Future EUC Wishlist

[zeke]

Hey y'all!

I've spent a year riding EUCs and ripping through upgrades (IPS i6, InMotion V8, KS18L w/Pedal Upgrade, MSX100V 1.23kWh, and now a MSX100V 1.85kWh coming in the mail). I started off thinking "bleh, I'm not a speed demon like those crazies riding GotWays" so I started off small, but I found that I really love the speed and safety of having more power and keeping up with cars at 70km/h. The big tires also lessen my fear of potholes and other road surface aberrations. Alongside my other hobbies (skydiving and alpine climbing), EUC riding is up there on my favorites list. The EUC is also a convenient tool for short errands, last-mile transport, and walking the dog. I truly believe it's the future of urban transport.

So having dropped another $2k on this hobby, I'm idly pondering the future directions that EUCs will take and how they can get better. Could we get together a wish list of near-term and long-term improvements that we'd like to see on the EUCs of the future?

Here's my list.

Short-term:

1. Kuji Pads standard.
   Besides enabling tricks like jumping up curbs, Kuji Pads are a safety feature, helping reduce foot slip when traveling over irregular terrain.
    
2. Long footpedals standard.
   To extract the most performance (and safety) out of your EUC, the pedals need to be as long as your foot. This allows your center of gravity to shift as far forward or backward as possible, allowing the greatest control input for rapid acceleration and deceleration. It also allows you to climb and descend steeper hills. With the upgraded pedals on the KS18L, I've climbed the steepest hills in San Francisco with no complaint. The same cannot be said for the standard short pedals on the MSX.
    
3. Footpedal grind guards. 
   Pedal scrape is no joke, especially if your pedal hits a bump in the road. Danger arises from the potential for the pedal to get "stuck," causing a sudden torque and launching you off the EUC. If the pedals had low-friction grind guards on their leading edge (made of acetal or UHMWPE, for example), this would lessen the odds of getting stuck. Of course, they would be consumables.
    
4. Dihedral footpedals standard.
   The angled dihedral footpedals of the MSX seem weird at first, but they really secure your foot against the EUC—a huge benefit for reducing foot slip when hitting unexpected bumps, or when riding one-footed. Especially if you must make frequent stops, such as when walking the dog, this latter point is important for lessening foot fatigue. They also lessen the odds of pedal scrape on sharp turns.

Long-term:

1. Higher speed. 
   Keeping up with cars is lots of fun, but also important for safety (drivers DGAF). I'd like to see future EUCs with a top speed of 80 or 90km/h.
    
2. Bigger battery.
   Since drag force rises quadratically with speed, you need a bigger battery to go long distances if you're going fast. I'd like future EUCs with 3kWh or more.
    
3. Shock absorbers.
   My knees are fine, but using them to dampen the resonant tank formed by the tire's spring force and the EUC's mass can be a challenge—as a human, my response time isn't fast enough to dampen it well; I need to anticipate and prepare for the shock. Especially on poorly maintained roads, it's difficult to keep up with the repetitive and unpredictable force impulses when traveling at speed, causing anxiety about foot slip when traveling on unknown paths at night. It would be preferred if shock absorbers (important: with dampeners) were integrated into the EUC structure, especially if the battery was kept unsprung. I imagine this would result in a supremely buttery ride.
    
4. Belt-drive.
   This one's debatable, because it introduces another point of failure into the drivetrain, but...
   
   The power you can get out of a motor is proportional to the product of its size (namely, its volume) and how fast you spin it. With direct drive, where the motor is integrated into the wheel structure, you aren't spinning the motor very fast so its power density is remarkably low. As a result, for a given power level the motor must be really big—and neodymium and copper ain't cheap. If you added gearing or a belt drive, then the motor could spin faster than the wheel and be much smaller—like a hobby motor. This would substantially reduce the cost and weight of EUCs. Additionally, the sprung mass could be reduced and it would be easier to carry around.
   
   I take pause because it adds another point of failure if the belt breaks. While a drivetrain failure on a motorcycle might cause a fall, a drivetrain failure on an EUC will cause a fall. Maybe some belt-drive experts can chime in.
    
5. Foot attachment.
   Having dihedral pedals and Kuji pads helps to reduce foot slip, but nothing can beat a true attachment. It needn't take much force, since it would only need to prevent your feet from slipping off while catching air, so "clip-in" pedals like bicycles or skis would be unnecessary. Preferably something that can be detached easily when you need to step or jump off.
   
