60 volt vs 72 volt

[E-HP]

I'm starting to look at other options, while I wait to see if the KT 60V controller comes back in stock somewhere. Actually, in the long run, I could end up in the same place, but maybe in a different sequence.

Here's the alternate upgrade plan, which defers some of the $ to later, but that depends on some assumptions. My thought is to upgrade my motor first, to either the Leafbike or Ebikeling 1500W (I read Thundercamel's thread on this one), and keep the current controller and battery for now. Not sure, but possibly the increased efficiency will have a similar effect to using my current motor and higher voltage. My apprehension comes from reading Neptronix's thread on the Leafbike motor and that you need a lot of battery to support it. I'm wondering if that's because you'd ride it harder and pull more current. Anyway, if I'm going to kill my battery in short order by going this direction, then I'll need think about it some more. If I do kill my battery, I'm wondering if the increased performance of the motor would be enough so that I would just replace the battery with one with better cells and stick to the current voltage.

Any thoughts or information from folks running either of these motors at 52V would be appreciated (climbing ability, typical currents under load, etc.).

PS. The upgrade 52v pack I'd be getting once my current pack is exhausted would be in the same UPP hard pack, but with Sanyo 3500 cells in a 14S8P configuration; 40 amp, 120 amp peak, 28 AH. I'm hoping that's enough battery for either of the two motors.

 

[thundercamel]

I would not bet on any differences in motor efficiency helping your range significantly, and I would bet your motor has comparable efficiency already.

My bike and my wife's bike have the same 52v 21ah battery. Her controller pulls 26 amps, and the motor is 25mm wide 0.35mm laminations, I believe a 5 turn. The current draw starts to drop at 30mph due to back EMF.
My controller pulls 30 amps and the ebikeling motor is 35mm wide 0.35mm laminations, I believe a 4 turn. I never even get to a high enough speed (40mph downhill) where back EMF starts to take effect. My battery runs out first every time the bikes are used together on the same trip, just because current draw is consistently higher.

I read back to remind myself what your upgrade goals are. More speed/power through the second half of your batteries range? If you're just looking for a higher top speed where back EMF is your (voltage) limitation, then sure, get a motor with fewer turns. The simulator shows the higher turns barely provide more thrust anyway:
Example 1
Example 2

If you're trying to get more power throughout a longer range, than I don't see any option other than a battery upgrade.

 

[E-HP]

I would not bet on any differences in motor efficiency helping your range significantly, and I would bet your motor has comparable efficiency already.

My bike and my wife's bike have the same 52v 21ah battery. Her controller pulls 26 amps, and the motor is 25mm wide 0.35mm laminations, I believe a 5 turn. The current draw starts to drop at 30mph due to back EMF.
My controller pulls 30 amps and the ebikeling motor is 35mm wide 0.35mm laminations, I believe a 4 turn. I never even get to a high enough speed (40mph downhill) where back EMF starts to take effect. My battery runs out first every time the bikes are used together on the same trip, just because current draw is consistently higher.

I read back to remind myself what your upgrade goals are. More speed/power through the second half of your batteries range? If you're just looking for a higher top speed where back EMF is your (voltage) limitation, then sure, get a motor with fewer turns. The simulator shows the higher turns barely provide more thrust anyway:
Example 1
Example 2

If you're trying to get more power throughout a longer range, than I don't see any option other than a battery upgrade.

Thanks, the A/B comparison is very helpful, so I'll need to do some more playing with the simulator. Actually, I'm only looking for the power level I feel at full charge to be maintained throughout the discharge of the battery. The speed increase would only be a byproduct of increasing voltage. In either case, the battery upgrade would be with better cells, but at what voltage is my predicament.

So since the ebikeling motor should be very efficient, is your wife's more efficient? Or are the efficiency curves such that at the speeds you are riding together at, her's is running in a more efficient range? (I definitely would be happy going with a more efficient motor, that is less efficient at my normal riding speeds).

 

[thundercamel]

I'm pretty much just hoping the ebikeling motor has a similar efficiency to the leaf motor, since they appear similar on the inside. I only monitor voltage and amperage through the smart BMS. I need to do as Neptronix suggested, and make a table of wattage for each bike at 10mph increments.

The difference between my two bikes, I believe is because it's easiest to use 100% throttle from every stop and up all the hills, all the while my bike is pulling 4 more amps. It does give more thrust, and I suppose I should be thinking more in terms of efficiency curves, but maybe someday I'll get a cycle analyst for both

With a flat current limit, all batteries will put out a bit less wattage through it's cycle as the voltage runs down. Maybe a smarter motor controller would be able to program a current boost as voltage goes down, and really surprise you when it runs out!

