Calling all math majors

[Chazmo]

Due to my hand & wrist issues, I need to use these "palm" support style grips with a half grip throttle. Full grip palm style grips don't work well with full length, full twist throttles.

View attachment 189373

My Juiced fat bike came with something like these. But they're just used as grips; i.e., the bike has a thumb throttle. Makes a lot of sense to have these as grips for a twist throttle (IMO).

 

[6zfshdb]

On a slightly different subject, I cured a lot of my hand & wrist pain by simply using padded gel riding gloves. A suspension stem also helped.

 

[PCeBiker]

When I got my first ebike my hands were sore as hell for the first few rides, then I read a thread here on the forum about the "death grip" that newbies have, and realized on my next ride that that was exactly what I was doing.

But I couldn't ease up on my grip and hold the throttle steady at the same time.
The throttle is so sensitive that only way to give it that mm of movement to go 3 kph faster, was to squeeze really hard and twist slow.

The thumb throttle was worse, and my thumb was aching.

The half twist throttle works best for me, because once I finally get my throttle speed set, I wrap the rest of my hand around the grip to lock it, then I can relax my grip.

 

[PCeBiker]

If it's a digital readout that reads from 0-60V, does it matter that the 0-40 never shows?

I meant making one of these,..

I know that you can make one using a regular analog voltmeter and zener diodes somehow.

Something to do with reverse bias breakdown voltage of zener diodes added together in series until 40 volts is reached?

 

[spokewrench]

A lot of zeners are rated at .125 W. If you use a 40 volt zener, the meter movement can't need more than 3 ma. You could use a higher-power zener or put them in series, like 2 20s or 4 10s.

 

[spokewrench]

Can you reset your computer or get it to recalculate or something?

30 miles using 1% of your charge doesn't make sense, and your computer should know that.

I've been 36 miles since my last charge, and the display still reads 99%. Before replacing the computer, I checked the battery: 53.28 volts. I guess it's not the computer. It must be those lentil beans, not to be confused with the beans I keep on the beam over the door. Those are lintel beans.

 

[6zfshdb]

I meant making one of these,..

View attachment 189428

I know that you can make one using a regular analog voltmeter and zener diodes somehow.

Something to do with reverse bias breakdown voltage of zener diodes added together in series until 40 volts is reached?

You could always make your own crude voltage scale using a bench power supply and paste it on the gauge face. Although I use these gauges on my bikes, I never checked to see if they can be disassembled to put such a scale under the glass.

With a little effort, a presentable voltage scale could be drafted. You can use padding resistors to get the needle centered between 40 and 60V. Half volt increments are all that is necessary since it's easy to interpolate with an analog gauge.

I find these gauges to be a good way to determine relative SOC, similar to a gas gauge in a vehicle. If I want specific voltage readings, I use a separate digital gauge.

 

[spokewrench]

With a little effort, a presentable voltage scale could be drafted. You can use padding resistors to get the needle centered between 40 and 60V. Half volt increments are all that is necessary since it's easy to interpolate with an analog gauge.

That takes me back. When stereos used discrete transistors and headphone jacks were fed through 220 ohm resistors, I used to make L pads to attenuate by perhaps 90% and reduce output impedance to less than 1 ohm. Attenuation let me turn the volume up so I didn't lose as much detail in crossover distortion. Low impedance meant a high damping factor for a smooth, detailed transducer response.

I used a movement like these for my console automobile meter.

https://www.amazon.com/YXQ-0-100uA-Current-Accuracy-Measurement/dp/B07MC3C7YM

I made it in the 20th Century and don't recall whether I used a zener or an IC regulator. I could have checked if I hadn't thrown it away in December. If it was a zener, I would have checked the spec sheet for its resistance and to see the shape of the knee when it started to conduct.

Suppose you chose a 40 volt regulator (zener or IC) and a 1 ma movement. In series with the regulator, the movement will start to move at 40 volts. 60 volts will be 20 above the regulator. If you want it to put 1 ma through the meter at 60 volts, you'll need 20 k ohms in series. Actually, 20 k would be the total of the series resistor, meter resistance, and any regulator resistance. If you used a fixed resistor in series with a potentiometer, you could tweak the gauge.

When I made mine, I took the cover off the movement, measured the length of the pointer, used a compass to draw an arc with that radius on a piece of paper, measured 90 degrees, calculated where 12 v, 12.6, 13, 13.6, 14.4, and 15 would be, marked them, and pasted this face onto the movement. I connected my gauge and, using a digital meter at the battery, checked it at various voltages due to state of charge, whether the engine was running, temperature, and load. The gauge always agreed closely with the DMM.