   My thought at the moment is to place a magnet on the pedal or the side of the EUC, and to have a small steel plate that pins to the bottom or side your shoe that is attracted by the magnet.
    
6. Articulating seats.
   Control of acceleration on the EUC arises from your ability to translate your center of gravity longitudinally, fore or aft of the tire's point of contact. Your ankles' articulation permits this motion. Fine control of steering is done by twisting your hips (and by extension the EUC) axially against your torso's rotational inertia, and course control by lateral translation of your center of gravity to the left or right of the tire's point of contact. The former is permitted by twisting articulation in your trunk, and the latter by articulation in your ankles and hips.
   
   On a seat that is rigidly mounted to the EUC, your ability to perform these translations and rotations is greatly diminished. In this case, you are reliant on the compliance in your butt tissue, which even for those blessed with child-bearing hips is not much. As a result, your control inputs on a seat are severely limited. This endangers you since you cannot steer or decelerate as quickly as may be needed in the event of an emergency.
   
   Articulating seats that permit a few centimeters of longitudinal and lateral translation, and several degrees of axial rotation, should greatly improve this situation.
    
7. Maintenance schedules.
   As EUCs become faster and more powerful, and as more people ride them, it becomes more critical to keep them well-maintained. Manufacturer-recommended maintenance and inspection intervals may be wise.

What's your wishlist?

Cheers!

[Legend27]

I just want an EUC that's damn 110% waterproof lol

[mrelwood]

I agree on most of OP’s points, but having the current wheels as fast and powerful as they are, my #1 wish is instead to avoid the continuing troublesome and sometimes even dangerous 1st batch issues. It might require a much larger userbase to allow for the manufacturers to dedicate more resources for this, so I’m hoping for more and more people to ride!

#2 is wheel weight. An MSX at the 16S’s weight of 17.5kg would already be an amazing improvement.

#3 A mobile app worth using.

The still larger pedal size, suspension, and Kuji pads might require for the manufacturers to understand the western EUC usage culture much better than they currently seem to. Does a profession exist for a ”behavioristic culture translator”? 

[Mono]

8 hours ago, zeke said:

Keeping up with cars is lots of fun, but also important for safety

We know this in particular because we have very reliable comparative risk numbers for bicyclists vs motorcyclists (motorbiking is at least three times more dangerous, even where bikers generally wear helmets and cyclists do not).

8 hours ago, zeke said:

I'd like to see future EUCs with a top speed of 80 or 90km/h.

Do you think these should be allowed to be driven without a drivers licence? (Full disclosure: this is a trick question)

5 hours ago, mrelwood said:

my #1 wish is instead to avoid the continuing troublesome and sometimes even dangerous 1st batch issues.

I have a simple solution to your #1 wish: just don't buy the 1st batch  Or are you concerned for those who are not aware that 1st batch buyers are alpha testers? Or concerned for those who do know better and still just cannot resist?

My V8 came with ankle pads, which I consider to be mini-Kuji-pads. For my taste they are not thick enough and wear out too quickly, but the idea is IMHO spot on.

I still struggle with the contradicting demands that (i) most of the time I want to be able to smoothly move my legs along the side of the wheel without losing contact (mainly to be able to bent the knees as smoothly as possible) but (ii) sometimes I want a have a grippy grab on the wheel for forcing it where it needs to be. Even worse, the latter additionally relies on the pants not gliding over the leg.

Edited November 17, 2019 by Mono

[mrelwood]

 

1 hour ago, Mono said:

I have a simple solution to your #1 wish: just don't buy the 1st batch  Or are you concerned for those who are not aware that 1st batch buyers are alpha testers? Or concerned for those who do know better and still just cannot resist?

I have so far been able to avoid buying first batch, but when the itch for a new wheel comes, I know I couldn’t resist. I was thinking about the hobby/community in general. So, yes to both.

[mike_bike_kite]

"also important for safety (drivers DGAF). I'd like to see future EUCs with a top speed of 80 or 90km/h." - I'm guessing your idea of safety is different to mine

"Belt-drive" - I believe some Rockwheel EUC's had gearing but it didn't seem to catch on. Not sure why.

"I'd like future EUCs with 3kWh or more" - I suspect this might add substantially to the weight and cost.

