Electric Bikes - Whats the farthest ebike distanse on 7 ah of battery power?

At any voltage from 36 to 72 volts the speed and distance can remain the same.Going faster than in this video of course your range will go down and you might too if you get a blowout. LOL Actualy this 20 mile trip was done on 6 amp hours of total battery power.
http://video.google.com/videoplay?docid=40059310945424798&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=3

You do realize that a single set of battery cells can be wired to make either (for example) 6 amp-hours at 72 volts or 12 amp-hours at 36 volts, don't you?

Amps and amp-hours alone tell you nothing about energy usage.

You do realize that a single set of battery cells can be wired to make either (for example) 6 amp-hours at 72 volts or 12 amp-hours at 36 volts, don't you?

Amps and amp-hours alone tell you nothing about energy usage. Do you relize that at 72 volts or 36 volts you can go the same distance with the same watt hours and speed ? Or you can go faster at 72 volts if you wish and
use twice the watt hours with the same amp hours ? LOL Or as you say you can paralel two 36 volt packs and go 40 miles on 6 amp hours at this pace.
http://video.google.com/videoplay?docid=-3958994458649051700&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=0

You do realize that a single set of battery cells can be wired to make either (for example) 6 amp-hours at 72 volts or 12 amp-hours at 36 volts, don't you?

Amps and amp-hours alone tell you nothing about energy usage.

Agreed, watt hours would be a much more useful measurement.

Agreed, watt hours would be a much more useful measurement. Amp hours X nomimal Voltage is easy to figure out.

Amp hours x actual voltage is more accurate. High capacity battery packs will put out significantly more than nominal voltage when lightly loaded and make efficiency calculated your way seem better than it actually is.

Aactual watthours from a watthour meter works fine too but after over 20,000 miles of checking the voltage, watt hours and amphours on 1000s of trips I pretty know how most ebike batteries work including many Li Poly cells..
Thanks for the tips.

At beginning of one of your videos it shows two batteries on top of frame in front of the seat, how did you build the structure to put them there? and were they the unsafe lithium or safe lithium batteries like dewalt lithium batteries uses or the unsafe like RC people use?
thanks

At beginning of one of your videos it shows two batteries on top of frame in front of the seat, how did you build the structure to put them there? and were they the unsafe lithium or safe lithium batteries like dewalt lithium batteries uses or the unsafe like RC people use?
thanks They are fastened to a angle aluminum frame I made that are on each side of the cross bar.With lipo batteries rated for 30 C discharges and a BMS used at a tipical 1 C discharge they are lot safer than gasoline! RC users had some of the older lipo packs flame out mostly because of the chemistory being different along with charging them too fast at high rates soon after being discharged in 10 minutes.

It doesn't appear you can pedal very much on your e-bike. Is that the case? You can get a lot more distance if you put in about 100-150 watts of pedalling. You can get even more if you changed to smooth tires.

Bionx's 36V Li-Ion battery is 9.6Ah. So with 360Wh, how far can your bike go? I'm trying to get an idea how efficient yours is compared to bionx.

RC lipos are mostly damaged by too high a discharge rate, overcharging (wrong cell count or over 1C) or overdischarging. In 3 years I've only had a couple of cells puff, and they were my fault. Out of over 30 or so.

It doesn't appear you can pedal very much on your e-bike. Is that the case? You can get a lot more distance if you put in about 100-150 watts of pedalling. You can get even more if you changed to smooth tires.

Bionx's 36V Li-Ion battery is 9.6Ah. So with 360Wh, how far can your bike go? I'm trying to get an idea how efficient yours is compared to bionx. Lithium batteries have short lives if they are discharged beyond 80% of the packs rating.Just like most other batteries.So when a battery is rated at 10 amp hours it only provides for 8 amp hours or 288 watt hours at 36 volts inless you want to ruin your batteries fast.

