Calling all math majors

[6zfshdb]

I came across this one that may be worth a look:

https://www.amazon.com/CoolschMax-Waterproof-Battery-Low-Voltage-Motorcycle/dp/B0DDXQ96BM/ref=sr_1_3_sspa?crid=2ZZCK9P87JVNY&dib=eyJ2IjoiMSJ9.gJP8MUkqx_fKzlXcoOWdgx55IV7kosQMDsrZ1nLVPMqRXJKh8iRN5290iicG9XsNruKMYSZAley2G15mLKxkxt5oS5DPV6EBHYoBGuQ02JIrXaCL1uZMSDdbHiy1ac31GSi-mQX6ORQ4o5Dz8Hj44SGk620m3qYcYywJ8U28dp2YAMbZI2sBHODHjEaVdeMnqEBPlGEeMNfGdH1TTtomBo8ErsXH39kVqUUAlWDdpnv11ZRmDVTG8tPvqlAD04TIhGcLA47SdT-1E029HOlDHUHeOZIfnuOapqVNkea_4yk.INpkVV0s6Ig9rsYzSy_pUGWh2w31XDynsfBHMBu-74g&dib_tag=se&keywords=golf%2Bcart%2Bbattery%2Bgauge%2B48v&qid=1740077385&sprefix=golf%2Bcart%2Bbattery%2Bgauge%2Caps%2C155&sr=8-3-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1

It's digital but the LED's are positioned in an analog fashion. It's also custom adjustable from 9.5 to 100V

 

[kevinmccune]

you cant assume the battery will discharge in a linear fashion,such variables as chemistry,temp,the list goes you can get an approximate range and batteries change as they age.If you want to be safe get another spare larger ah battery and run the main battery to cut off,when it peters out change to the larger battery and return home"whistling away the dark"
There was an old saying about 4wd and 2wd in the outback,run in 2wd till you get stuck,then switch to 4 wd and return home.

 

[6zfshdb]

you cant assume the battery will discharge in a linear fashion,such variables as chemistry,temp,the list goes you can get an approximate range and batteries change as they age.If you want to be safe get another spare larger ah battery and run the main battery to cut off,when it peters out change to the larger battery and return home"whistling away the dark"
There was an old saying about 4wd and 2wd in the outback,run in 2wd till you get stuck,then switch to 4 wd and return home.

What you say is true and this is the way I usually ride.

I do however, like to monitor the SOC so I can switch batteries when the voltage drops into the acceptable storage range. That way, I only have to partially recharge one battery for storage instead of two.

 

[why?]

I can’t tell you because…………..the last thing I’m going to be concerned about are those perhaps slight variations. Fifteen miles per volt works for me!

Highly unlikely unless you're a featherweight with wind at your back, and highly efficient ebike with level urban paved paths (no inclines), even then you'd have to provide at least 50% power using pedal assist.

Whoever told you 15 miles per volt (with pedal assist) is trying his/her best to sell you an expensive ($2,000 and up) ebike. Then again if you only weigh 95 lbs. it might be possible with a wind at your back not exceeding 15mph and with you providing sufficient pedal assist power.

YES, i'm being conservative because ebike (battery) manufacturers overrate performance.

 

[PCeBiker]

you cant assume the battery will discharge in a linear fashion,
There was an old saying about 4wd and 2wd in the outback,

Just look at it like an old-school fuel gauge in your car.

It's not trying to tell how far you're gunna go, it's only telling you how much gas you got.

If you start going through a tank of gas in half the time or distance it could be any of these things,..

such variables as chemistry,temp,the list goes you can get an approximate range and batteries change as they age.

Or you forgot that you have your 13 ah gas tank plugged instead of the usual 25 ah gas tank and you forgot to fill it before you left the house.

 

[PCeBiker]

YES, i'm being conservative because ebike (battery) manufacturers overrate performance.

YES, and ebike riders like overrate their performance and give no credit to the machine.

This Lie Detector helps to expose the truth,..

 

[PCeBiker]

https://www.amazon.com/DROK-Capacity-Voltmeter-Multimeter-Shielded/dp/B08HP5VD4M

In 1879, 24 y-o Edwin Hall discovered that he could count watt hours without cutting the wires from his e-bike battery.

And your post from yesterday,..


"I was thinking of putting one of these on my bike.

Amazon.com

I would expect a 2.3 battery volt drop at 15 or 20 amps, depending on how your battery pack is made. If you're not getting much power, I imagine there's a short in the motor."