"still larger pedal size" - if the pedal attachment was standard across different wheels (and different EUC makers) then you could order your pedals separately to suit your feet or application. If the dihedral angle was adjustable then that might be nice. Perhaps have a choice of grips as well. Maybe choose between magnetic or friction closure. 

Personally, I think it would be nice to have standards on how pedals are made so you could have your favourite pedal on any EUC. Size, grip, dihedral angle, magnetic or friction. This should mean it would end up cheaper for manufactures and also better for consumers. 

Front and rear lighting with brakes should be standard on all wheels and at a useful height.

It would also be nice to have independent standards on wheels. Waterproofing, crash resistance, speed and range for different weight riders (not just 70kg asian guys), safe speed for a given rider weight using a standard surface with bumps and dips. Braking distances at set speeds for different rider weights. Build strength by repeatedly simulating jumping off kerbs. Noise levels (for humans and dogs). I think it should be straight forward to build a machine to destruction test the wheels.

 

 

[Mono]

 

38 minutes ago, mike_bike_kite said:

Front and rear lighting with brakes should be standard on all wheels and at a useful height.

IMHO more importantly though, front lights not just for visibility but strong enough to work as active lights over a reasonable range, as they are standard on modern bicycles or kick scooters.

[Nic]

1. Have the charger built-in so that you only need to carry a standard kettle lead for charging.

2. Have a display panel and controls built-in so that there is no need for a smartphone, though keep the App for downloading data on the smartphone. This will mean that you can still access features even if the App won't run on your smartphone.

3. Tougher shell with replaceable rubber armour.

4. Easier tyre change.

5. Better water sealing.

6. Most important of all ... MORE RANGE.

[xorbe]

1. Access to firmware code so I can customize it.

[RockyTop]

3 hours ago, Nic said:

1. Have the charger built-in so that you only need to carry a standard kettle lead for charging.

My first MSv3+ had space inside for a changing brick so I incorporated it into the build and added a connector for the cord. Now it can be charged either way or both ways at the same time for a quick charge.

Keep in mind that the brick gets hot and that it is the most likely part to fail. I would hate to have to tear my wheel apart to replace a $200 control board just because the charger failed and was incorporated into it. 

So I am with you but I would want the charger to be modular and easy to replace if it were part of the wheel.

[Nic]

31 minutes ago, RockyTop said:

My first MSv3+ had space inside for a changing brick so I incorporated it into the build and added a connector for the cord. Now it can be charged either way or both ways at the same time for a quick charge.

Keep in mind that the brick gets hot and that it is the most likely part to fail. I would hate to have to tear my wheel apart to replace a $200 control board just because the charger failed and was incorporated into it. 

So I am with you but I would want the charger to be modular and easy to replace if it were part of the wheel.

The Segway Ninebot MAX eScooter has a built-in fast charger, so hopefully this will be standard on other devices soon. I would expect such a feature to be on a separate module as it could be reused on many similar products.

A compartment to store the lead for the charger would be a nice touch too.

Edited November 17, 2019 by Nic

[Jason McNeil]

I'd like to a see a new version of the MTen3 with 4x modular battery packs, so in theory it could be taken aboard a plane. 

At least one manufacturer is working on a suspension, with the added weight & complexity, is it worth it? It could be argued a large 19x3" tire can absorb the brunt road irregularities, I guess we'll see if this ever makes the light of day.   

Another idea that I think would be cool would be to add an XT90S (anti-spark) output connector, for using this massive energy reservoir with an inverter for use a backup power supply for laptops, or other purpose.   

[Mono]

16 minutes ago, Jason McNeil said:

Another idea that I think would be cool would be to add an XT90S (anti-spark) output connector,

How about USB-C?

[Nic]

Maybe we will see a modular EUC design at some point (?), where customers can combine components from various sources and build their own EUC ...

1. Body Shell (inc. custom graphics)
2. Wheel/Motor
3. Tyre
4. Battery
5. Controller

... a bit like building with LEGO.

[Planemo]

7 hours ago, Nic said:

1. Have the charger built-in so that you only need to carry a standard kettle lead for charging.

I would have been 100% in agreement with this when I got my first wheel but I think things are very much different now (and I suspect they would be for many riders who upgrade their wheels).