@Robbie: don´t know what you are speaking about here, also not what this should have to do with the topic of the thread ?!?

have seen your name today 3 times, and 3 times you answered to a post from EbikeHawaii in a rude tone with some strange stories (...committed suicide by jumping into your damned volcano after)

iam from Austria, maybe my English is too bad, and i do not realy get if this is for real, jokes, if you have a problem with EbikeHawaii or if you are friends and this is joking ?!???)

however: for me
- and i think i know a little bit about lipos for myself (using them 5 years in rc-hobby, used sofar about 10 different brand (from kokam (3 generations) to thunderpower (4 generations), Xcell, hyperion, Flightpower, Polyquest, a lot of Konion (Sony), A123 Fepo4 M1, ....) -
EBikeHawaii seems to be very competent when it comes to batteries (lipos) and drivetrains..
for example the hub-motor discussion and the efficience of these kind of motors at a hill.. (which is very bad)

so when i comes to competence i think EBikeHawaii owns most people here around..

the only thing which is maybe a little bit weird:
when EBikeHawaii is argueing about his bikes he sounds sometimes a little bit bigheaded / arrogant..

i think this is maybe just so when reading it in the forums and in real life you would not have that feeling when speaking with him..

and maybe its also this way, like fighting against windmills:
when you know that your concept is better because tested and compared and there are still people knowing obviously less about the facts and nevertheless don´t believe, it can be hard...
some people can take this away with an angels patience and arguee again and again and again,
others can not... (and i think EBikeHawaii is not such a patience person ;) )

EBikeHawaii: hope i made not a affront (http://dict.leo.org/ende?lp=ende&p=/gQPU.&search=affront) to you now..

i really respect your posts of facts and datas !
they are in many ways similar to my experiences (Lipos, ...) and my knowledge

[SIZE=2]It doesn't appear you can pedal very much on your e-bike. Is that the case? You can get a lot more distance if you put in about 100-150 watts of pedalling....
This is exactly the mentality I do not understand about e-bike enthusiasts--that you would spend so much money for a motor system, and then still have to pedal to get a useful range out of it anyway. ....Kind of like saying your car gets 80 mpg if you get out and push it the first 40 miles.
~

This is exactly the mentality I do not understand about e-bike enthusiasts--that you would spend so much money for a motor system, and then still have to pedal to get a useful range out of it anyway. ....Kind of like saying your car gets 80 mpg if you get out and push it the first 40 miles.
~

Why do you have a problem with ebikers spending money? I've bought plenty of parts for my other (pedal only) bikes, some admittedly with questionable dollar to value ratios. I was just looking at road bikes yesterday in the $5k range, but it's pretty hard to justify that sort of cash when it will be only slightly quicker and a few lbs lighter than the steel road bike I have now which is easily worth less than $1k.

On the other hand, having ridden some $$ road and mtn bikes, I can appreciate them for what they are. It's not about speed per dollar, it's about the overall riding experience. What is your definition of useful range anyways?

@Robbie: don´t know what you are speaking about here, also not what this should have to do with the topic of the thread ?!?

have seen your name today 3 times, and 3 times you answered to a post from EbikeHawaii in a rude tone with some strange stories (...committed suicide by jumping into your damned volcano after)

iam from Austria, maybe my English is too bad, and i do not realy get if this is for real, jokes, if you have a problem with EbikeHawaii or if you are friends and this is joking ?!???)

however: for me
- and i think i know a little bit about lipos for myself (using them 5 years in rc-hobby, used sofar about 10 different brand (from kokam (3 generations) to thunderpower (4 generations), Xcell, hyperion, Flightpower, Polyquest, a lot of Konion (Sony), A123 Fepo4 M1, ....) -
EBikeHawaii seems to be very competent when it comes to batteries (lipos) and drivetrains..
for example the hub-motor discussion and the efficience of these kind of motors at a hill.. (which is very bad)

so when i comes to competence i think EBikeHawaii owns most people here around..

the only thing which is maybe a little bit weird:
when EBikeHawaii is argueing about his bikes he sounds sometimes a little bit bigheaded / arrogant..

i think this is maybe just so when reading it in the forums and in real life you would not have that feeling when speaking with him..

and maybe its also this way, like fighting against windmills:
when you know that your concept is better because tested and compared and there are still people knowing obviously less about the facts and nevertheless don´t believe, it can be hard...
some people can take this away with an angels patience and arguee again and again and again,
others can not... (and i think EBikeHawaii is not such a patience person ;) )

EBikeHawaii: hope i made not a affront (http://dict.leo.org/ende?lp=ende&p=/gQPU.&search=affront) to you now..

i really respect your posts of facts and datas !
they are in many ways similar to my experiences (Lipos, ...) and my knowledge
I think this post just about sums up some major issues here. Plenty of expertise, plenty of foolish misjudgements and provocation of the authorities and others, plenty of boasting, and plenty of stupid infighting and name calling. Pity really. Why would someone whose activities have already raised some bad publicity and a ban, then say gleefully that he was going to now going to stalk the Segway tours on his new electric go-ped? I can't understand that any more than the people who taunt the same fellow about past competitions.

