, this will destroy the Yamaha motor.

OLYMPUS DIGITAL CAMERA         Be careful not to short-circuit the data pad:

Electronics soldering iron with rosin core solderUse a soldering iron with large tip and rosin core solder

 Battery dongle wiring top side

Battery dongle wiring bottom side

Poor soldering can cause short circuits and ruin the motor and dongle

Yamaha battery dongle wiring

The dongle should be connected to the 3-wire cable coming out of the Yamaha motor, that was previously connected to the Yamaha battery:

Yamaha 3rd party battery hacking dongle connections

Note that the charger cable can no longer be plugged into the charge input of the battery. Because the dongle contains the coulomb counter for measuring the battery capacity, the charging current must also flow through the dongle. It is best to use the anti spark XT90S for the charge connector.

Setting the battery capacity and voltage

To correctly display the battery capacity on the Yamaha display and the 6 LEDs, the battery capacity must be set on the dongle, see the menu system here. Normally you only need to use the menu once, when installing a new dongle or when the battery capacity changes.

  • Set the specified battery capacity with menu 1
  • Fully charge the battery
  • Set a new charge cutoff voltage with menu 4


The Yamaha system must be switched on during charging, otherwise the fuel gauge will not display the correct value during loading (0% - 99%). Else you have to disable the power-saving function with JP2.

When the battery is fully charged, the fuel gauge will always be automatically set to 100%. All leds will blink as long as the battery is 100% full. View the menu system for the other options.

How to charge a removed battery?

When you remove the battery from the e-bike for charging, the dongle will no longer be connected to the Yamaha motor, and the dongle will have no power, due to the power-saving function. As a result, the dongle will no longer measure the charging current, and the LED bar will not rise. However, if you always charge the battery fully,  there is no problem, because when the charge cutoff voltage is reached (default 41V), the fuel gauge will be set to 100%. If you would like to know the charging status in between, you must disable the power-saving function:

Disabling the power-saving function

Disabling the power-saving function can be done by jumper JP2, solder it with a tiny bit of solder. However, now the dongle will constantly draw power from the battery, which is approximately 12mA. If you don't want the battery to slowly drain, it should have with an on/off switch and you should turn off de battery when the ebike is not used.

Disabling the power-saving function with JP2


  • Is it necessary to dismantle the motor?
    Not, the wiring is on the outside.
  • Which Yamaha motors are suitable for the battery hack?
    The dongle is till now just tested on the PW-X2 and the PW-SE motor, but it should work on all Yamaha mid-drive motors. If it unexpectedly doesn’t work on your motor, you will get the money back.
  • Which Yamaha motors are NOT suitable for the battery hack?
    Yamaha motors used on Giant ebikes.
  • Is it waterproof?
    No, it is not waterproofed, you have to take care of that yourself.
  • Can it be used with batteries of different chemistry, for example LiFePo4?
  • Yes, it is suitable for all kind of batteries up to 48V, but the maximum voltage never may exceed 60V.

Connecting a second battery to a Yamaha battery

Instead of a battery hack, you can use the original (possibly worn out) Yamaha battery only because of the data signal and connect a new extra battery in parallel with it. I have described this in the article: Battery management system BMS.

Connecting an extra battery to a Yamaha battery


  • If the displayed capacity is incorrect.
    The capacity is shown on the Yamaha display and via the LEDs on the dongle. The LED bar should decrease from 100% to 0% while driving. To test, you can speed up that process by temporary set the capacity to 1Ah via the menu. Then the display should quickly decrease from 100% to 0%. If this doesn't work, then probably the connections motor+ and bat+ are connected wrong.
  • If the displayed capacity doesn't increment during charging, but is still 100% when the battery is full.
    The Yamaha system is not switched on during charging. Else you have to disable the power-saving function with JP2.
    You have a dual port battery which is connected incorrectly. Connect the battery according to the drawing: Connections Dongle - Yamaha ebike dual port battery.

Example of other 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.

Protected data output circuit

The Yamaha PW-SE data output circuit is not protected against short circuit to the battery +, the transistor TR320 will be blown up then (which can be replaced). That's why I reverse engineered the data output circuit. The dongle has, unlike the Yamaha motor, a protected data output that is protected against short circuits. 

Blown up transistor TR320 (EMG9) PW-SE Yamaha


I started with the Yamaha dongle in August 2019. Many improvements have been made since then, see the earlier versions of the Yamaha dongle here:

Previous dongle versions

Dongle during development 

Yamaha PW X2 serial data

Yamaha battery dongle development

Pedelec forum