Matt Gruber
1 MW
TUZ
existing wiring works great as a shunt. TRY IT!
existing wiring works great as a shunt. TRY IT!
* * * The Minimal Ammeter? * * *
- Thread starter safe
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My Fluke reads to the nearest 0.1 amp with a maximum of 200A. It seems very reliable, but it's pretty bulky and hard to keep from bouncing around. I have to duct tape it on to the scooter when I try to use it.
They make much smaller inductive hall sensors that would be good for a permanent measurement device.
As Matt points out, existing wiring works great as a shunt, but you need to calibrate it and make sure it doesn't change resistance.
The nice thing about a hall current sensor is it can be calibrated "in the shop" before installing it.
They make much smaller inductive hall sensors that would be good for a permanent measurement device.
As Matt points out, existing wiring works great as a shunt, but you need to calibrate it and make sure it doesn't change resistance.
The nice thing about a hall current sensor is it can be calibrated "in the shop" before installing it.
Matt Gruber
1 MW
it does exactly what safe wants WITHOUT CALIBRATION
Matt Gruber
1 MW
Mathurin said:
safe
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Why, Why, Why?
Sometimes we have to take a step back and ask "why" do we even care about amps in the first place? The "reason" is that most motors are set up with a controller that allows torque to be generated in areas where "waste" dominates. The result is that we can't "just ride" a motor like that with the knowledge that "whatever" we do it okay... no... we are forced to THINK about what we are doing and REACT to those thoughts. The ammeter is really an "after the fact" attempt at correcting an error that NEVER should have happened in the first place.
Just for comparison I'm posting the powerbands of a typical 1200 Watt Unite motor verses a PMG 132 that is "heavily restricted" so that it NEVER runs outside the most efficienct areas of the powerband for any given voltage. They both produce the EXACT same peak power.
It's a world of difference to get it right in the first place... :wink:
(why bother even having an ammeter for the PMG 132 since it's "always good" no matter what you do)
Sometimes we have to take a step back and ask "why" do we even care about amps in the first place? The "reason" is that most motors are set up with a controller that allows torque to be generated in areas where "waste" dominates. The result is that we can't "just ride" a motor like that with the knowledge that "whatever" we do it okay... no... we are forced to THINK about what we are doing and REACT to those thoughts. The ammeter is really an "after the fact" attempt at correcting an error that NEVER should have happened in the first place.
Just for comparison I'm posting the powerbands of a typical 1200 Watt Unite motor verses a PMG 132 that is "heavily restricted" so that it NEVER runs outside the most efficienct areas of the powerband for any given voltage. They both produce the EXACT same peak power.
It's a world of difference to get it right in the first place... :wink: (why bother even having an ammeter for the PMG 132 since it's "always good" no matter what you do)
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xyster
10 MW
By your graphs there, the unite has a maximum efficiency of what looks like about 50% (3600W in 1800W out).
Is that correct?
Seems unfair to compare a motor's efficiency at a power well outside whatever it's designed for. Since this unite is a 1200 watt motor, what would these graphs show at 1200 watts out?
Is that correct?
Seems unfair to compare a motor's efficiency at a power well outside whatever it's designed for. Since this unite is a 1200 watt motor, what would these graphs show at 1200 watts out?
safe
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xyster said:
The Unite motor at 75 amps has 3688 Watts input and 1772 Watts output at an efficiency of 48%. I know, it sucks... but that's what you have to do if you are trying to go for the "big power" with a motor that isn't big enough. That was my POINT actually.
Ammeters are for people that run small motors with too much current and wonder why they don't work that great... (the "self restriction mindset" is a way to cover for a more profound design problem, namely, using the wrong sized motor for an application)
Matt Gruber
1 MW
WOW safe u sure have a lot to learn! Or maybe it's part my fault. Anyway, your brain will explode when u read my ammeter article.