It would seem to me that a spirit of cooperation, enquiry and sharing experience would be better - but what do I know?

I think this post just about sums up some major issues here. Plenty of expertise, plenty of foolish misjudgements and provocation of the authorities and others, plenty of boasting, and plenty of stupid infighting and name calling. Pity really. Why would someone whose activities have already raised some bad publicity and a ban, then say gleefully that he was going to now going to stalk the Segway tours on his new electric go-ped? I can't understand that any more than the people who taunt the same fellow about past competitions.

It would seem to me that a spirit of cooperation, enquiry and sharing experience would be better - but what do I know?I have shared my experences, and how to build such a ebike.If one can not figure out how to make a motor mount or connect wires they should stick to a ready made ebike.

^ Huh? You're talking about a 2003 design? Three speed SRAM? A cyclone kit with a vision stoker freewheeling crank can give you 21+ speeds through the motor which is far superior to what you're talking about. Who would want to waste their time rebuilding your old, dated design?

I have shared my experences, and how to build such a ebike.If one can not figure out how to make a motor mount or connect wires they should stick to a ready made ebike.

And I appreciate that and say 'thanks'. It was interesting.

^ Huh? You're talking about a 2003 design? Three speed SRAM? A cyclone kit with a vision stoker freewheeling crank can give you 21+ speeds through the motor which is far superior to what you're talking about. Who would want to waste their time rebuilding your old, dated design?
Since electric motors have a wide range of usable torque and can work efficiently throughout that range, and since many front / rear derailleur settings are inefficient and hard on the chain and cogs even for a person inputting modest power, maybe a lot of those gears wouldn't be so much use. The internal hub design can use a bigger chain and keeps it running in an exactly straight line the way it is supposed to be. I'd say that is a superior specification on paper at least.

Personally, although I can see why someone might be interested in working out the problems, I think running a mountain bike at 45 mph is a dangerous thing to do. None of its parts are meant for that kind of punishment. What's more, doing so is bound to cause draconian response from the authorities. 'In your face' behaviour like that is extremely unwise, I'd say. That said, I think Randy has made some very useful contributions to developing very practical solutions. I think the twin freewheel thing to an internal hub is a master stroke actually. Coupled to a lower power motor running at its spec voltage, we could see the same weight battery pack having twice as many cells in parallel, or larger cells. That would mean phenomenal range. Poor range is the biggest limiter of the ebike market at the moment.

Most ebikers don't drive up volcanoes. They want to go practical distances on reliable durable machines at modest speeds. The light motorcycle / scooter market is already very well served by dozens of designs. It is a very different market to that for ebikes.

Since electric motors have a wide range of usable torque and can work efficiently throughout that range, and since many front / rear derailleur settings are inefficient and hard on the chain and cogs even for a person inputting modest power, maybe a lot of those gears wouldn't be so much use. The internal hub design can use a bigger chain and keeps it running in an exactly straight line the way it is supposed to be. I'd say that is a superior specification on paper at least.

Personally, although I can see why someone might be interested in working out the problems, I think running a mountain bike at 45 mph is a dangerous thing to do. None of its parts are meant for that kind of punishment. What's more, doing so is bound to cause draconian response from the authorities. 'In your face' behaviour like that is extremely unwise, I'd say. That said, I think Randy has made some very useful contributions to developing very practical solutions. I think the twin freewheel thing to an internal hub is a master stroke actually. Coupled to a lower power motor running at its spec voltage, we could see the same weight battery pack having twice as many cells in parallel, or larger cells. That would mean phenomenal range. Poor range is the biggest limiter of the ebike market at the moment.

Most ebikers don't drive up volcanoes. They want to go practical distances on reliable durable machines at modest speeds. The light motorcycle / scooter market is already very well served by dozens of designs. It is a very different market to that for ebikes. Shifting your pedal gears more than two times to 30 mph in seconds would be useless.Most people here would need a ebike that will climb steep hills if they wanted to go around this island.The volcano only proves this can be done efficiently without the system breaking down or depending on pedal power if your human power whimps out.
http://video.google.com/videoplay?docid=54683645398356399

The whole video
http://video.google.com/videoplay?docid=6193354267582670871&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=1

This is exactly the mentality I do not understand about e-bike enthusiasts--that you would spend so much money for a motor system, and then still have to pedal to get a useful range out of it anyway. ....Kind of like saying your car gets 80 mpg if you get out and push it the first 40 miles.
~

Most e-bikers aren't trying to avoid pedalling. They just want to go faster with the same or less effort. I'd pay money for that!

