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Introduction

This device has two uses: 

DIY accurate Battery monitor / fuel gauge / Watt meter
DIY accurate Battery monitor / fuel gauge / Watt meter

DIY accurate Battery monitor / fuel gauge / Watt meter
DIY accurate Battery monitor / fuel gauge / Watt meter

Update:

Ten PCBs are manufactured in April, which have already been reserved. After that, larger numbers will become available for sale, but I don't know when this will be, just check my website regularly to see if they are available.

Properties

  • The measured values (Volt, Ampere, Watt, Amperehour) are sent by bluetooth to one or more meters on the handlebar.
  • The capacity is also displayed with 6 LEDs on the board.
  • The absolute maximum voltage is 50V, which corresponds to so-called 36V batteries.
  • In this application, it has nothing to do with Yamaha and it is just a universal fuel gauge / Watt meter.

Advantages

These are the advantages compared to other fuel gauge / Watt meters:

  • It measures the real capacity in Ampere x hour
    Other fuel gauges often calculate the capacity based on the battery voltage, which is very inaccurate.
  • The capacity is stored in a non-volatile memory.
    Normally, a fuel gauge should never be disconnected from the battery, otherwise the capacity value will be lost. Therefore a fuel gauge is always built inside the battery case. But an externally connected fuel gauge, like this one, will be disconnected from a battery often since a battery can have a power on/off switch. So we store the battery capacity in an EEPROM.
  • Bluetooth connection to meters on the handlebar
    The big advantage is that the system is split in two, no thick power cables are needed to the meters on the handlebar as with other gauges. The meter board can be connected directly and nearby to the output of the battery. The measured values (Volt, Ampere, Watt, Amperehour) are sent by bluetooth to one or more meters on the handlebar. I have developed special lightweight round 40mm LED meters for this.

Watt meter 40mm on the handlebarWatt meter 40mm on the handlebarWatt meter 40mm on the handlebarWatt meter 40mm on the handlebar

Connections

The connections differs according to the type of battery:

Wattmeter connections to battery with common port
Wattmeter connections to battery with common port

Wattmeter connections for dual port battery
Wattmeter connections for dual port battery

User manual

Charging

When the battery is fully charged, the fuel gauge will be automatically set to 100%. All leds will blink as long as the battery is 100% full.

Menu selection

There are 5 menus. Click the button for 2 seconds to select. The leds will now flash. Example: to select menu 2, click after the 2e flash, The selected menu will be executed now.

Menu 1-5

  1. Set the specified battery capacity in Ampere hour [Ah]. This is default set to 12Ah. See also “Set battery capacity”. To show the Ah value, see menu 2.
  2. Show the specified battery capacity in [Ah]. See also “Show values”.
  3. Set the fuel gauge temporarily to full.
  4. Set a new charge cutoff voltage. Enter this menu when the battery is fully charged. The battery voltage will be measured and stored automaticly. The default value is 43V.
  5. Show the charge cutoff voltage. See also “Show values”.

1 Set the specified battery capacity

We have to set the battery capacity manually before use. The default value is 12Ah. The allowed range is from 1.0Ah to 69.0 Ah.

  • The ledbar flashes fast.
  • Enter the tens 1*)
  • The ledbar flashes fast.
  • Enter units.
  • The ledbar flashes fast.
  • Enter the decimal. You can skip the decimal by doing nothing anymore.

1*) For a zero: click the button immediately after the ledbar flashes fast. For a number n from 1-9: click after n flashes.

Example 23Ah

  • The ledbar flashes fast.
  • Count 2 led flashes and then click.
  • The ledbar flashes fast.
  • Count 3 led flashes and then click.
  • The ledbar flashes fast.
  • Click the button immediately or do nothing anymore.

Example 20Ah

  • The ledbar flashes fast.
  • Count 2 led flashes and then click.
  • The ledbar flashes fast.
  • Click the button immediately for the zero.
  • The ledbar flashes fast.
  • Click the button immediately or do nothing anymore.

Example 1.2Ah:

  • The ledbar flashes fast.
  • Click the button immediately (since tens = 0)
  • The ledbar flashes fast.
  • Count 1 led flash and then click.
  • The ledbar flashes fast.
  • Count 2 led flashes and then click.

Example 300mAh = 0.3Ah

  • The ledbar flashes fast.
  • Click the button immediately (since tens = 0)
  • The ledbar flashes fast.
  • Click the button immediately (since tens = 0)
  • The ledbar flashes fast.
  • Count 3 led flashes and then click.

If the battery capacity is set too low, the fuel gauge will display 0% while the battery is still not empty. This is shown with a blinking red led.

Show values

This works in the same way as setting the specified battery capacity but with just showing flashing leds.

Example 45Ah

  • The ledbar flashes fast.
  • The led flashes 4x.
  • The ledbar flashes fast.
  • The led flashes 5x.
  • The ledbar flashes fast.
  • No flashes since there are no decimals
  • The ledbar flashes fast.

Example 4.6Ah

  • The ledbar flashes fast.
  • No flashes since there are no tens.
  • The ledbar flashes fast.
  • The led flashes 4x.
  • The ledbar flashes fast.
  • The led flashes 6x.

Dongle during development 

Yamaha PW X2 serial data
Yamaha PW X2 serial data


Pedelec forum

 

Do you have any comments about the website? Please let me know.