The problem is that the standard chargers (1.5~2A) are only of any use when charging for many hours. That limits their use to home or work, and in either of those cases an external charger isn't really a problem. However, I still liked the idea of fitting the stock charger into the wheel and many wheels can accommodate it (MSX/Monster/Nikola unless you have the huge battery options) but the reality is that it's a bit pointless. Batteries are now at such a size that we need at least 5A, preferably more to make a dent in battery percentage within a reasonable time period. By 'reasonable' I mean workable if using it to charge whilst out and about. But taking into account that even a 6A charger will still take 4hrs to fill an 1859Wh MSX, the issue becomes size, weight and heat management. I just got my 6A 84v charger and it's massive, because it's necessary. A huge aluminium box with a large fan is needed to keep it happy and I'm not entirely sure you could ever fit the guts inside a wheel without issues. At the very least you would need to consider splashproof inlet and exhaust ports for the fan because you would need a huge heatsink otherwise.

Admittedly I think there are smaller 6A chargers out there but the ones I like (Wate) are built properly and I wouldn't want anything of a lesser quality either inside or outside the wheel.

Go to say 10A chargers (which I think is what EUC's will need soon when everything is above 2200Wh) and the problem of size and heat management becomes a real big issue if fitting internally.

[Planemo]

3 hours ago, Nic said:

The Segway Ninebot MAX eScooter has a built-in fast charger, so hopefully this will be standard on other devices soon.

Bear in mind that the MAX only has a 550Wh battery. And if I am not mistaken, it still takes 6hrs to 'fast' charge.

[JZT-Colorado]

3 hours ago, Jason McNeil said:

I'd like to a see a new version of the MTen3 with 4x modular battery packs, so in theory it could be taken aboard a plane. 

this is a FANTASTIC idea!!!

[Joker10]

I think it’s best to keep the charger separate from the wheel.   If the charger goes bad it’s easily replaceable if it’s not built into the wheel, and it’s going to add to the weight.  Licensing?  Once the PEV culture gets large enough that the politicians see money worth stealing, they will enact laws to begin the plunder.  As far as speed goes, why not 200km?  Yea right, to me 50 km is pushing it.  If all riders had common sense it might not be a problem to go faster, but with the videos I am seeing out there, a non rider is going to get seriously hurt and things will drastically change.  You can keep the angled pedals, I like my very large kingsong  pedals perpendicular to the ground.  

[zeke]

7 hours ago, mike_bike_kite said:

"also important for safety (drivers DGAF). I'd like to see future EUCs with a top speed of 80 or 90km/h." - I'm guessing your idea of safety is different to mine

Yes, yes it is.  IMO, learning how to safely do intrinsically dangerous things offers a well-rounded view of risk.

Also we sometimes forget in these discussions of speed that, unlike other vehicles, for an EUC a higher top speed provides more margin to avoid overlean even at lower speeds. So even if you don't choose to go fast, having the ability to go fast is safer. I happen to like wide safety margins.

11 hours ago, Mono said:

I still struggle with the contradicting demands that (i) most of the time I want to be able to smoothly move my legs along the side of the wheel without losing contact (mainly to be able to bent the knees as smoothly as possible) but (ii) sometimes I want a have a grippy grab on the wheel for forcing it where it needs to be. Even worse, the latter additionally relies on the pants not gliding over the leg.

Perhaps if the pads were vinyl-wrapped to lower their friction. Well-shaped pads that lock your ankles in should provide a good grippy grab, without needing to have high friction. 

14 hours ago, mrelwood said:

The still larger pedal size, suspension, and Kuji pads might require for the manufacturers to understand the western EUC usage culture much better than they currently seem to.

I think the "west vs. east" thing is overblown. In the vids from the manufacturers, such as this, it is clear that the pedals are too small for Asian feet too. Why, then, do they not demand bigger pedals in Asia? Not sure. They should. And Kuji goes to China all the time. As for suspension, I think that's just too big of a project for them to prioritize it.

8 hours ago, mike_bike_kite said:

Personally, I think it would be nice to have standards on how pedals are made so you could have your favourite pedal on any EUC. Size, grip, dihedral angle, magnetic or friction. This should mean it would end up cheaper for manufactures and also better for consumers. 

Yasss........!!

8 hours ago, mike_bike_kite said:

It would also be nice to have independent standards on wheels. Waterproofing, crash resistance, speed and range for different weight riders (not just 70kg asian guys), safe speed for a given rider weight using a standard surface with bumps and dips. ... Build strength by repeatedly simulating jumping off kerbs. Noise levels (for humans and dogs). I think it should be straight forward to build a machine to destruction test the wheels.

