1. WHY TWO-X
Q: What the heck *is* Two-X?
A: Two-X is a set of separate battery packs, which form a single massive battery array once they are connected together. They come pre-wired to install into a Onewheel skateboard and connect to it in place of its original battery. We provide a detailed installation video that can be followed step by step to put it in.
The battery cells used are unique to the Two-X system, and out-perform every other known brand of the same chemistry in key metrics critical to the Onewheel. They make full use of the board's built-in automatic cell balancing circuitry and charge using the stock charger, same as the original.
A Onewheel with a Two-X installed will exhibit a profoundly improved performance, for example: Noticeably greater torque, faster acceleration, unprecedented hill climbing ability, reduced tendency to nosedive, and at least 12-16 mile range.
Q: Who can benefit the most from buying a Two-X, considering everything available today?
A: Here are the most compatible customers of Two-X:
- Anyone with a V1 or Plus who considers nosediving simply unacceptable.
- People who are looking at paying for a stock battery replacement. Two-X makes a lot more sense.
- People who want their older board to keep up with their XR.
- Bargain-ninjas maximizing performance of cheap used V1/Plus boards.
- People who prefer the ride dynamics of the Plus over the XR, but need better performance and range.
- Onewheel owners interested in keeping their investment relevant longer than one FM product cycle.
- Gearhead hacker types looking to wrench of something.
That's who we expect would be most interested in the Two-X, and for whom it presents the most obvious immediate value.
Q: How does a Two-X upgraded Onewheel+ compare to a Onewheel XR?
A: The Two-X gives you a lot more range, almost what you get with a new XR. But it should age better, so this gap will close over time. While the XR becomes prone to nosediving toward the tail of its discharge curve, the Two-X is more consistently safe.
XR has smaller protrusions underneath footpads but neither of them truly gets in the way during actual riding. Two-X won't explode when you fold it around an oncoming truck axle - don't try that with XR. (This actually happened to me)
XR includes the much-discussed world-class FM customer service, and Two-X includes support from Two-X's smart little dedicated team.
If you don't have a onewheel, it makes sense to get an XR. But if you have a V1 or Plus and don't want to abandon that investment while shelling out for an XR, then the Two-X is your answer.
Of course, you're gonna need to have a bit of skillz and attitude to put in a Two-X. Anyone can unwrap an XR.
Q: I prefer the ride feel of the Plus over the XR. Does Two-X make a Plus *feel* like an XR?
A: No. We totally know what you mean, and no, it does not.
Although a Two-X does rival an XR in most measurable ways, it still has the basic smooth reliable feel of a Plus.
Q: How does an original Onewheel compare to a Onewheel+ or XR when upgraded with Two-X?
A: An original OW with Two-X will have torque similar to an OW+. It rides with a lot more confidence and is less choppy.
Range-wise, the Two-X upgrade makes an original OW cover distance just shy of an XR.
The closet is no longer the right place to keep your old Onewheel. Bring it out and make it awesome again.
2. STORE STUFF AND CUSTOMER RESOURCES
Q: What is the availability of Two-X?
A: We try to keep a healthy amount of units in stock. In times when we are succeeding at that, then units will ship out within a few days of an order.
When our stock starts getting low then we make a factory order for a new batch of parts, which takes about a month, and then we build up lots of new ones to fill any backlog and replenish our inventory.
Sometimes we get a bunch of orders and run out of units. Then customers might have to wait a little while to get their stuff. When this happens, you can bet we are running around trying to get them built as fast as we can.
Q: Can Two-X ship internationally?
A: Usually. If your address isn't working in the checkout page, we probably haven't configured the shipping for your area, so message us with your exact address and we can see if we can ship there.
Hook up with one of these shipping forwarding services which many customers have used with success to get Two-X delivered to far out places and often for cheaper than we can ship direct international. They let you set up a domestic US address which will automatically forward stuff to wherever you are.
For convoluted reasons, we cannot ship to Hawaii. Which is lame. Several customers in HI have successfully used the forwarding services though. Check it.
Q: Isn't the price kind of expensive?