 

[thundercamel]

Also, today was my first real ride with my new front wheel/suspension setup. It's possible, my old front hub which the bearings feel crummy on was causing measurable drag, lol!

 

[E-HP]

I'm back on this subject, looking for some real world confirmation of what I see on the Grin simulator. Theoretically it would seem that if I have a 52v, 60v, or 72v battery, with the same capacity (say 1000 watt-hours), then there should be no difference in the range, when using the same motor and ridden with comparable output. I ran this through the simulator, which confirmed that the range remains the same, when the bike is ridden at the same speed with the three voltage levels.

I realize that it is difficult to ride the bike in the same manner, with more power on tap, but my thought is to use PAS to provide some discipline around how the power is used. With my KT controller, and likely with an upgraded KT controller, there is a parameter to turn the overall PAS contribution up or down, so PAS 1 for my current set up provides 250 watts, with the lower setting, PAS 1 is closer to 150 watts.

Based on the simulator, it looks like 100% throttle on a 52v pack is around 67% throttle on a 72v pack; so using the turning down PAS via the setup gets the PAS 1 at 72v close to what it would be on my 52v pack, and yield a similar overall range.

Any real world observations on this would be very helpful to isolate the pros, cons, and neutral considerations of moving to 60v or 72v. Thanks ahead of time for any input. I'm not confident that I'd have the discipline to actually achieve the same range, so I may need to up the battery capacity by 20% or so to account for that.

 

[Alan B]

Lipo is really excellent for testing out voltage configurations. Vet Wrap is good for making different size temporary packs. I played with this early on in the Bonanza thread. In the Borg I made a large pack and the performance was amazing, 66V at 32 amp hours of 10-25C Lipo can deliver 100 amps with minimal sag compared to small cylindrical cells with hundreds of interconnects. The convenience of small cell packs is high but you pay a big price in many ways. I am moving toward small cell packs for moderate performance but for experimenting the Lipo is really nice.

As the voltage goes up control becomes much more "sensitive" especially with simple controllers - mapping throttle to PWM is cheap and easy to manufacture but not very smooth in operation. Moving to FOC sinewave is a major improvement in controlling motor current smoothly. It feels like less power because it is so smooth, which is an illusion. Buttery smooth power is more useful and desirable, especially on a lightweight vehicle like a bicycle.

One problem with low voltage (fast wind) motors is the high current they require. Compare the bulk of a PhaseRunner FOC Sinewave controller to a 12, 18 or 36 FET controller. On a bicycle the 6 FET controllers fit into the infrastructure much more smoothly than the larger models.

I have used 10S, 12S, 14S, 18S and 20S on my ebikes, and they all have their place. I've retired 10S and probably will retire 12S soon. Perhaps in the long run I'll settle on 14S and 20S. Looking at commercial packs there are some sweet spots, and having the option of buying instead of always building is nice.

"Riding the Same regardless of voltage" is an interesting theory, but realize in practice it happens only rarely. As voltage goes up speed goes up and efficiency takes a big hit. This necessitates bigger heavier batteries and controllers and hotter motors. The bike quickly goes from 65 pounds to well over 100, or the range goes down if the pack doesn't grow to account for efficiency loss. Consider what you really want, and how many ebikes it takes to get there.

 

[thundercamel]

This topic, with the relationship between KV and battery pack voltage has been on my mind as well. Here is a simulator setup matching what you describe 52 vs 72 volts, with no difference in range. Reading Justin's comment on this old thread however would have you believe that the higher voltage wastes heat in a standard trap controller, making the setup less efficient.

 

[Alan B]

The simulator is pretty accurate, but it doesn't factor rider behavior into the mix. Harder acceleration and higher speed reduces range.

 

[thundercamel]

I would not bet on any differences in motor efficiency helping your range significantly, and I would bet your motor has comparable efficiency already.

My bike and my wife's bike have the same 52v 21ah battery. Her controller pulls 26 amps, and the motor is 25mm wide 0.35mm laminations, I believe a 5 turn. The current draw starts to drop at 30mph due to back EMF.
My controller pulls 30 amps and the ebikeling motor is 35mm wide 0.35mm laminations, I believe a 4 turn. I never even get to a high enough speed (40mph downhill) where back EMF starts to take effect. My battery runs out first every time the bikes are used together on the same trip, just because current draw is consistently higher.

So since the ebikeling motor should be very efficient, is your wife's more efficient? Or are the efficiency curves such that at the speeds you are riding together at, her's is running in a more efficient range? (I definitely would be happy going with a more efficient motor, that is less efficient at my normal riding speeds).