I ended up checking both those links, then got sucked into a 🕳

I did check out your first link a month ago but I didn't like the display, then I checked your second link yesterday and I don't like that display because it doesn't keep track of total Watt Hours.

All the choices of battery monitors with a HAL sensors that I could find require me to reprogram the display when I swap batteries, and that would be a PITA.

So you installed a shunt. I don't feel so bold!
It looks like 750 micro-ohms. I imagine the resistance could easily vary by a lot of micro-ohms. That meter is going to lie to you and laugh at you when you aren't looking!
View attachment 189452

The display I like though requires me to cut the power wire to install a shunt, and I really don't want to do that for the reasons you mention, but I Really like this display,..

All I have to do is hit the Only Button on the display 8 times in a row to reset the energy meter to 0, then it counts up from 0 until you reset it again.

Stoopid EZ,..


Sooo,...

I did a bunch of searching and came up with this other version,.

And it's available with a different display that I like better,..

This one looks like it might work for me, but it has a lot of buttons, and I want to be able to reset it easily to zero "0".

Sooo,...
Then I got to thinking that I could perhaps buy a HAL effect ammeter sensor, and plug it into the display that I already have so that I don't have to cut any wires.

This one even opens up so that all I have to do is clamp it around the battery "-" negative cable without disturbing the battery cable at all,..

The Only thing about it that doesn't work too great for me is that it runs off 12 VDC, but it only draws less than 25 ma, so maybe I could run it off button cells?

Or,..
Apparently I can have one custom built that will run off whatever voltage I choose??

I'm pretty sure that this will work, but I'm trying to figure out how to compare a 75 mv output of a shunt to a 4-20 ma output of the HAL sensor?

I'm pretty sure that the shunt and HAL sensor are interchangeable.
After all, 4:20 is my lucky number.

With a simple Hall Effect meter, if you want 10 times more sensitivity, you just wrap the amp conductor 10 times through the donut.

^^^ ,.. I'm sure that applies to what I want to buy, but I'm not sure how ?

Perhaps you and @6zfshdb can make some educated guessing about what you think will happen?

I'm pretty sure that I'm going to take the gamble and buy one to see what happens.
I'm willing to waste $40 if it allows me to connect the display I want without cutting and splicing my 12 gage battery cable.
Or I can get that last meter I displayed and just get used to resetting it to zero.
It does look like it counts up from "0" without having to enter the battery size?


And then I can further procrastinate my installation of the meter which I still haven't gotten around to.

 

[6zfshdb]

The only way to know for sure is to experiment.
If it works well enough, then you face the problem of how to house the sensor and meter on the bike since neither is weatherproof.

 

[PCeBiker]

I'm going to let it sit in my shopping cart while I try to do more research.

One thing that I want to ask you @6zfshdb , is what do you think would happen to the output of the HAL sensor if my voltage supply input isn't EXACTLY 12VDC?

If the supply voltage was off by 10%, do you think that the output (4-20 ma) would also be off by 10%?

Or would the voltage input be more like the 120-240 VAC inputs on power supplies for laptops that automatically convert the input voltage?
(And also like how different B+ voltages to an e-bike display also get converted to power the display. )

 

[PCeBiker]

If it works well enough, then you face the problem of how to house the sensor and meter on the bike since neither is weatherproof.

That part isn't a problem.

I've got silicone conformal gel, regular silicone, Black RTV silicone, ACF-50 spray, electrical contact cleaner (and MAF cleaner), Seal-All, tape, hangers, and cans.

And over a dozen assorted handlebar clamps.

 

[6zfshdb]

I'm going to let it sit in my shopping cart while I try to do more research.

One thing that I want to ask you @6zfshdb , is what do you think would happen to the output of the HAL sensor if my voltage supply input isn't EXACTLY 12VDC?

If the supply voltage was off by 10%, do you think that the output (4-20 ma) would also be off by 10%?

Or would the voltage input be more like the 120-240 VAC inputs on power supplies for laptops that automatically convert the input voltage?
(And also like how different B+ voltages to an e-bike display also get converted to power the display. )

It's only a guess but I would think there is some allowable variation with the input voltage. Most 12V devices are designed to work in vehicles where the alternator varies the battery voltage in the 11 to 14V range.
No way to be sure without experimenting though. Too many variables.

 

[PCeBiker]

It's only a guess but I would think there is some allowable variation with the input voltage. Most 12V devices are designed to work in vehicles where the alternator varies the battery voltage in the 11 to 14V range.
No way to be sure without experimenting though. Too many variables.