A: Not compared to a Onewheel. It's no mystery why that is: The Onewheel is a premium, well-designed product. So is the Two-X.
Two-X is engineered to be optimum for its purpose, with a quality level appropriate to the board it's mounted on. It really works, and we stand behind it diligently. Without sacrificing any of that, the price you see is the best we could do.
And of course, Two-X contains a lot of new high-performance battery cells, which is something we weren't willing to compromise on. That's a big chunk of money we can't do much about. That being said, sometimes we do find ways to streamline things so it costs less to make, and when that happens you will see the price drop.
3. MECHANICAL DESIGN
Q: Will it be possible for me to remove the Two-X upgrade and go back to normal?
A: Yes. The Two-X was designed thoughtfully such that no original functional parts must be permanently modified. This means you can reverse the upgrade process to revert your board back to its stock configuration. If you ever want to for whatever reason.
Q: Why are the additional batteries located under the footpads?
A: Because it's efficient, functional, and looks slick!
Once we decided we wanted a physically larger battery, the question became, where would we put it? We considered the fender ... but a lot of people prefer their ride raw and sporty over the pack-mule configuration. We decided the fender is off-limits. If folks want to get creative with fender accessories, they still can!
So we experimented with a few other ideas, including under the footpads.
We were very skeptical about putting them under the board, because, obviously, we didn't see them lasting 8 minutes under there unless they're built like a tank. We taped some batteries under the footpads for a test, and got to work researching how we would create steel armored housings that were light and cheap enough.
But the batteries *did* last 8 minutes. Before we knew it the 8 minutes had become 8 days. And then, 8 months. Not only did the batteries survive just fine with only a few scratches on them, but after all these months of riding this way, we noticed with the batteries down there the feel of the ride was improved (see next question).
In summary, if your first impression of our housing location is, "that thing wouldn't last 8 minutes under there", we totally understand, and recommend riding one around for 8 months.
Q: How will the additional weight affect my ride?
A: As far as the extra mass affecting acceleration, etc. it's a negligible factor compared to the mass of the rider. But interestingly, it does have an effect on the board's stability and ride feel.
Ask yourself, when adding weight to a vehicle, where's the best place to put it? As I'm sure you know, the answer is low down. Two-X, exclusively, will lower your board's center of gravity.
The stock onewheel's center of gravity is around a couple inches behind and slightly above the center of the wheel. Two-X ends up moving it a bit forward toward the center, and also downward such that it is now beneath the axle center. Our understanding of weight in vehicles tells us this should improve the ride, stability, and control.
The Two-X feels more stable and in-control to ride, and this is part of the reason why.
Q: Are the housings weather resistant? What if I ride thru a puddle?
A: Yes, they are sealed, so your puddle won't affect them. It is necessary every few months to inspect the seals, and maintain them. The more critical concern is to make sure never to get water into your battery box. The results from this can be catastrophic. All Onewheelers, with Two-X or not, should check their battery box seal.
Go read the "Notes on Weatherproofing" section on the Installation page. You do *not* want any water to get into your battery box.
Do research on sealing your board, and be paranoid about riding through water. We've seen so many examples of boards dying this way
Q: How does the Two-X handle curb drops, curb hops, and other such trickery?
A: When going off a curb, you just need to make sure your speed is at least 4mph in order for the curb to miss the two-x housing. Below check out the physics showing this for cases of the tire having high and low pressure. Science!
If you are going off slower than that, do the housing a favor and jump a bit as you ride off, to take your weight off the board right at the moment it hits. Anyway the housing can take a significant amount of abuse, but can wear out eventually.
Climbing curbs: some people use the Two-X to get up curbs. We want to know details.
If you're into more nutty stuff like sliding the rails along curbs, or bombing down long flights of stairs, then Two-X is not for you I think.
See the later question about what to do about it if you trash your housings.
Q: OK, let's say I'm *not* trying to grind rails or do skateboard tricks. But I do ride hard, on and off road on all kinds of terrain. How will those Two-X housings, being physically under my board, affect my ride?
A: They won't. The under-footpad housing location is more out of the way than you might think.