But, thanks, as i had no idea what novices were thinking, i'll try to explain better
But, thanks, as i had no idea what novices were thinking, i'll try to explain better
xyster
10 MW
It's part all our faults that our wayward, rebellious, speed-freak of a man-child is still flunking his remedial electric vehicle comprehension tests. We must be good role models, demonstrating the patience and humility he lacks, showing support for his progress and confidence that one day he'll see the light! At least Safe's in the right place to receive plenty of the specialized attention he needs.
Not true, Safe. Ammeters are for people with electric motors of all sizes who wish to employ its feedback as input to an internal, ultra-flexible, no-extra-parts-needed, on-the-fly current limiter using the throttle as the output; or whom are simply EV statistics/data logging enthusiasts.
You're doing great, Safe, keep (pun intended) plugging away, and all this will become crystal clear one day!
TylerDurden
100 GW
safe said:
Let's turn the assertion around for a moment. "The people who don't need ammeters are those that:...
just buy the biggest motor available
accept the manufacturers' motor ratings and specifically underpower the motor
buy the off-the-shelf turnkey system and enjoy the ride
don't care about the system activity (no speedo, amps, Vs, miles, etc.)
run continuously at WOT and need to buy a motor that can handle the desired power indefinately
"
safe
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TylerDurden said:
Exactly... in a "perfect world" we would never need an ammeter because the efficiency of the motor would be so good that we wouldn't need to care what rpm we were running in. (because for an overamped motor rpm and efficiency are closely related)
Ammeters are specifically used for the case of the smaller motor that is "over amped" so as to get more power than it's rating would suggest. I repost that comparision to emphasis the point. If you were "starting from scratch" and could pick your motor then you would always pick the motor on the right and not the one on the left. There is nothing to be gained by overamping if you compare it to oversizing the motor.
Of course... this is all in a "perfect world"... which we don't actually live in... yet.
And another thing... the "perfect motor" actually would enhance the riding experience with gears because you could know by feel that the accelleration would be strong from bottom to top in an INCREASING manner and then after peak you would know when to shift. As it is with the "overamped" motors you have the first half INCREASING and the second half of your powerband is DECREASING. So you are encouraged to shift before you even get to your efficiency peak. (I have to mentally remember to "rev out" the motor in order to get those "sweet" high efficiency rpms)
The combination of "perfect motor" and gears would be sweet all the time!
safe
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But in the "real world" of the present we need ammeters so that on things like single speed hubs we can still have power to climb hills and also be able to have some top speed. It's a less "ideal" solution, but the simplicity of the hub motor (obviously) demands a huge following.
The "Boost Control" seems another way to go... you can decide while riding what kind of controller you want, whether you want high amps (for things like accelleration or hill climbing) or if you want low amps for things like long range. You might even combine an ammeter with the "Boost Control" since they both need to read the current using a shunt. (kill two birds with one stone)
The "Current Based Throttle" would also be good because then you could have absolute faith that 1/4 throttle equals 1/4 of the current limit so you could also be able to ride without looking at dials or lights.
But if all else fails... the ammeter is there to be used as a way to manage the power supply... it's a reliable, though definitely "manual" process to do the job.
The "Boost Control" seems another way to go... you can decide while riding what kind of controller you want, whether you want high amps (for things like accelleration or hill climbing) or if you want low amps for things like long range. You might even combine an ammeter with the "Boost Control" since they both need to read the current using a shunt. (kill two birds with one stone) The "Current Based Throttle" would also be good because then you could have absolute faith that 1/4 throttle equals 1/4 of the current limit so you could also be able to ride without looking at dials or lights.But if all else fails... the ammeter is there to be used as a way to manage the power supply... it's a reliable, though definitely "manual" process to do the job.
TylerDurden
100 GW
safe said:
This is where the NuVinci CVP comes in... maximizing efficiency without the peaks and valleys.
But, unless the tranny automatically varies based on measured amps and motor temperature, the operator will want to see those readings and adjust the CVP accordingly.
Eh?
8)
safe
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TylerDurden said:
The NuVinci is that transmission that uses that odd chemical that provides the "grip" under the desired conditions right? It sounds very high tech and also very high efficiency. I'm sure one day it might be possible to have a hub motor with a NuVinci gear built in.