OK, Well I think that I'm going to go for it.

I'll make sure that I get one like this that runs off 12 Volts DC and reads to 50 amps so I can try installing the HAL sensor on the meter I already have,..

Or,.. I think that I can get a 30 amp DC version that would match my BMS exactly if I can figure out what all is involved in resetting it to "0" ?

It looks like it has 7 different buttons to push and if it's too much button pushing to remember, I can just cover the right side if the screen with tape.
(I can't use a 30 amp shunt (and probably not a 30 amp HAL sensor) on the display I have because it has a built-in 20 amp shunt then switches somehow to accept an external 50 amp shunt that keeps the Watt Hr Meter accurate.)

 

[Slaphappygamer]

Phase amps will be higher than battery amps. I’d get the 100A version of a meter like that. Your motor could pull 60 phase amps, at times. Duck tape is great. You can weatherproof something, or make pants.

 

[PCeBiker]

Phase amps will be higher than battery amps. I’d get the 100A version of a meter like that.

I've decided to not care about the phase amps, because my controller is limited to about 21 amps according to the built-in Watt meter (which is a digital dummy gauge that does a lot of lying. )

I've pulled over and checked my motor more than a few times and it never felt anything close to what I would consider hot.


So I mostly want to keep track of my battery to see what my Total Watt Hours really are. At least whatever measurements I can get, considering all the variables involved.

I was quite surprised to hear how much cold weather affects the total Watt Hours of a battery.
I think that it was @6zfshdb that mentioned it?

 

[kevinmccune]

And your post from yesterday,..


"I was thinking of putting one of these on my bike.

Amazon.com

I would expect a 2.3 battery volt drop at 15 or 20 amps, depending on how your battery pack is made. If you're not getting much power, I imagine there's a short in the motor."





I ended up checking both those links, then got sucked into a 🕳


View attachment 190666




View attachment 190667



I did check out your first link a month ago but I didn't like the display, then I checked your second link yesterday and I don't like that display because it doesn't keep track of total Watt Hours.

All the choices of battery monitors with a HAL sensors that I could find require me to reprogram the display when I swap batteries, and that would be a PITA.






The display I like though requires me to cut the power wire to install a shunt, and I really don't want to do that for the reasons you mention, but I Really like this display,..

View attachment 190668

All I have to do is hit the Only Button on the display 8 times in a row to reset the energy meter to 0, then it counts up from 0 until you reset it again.

Stoopid EZ,..


Sooo,...

I did a bunch of searching and came up with this other version,.


View attachment 190669


And it's available with a different display that I like better,..

View attachment 190670


This one looks like it might work for me, but it has a lot of buttons, and I want to be able to reset it easily to zero "0".
View attachment 190671View attachment 190672



Sooo,...
Then I got to thinking that I could perhaps buy a HAL effect ammeter sensor, and plug it into the display that I already have so that I don't have to cut any wires.

This one even opens up so that all I have to do is clamp it around the battery "-" negative cable without disturbing the battery cable at all,..


View attachment 190673View attachment 190674View attachment 190675View attachment 190676View attachment 190677



The Only thing about it that doesn't work too great for me is that it runs off 12 VDC, but it only draws less than 25 ma, so maybe I could run it off button cells?

Or,..
Apparently I can have one custom built that will run off whatever voltage I choose??

View attachment 190679



I'm pretty sure that this will work, but I'm trying to figure out how to compare a 75 mv output of a shunt to a 4-20 ma output of the HAL sensor?

I'm pretty sure that the shunt and HAL sensor are interchangeable.
After all, 4:20 is my lucky number.



View attachment 190680







^^^ ,.. I'm sure that applies to what I want to buy, but I'm not sure how ?

Perhaps you and @6zfshdb can make some educated guessing about what you think will happen?

I'm pretty sure that I'm going to take the gamble and buy one to see what happens.
I'm willing to waste $40 if it allows me to connect the display I want without cutting and splicing my 12 gage battery cable.
Or I can get that last meter I displayed and just get used to resetting it to zero.
It does look like it counts up from "0" without having to enter the battery size?


And then I can further procrastinate my installation of the meter which I still haven't gotten around to.

oh my look at that vado!

 

[PCeBiker]

oh my look at that vado!

Thanks.
It's not the biggest plant I've ever grown, but it still has about a month to go.