I don't see how resistors alone could make a movement read 0 at 40 volts and full scale at 60.

 

[spokewrench]

@PCeBiker The great thing about an analog meter is that the info doesn't have to go through the part of the brain that reads numbers. It's good for seeing at a glance and for catching quick changes. I'm tempted to put one on my bike to see voltage dips when I open the throttle. The size of the dip could be a good indicator of how low my battery is or how unbalanced the cells are.

 

[6zfshdb]

I don't see how resistors alone could make a movement read 0 at 40 volts and full scale at 60.

They won't. I didn't mean to imply they would. I may have missed something in the above posts and we may not be talking about the same thing. I'm referring to this gauge which is designed to read a range between 43 and 52V:

A padding resistor can be used to adjust the position of the needle relative to a home made 40 - 60 volt scale, which can be pasted on the gauge face. The gauge pictured, at least the ones I have, are designed to read from 43 to 52V. When used on my 52V system (58.8V fully charged), it pegs the meter on the upper end. I use a padding resistor to move the needle down into the fully charged portion of the scale.

That same resistor moves the needle further down the scale into the red zone when the fully discharged voltage of 43V is reached. All the resistor does is to alter the needle position on the gauge face.

Rather than fool around with zeners and another meter, my suggestion was simply to make another scale to put on the face of this one, marked with voltages between 40 and 60V. Then use a bench power supply to determine the appropriate value padding resistor to make the needle match the gauge.

Yeah, this gauge has only a 40 degree arc which makes it difficult to create a voltage scale but, as I said earlier, half volt increments are all that is necessary.

Sorry if I caused any confusion.

 

[spokewrench]

They won't. I didn't mean to imply they would. I may have missed something in the above posts and we may not be talking about the same thing. I'm referring to this gauge which is designed to read a range between 43 and 52V:

A padding resistor can be used to adjust the position of the needle relative to a home made 40 - 60 volt scale, which can be pasted on the gauge face. The gauge pictured, at least the ones I have, are designed to read from 43 to 52V. When used on my 52V system (58.8V fully charged), it pegs the meter on the upper end. I use a padding resistor to move the needle down into the fully charged portion of the scale.

Ahh... I see them on Amazon for golf carts. I wonder if they contain zeners. If they show voltage while the cart is on a charger, I wonder why they don't draw current whenever battery voltage is above the minimum.

The instrument panel of my 1984 Nissan had a 10 to 16 volt gauge. I think the panel supply was regulated by a thermostatic switch that opened and closed in response to heat from a high-resistance wire. The voltage was bound to go up and down, so the voltage and fuel gauges had to work slowly by resistance wires wrapped around bimetallic springs. I think the voltage indicator spring was warmed by vehicle voltage draining to panel voltage, and the fuel indicator was warmed by panel voltage draining to ground through a rheostat on the fuel float. After I turned the key on, it would take a couple of minutes to get a fuel reading. The volt reading was similarly slow and never agreed with DMM readings.

I'm sure yours works better than that!

 

[PCeBiker]

@PCeBiker The great thing about an analog meter is that the info doesn't have to go through the part of the brain that reads numbers.

That's what I like about it.
My Watt meter is a dummy gauge on display on my e-bike that is not telling the truth.

I want to see how much current/voltage/power is being drawn from the battery, not what the computer decides to tell me.

There is always something being drawn from the battery when the power is on, but my built-in Watt meter reads 0 when I'm stopped.
And it takes more than 10 second from when I kill the motor (by hitting the brake and activating the brake switch) for my meter to finally read zero.

I don't care how much power is going to the motor (or the lies my display is telling me about it), because I'm not going to overheat my motor with everything turned down.

I want to see exactly what is being drawn from my battery, in real time.


I would turn on my e-bike with a fully charged battery, and after ten minutes the battery voltage was reading almost a volt less, even though the e-bike was just sitting there.
I couldn't figure it out until I realized that the controller simply being turned on was drawing power.

Having an ammeter/voltmeter/Wattmeter showing me the output of the battery would allow me to see how efficient the controller is by seeing the idle current drawn without any interference from the displays programming fudging all the numbers.

 

[spokewrench]

I want to see how much current/voltage/power is being drawn from the battery, not what the computer decides to tell me.

Hall effect: I'm tempted...

Amazon.com

My Radpower bikes would run down with the controller off unless I switched off the battery with the key. My Aventon battery can't be switched off with a key. It switches itself off. I've ridden 7 hours since my last charge, and it's still at 99% and the voltage is still over 52, so the controller, brake light, tail light, head light, and occasional motor must average under 21 milliamps combined, or 1.09 watt!

