ElectricMotorcycleForum.com
Makes And Models => Zero Motorcycles Forum | 2013+ => Topic started by: Rugby4life on August 30, 2017, 11:02:52 PM
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I'm trying to figure out how electrical efficiency differs from ICE efficiency. When you put a bigger motor in a car and leave the gas tank the same size, range decreases due to higher fuel consumption. How then does Zero claim the same range, with the same battery, for the S and SR models? Doesn't it take more electrons to produce 70hp/116ft-lb than 60hp/81ft-lb?
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Power output varies; you seldom use maximum. It takes the same energy to carry the same mass the same distance and speed. Bigger ICE engine weighs more and has higher consumption at idle. Any electric motor uses zero energy at idle.
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I would add that an SR at maximum output probably has less range than an S at max.
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Power output varies; you seldom use maximum. It takes the same energy to carry the same mass the same distance and speed. Bigger ICE engine weighs more and has higher consumption at idle. Any electric motor uses zero energy at idle.
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I guess it depends on what their test parameters are (maybe full throttle wasn't part of it). As for me, if I'm spending $2k more for the extra hp, I plan to use it often. I guess that's where we get the difference between advertised and real world MPGe.
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Also, the motors are almost the same. Maybe there are differences in materials to improve conductivity in the SR, which would improve efficiency. The major difference between the SR and S powertrain is the amp rating of the controller. This might give the S a negligible weight advantage because of smaller or fewer electronic components.
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Not exactly sure that answers the question. For example, the same car can come with different engine sizes. The larger one gets less gas mileage. Why? Ok that engine added weight. But not that much compared to the overall weight of the car. I think the added weight is not the main factor. Put a 30 pound sandbag in the smaller engine car and I bet it still gets better mileage. What about this theory: it takes a certain amount of energy to take this mass of car up a hill. We can calculate that. So the larger engine car only needs to use that much energy. However, it seems like it uses more than it needs. I think that is the point in original post. All those V8's I used a long time ago sure used way more gas than the smaller cars. I was trying to be easy on the gas pedal. These high power sports cars are not very heavy, probably lighter than my little car, and they don't have good fuel mileage. When I was a kid I remember some old people (Grandpa maybe) telling me you have to feed that big engine all the time no matter how hard you are using it.
So does this apply to electric or not? Say you have 2 motors sitting on a work bench, one is 50hp and the other 500 hp. We use them both to hoist a concrete block 30 feet up at the same speed. Both will use the same energy? Seems like the big motor will use more energy and the weight of the motor (at least the non spinning portion) does not matter in this setup.
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So does this apply to electric or not? Say you have 2 motors sitting on a work bench, one is 50hp and the other 500 hp. We use them both to hoist a concrete block 30 feet up at the same speed. Both will use the same energy? Seems like the big motor will use more energy and the weight of the motor (at least the non spinning portion) does not matter in this setup.
This assumes that the differences between the 75-7R and 75-7 are huge. Someone from Zero can chime in, but the R rating might be mostly a materials upgrade that allows the motor to handle higher currents, and therefore also run more efficiently. The biggest powertrain difference between the bikes is the electronic controller.
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What I'm saying is that it must take more electricity to produce 70hp than 60hp. If the testing regime consisted of "accelerate to 60mph in 4.2 sec" vs "accelerate at 100% throttle to 60mph" the energy usage should be about the same. I guess if you drive a 911 like a Jetta you'll get similar fuel mileage, but honestly, how many of us could do that. I'd just like to see an estimate based on riding an SR like an SR, not an SR acting like an S. I know it would be lower and I'm cool with that, I would just like an accurate estimate.
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What I'm saying is that it must take more electricity to produce 70hp than 60hp. If the testing regime consisted of "accelerate to 60mph in 4.2 sec" vs "accelerate at 100% throttle to 60mph" the energy usage should be about the same.
Right, but as you know the published distance range specs are based on speed ranges assuming steady cruising, not acceleration. So much affects range; acceleration, regen, terrain, riding position, speed, attitude. I ride my bike like an SR when I'm only going 6 miles and like an S with R benefits when I'm farther away from home.
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> So much affects range; acceleration, regen, ...
Indeed, Regen is a big difference between the S and the SR. The SR has a more powerful controller, so indeed, the same regen setting is stonger on an SR than on an S, and you do feel it kick in more strongly and more power goes back to the battery. So you put out power faster but you get to the same top speed, and when you slow, you get more of it back. Not much, but it seems to net out in my case. Also with the more powerful motor and the more powerful regen, the hills seem to net out better, and the extra weight of a passenger much less than you'd expect.
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Interesting that the S and SR have the same EPA UDDS rating.
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Yeah, bigger electric motor is more weight to move, but that seems to mean better downhill regen, so the effect of engine size on efficiency is not nearly as big an issue as bigger gas engine. Indeed, with electric, there's an efficiency band, and having a motor undersized for the load seems to do even more harm than having a motor that's too big.
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Yeah, bigger electric motor is more weight to move,
Is the SR motor bigger? The S motor is designated 75-7 and the SR 75-7R. The difference might be similar to the difference between a Tesla P100D and a P100DL, expensive connectors that handle higher currents.