Then you really have it all!
xyster
10 MW
I was thinking the same thing when I first read about the nuvinci CVT. Best of both worlds! No doubt gears are helpful or necessary for any motor not equally efficient at all speeds -- which is all of them at this time. In many cases like mine, gears are neither necessary, nor helpful enough to justify their inclusion.
safe
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If you have the choice between using a small motor and gears or a large motor and no gears then the large motor seems the easier way to go.
About half an hour after my "speed run" yesterday I rode back to that area and the police were just starting to set up their usual "speed trap" along that stretch of road. (people speed like crazy there) So I decided to stop and chat with them for awhile. These two cops really liked the bike and from their perspective didn't see it as any kind of problem. Right off the bat I said:
"The bike has one horsepower"
...and so immediately they knew that there wasn't anything to worry about. "One horsepower" is the nationwide limit, so unless you are caught speeding (which might have been fun except for the ticket part :lol: ) the cops don't find my bike a problem at all. In fact given the situation with oil and all they really liked to hear my story. People like the bike... kids in my neighborhood come over just to look at it... cops like to look at it...
The "larger question" becomes "cost".
For the same number of dollars which system is more efficient for the same performance levels? (given todays high priced batteries this is a real issue)
In that area the geared bike with a small motor and minimal battery seems to clearly beat the "big daddy" hub motor and massive lithium pack.
My ENTIRE bike... from start to finish... has so far cost only about $700.
Can you compete on price at all?
Do you even have any idea how much your bike has cost so far? (are you intentionally not wanting to think about it
)
About half an hour after my "speed run" yesterday I rode back to that area and the police were just starting to set up their usual "speed trap" along that stretch of road. (people speed like crazy there) So I decided to stop and chat with them for awhile. These two cops really liked the bike and from their perspective didn't see it as any kind of problem. Right off the bat I said:
"The bike has one horsepower"
...and so immediately they knew that there wasn't anything to worry about. "One horsepower" is the nationwide limit, so unless you are caught speeding (which might have been fun except for the ticket part :lol: ) the cops don't find my bike a problem at all. In fact given the situation with oil and all they really liked to hear my story. People like the bike... kids in my neighborhood come over just to look at it... cops like to look at it...
The "larger question" becomes "cost".
For the same number of dollars which system is more efficient for the same performance levels? (given todays high priced batteries this is a real issue)
In that area the geared bike with a small motor and minimal battery seems to clearly beat the "big daddy" hub motor and massive lithium pack.
My ENTIRE bike... from start to finish... has so far cost only about $700.
Can you compete on price at all?Do you even have any idea how much your bike has cost so far? (are you intentionally not wanting to think about it
)
xyster
10 MW
No. In part because I didn't 'roll my own' bicycle, so to speak. Of course your tools to fabricate the bike must have cost a pretty penny as well. I'm guessing you owned those tools already though.
I know exactly what it's cost. I keep a spreadsheet listing all prices, sources, etc. My ride cost more than yours', but much less than one-year's equivalent miles riding trains, planes, buses or automobiles.
My maintenance and upkeep costs, including battery replacement, I bet is much less than your maintenance and upkeep costs. Tallying the five year comprehensive cost totals and dividing by miles ridden would make for a more practical, dollars per mile comparison.
safe
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xyster said:
Both our maintenance costs are essentially zero except for the battery. At some point tires wear out ($25 each) and other than that there's not much that needs maintenance. (a chain lasts for a couple thousand miles before it needs replacement at $10)
So it comes down to replacing the battery.
But my point was that since we "know" that from an efficiency / performance standpoint that gears allow for either more power or more speed for a given amount of energy with less losses (because you can always have the best of everything all the time) then you are always going to be getting "more" out of "less".
So if you need to buy $1000 worth of batteries to get "X" amount of performance. And I can maybe buy $500 worth to do the same job. And assuming that both battery chemistries are the same. Then no matter what one does the "more efficient" solution is better.However, you raise the point about mine being a "home grown solution" and in that regard you are correct. I am a "pioneer" right now discovering the "new land" and so for me the possibilities are unlimited. For MOST (and I'd say almost ALL) of the people on this messageboard the choices are LIMITED to what you can buy. So if you can buy a hub motor and a 72 Volt controller and then make due with that you can achieve a lot given what your restrictions are. But if you are "freed" to do "whatever you damn well please" like I am you can explore new avenues.