 

[PCeBiker]

I may have missed something in the above posts and we may not be talking about the same thing.

Sorry if I caused any confusion.

It was me causing the confusion.

I really like the analog golf cart gauge and was curious about how it works.
That padding resistor makes sense.
I figured something like that was possible. (but I figure that you probably can't de-pad the meter to read a 36V battery the same way? Probably not as easily anyway?)


What I'm in the process of doing now is installing this gauge,..

It shows me everything that I want to see at the same time on one gauge.

In fact, now that I ride with two batteries, I don't really need any of the gauges, except for the Watt hour/energy meter to track the capacity of my battery.
My e-bike display doesn't do that.

I've set my maximum speed to 32 kph on my e-bike, so I don't even need to look at my display anymore.
It only tells lies anyway.

I'm not sure how I'm going to do it, but I may just replace my display with the gauge, and just hide the display somewhere (the bike won't run if I unplug and remove it) but I don't really need to see my new gauge either.

I just need to check it before and after a ride, or after a full battery drain test.

I need to stop compulsively checking my gauges, so removing them might be the way to do it.

 

[PCeBiker]

Hall effect: I'm tempted...

That's pretty cool,..

I didn't think you could use that kind of sensor for DC power, but then I saw one on a lawn tractor for an analog voltmeter on the dash.

I'm guessing that it may not be too accurate?
Especially with lower voltages and currents?

 

[spokewrench]

How come your displayed watts aren't the product of displayed volts and displayed amps?

 

[spokewrench]

That's pretty cool,


I didn't think you could use that kind of sensor for DC power, but then I saw one on a lawn tractor for an analog voltmeter on the dash.

I'm guessing that it may not be too accurate?
Especially with lower voltages and currents?

It's advertised at plus or minus 1%. A lot of cheap stuff is accurate these days.

It was only a few years ago that I learned that modern clamp-on meters can measure DC amps. I bought one and discovered that my 12 hp mower takes a lot more cranking amps than my car. That's because the mower is cranked much faster.

 

[PCeBiker]

How come your displayed watts aren't the product of displayed volts and displayed amps?

I had just powered it up to test it and try to "program" it.
You have to push the single button 8 times to reset it, but you can't push the button too fast or too slow.

I forget why it was reading 50 amps?
It wasn't fully connected, so I think it went to "full scale"?

The meter comes complete in a box that isn't too huge, but it's kinda junky and not waterproof so I sprayed it down with undercoating oil inside before I connect the wires, then I'll seal it up with silicone or shoe-goo.

The oil seeped into the display, and now it looks kinda wonky.


That golf cart meter BTW is Great because it's more durable and built for more extreme use by drunken golfers driving like idiots.

 

[PCeBiker]

I've got one of these ammeter too, but it's really delicate and not meant for outdoor use.

Just the constant vibration alone might wreck the meter, or make the needle bounce around and make it unreadable?

I know they have oil filled analog meters where the oil cushions the needle and provides natural damping to the movement to smooth out the spikes and slow down the movement a bit.

Digital meters do the same thing with electronic damping using AI and logarithms and crap, then your readings are all lies.

 

[6zfshdb]

It was me causing the confusion.

I really like the analog golf cart gauge and was curious about how it works.
That padding resistor makes sense.
I figured something like that was possible. (but I figure that you probably can't de-pad the meter to read a 36V battery the same way? Probably not as easily anyway?)


What I'm in the process of doing now is installing this gauge,..

View attachment 189444

It shows me everything that I want to see at the same time on one gauge.

In fact, now that I ride with two batteries, I don't really need any of the gauges, except for the Watt hour/energy meter to track the capacity of my battery.
My e-bike display doesn't do that.

I've set my maximum speed to 32 kph on my e-bike, so I don't even need to look at my display anymore.
It only tells lies anyway.

I'm not sure how I'm going to do it, but I may just replace my display with the gauge, and just hide the display somewhere (the bike won't run if I unplug and remove it) but I don't really need to see my new gauge either.

I just need to check it before and after a ride, or after a full battery drain test.

I need to stop compulsively checking my gauges, so removing them might be the way to do it.

There is a 36V version of that analog gauge:

https://www.amazon.com/gp/product/B06ZXWF8ZM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

There is also a 48V LiFePO4 version, which may give better results.

https://www.amazon.com/gp/product/B0DJ9SKY2Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I'll have to play around with that one. Probably wouldn't require any padding for a 48V bike.