I like this. For speed and range, this can largely be performed on a dyno. Range can be math'd based on rider weight and height (tall people are draggier than short people), and perhaps a standard set of attire (baggy clothes are much draggier than tight-fitting clothes).

As for the rest, well, that'll be a bit more tricky. Maybe if we can draft up a standardized set of destructive tests, Jason McNeil is probably in the best position to implement them (if he ever finds the time for it, which is likely never lol).

9 hours ago, mike_bike_kite said:

Braking distances at set speeds for different rider weights.

All of the braking distance test videos I've seen so far have been performed with lines drawn on the ground, so the rider has a priori knowledge of when to prepare to stop. This is not representative of an actual emergency braking situation. These tests would be better if the rider made an unexpected stop, initiated by an observer with an air horn.

As far as I'm aware, at speed, all of the EUCs are capable of providing a greater braking force than the tire's friction can handle (for riders of reasonable weight). So as a result, they all are limited to decelerating at the same rate (unless you use sticky tires). Thus, what primarily differentiates them is not how long it takes to stop, but how long it takes to prepare to stop. Preparing to stop is done by throwing the EUC in front of your center of gravity so that you begin to decelerate.

How quickly you can throw the EUC in front of your center of gravity is limited by the EUC's ability to accelerate at speed (its torque margin divided by its mass and rotational inertia) and your ability to command a large acceleration input by momentarily placing your weight on your toes (so length of footpedal and the ratio of rider mass to EUC mass). And how quickly you can actually decelerate is pretty much just a function of how big the pedals are (how far back you can shift your weight onto your heels), and how well you can maintain balance while decelerating. A skillful rider who bends knees to reduce the EUC's torque load while throwing it will be capable of stopping in a shorter distance. Also, a heavier rider on a lighter EUC with lower rotational inertia and bigger pedals can stop faster, as long as the EUC's power MOSFETs can handle the current.

7 hours ago, Nic said:

1. Have the charger built-in so that you only need to carry a standard kettle lead for charging.

Good idea! 

7 hours ago, Nic said:

2. Have a display panel and controls built-in so that there is no need for a smartphone, though keep the App for downloading data on the smartphone. This will mean that you can still access features even if the App won't run on your smartphone.

Well, if only the smartphone apps were better this wouldn't be such a big deal.

Now, if you could lock and unlock the EUC without an app, that would be great. Perhaps some sort of USB key that you plug in to enable turn-on.

7 hours ago, Nic said:

4. Easier tyre change.

I don't know if this has an easy solution, but yes yes and yes.

7 hours ago, Nic said:

5. Better water sealing.

6. Most important of all ... MORE RANGE.

3 hours ago, RockyTop said:

Keep in mind that the brick gets hot and that it is the most likely part to fail. I would hate to have to tear my wheel apart to replace a $200 control board just because the charger failed and was incorporated into it. 

Not if you do it right; most of these chargers are the cheapest things the market has to offer, so poor reliability is expected. I work in power electronics to pay the bills, so I know it can be done right. Of course, the question is whether they'll do it right.

3 hours ago, Jason McNeil said:

I'd like to a see a new version of the MTen3 with 4x modular battery packs, so in theory it could be taken aboard a plane.

Ooooh I like this. Yeah I guess if the batteries can be removed from the device, what the FAA cares about is the energy storage per unit, not the total energy you're bringing on the plane. After all, you can bring multiple laptops on a flight. I would loooooove love love to travel with a baby EUC. Oh excuse me I'm drooling now.

3 hours ago, Jason McNeil said:

At least one manufacturer is working on a suspension, with the added weight & complexity, is it worth it? It could be argued a large 19x3" tire can absorb the brunt road irregularities, I guess we'll see if this ever makes the light of day.  

The 19x3" tire definitely helps. The large tire diameter lessens the force impulse, and the wide tire provides a lower spring constant and more travel. And MSXs' large mass lowers the resonance frequency so it's easier to keep your feet planted. But it's not the end-all be-all; the damping ratio of the tire is pretty low, so the resonance is still difficult to actively dampen as a human.

Perhaps, however, with sufficient foot attachments this wouldn't be an issue.

3 hours ago, Jason McNeil said:

Another idea that I think would be cool would be to add an XT90S (anti-spark) output connector, for using this massive energy reservoir with an inverter for use a backup power supply for laptops, or other purpose.

