BattMeter - just another wattmeter

Ghozt

1 mW
Joined
Feb 10, 2019
Messages
10
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


Consumption
  • 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


Recuperation
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:

13xghxw.jpeg

1nymlo9.jpeg

1im29r5.jpeg

tsupfb.jpeg

19ks9db.jpeg

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

uz0pm1.jpeg


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
 
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..
 
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):

qivoml.png


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
 
Much smaller, old farts like me won't be able to read it. Its fine.
 
It's been a long time since last post. But it doesn't mean that the project is dead. Project just keeps getting better on local market - it was a lot of bugs in firmware, and hardware needs some work too. Some features still not tested. For example measuring distance in miles and all parameters bonded with it - in country with metic units no one needs it.

Here's changes in firmware, hardware and case:
Firmware
- added two more features, charging mode and acceleration test.
Charging mode allows you to charge a bike, and all charged energy will be measured and displayed during process. Wattmeter can notify with buzzer, when charging is over. And also there is various options for after-charging daily stats reset

Acceleration test allows you to measure time for acceleration from start speed to target speed. For example 0-60, 20-40, etc. Values can be up to 255. Also it measures acceleration in g-units.

Hardware
- added circuit for adjusting contrast from firmware
- new current-sensing scheme, more stable and protected
- added one more dcdc step-down for better energy efficiency and less heat dissipation

Case
Lot of work done with case too. I tried to make it more prettier and ordered 3d-model. Here's result:
1g7qwin.jpeg

17rr8ba.jpeg


It looks nice, but in real life it's too big. Very big borders around visible area of display also disappoints me. So I decided to stay on my simple version soapcase-like version

1hsdkix.jpeg

1ow36fz.jpeg


There's some changes in bottom panel too, just compare photos below with first post

143pfit.jpeg

1c6gc2s.jpeg

1emey31.jpeg


And also I look for plastic molding for case. But it's very expensive in my country
 
I'd like to see an ebike computer that displays each cells voltages in an easy to read graph.
 
TrotterBob said:
I'd like to see an ebike computer that displays each cells voltages in an easy to read graph.

Integrating a wattmeter is very easy

Integrating a meter that displays individual cell voltages is about as non-trivial to integrate as a wattmeter is trivial

Wattmeter info is very useful for every ride to have at a glance - I've got one (not this one) and find the data it provides at a glance near (at?) the top of the value scale for bike data

Not saying individual cell voltage isn't valuable but not so much all the time, every ride, on the bars

Cost/benefit between the two very different devices is opposite extremes IMO


Seems like something I'd be asking a battery manufacturer to do... maybe wireless and logging instead of on the bars
 
TrotterBob said:
I'd like to see an ebike computer that displays each cells voltages in an easy to read graph.

It's a feature more for BMS than for wattmeter. There are lots of bluetooth bms with individual cell control through android/ios app
 
neptronix said:
We need smaller displays that don't scream 'i'm an ebike!!'.
as example of Cycle Analyst shows:
old CA was much smaller than current CA, current CA has display twice the size of old one.
Grin just followed demand for bigger CA and display.
please, do not make it smaller.
 
miro13car said:
neptronix said:
We need smaller displays that don't scream 'i'm an ebike!!'.
as example of Cycle Analyst shows:
old CA was much smaller than current CA, current CA has display twice the size of old one.
Grin just followed demand for bigger CA and display.
please, do not make it smaller.
scream?
with all those gadgets riders of non-electric bikes attach to handlebars: cellphones, GPS, radios, lamps, etc.
how could CA analyst be even noticed.
 
So it sounds like you went back to the original design can you post a recent picture? Also this would be much more appealing if it had a modern style screen and not the older style similar to the cycle analyst. Full color LCD display and just charge more for it 👌

Or you could make two versions the older style and then an LCD display version. Most people probably wouldn’t care what type of display it is as long as it works but I would pay extra if you had an LCD version. I really like all the features.

Also if you could possibly create an LCD version would it be easier to create a smaller version?
 
miro13car said:
old CA was much smaller than current CA, current CA has display twice the size of old one.
Yeah, they used bigger display. But amount of characters stays the same, it's 16x2 display in old and new CAs. I used display 20x4. It bit smaller than big 16x2, but can display more than twice the characters

Eastwood said:
Full color LCD display and just charge more for it
No, display will stay as it was. There's a reason: readability on sun. Only FSTN displays can be readable on direct sunlight. Any tft/color display loses its readability on sun. But I developed version with RGB backlight, about 11 variants of backlight color in it, if you interested

Eastwood said:
So it sounds like you went back to the original design can you post a recent picture?
Yes, there's no major changes, first three pictures from first post are almost actual. Some changes on rear panel were posted above
 
Here's s some videos about RGB display. Changing colors and LCD alarm. For alarm I decided to use cyan and red colors. Cyan as the most brightest and red as the most alarmest lol

[youtube]GF3mqRYuB4k[/youtube]

[youtube]G1KuBMUHe44[/youtube]

Also there's big 2004 displays also exists. It's about 146x62mm of outer dimension. Here's photo of 1:1 comparison with regular 20x4 (98x60mm)
r61oyx.jpeg


It is too big for ebike's handlebar. May be useful on e-scooters, e-cars and other bigger vehicles
 
Nothing beats the CA.
I use it to monitor and tune each new bike I build. Then it goes back to its box in a drawer.

After I know the bike enough and tuned for the best, the only instruments I keep to ride are a small voltmeter on the stem, and temp sensor alarms in each battery bags/cases.

Any bike computer does fail for crashes or weather, sooner than later. Justing fixed and shipped mine free and quick, even though I said it was my fault. Best guarantee ever. I still use the same, from a decade ago. For me, it is a must have tool for all ebike builders.
 
I've been running a similar product to the CA and find it silly valuable for the Ah/Wh totalizers and calibrated (I calibrated it!) voltmeter/ammeter/wattmeter - gives the full status of the battery at a glance!
 
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