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I am currently developing this device. It will be ready in Nov. 2019.

Intro

The battery dongle has two functions:

  1. A battery hack that let you mount any battery on a Yamaha e-bike, so not just a Yamaha battery
  2. A very accurate battery fuel gauge, so not just simple voltage measuring

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

1. 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.

2. MAX17263 accurate Fuel Gauge

Most cheap fuel gauges that are for sale, only measure the voltage, but that is very inaccurate. It is also necessary to measure the battery current. With the measured voltage and current, complicated software is able to determine exactly the accurate state-of-charge (SOC). Manufactures have many ICs for this application. We use the MAX17263 here because it has one important advantage: it needs no time-consuming battery characterization.

The used algorithm of the MAX17263 is the so-called ModelGauge m5 algorithm, which uses among others self learning routines: as the cell ages, its change in capacity is monitored and updated.

MAX17263 accurate battery Fuel Gauge
MAX17263 accurate battery Fuel Gauge

MAX17263 most important features

  • No Characterization Required
  • No Calibration Required
  • Robust Against Battery Variation
  • Eliminates Coulomb Counter Drift
  • Compensates for Age, Current, and Temperature
  • Integrated LEDbar Control with test Push-Button
  • Accurate Current Sensing
  • Supports Li+ and Variants Including LiFePO4

 

Yamaha battery dongle development
Yamaha battery dongle development

 

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