To conclude our previous conversation, the difference in wattage draw between my two bikes is negligible, until you get faster than 25mph, which we don't do for endurance trips. This confirms that my battery just dies first because every full throttle application from a stop draws 4 more amps during that period. I need to test my recumbent now, because things look like it's drawing only 750 watts at 30mph with no pedaling!

Speed	StefEbike	Prancing Pony
10	115w		115w
15	325w		325w
20	600w		590w
25	950w		960w
30	1425w @ 29	1560w

 

[john61ct]

> "Riding the Same regardless of voltage" is an interesting theory, but realize in practice it happens only rarely.

All it takes is limiting the watts/amps, right?

Is going to a higher voltage for that low-speed scenario, say 72V and never using over say 500W on the flats, inherently less energy efficient than doing the same with 48/52/60V ?

One problem with low voltage (fast wind) motors is the high current they require. Compare the bulk of a PhaseRunner FOC Sinewave controller to a 12, 18 or 36 FET controller. On a bicycle the 6 FET controllers fit into the infrastructure much more smoothly than the larger models.

What do you actually mean, in concrete terms, by that last? Just physical size, aesthetic unobtrusiveness?

If a use case actually requires 5kW (for low speed torque), not really much choice, right? Do you still reco FOC Sinewave controllers there?

Apparently Lyen's big 18 FET controllers are still "trap wave" (I assume means square wave?).

Does adding a CAv3 help give some of the FOC Sinewave advantages?

Also, are all Sinewave controllers also FOC?

 

[Alan B]

A motor controller is in principle just a fancy DC-AC converter, and the efficiency is related to the voltage ratio (input to output) of the conversion. The larger the ratio the lower the efficiency. However the efficiency is still pretty good with moderate ratios.

Limiting the speed and acceleration is key to efficiency. Speed is voltage and acceleration is torque/current/power. So setting lower speed limit, power limit, motor current and battery current limits, and lengthening out ramp times will improve efficiency. I really see this in my electric car. When there's a traffic jam on the freeway my efficiency goes way up. High speeds just eat efficiency, much more than moderate speed or even moderate velocity stop and go (with regen).

The CA3 gives you some feedback loops sort of like FOC Sinewave, but not as smoothly, and the CA has no measure of motor current that is needed for torque control. The controller can do it better, it has the actual data necessary. The ratio between motor current and battery current shifts as the speed and back EMF change. The CA can do feedback on battery current, not motor current.

I have a bunch of Lyen controllers and they are all trapezoidal which is commutated square wave. I don't know if he has anything sinusoidal more recently. One great thing about his controllers is he repairs them, most vendors won't do that.

Sinusoidal controllers are NOT all FOC (field oriented control). FOC determines rotor position by measuring and analyzing the motor phase currents in real time and doing some heavy math. There are other ways to measure the rotor position that aren't as accurate but are cheaper, like interpolating from the hall sensors. These other techniques don't work as well. Measuring the motor current in real time has another major advantage - this gives accurate access to torque information, and controlling torque is the way to smooth control. Test drive a Zero electric motorcycle sometime - buttery smooth control even though it has 40 times the power of an ebike.

The Borg Cromotor/Sabvoton is Sinewave FOC. 5k is easily achieved there.

 

[john61ct]

Thanks, very helpful.

Limiting the speed and acceleration is key to efficiency. Speed is voltage and acceleration is torque/current/power.

So is slowly but continuously pushing a heavy cargo up steep mountain roads.

High amps is not optional there, so throw energy-efficiency optimizations out the window?

Where I'm stuck, is satisfying that primary need with the desire for maximizing range once back on the flat, keeping to 20-25mph max and gentle starts plenty human power assisting.

Is multiple motors more practical than trying to satisfy both goals with just one?

 

[john61ct]

The Borg Cromotor/Sabvoton is Sinewave FOC. 5k is easily achieved there.

I've read that it is very difficult to DIY tune the Sabvotons when trying out different motors.

Are there vendors selling such motor+controller **kits** that are well-tuned out of the box, **and** give responsive after-sales support, even if on a paid basis?

Also, some say the Lyen controllers work well with Cromotors

not so much with the QS motors.

 

[Alan B]

The energy it takes to lift the cargo is essential.

Energy going into aerodynamic loss is waste.

Making your setup more aerodynamic, accelerating gently and going slowly is all you can do.

I cannot speak to presently sold Sabvoton controllers. My experience was good, but things may have changed.

