6 fet controller with hub drive more efficient?

Sidotian

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Jun 24, 2017
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Buffalo New York
I just ordered a 6 FET IRFB4110 with a half throttle/3speed switch I want something that is efficient as possible I thought this combo would be the one with a (48v) 500w hub motor. Im I right the less FETs the more efficient it would be? I would still like same or similar speed possibly with less amp draw at full throttle currently I am running 12s with 20 max amp draw and settles down to 13ish amps once top speed is reached at 31mph.
 
Sidotian said:
I just ordered a 6 FET IRFB4110 with a half throttle/3speed switch I want something that is efficient as possible I thought this combo would be the one with a (48v) 500w hub motor. Im I right the less FETs the more efficient it would be? I would still like same or similar speed possibly with less amp draw at full throttle currently I am running 12s with 20 max amp draw and settles down to 13ish amps once top speed is reached at 31mph.
No, I don't think that's a general statement that you can make. Just the opposite, in general, I believe. FET's resist current flowing through them -- voltage drops a small amount. This drop results in a small amount of waste heat. The amount of drop is dependent on the current and if you're splitting the work among more FETs then the current going through each will be split -- lower current per FET, lower voltage drop in the whole system, less watts wasted as heat. Yes, you have to drive more FETs, but the power to switch them on and off is usually relatively small.

For just 20 amps, however, there's not going to be any big savings from multiple FETs. 20 amps going through a 4110 is only supposed to have a .2v drop (at 175 degrees C, even less at lower temperatures) and you're not going to be averaging anything close to 20 amps if that's your peak. Nor will your controller be getting very warm. You'll lose a little driving more FETs, so that would eat into any savings and might even make a bigger controller a little less efficient if your power draw is small enough. But I doubt you'd notice much difference either way.
 
I agree w/ the above.
I would add that if you can see over 30 mph on 12S LiPoly, you must be using a high speed motor/big wheel combo, which makes for an inefficient system. In terms of efficiency, a higher Volts/lower speed motor would have been better. This can be seem clearly on the Eike CA sim.
Having said that, ebike efficiency is over-rated. Dogman, a member here, has stated that what the rider has had for lunch, or how tightly his/her clothing fits, will have more effect on range than a few % plus or minus in system efficiency.
 
Number of fets is so far down the list of what will make or break your efficiency you shouldn't worry about it. The exact mosfet, battery voltage as matched to the motor, and the motor's windings all in relation to how fast you will cruise at, are much more important.

Basically you want to select a motor with windings where the efficiency curve with the voltage you intend to use is at its peak with your intended cruise speed.
 
I was useing a yuyang controller with the phase and battery amp limited as low as it would go but then the bluetooth failed and I couldn't get into the settings anymore... I'm sick of changeing break pads also I thought the regen breaking would save me the money spent in pads alone after a few months...
 
motomech said:
I agree w/ the above.
I would add that if you can see over 30 mph on 12S LiPoly, you must be using a high speed motor/big wheel combo, which makes for an inefficient system. In terms of efficiency, a higher Volts/lower speed motor would have been better. This can be seem clearly on the Eike CA sim.
Having said that, ebike efficiency is over-rated. Dogman, a member here, has stated that what the rider has had for lunch, or how tightly his/her clothing fits, will have more effect on range than a few % plus or minus in system efficiency.

So are you saying if I spit my 12s 32amp hour to a 18s 16 ah it would be more efficient at low speeds? If so I wouldn't mind spending money on 2 more mulistars for the same amp hour IV ran 18s but only at night when it's safe with less traffic/people this has quickly turned into a hobby for me I own a car but seem find my self driveing it alot less I don't mind experimenting thats the fun part. I have 3 hubmotors one has a hall fualt so I'll look into what it takes to wind a motor sensorless
 
No. Within reason you can run whatever voltage you want, the important thing is to make sure your motor is wound / geared so that it gets max efficiency at your intended cruise speed. If you increase the voltage on your setup you have right now, all it will do is shift your efficiency curve to the right and give the motor a higher unloaded top speed. With a 6 fet I doubt you'll go much faster than mid 30s anyway unless you want to blow it.

How fast are you cruising? Google "ebike simulator" and plug in your motor and battery info and it will show you an efficiency curve for various speeds.
 
I'm sure there are controller/motor combinations that are less efficient than others. However, once at cruise speed, say 20 mph on up, I think you are looking to pick some high hanging fruit trying to get more range by your choices.

1%, or even a 5% difference at cruise speed is tiny, compared to the changes you can get by riding just 1 mph slower, like 19 mph vs 20. Once you get below 20 mph, then pedaling can cause as much as a 50% increase in range vs 10 mph faster.

As for full throttle efficiency, think about it, What difference would 6 fets not pwm ing make vs 12 fets not in pwm. both are going to be feeding straight current to the motor. Your controller runs at peak efficiency full throttle, but the wind will steal back 2000% of the tiny gain in controller efficiency.

