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BattMeter - just another wattmeter

Posted: Nov 12 2019 8:04am
by Ghozt
Hello, greetings from Russia! I'm new here but I'm not a beginner in electric vehicles. I'm here to tell you about the wattmeter I started to develop about 3 years ago. At this moment I have almost 15 prototypes on different bikes around my country, they need some testing and additional firmware coding. So I want to tell you about what has been done during these years of development, about technical specs, etc.

So let's start. Current technical specs and features look like this:
  • Voltage: 25-300v (absolute maximum about 400v)
  • Current: there is no actual limit for current sensing, maximum resolution is 26665 values for both forward and reverse current. It supports shunts with up to 140mV voltage drop. For example: with 140mV shunt it can sense 1000A current with resolution about 0.04A
  • 4 thermosensor inputs: 2 motors, battery and controller
  • Clock. Why not? Every bicycle trip computer has it
  • Buzzer with overheat, max amps and low volts alerts
  • Relay output. It's a simple thermostat. It will be useful for creating an automatic cooling/heating system on an e-bike. For example, it can enable the motor water pump only when a certain temperature value is reached, and disable it if temperature drops below threshold
  • Character LCD 20x4 and two buttons for control and setup
All measured and calculated values:

Main screen
  • V
  • A/W (customizable)
  • Ah/Wh (customizable)
  • Daily distance
  • Current speed
  • Clock/battery gauge (in rotation, if gauge is enabled)
  • All the temperatures from thermosensors, if enabled

  • Instant - Instant consumption in Wh/km (or mi)
  • Average - Average consumption in Wh/km (or mi)
  • Spent - spent watt-hours

Driving stats
  • Avg speed - overall average speed
  • In move (in rotation with Avg Speed) - average speed when EV is moving
  • Max speed - max speed, obvious
  • Drive Time - overall driving time, HH:MM:SS
  • In move (in rotation with Drive Time) - time, when EV is moving

Battery stats
  • Max Amps/Max Power - max registered current/max registered power (in rotation)
  • Max VDrop - max voltage drop: delta between idle battery voltage and loaded (current > 1A)
  • Battery R - internal battery resistance, calculated on Max VDrop

This screen can be disabled due to unnecessary in geared/mid drive setups
  • Max Regen/Max power - biggest registered current/power of regen (in rotation)
  • Restored - restored battery capacity in Ah
  • Regen/Fwd - Regen Ah divided by forward Ah in percents

Temperature screen
This screen can be disabled due to unnecessary. Here can be found current and maximum temperature of every component. For battery also available lowest temperature stat, it can be useful for riding in winter conditions

Overall stats
  • Total km - odometer (can be in miles)
  • Total Ah - overall drained capacity
  • Cycles - number of battery cycles
The last thing I want to tell you about is the wattmeter case. Currently it's a bit rough because it's fully 3d-printed. But it is functional and protects the wattmeter from water. Control buttons are situated on the bottom surface, which provides protection against water and simplifies the production process. Handle the wattmeter with some sort of paddle shifters, lol. But it is quite convenient. This is how it looks on table and on some bikes. Some prototypes has old version of case, actual look on first photos:


Another option is possibility to add an extra bar for lighting, cell phones, etc.:


Currently I'm preparing all the stuff for producing small batches for my country, but of course I'm interested in selling my wattmeter in another countries too. I hope, some day I will see my wattmeter on bikes of ES community

Re: BattMeter - just another wattmeter

Posted: Nov 12 2019 9:44am
by SlowCo
Very interesting!
I'll follow this thread. Any idea on price when you start to sell?

Re: BattMeter - just another wattmeter

Posted: Nov 12 2019 11:21am
by Ghozt
I think price will be around 100$ ±

Re: BattMeter - just another wattmeter

Posted: Nov 12 2019 9:57pm
by Matador
:bigthumb: subscribed

Re: BattMeter - just another wattmeter

Posted: Nov 13 2019 9:18am
by neptronix
Very cool. I'd recommend making it as compact as possible, if you're going to compete with the cycle analyst, which is kinda bulky in itself. Maybe for v2?

We need smaller displays that don't scream 'i'm an ebike!!'. The eggrider is amazing in this regard, yet it is limited, can't adapt to a CA DP connector, and i think only works on bafang systems. I contacted the company in regards to adapting it to a CA DP connector, and they don't even know what that is.. :lol: i was unable to get a pinout as well..

Re: BattMeter - just another wattmeter

Posted: Nov 13 2019 10:53am
by Ghozt
My prototype already passed eight iterations, unfortunally I can't make it smaller. But my wattmeter already smaller in length than CA (but a little bit thicker):


Eggrider has a digital bus, 5 pins, if I remember this right. Vbatt, GND, Key, Rx, Tx. It cannot be easily converted or adapted with CA connector because of a digital bus

Re: BattMeter - just another wattmeter

Posted: Nov 14 2019 7:13am
by dogman dan
Much smaller, old farts like me won't be able to read it. Its fine.