For the most part, the bumpers hit first, and there is further clearance to the housings at that point. If the housings do come into contact with uneven terrain when off-roading, they'll slip right over it and it's no problem.
The most likely way to actually shatter a Two-X housing is by repeatedly dropping onto it onto curbs or rocks with the rider's full weight (this has happened twice), or to wipe out at high speed and have the bad luck to have the Two-X slam directly into a concrete curb at full speed (this has happened once). So avoid these things.
Q: I managed to crack open, or otherwise trash my housings. What can I do?
A: Contact our support. We will swap your f'd up housings for new ones for a reasonable fee that's just enough to cover our time, cost of new housings, and shipping.
Q: Are the batteries in the Two-X safe?
A: The Two-X uses Lithium Iron Phosphate (LiFePO) batteries, same chemistry as those that came in the original.
LiFePO is widely recognized as the safest Lithium chemistry for electric vehicles.
Q: My original battery doesn’t last like it did when it was new. Will the Two-X upgrade still perform as well?
A: Yes. The Two-X upgrade completely replaces the original pack with brand new batteries. It doesn't matter what condition the original pack is in. You don't need your original pack any more. But do keep it around, it is handy for troubleshooting.
Q: What's so special about the Two-X cells in particular?
A: We scoured the world for LiFePO cell manufacturers and tested samples from dozens of factories. Compared to an original Onewheel cell, a Two-X cell has measurably improved voltage stability when subjected to the conditions known to increase chances of nosediving.
Take these improved cells and double them up, then you have two of them working together for every one you used to have, and the result explains the Two-X's significantly improved voltage stability.
These cells also have measured about 4% higher charge capacity than the Onewheel cells, (just a tiny bit more). But considering there are twice as many of them, the total increase in your range with Two-X, compared to a new Onewheel, will be 2.08x.
Of course, if your battery is used and/or old then it will have degraded in performance, and your results will be proportionally even better. For example, when I replaced my 1-yr and 1000-mile old battery for Two-X, I measured the improvement to be 3.14 times better.
That's right, my range had gone up by exactly a factor of pi.
And sure enough, whereas before I could barely make it straight across town from one end of town to the other, now I can ride a whole complete circle around my town on one charge.
Way to go, math.
Q: How does Two-X improve battery calendar life?
A: The Two-X provides an improved service life compared any stock onewheel. This isn't mentioned on our front page because it isn't easy to test this. But here's why we're certain it will last longer:
Q: How does Two-X compare to other aftermarket battery extension solutions?
A: Two-X is the only available fully-integrated range extension solution. That is, it connects in place of your original battery in every way, including cell balancing and thermal management. Once installed, you'll be riding on a perfectly-matched battery array, rather than a bunch of different cells stapled together in parallel. And you can still charge normally.
And, it's the only one that mounts below and inside the board, not requiring fender-mounted or user-carried batteries. You don't have to have a fender loaded with top-heavy hardware, or risk smashing up your charging port against a curb. Just install it, then forget it.
Not to disparage other systems too much, they definitely work, and cost less and are easier to put in. But none of them are as properly integrated and engineered to fit a onewheel as Two-X.
The cool thing is, it's fine if you want to use them both. For example, you can install Two-X for better baseline range for everyday running around or commuting, and then plug in your CnR or Ranger Ego pack when you need even more range for those longer weekend journeys.
Basically, Two-X is more of a permanent, fully integrated upgrade, if you can afford it and can deal with installing it. But again, it's OK to go ahead and use both.
Q: Can I connect my original battery to my charging port and get even more range than Two-X alone?
A: Actually, yes. You will need to create a long EC3 Female (w/ Male pins) to XLR Female cable, and you're good to go. You'll also need a short EC3 (same configuration) to Male XLR adapter, so you can recharge the external battery later.
Try to connect the external battery when both are at similar charge levels. You can find out more details on this via the links in our Community page or ask about it in the forum.
Q: What other general battery advice can you give me?
A: The battery cells suffer degradation when they are stored with a full charge for extended periods. This is a minor effect but can add up significantly over time.
By being smart you can mitigate this effect by running it down to 80% or less before putting it away, whenever you know you’re not going to use it for a while. If you're using the board often, this is not worth worrying about.