I used three different Lyen Infineon controllers on my Cromotor. I used a 12 FET and a high voltage 18 FET on it and they both heated up at 66 volts on my hilly commute ride at 25mph. The 24 FET was the primary controller and it failed 5 times at the 5-6 kw level. Edward repaired it each time, one time replacing the entire pc board. I sold it to another Cromotor user (with full disclosure and for a very good price) and he had no trouble with it.

I'm pretty shure I know what the "problem" was with my setup that caused these failures. Note that some cases took months before it failed while other times it took one hit on the throttle with the tire on the pavement. The bottom line was that I built a very low impedance battery with series/parallel lipo, heavy wires paired to reduce inductance, high current connectors and a high current circuit breaker. The wiring to the Cromotor (a low impedance motor) was also paired, short and heavy copper. The bottom line is that the current peaks were higher than average setups. I also had a very steep hill to climb right at the start of my trip and the battery voltage was 75V at the start. All well within the ratings of the controller, but pushing it.

A 24 FET controller has four FETs in parallel in each switch. If they are not precisely matched the current can concentrate in one FET and pop that one, then move to the next, like tearing a phone book using a bending technique. The Infineon controllers were really designed to have one or two FETs in parallel, extending this to larger numbers doesn't always work well. Using FETs from the same batch isn't always good enough to insure balanced currents.

The Infineons also have an old feature called "block time". We generally need to turn this off (if possible but it isn't always), it was put in to allow small controllers to temporarily exceed their current limit settings to get the motor going, it depends on circuit resistance to limit peak current. In my case the circuit resistance is very low and so the initial current can rise to a level that is quite high for a very brief time. With a high power system it is important to not ignore the current at any time.

Whatever the cause the effect was occasional burned FETs - legs missing, soot on things, etc. From the outside it just stopped working. Inside it looked like a small fire started and went out instantly. The controller was cold, so the problem was not temperature, but short term very high current.

The Sabvoton (and other FOC controllers) sense current all the time and just don't allow it to rise that far before opening the FET. Totally controlled.

When my 24 FET Lyen controller was used on another bike with the same motor type the big difference was the battery. A pair of 36 volt packs were connected in series so the voltage was actually higher (20S vs 18S or 84V vs 75V full charge). But the big difference is in the battery impedance. With hundreds of nickel interconnects and a BMS it could not deliver those really high current peaks without sag and there were no more failures.

 

[E-HP]

As the voltage goes up control becomes much more "sensitive" especially with simple controllers - mapping throttle to PWM is cheap and easy to manufacture but not very smooth in operation. Moving to FOC sinewave is a major improvement in controlling motor current smoothly. It feels like less power because it is so smooth, which is an illusion. Buttery smooth power is more useful and desirable, especially on a lightweight vehicle like a bicycle.

I'm adding FOC to my controller criteria, which currently is:

• Capable of voltages between 48v -72v

• Sine wave

• FOC

• Regen (variable preferred)

• 40A+ continuous

The problem is most of my searches turn up with Sabvoton, which per threads on the forum appear to be unreliable since Sabvoton stopped making them. I'd like a display, but going the higher end (Phaserunner) route, with a CA3 is too pricey for my econo ebike. I found this one, that doesn't appear to be a Sabvoton clone, but now sure about the quality, but it does meet the specs:

https://www.ebay.com/itm/Electric-Bike-45A-1000W-2000W-Sine-Wave-Intelligent-Controller-36V-72V-LCD/183957471067?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D57922%26meid%3Dca846500357048ca8b214a0592534850%26pid%3D100005%26rk%3D7%26rkt%3D12%26sd%3D174013681607%26itm%3D183957471067%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

It also has a bluetooth option, which wasn't on my specs, but would make programming easier. Any thoughts or experience with this no name controller? (It says Risunmotor, but so did my last controller, that turned out to be a KT). Once I have a controller that's sufficiently flexible, I'll have more options on the battery voltages, so this would be a good first step.

 

[Alan B]

It is not clear what happened with Sabvoton, there may never have been a company with that name and it may be the same people making it, but there have been reports of difficulty. The one I have is definitely not suitable for a small ebike, it is huge. I would only consider it for something like the Borg, even then I had to relocate the controller to the lower battery area and relocate 1/3 of the battery to the controller space to get it all in.

I would probably stick with the Phaserunner / CA3, but the controller package you link looks interesting and cheap enough so it may be a good experiment to document it for others. First I would search and see if others have already done work with it. And consider the entire investment, plus your time completely "at risk".

The Phaserunner is much more compact that most controllers, and well supported, and optimized for ebikes. They are not the cheapest but do we want to reward the cheap hardware cloners or the real developers of the technology?