On the other hand, matching your voltage, controller specs, motor, and wheel size for the particular needs of your vehicle, can easily result in 20% difference in overall efficiency, because of how it works during the start up part of the ride. I you want to dial in that acceleration part of the rides efficiency, then you need to tell us everything. The total weight of you and everything, grades, speeds you want to go, wheel size, how often you do have to stop or at least slow down, etc etc. If you have a big wheel, high speed winding, and not enough wattage, then bumping watts with a voltage increase can help. Quicker you get to speed, the sooner your amps draw drops. five seconds at 1000w is less watt hours than 30 seconds at 500w. But it still will not be more efficient than pedaling to 10 mph, then grabbing throttle.
 
My bike is about 80ish to 100 lbs if I run 18s I get a constant 20amp draw at full throttle it never settles. I have a yescom 500w hub motor I like to stick to 12s there are alot of 55mph streets around me that are straight for miles so I'm usually full throttle for sometimes 20 minutes at a time so better efficiency at full throttle would be ideal in my situation
 
I'd recommend going to http://ebikes.ca/simulator , finding your motor in the list, and the closest controller and battery to what you have (or entering the needed info in the custom fields, if you have it). If you haven't used it before, I recommend reading all the info on the page to help understand how it works, and what to do with it.

Then you can experiment with settings until it matches what you see now, to verify you've gotten the settings right for your system.

ONce it matches what you are already getting, you'll see what efficiency you have now, at different throttle values and different conditions.

Then you can change various things (system voltage, controller current/type, etc), and see what you'll get for efficiency under the same throttle values and conditions you get on your present rides.
 
And your ass weighs?

Assuming your ass weighs 200 pounds or less, you are going at least 35 mph, running 1400w continuous. Nothing on earth will make your 35 mph more efficient, except aero. Your motor is running flat out, your controller is not pwm ing. To get better efficiency, buy a recumbent bike, or even make a bent into a velomobile.

At that wattage, you won't see huge improvements by changing motor windings or controllers. A bigger motor would help some, a smaller wheel would help a lot on the starts. But once at cruise, 35 mph just simply takes power to push a guy sitting upright on the bike, with his coat open flapping away. In the city, you need to see that car coming too much to tuck. So lowering the bars is not the answer. get a bent and improve your aero. Or just suck it up and buy more battery.

The simulator, or just lots of riding while watching a watt meter can help you learn how to stretch your range when you need to. But flat out riding trying to keep up with cars aint it. Find better routes as best you can. Full speed is getting you 5% better on the controller heating or something like that, while 35 mph is something like 100% worse than riding 20 mph. Stop worrying about the controller heating, and put your motor in the butter zone.. Heres a hint,,, its a 500w motor. :wink: Motor 500w, you pedal 100w, and you get about 20 mph. That is e bike efficiency. Ride like its a motorcycle, and get motorcycle mileage, about 100 mpg equivilant. instead of e bike mpg.
 
Im only 120 125lbs sorry lol IV been looking into the velos
but I'm 100 % positive that those are not legal in NYS along with any ebike for that matter...also i got a amp reader and noticed 13-14mph is useing less than a amp at 12s!
 
FWIW, ALL ebikes are still illegal in New York State. Thank the NYC taxi lobby for that.

So you might as well cruise 35 mph. :twisted:

Actually though, without the humor, your best bet might be a typical speed around 15-18 mph, so you blend in. You'll find if you pedal and ride that speed, you get a ton of range from any motor setup.

What Don and the other lobbyists are trying to get to pass in NY, is the same law they put into place in California. 28 mph top speed, and no throttle if you go that fast. 20 mph top speed with throttles. So get that big front gear on your bike, so that when you haul ass you can still pedal and appear legal, now, and later if they ever get that law to pass.
 
I haven't had a single problem with the law ( knock on wood) I use to drive around one of those 80cc kits and they put an end to that super quick. They have noticed but dont seem to care I don't drive over 20 unless I drive out to the country roads that seem to go straight for miles. I also stay off bike trials because I feel like in some way that's reason to take my bike because the trails clearly state"no motorized vehicles"
 
dogman dan said:
And your ass weighs?

Assuming your ass weighs 200 pounds or less, you are going at least 35 mph, running 1400w continuous. Nothing on earth will make your 35 mph more efficient, except aero. Your motor is running flat out, your controller is not pwm ing. To get better efficiency, buy a recumbent bike, or even make a bent into a velomobile.

I'm surprised I don't see people here using fairings. Those can make a significant difference. And, with winter coming, the reduction in wind would be nice too.

Ok, the fairing discussion deserves its own topic here: http://tinyurl.com/y9v6r3m5
 
THere have been a few fairing discussions over the years, so if any of the info in them is useful, most are listed here
https://endless-sphere.com/forums/search.php?keywords=fairing&terms=all&author=&sc=1&sf=titleonly&sk=t&sd=d&sr=topics&st=0&ch=300&t=0&submit=Search
though not everything in that list is relevant, it's fairly obvious which are not. ;)
 
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