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I'm trying to figure out how electrical efficiency differs from ICE efficiency. When you put a bigger motor in a car and leave the gas tank the same size, range decreases due to higher fuel consumption. How then does Zero claim the same range, with the same battery, for the S and SR models? Doesn't it take more electrons to produce 70hp/116ft-lb than 60hp/81ft-lb?
Only if you use it. You are not at that 70 HP when you're taking it easy with a motor that is simply capable of 70HP. You might only be using five HP.
Still somewhat true with an ICE. But larger ICEs are much less efficient under light loads. This is not true with electric motors. They are more efficient under light loads, along with almost infinite torque at zero RPMs. That's why our range doubles on a charge at slower speeds.
One thing I have wondered about is if I put the bike in the Sport Mode, but ride it no faster and do not accelerate faster than the eco. mode, would the range be exactly the same on a charge in either mode?
I assume it would be. AFAIK, all the Eco mode does is to put limits on your speed and acceleration. If we have the bike in the sport mode and ride it exactly as in the eco. mode, I assume the range will be exactly the same.
-Don- Auburn, CA
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I agree as far as Eco mode. I wonder if acceleration is really that important for efficiency. If you accelerate quickly (fun! 8)) but don't overshoot on speed it seems that most of the time the motor current conditions are the same as if you accelerated very slowly to the same speed. Yes you are at full speed for slightly longer but most of the power over time is used against drag. I don't see an significant efficiency problem with high current acceleration as long as the maximum speed is the same. Sure there are small losses at high current in wiring and winding resistance but probably not significant at low duty cycle. Am I missing something?
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If you look at energy needed to overcome engine weight and such, the only thing that matters in the comparison of the S vs the SR is the rotor of the motor. Since they are both IPM, the weight won't really be different I guess. And since the rest of the drive train is virtually identical (The stator mass might differ a bit) the opposing forces when accelerating or keeping speed will be the same, hence the same energy is used. So only the added weight of the static part of the motor and the added weight in the rotor together with the controller are different...
For combustion engines, my old teacher told us that a four-stroke uses around 5% of it's mechanical output power to drive the valves. A small 40kW engine would then need only 2kW to drive the valves, but a big 375kW engine would use 18,75kW energy just to idle! This energy comes from the fuel, so the mileage of an 8-cylinder would be way worse than a 3-cylinder.
And that's the beauty of electrical drive systems. If you need 5kW to go 50mph, the system uses 5kW. No more, no less. No choosing the right gear, no pesky valves to run, no generators, no ignition systems...
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That's a good way to put it, yes.
And yes, I think the more powerful controller is the main difference, you may be right about the motor connectors.
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> So much affects range; acceleration, regen, ...
Indeed, Regen is a big difference between the S and the SR. The SR has a more powerful controller, so indeed, the same regen setting is stonger on an SR than on an S, and you do feel it kick in more strongly and more power goes back to the battery. So you put out power faster but you get to the same top speed, and when you slow, you get more of it back. Not much, but it seems to net out in my case. Also with the more powerful motor and the more powerful regen, the hills seem to net out better, and the extra weight of a passenger much less than you'd expect.
I finally completed my semi-scientific range comparisons of the 2017 FXS, DS 13.0 and the SR 13.0 on the same route simulating my local usage. Each bike was charged to 100% and left on the charge overnight to complete cell balancing. Max range of the FXS was 42 miles (mostly in eco mode) rolling back into the dealership with 0% left. The DS completed 85 miles (2 to 1 sport/eco modes) with 2% left. The SR completed 91 miles (mostly sport mode) with 9% left. It was surprising that the bike with the most powerful motor, ridden most aggressively would return the best mileage. Your results may vary since I'm 300+ lbs and present a rather large aerodynamic cross-section. Basically, I replicate riding 2 up. My take is that the "R" motor allowed me to accelerate to cruising speed much quicker, allowing me to roll off the throttle sooner. Also the regen was much stronger, harvesting much more energy back to the battery.
As a side note, on the SR, I set up the custom mode with full top speed, full torque, full braking regen, and 0% coasting regen. My thought was that when I was coasting on a downgrade or as I was approaching an intersection I would be consuming no electrons and gaining free miles. After a 10 mile loop in sport and then in custom modes, I got marginally better watt hrs per mile in sport mode (about 1%). I guess regen is a larger contributor than I thought. BTW, I'm sold on the SR, just looking for one with a power tank... or maybe a 2018 depending on what upgrades they announce next week.
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Coasting is always more efficient than regen if you ride with care. With coasting you can use up to 100% of the kinetic energy you have, with regen only up to ~60%. However regen is still better than turning kinetic energy into pure heat with the brakes.
Don't forget the DS tires, which make a huge difference. If there was also a windshield involved that makes another 5% difference.
In contrast with ICE engines, electric motors aren't necessarily less efficient just because they have more peak power, because peak power mostly makes temporary use of thermal reserves which are not available forever (a Zero motor will do thermal throttling if you push it too hard).