I "artifically" am "holding back" in the money area. I've wanted to be self disciplined in spending because I know how easy it is to accomplish any task if you throw enough money at the problem. So I could easily go out and buy a $1000 worth of Lithium cells and a PMG 132 and set that all up to make a machine that is "untouchable" to anyone in performance. And I still might do that eventually. But I'm PURPOSELY forcing myself to "do better" with less for now since I'm still experimenting. Research and Development means you keep trying new things and advance at each step.
My spending capacity is unlimited if I want it to be... but my self discipline wants to control that urge and try to built things that one day could even make it to market.If you could buy a frame and fairings that you could easily bolt together with a multi-speed hub and be able to do amazing things wouldn't you be tempted to buy it?
If you had "access" to the things I have created from scratch you might change your tune... maybe one day you might even be a customer of mine?
We even have a joke in our family that we have a "cheap gene". My father was like that... he would always seek to do with "less" more than you would expect could be done. It's a family trait...
xyster
10 MW
Just estimated 5 year cost riding 3000 miles per year, including initial construction costs, extra batteries, tires, everything I can think of, of $0.18 per mile. The electricity, at cost here, is less than a penny per mile.
Total of about 19 cents per mile of ebike operation.
A year pass for the bus here costs $814. So 3000 miles per year of bus riding would cost 27 cents per mile, plus unfathomable costs of time waiting, inability to go as many places without a ride on the other side, etc. On the plus side, I could get further per single ride on the bus, but I don't often need to do that. And I own a car anyway.
Five year car costs to travel 3000 miles per year, including initial car price of $2000, and gas of $3 per gallon would be about
fuel: $1800
initial car price: $2000
insurance/registration: $500
maintenance and upkeep: $400
five car costs = 31 cents per mile.
Total of about 19 cents per mile of ebike operation.
A year pass for the bus here costs $814. So 3000 miles per year of bus riding would cost 27 cents per mile, plus unfathomable costs of time waiting, inability to go as many places without a ride on the other side, etc. On the plus side, I could get further per single ride on the bus, but I don't often need to do that. And I own a car anyway.
Five year car costs to travel 3000 miles per year, including initial car price of $2000, and gas of $3 per gallon would be about
fuel: $1800
initial car price: $2000
insurance/registration: $500
maintenance and upkeep: $400
five car costs = 31 cents per mile.
safe
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On a scale of 1 to 100:
A car ranks at 100 for cost.
Your bike costs 4.25
My bike costs 4.22
So in the "big picture" we are debating trivia. Compared to the "enemy" we are all on the "same side"... (but we need the competition because it drives us to achieve more... so rivalries are a "good thing" if it improves the technologies)
A car ranks at 100 for cost.
Your bike costs 4.25
My bike costs 4.22
So in the "big picture" we are debating trivia. Compared to the "enemy" we are all on the "same side"... (but we need the competition because it drives us to achieve more... so rivalries are a "good thing" if it improves the technologies)
xyster
10 MW
What tune? I have deep respect for the bike you've built. I wish I had the tools and experience with metal working to build my own too. In time I will. It'll still probably have a hubmotor
And as far as being your customer, I'd demand a free sample of the bike first!
xyster
10 MW
Is this a serious estimate based on the five year per mile costs I listed?
Absolutely! If you or your ride somehow represented the "enemy", the tone of any discussions would be very different.
That said, we're all here to, in some way, improve our transportation solutions so the "enemy", whatever that be, never owns us again.
safe
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xyster said:
Actually I did that once already back in 1980 or so.
There were a group of "Gravity Bike" racers in Arizona that lived near where the magazine that did the article on my bikes was located. I gave them a frame and fairings for free to let them try it out. I gave a free bike to the magazine too.
No wonder I never made any money...