 

[kevinmccune]

Thanks.
It's not the biggest plant I've ever grown, but it still has about a month to go.

again vados! must be a trend,there seems to be a trend of way less alcohol consumption in the US,could relaxing the rules on Vado have anything to do with that? ( as an "aside" is there something Vado related besides Delta 9? Delta 9 makes me feel like I am losing my mind,I have a few "buzz packs" they don't seem to affect me like that.)

 

[PCeBiker]

again vados! must be a trend,

We're allowed to grow 4 plants in Ontario, and it was my hobby before I got my first e-bike.
A single plant lasts me a year.

I spent a couple thousand dollar on that hobby in about 5 years, but I've spent more than 3 times as much in half the time on my new e-bike hobby.

I don't drive anymore, so I spend all the money I save on my e-bikes.

It's probably cheaper for me drive than own a couple e-bikes, so I'm just going to ignore the numbers.

 

[Slaphappygamer]

Watch out for some drinks. Some drinks are meant to share. I had a single 16oz can. It was 100mg. That was the whole can. The serving size was 10mg. This drink was supposed to be drank as a shot, or a mixer. Check the serving size of the drink before consuming it.

There are a bunch of different types of drinks. I would visit a few dispensaries and chat with them.

 

[PCeBiker]

It looks like 750 micro-ohms. I imagine the resistance could easily vary by a lot of micro-ohms. That meter is going to lie to you and laugh at you when you aren't looking!

That's the part that I'm worried about and that's why I wanted to get at least a high quality shunt with a stable resistance so that my results aren't all erroneous.

So you installed a shunt. I don't feel so bold!

I haven't gotten around to installing the shunt or meter yet, and I didn’t know that there was a HAL sensor option.
I thought HAL sensors only worked with AC current?


As a bit of anecdotal test, I measured the current for my power supply that's powering my lights,..

This power supply is powering 24 LED strips with 12 strips on each of the two beige 20 VDC output wires,..

It's drawing 134.1 Watts total for the 24 LED strips.

I disconnected one of beige wires and connected my ammeter between the output terminal and the wire.
(I set the ammeter to the 10 amp setting)

The power draw dropped to 110 Watts simply by having half the power running through my test leads and meter with its built-in internal shunt.
The meter was reading about 1.8 amps during the test.

If I had both outputs of the voltage supply running through the meter, I probably would have a 50 Watt drop at the outlet, just by having the power running through the meter.
(I looked into getting proper Fluke test leads for my multimeter,..

Forget that.
I'd rather spend the money on some sort of HAL sensor adapter for what I've got.)


So,...
I'm really not too keen on installing a shunt on my e-bike.

Another good thing about the HAL sensor option, is that it is completely separate from the circuit that it's measuring.
It can fail completely but not disable my ebike or create any kind of safety issue.

I'm thinking that the only way that a HAL sensor could cause problems is if it wears through the insulation on the wire it's monitoring and creates a short or something?

If it works well enough, then you face the problem of how to house the sensor and meter on the bike since neither is weatherproof.

That's the part that I'm thinking about now.
The HAL sensor itself looks like it's completely sealed but my shunts are all huge and I would hesitate from covering it with tape or silicone or whatever, thinking that might affect the resistance that could have a Huge affect on the readings?

If I'm only really going to use the meter as a Watt Hour meter once in a while to try and check my battery capacity, then I don't really need to see the display?

I can just stuff the whole thing in my down tube, or temporarily attach it somewhere ( tape, zip ties ) before my ride, then check it when my battery shuts down.
I can use my ebike display to keep an eye on the battery, and just run the e-bike until it shuts down.

Or,.. I could get this Watt Hour meter,..

It's a complete meter with the HAL sensor, and it could actually replace my ebike display?
It won't show my speed, but I don't really care because I set my ebike to 32kph maximum anyway.

I'm not sure what I'm going to do?
I could actually just temporarily attach the meter display on top of my ebike display if I'm only using it occasionally to check my capacity?

My ebike display has dummy gages for the voltage, amperage, and power though, and the battery monitor doesn't have all kinds of AI crap fudging all the numbers.

This display is all I really need,..

The only things I really care about now is the actual voltage and current in real time so I have an idea about how fast I'm draining the battery.

I would trust this display to tell the truth without any logarithmic crap turning the actual numbers into what it thinks that I need to see.

I figure that the only built-in fudge factor is the "damping" and sample rate averaging to make the display readable.

My ebike display takes a full 10 seconds to read zero after I hit the brake and kill the power.
I don't like that.
It should read "0" the instant I hit the brake lever.