Many controllers claim to be Sinewave FOC when in fact they use sinusoidal commutation but not FOC. That would be one thing to figure out. The Sinusoidally commutated controller does offer benefits over a trapezoidal, but not everything that FOC has. The Sabvoton and the PhaseRunner are FOC.

https://www.motioncontroltips.com/faq-whats-the-difference-between-field-oriented-control-and-sinusoidal-commutation/

PowerVelocity is here on ES and has some Sinusoidally Commutated controllers, and you can get support.

If you really want FOC it may be a waste of time to get involved with the Sinusoidal Commutation controllers.

The RadCity we bought recently is Sinewave, probably SC. It feels weak and slow, but that is probably due to the settings and ramps that we can't adjust. It is quiet, and the regen is also quiet.

A good controller can do with 6 FETs what a cheap controller takes 12 or more to do. One of the returns on investment.

FOC controllers can generally protect their FETs very well since they are looking at instantaneous currents. We had some at work that pretty much no matter what was done wrong they would just stop and display an error code. I don't think we ever blew one up due to a fault. They did occasionally fail after years of service but I suspect line transients and general electronics ageing was more to blame for that. Making a similar mistake with a trap controller can blow the FETs right off the board. They have no quick-response shutdown sensing. Part of the cost of FOC is the high bandwidth motor current detection. These days the faster CPU required doesn't cost much. There's also more engineering and support as they have to tune to the motor to properly interpret the signals and predict the rotor angle.

 

[E-HP]

I would probably stick with the Phaserunner / CA3, but the controller package you link looks interesting and cheap enough so it may be a good experiment to document it for others. First I would search and see if others have already done work with it. And consider the entire investment, plus your time completely "at risk".

Well if it's for the benefit of the forum, then I'm all in! But seriously, I have no problem with the "at risk" part, since it's not about the money, but that it fits the theme of my economy build, so if I can get the features that I want economically, then I'm willing to give it a try. I'll do more research and if this is the best option (bang for the buck), I'll go for it. I'll keep the Phaserunner on my list for the next, non-econo bike though.

 

[john61ct]

I wish Grin made a peak-150A Phaserunner.

 

[Alan B]

Sounds like a plan. Be good to figure out which controller it really is.

A peak 150A PhaseRunner would be nice. Doesn't ASI make something like that?

 

[john61ct]

Maybe it was Sevcon not Sabvoton that was reported to be such a pain to DIY configure?

Many say good stuff though, why I keep asking for handholding support even if paid third-party.

BAC is apparently almost as hard to DIY configure need expensive programming hardware as well as their software?

 

[Alan B]

Sevcon is not user friendly to configure. Requires special software, hardware interface and extensive training. This is not uncommon for commercial motor controllers as they are designed to be programmable for a wide range of applications. They expect you to take their training and have all their expensive tools and software.

The Sabvoton was like the PhaseRunner. Run some auto config and when it works it is pretty nearly done. It is fundamentally set up for a vehicle. Also Adaptto.

The ASI software for the BAC was somewhere in between.

 

[E-HP]

After a lot of thought and monitoring my current set up, current draw and voltage sag under load, I think I'll be happy at 60V, with decent cells. So, I'd be looking at $800-$900 to get me from 52V to 60V, with the same pack format, but at 60V, and replacing the controller and screen.

But, since I don't want to write off my current pack, I'm now planning on going with the controversial solution of a 2P series pack. That would get me to 60V for a litlle over $200, between the mini pack and new controller.

My current pack is 14S9P with cheap Chinese cells, and rated at 20Ah and 30 amp continuous. For the piggy back pack, I'm looking a 2s6P of Sanyo GA cells. This seems to be an OK match for capacity and current, since 6P should provide 30A continuous, over 50A peak, and 20Ah. If I make the pack with a single cell thickness, then it should fit nicely behind the seat tube.

I will be charging and monitoring the voltage on both packs separately.

 

[Alan B]

I would make the series pack have a bit higher amp-hour and current capacity than the main pack. That way the main pack will be the limitation, not the add-on. I've used Lipo for this, as long as it has more capacity than the main pack it can be run without a BMS since the main pack will always deplete first.

 

[E-HP]

I would make the series pack have a bit higher amp-hour and current capacity than the main pack. That way the main pack will be the limitation, not the add-on. I've used Lipo for this, as long as it has more capacity than the main pack it can be run without a BMS since the main pack will always deplete first.

Thanks, this make sense. I calculated the piggy back pack to have 20.7 Ah. My thought is that the existing pack may be degraded from the original 20 Ah, so that would be some additional margin (plus who knows if the cheap Chinese cells were good for 20 Ah in the first place). Do you think ~1 Ah of headroom is sufficient?