Since electric motors have a wide range of usable torque and can work efficiently throughout that range, and since many front / rear derailleur settings are inefficient and hard on the chain and cogs even for a person inputting modest power, maybe a lot of those gears wouldn't be so much use. The internal hub design can use a bigger chain and keeps it running in an exactly straight line the way it is supposed to be. I'd say that is a superior specification on paper at least.

I wouldn't be so quick to dismiss what Clay is saying. I don't think you're completely understanding what he meant either by your comments? I'll help elaborate for you.... If you were to use a Vision freewheeling stoker crank, the motor would power the front crank through an independent chain and chainring. More specifically, the motor would power the outermost chainring. The remaining 3 front chainrings and derailleur and standard chain would remaind the same. The motor would have a freewheel as well as the aforementioned Vision crank having its own freewheel. This would allow one to run power without pedaling or pedaling without motor resistance. This greater gear range would allow for a smaller motor than Randy is using. This combination under a skilled rider would run with Randy' s setup all day long without producing torque that could otherwise damage standard bicycle components. I also think that it's been so long since Randy actually pedaled a bike that he believes it's really true that it's impractical to shift gears a few times within a few seconds while on the way up to 30mph. Hogwash!

Oh, and perhaps Randy can produce a document from the manufacturer of his SRAM stating that they'll stand behind or even warranty their product in his application where he's stomping on the throttle like he does in his videos? I'll bet they won't! He's using a 750W motor for God's sake! Those SRAMS were NEVER designed to take such high torque! At best, Randy's ebike is a clever one-off that's had its day in the sun. (behind 3 team Mavic riders that is...LOL)

Robbie

Thank you Robbie Hatfield. The explanation makes Clay's point much clearer. You are right - I don't know that much about this stuff. I'm just trying to find out.

Thank you Robbie Hatfield. The explanation makes Clay's point much clearer. You are right - I don't know that much about this stuff. I'm just trying to find out.Just listen to Robbies BS and forget the results of actual testing. . LOL

^ I noticed that you didn't even attempt to challenge the technical aspects of what I said. That's because you can't and that's because what I'm saying makes undeniable sense.

Setting up a video camera on your bike does not make for controlled testing under controlled conditions. At best it's a stunt. At worst, your videos contributed to making ebikes illegal in Hawaii. Congratulations!!

Do you have any actual documentation from the manufacturers of your SRAM that states they stand behind their product the way you're using it? This question has been asked of you by many people on many different message boards in the past, and I've never seen you offer up documentation yet? Why?

Your idea of using the SRAM as you have is clever, but definitely not engineered. I'd consider getting someone with actual engineering credentials to validate this approach before telling the world that this is the only way to go. With only your word, I wouldn't let my dog on such a bike.

Robbie

^ I noticed that you didn't even attempt to challenge the technical aspects of what I said. That's because you can't and that's because what I'm saying makes undeniable sense.

Setting up a video camera on your bike does not make for controlled testing under controlled conditions. At best it's a stunt. At worst, your videos contributed to making ebikes illegal in Hawaii. Congratulations!!

Do you have any actual documentation from the manufacturers of your SRAM that states they stand behind their product the way you're using it? This question has been asked of you by many people on many different message boards in the past, and I've never seen you offer up documentation yet? Why?

Your idea of using the SRAM as you have is clever, but definitely not engineered. I'd consider getting someone with actual engineering credentials to validate this approach before telling the world that this is the only way to go. With only your word, I wouldn't let my dog on such a bike.

Robbie The older Sachs 3x7 hub and the new Sram 3x9 (http://www.sram.com/dualdrive/) hub are used on the Bike Friday (http://www.bikefriday.com/) tandems with a 20" (406) wheel. Tourque at the hub is lower with a 20" wheel then with a 26 or 700 wheel. The 3x7, 3x8 or 3x9 hubs are not suitable for tandems with larger wheels. Even when used with a 20" wheel if you tell Sram that it was mounted on a tandem they will not warrenty the hub should it fail. If the hub was mounted on a Bike Friday, you return the hub to Bike Friday and they will warrenty the hub.

Now before the flames start flying...the Sachs and Sram hubs are great products as are the bikes offered by Bike Friday. I have had both with out any problems.
http://www.bikeforums.net/archive/index.php/t-110070.html

Errrr okay.... The pictures of your bike look like you're using your dual drive 3 speed SRAM hub with a 26" wheel? By your last post, this is a questionable practice? No?