Hmm... If the EUC had an integrated charger, then (if it's done right) it could be used in reverse as an inverter.

3 hours ago, Mono said:

How about USB-C?

Yup, this would be pretty easy to implement and very handy to have.

 

Loving the ideas, keep 'em coming!

[zeke]

59 minutes ago, Planemo said:

But taking into account that even a 6A charger will still take 4hrs to fill an 1859Wh MSX, the issue becomes size, weight and heat management. I just got my 6A 84v charger and it's massive, because it's necessary. A huge aluminium box with a large fan is needed to keep it happy and I'm not entirely sure you could ever fit the guts inside a wheel without issues. At the very least you would need to consider splashproof inlet and exhaust ports for the fan because you would need a huge heatsink otherwise.

Much of the size of a conventional charger comes from its need for energy storage for the PFC boost. (By law, high-power circuits require PFC, or power factor correction, which draws a sinusoidal current that follows the utility power's sinusoidal voltage to avoid placing an unreasonably pulsatile load on the utility's infrastructure. As a result, chargers take a two-stage approach with a PFC boost and a huge capacitor to store energy, followed by an LLC to regulate the voltage to what is needed by the load and provide safety isolation.)

If you integrated the charger into the EUC, you could take advantage of the fact that there is already a massive energy-storage element in the chain: the battery. Then you could get rid of the PFC boost's huge (and reliability-limiting) filter capacitor. Sure, the charging ripple current would be huge, but I'm pretty sure the battery can handle it. It takes much worse abuse during normal use anyway.

If you took it a step further and chose to use a 400V battery stack (yeah, this would require re-architecting a lot of stuff in the EUC), then you could also get rid of the LLC and just have the PFC boost feed the battery directly. Unfortunately, this would also have ... interesting safety implications, since you would no longer have safety isolation.

Anyway, the big EUCs already have fans so keeping it cool while charging shouldn't be an issue.

[Nic]

18 minutes ago, zeke said:

Perhaps some sort of USB key that you plug in to enable turn-on.

That is actually a good idea ... a dongle that plugs into the USB port to turn on the EUC and to render the EUC useless without it ... great security idea! Although, as EUCs are so portable the idea would be to not leave your EUC out of sight. Thankfully, most people can't ride a EUC yet and wouldn't know what do do with one.

[zeke]

6 hours ago, xorbe said:

1. Access to firmware code so I can customize it.

Yes! It would be wonderful to customize the tilt-back behavior, PID coefficients, and light show, and would open up a whole new dimension of the sport. If I had a Z10, I know that I'd want to disable the over-charge protection which protects the battery from excessive regen current by suddenly disconnecting the battery from the motor driver but, in doing so, causes falls as documented by Marty; I'd rather kill the EUC than myself. 

Of course, if you used custom firmware the manufacturer would need some way to know that you did; the worst thing for them would be if your custom firmware broke the EUC, for example, by setting the current limit or over-temperature protection too high, and you then re-flashed it back to factory settings and sent it back demanding warranty repairs.

At the very least, visibility into the firmware would great to know what parts of the EUC's behavior can be trusted, and what parts are sketchy. For example, if a new EUC comes out with new firmware, I won't know exactly how the protection and cutoff features are implemented until somebody (hopefully somebody else) tests them, crashes, and reports back. That's not my preferred way to learn the limits of a new EUC.

[Planemo]

20 minutes ago, zeke said:

Anyway, the big EUCs already have fans so keeping it cool while charging shouldn't be an issue.

Granted, but from what I have seen the implementation leaves a lot to be desired imo. It seems more of an 'afterthought' than a real cooling solution. Plus most wheels aren't vented either.

And going by the sheer amount of air going through my charger, and the heat it exits at, the charger does require a very good cooling system.

Point taken re PFC though.

[Nic]

Most users don't need a fast charge so a normal charger built-in will do ... just include a booster port for an external charger for those that want to fast charge. Chargers are pretty reliable these days and would probably out last your battery pack.

[Planemo]

37 minutes ago, Nic said:

Most users don't need a fast charge so a normal charger built-in will do ...

I just don't see the point of a built-in slow charger when the wheel will always be at home where a normal external charger would be. I think it would be more beneficial to use any spare space in the wheel with more batteries instead of slow charger components but YMMV.

A built-in fast charger would make sense as it could be used when out and about rather than carrying a brick in a rucksack.