I doubt that Black Friday bicycles would warranty YOUR SRAM hub. LOL

You still have yet to challenge what I've suggested is a equal to superior design approach? I'm going to take this as an acknowledgement that you agree with me.

Robbie

Errrr okay.... The pictures of your bike look like you're using your dual drive 3 speed SRAM hub with a 26" wheel? By your last post, this is a questionable practice? No?

I doubt that Black Friday bicycles would warranty YOUR SRAM hub. LOL

You still have yet to challenge what I've suggested is a equal to superior design approach? I'm going to take this as an acknowledgement that you agree with me.

Robbie It's only to my benifet if no one utilizes the sram DD hub in a ebike product.

^ Good! Then you'll be quiet about it once and for all?

Robbie

^ Good! Then you'll be quiet about it once and for all?

Robbie Other people may want to learn or even want to test the truth themselves.. No one will stop it. So except it you foo LOL

Dual Drive hubs are the greatest little known secret to cyclist (AND EBIKERS) so far developed. This hub can replace the need to have a double or even a triple chain ring on the front of you bike all while also increasing both you high and low gear options.
The SRAM Dual Drive hub works with many indexed front shifter systems and the external portion of the hub will except any thing from 5 to 10 gears. The SRAM Dual Drive hub is perfect for Folding bikes, Recumbent's, Tandems, and Touring bikes. ProWheelBuilder.com will build your custom bicycle wheel using the SRAM Dual Drive hub onto Zipp, Reynolds, Blackwell Research, Velocity, Mavic, and Sun Ringle rims. SRAM Dual Drive hubs are a ProWheelBuilder.com approved product.

http://www.prowheelbuilder.com/sram.php

Check out our SRAM products.

ProWheelBuilder.com will build your custom bicycle wheel using the SRAM Dual Drive hub onto Zipp, Reynolds, Blackwell Research, Velocity, Mavic, and Sun Ringle rims.

You're still not facing the reality that the manufacturer never designed the dual drive SRAM hubs to withstand the torque of 750+W motors! What you're doing is a stunt.

Didn't three Mavic racers show you their rear wheel during the volcano climb? You ought to look at the pictures you took of them to see if they used your dual drive SRAM hub.

Robbie

You're still not facing the reality that the manufacturer never designed the dual drive SRAM hubs to withstand the torque of 750+W motors! What you're doing is a stunt.

Didn't three Mavic racers show you their rear wheel during the volcano climb? You ought to look at the pictures you took of them to see if they used your dual drive SRAM hub.

Robbie

Can we please make Robbie here a moderator, he makes so much sense.

While testing the new Crystalyte 5304/24" combo today I rode 35km on 4.69Ah, so that would be about 32.4 miles on 7Ah...

Probably the 2 biggest problems with the dual drives etc. is that they tend to fail in no drive position so you have to push it home, a derailleur system can be stuck in a single gear if something brakes. (there are a lot of reports of sram and dual drives failing if you visit may bike forums especially recumbent.)
The other issue is really 2 in 1 they are less efficient than a derailleur system and weigh more.

If I had one it would be in conjunction with a front deraillieur to get a bigger range and then use a b/b drive and get more than 80 gears driven.
3 speed is a 70s solution.

Does an electric bike really need 80 gears? I thought the idea of the Dual Drive hub is so you can use a single front chain ring while giving the motor three ratios to drive the wheel through.

It does if the battery pack dies and it is lead and you live where I do. :)
I always find I could use a bit more low and high gearing every ride unpowered.
Especially with a trike you can use gears from 10" through to whatever you are brave enough to assist on a downhill, so being able to pedal from 1kph to 80 would be great :) , it would allow you to wind up your speed on the downhills to get over the next uphill with a legal motor setup (legal here is 200w) without bogging down. There is no legal e-bike speed limit other than the marked road speed in OZ.
Such a setup could be great fun in my faired trike.
The 80 plus gears give alot of over lap but would still allow a huge range.
And just think of the bragging rights. :)

It does if the battery pack dies and it is lead and you live where I do. :)
I always find I could use a bit more low and high gearing every ride unpowered.
Especially with a trike you can use gears from 10" through to whatever you are brave enough to assist on a downhill, so being able to pedal from 1kph to 80 would be great :) , it would allow you to wind up your speed on the downhills to get over the next uphill with a legal motor setup (legal here is 200w) without bogging down. There is no legal e-bike speed limit other than the marked road speed in OZ.
Such a setup could be great fun in my faired trike.
The 80 plus gears give alot of over lap but would still allow a huge range.
And just think of the bragging rights. :)

Good points. I guess a faired recumbent needs wider gearing ranges than an upright.

So how far can you cruise on 7Ah of battery power?

While testing the new Crystalyte 5304/24" combo today I rode 35km on 4.69Ah, so that would be about 32.4 miles on 7Ah... Lets see a 20 mile video of your ride.

http://video.google.com/videoplay?docid=40059310945424798&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=3

Lets see a 20 mile video of your ride.

http://video.google.com/videoplay?docid=40059310945424798&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=3

There are plenty of videos on my google account. http://video.google.ca/videoplay?docid=-6766001556590638926

Videos don't prove anything about amps or watts though, just that the bike went on a certain route. Do any of your videos have a wattmeter visible in the frame?

There are plenty of videos on my google account. http://video.google.ca/videoplay?docid=-6766001556590638926

Videos don't prove anything about amps or watts though, just that the bike went on a certain route. Do any of your videos have a wattmeter visible in the frame? All figures can be fudged if you are into deciving people.The size of the batteries used tells a lot.For instance I use two 36 volt 12 ah batteries in series for 72 volts and they cut out at just under 7ah worth of use measured on several watt meters.You could figure 70 nominal volts X 6 ah = 420 watt hours for a 20 mile round trip with a few stops at slow and fast speeds.A bit faster than I like riding so there was no pedaling except making it look like a bicycle in places.We can give honest figures and videos to go with them or keep bickering LOL videos of the battery used shows a lot on the trip details.Notice the video of 20 miles using 6 ah at 36 volts using 1/2 the wattage and batteries.Adding 1 more battery in parallel = 36 volts at 12ah is good for 40 miles without pedaling at 20 mph speeds using less than 750 watts of power at any time. Believe it or not. LMAO The Idea is to get the job done with as little battery costs as possiable! when using lithium.A lightweight motor sysyem designed to operate at its optimum efficiency range at all load and speed levals will always have better results with any size of rider or wheel than using any hub motor weighing four times as much.
Untill a standard bike was used a kit would be hang on the back axel like a Currie USPD but not hanging out so much.I prefer mounting 1" in front of the rear wheel.
http://video.google.com/videoplay?docid=-3958994458649051700&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=0

Do you relize that at 72 volts or 36 volts you can go the same distance with the same watt hours and speed ? Or you can go faster at 72 volts if you wish and
use twice the watt hours with the same amp hours ? LOL Or as you say you can paralel two 36 volt packs and go 40 miles on 6 amp hours at this pace.
http://video.google.com/videoplay?docid=-3958994458649051700&q=ecyclemaui&total=6&start=0&num=10&so=0&type=search&plindex=0

At 72v, the motor is bigger and heavier. You also need a heavier stronger bike. You'd get better mileage out of a 36v motor and lighter frame.

I guess it personal preference regarding how fast you want to go on a bike. On the flats, I'm content staying around 25mph. On the steep hills, if it takes me from 6mph with my own pedalling to 12mph, that's plenty for me. It's also a matter of safety. The higher speeds require more safety gears. And the heavier bikes are more dangerous to peds on the trails.

At 72v, the motor is bigger and heavier. You also need a heavier stronger bike. You'd get better mileage out of a 36v motor and lighter frame.

I guess it personal preference regarding how fast you want to go on a bike. On the flats, I'm content staying around 25mph. On the steep hills, if it takes me from 6mph with my own pedalling to 12mph, that's plenty for me. It's also a matter of safety. The higher speeds require more safety gears. And the heavier bikes are more dangerous to peds on the trails. I find a $80.MTB and a 5 lb motor that is 4 years old with over 20,000 miles on it works fine at any voltage to 80 volts or 1600 watts all at the same great efficiency.
I'm happy that everyone can find what they need.
My heavy Huffy that is a total of 65 pounds will go 40 miles at 20 mph with no pedaling.Or go 25 miles at 30 mph with a top speed of 47 mph on the flats geard the way it is and still climb a 10,000 ft volcano by adding another 14 lbs of batteries or keeping the ebike weight the same 65 lbs and using a 30 lb aluminum bike instead of the stronger 45 lb steel Huffy that I ride off road a lot..