Also, don't be in the habit of always plugging your board in to charge whenever you can. If there's a bunch of charge left, leave it unplugged instead. Remember every charge cycle slightly ages and degrades the battery cells. This was not plausible with the Plus due to its really short range, but with Two-X you won't need to always be charging.
Lastly, be conscious that batteries perform worse in extreme cold temperatures. LiFePO chemistry is susceptible to this effect. When it starts approaching down to around freezing level or below, your performance will be noticeably diminished. Same goes for charging - try to charge where it is at least 45F. Do not charge at all when temperatures are near freezing.
Q: What is nosediving?
A: This refers to an unpleasant Onewheel phenomenon where a fast-moving board tilts forward suddenly such that the front bumper slams into the ground.
Nosedives can be the result of general user fails, but here we are going to focus on ones that are the result of the board losing power independent of the user and stalling without warning. As dangerous as that may sound, this is nonetheless a present design flaw known to affect all Onewheel models: the V1, Plus, and XR.
A Onewheel stall is is not a casual event like it would be with practically any other type of vehicle ... The front of the board violently slams into the ground and the rider is then thrown forward in accordance with the Law. The Law of Conservation of Momentum.
Inconveniently, nosedives tend to happen specifically when the board is being pushed the hardest, such as, when the rider is cruising along at top speed. They also happen more when the batteries are getting low or old and degraded.
As you can imagine, this sort of thing can lead to you eating sh!t. You can read all about people’s experiences with nosedives in the major online forums.
In our opinion, the tendency of the Onewheel to nosedive is its most heinous flaw. Our goal isn't to whine about it, we still regard the Onewheel as an amazing triumph of an invention. We just want to fix this issue and keep on riding :)
Q: What causes nosedives?
A: There are different types of nosedives. Most types occur very rarely to experienced riders, and so are less of a concern. Included in this category are nosedives resulting from open foot sensors, internal hardware or software failures, or when some sensor exceeds a threshold (such as temperature extremes).
Two-X doesn't attempt to help with these. But they're either too rare to care, or an experienced rider can learn how to avoid them.
But there is another type of nosedive, which strikes without warning, even to many seasoned riders. This is the one the Onewheel community lives in fear of, and the one the Two-X endeavors to prevent.
We noticed some trends from our own experience, and from subjective accounts of other riders: Sudden unexplained nosedives tend to happen more often when the board has old or low batteries, and the rider is sustaining a very high speed, accelerating hard, or scaling a slope. But rarely with full batteries or when going downhill. Reports suggest they affect heavier riders more than light ones, and occur more frequently with lower tire pressure or in really cold temperatures.
We recognized these conditions as the same as those which make batteries struggle. So we did some tests in our lab and verified these nosedives are due to the board demanding so much energy that the batteries fail to maintain their voltage.
So we engineered a way to help prevent it. Welcome to Two-X.
Q. How does Two-X help prevent nosedives?
A: Two-X replaces each original cell with two fresh, matched cells working together, each of which is better than the original. Thus, it has a lot more ability to dump out current.
Here are data logged by a Two-X customer, showing the current (in red) and voltage (in yellow) of their Two-X as they rode from full to dead:
This guy was riding super hard, as you can tell by the wild current spikes. But just look how stable the voltage stays. Well out of range of nosedive territory.
That's what we are offering here.
Q: Explain what testing you did exactly? And what are the limitations of the Two-X? Do you even know what you're talking about?
A: Our lab tests confirmed that we can drop the voltage through loading the motor, and the result appears to be a sudden cutoff below a specific threshold.
First, we took a full-speed running onewheel and mechanically loaded it at increasing levels while monitoring its voltage. At a certain point, it suddenly stalls. We had reproduced a nosedive.
Then, we characterized the current draw while going on rides, pushing the board hard and measuring the max load that put on the battery. (Onewheeling while monitoring an oscilloscope? Yeah, we did that.)
Back in the lab, we took a stock battery within operational state of charge, and introduced an equivalent load, and saw the voltage drop in the same way.
So, we designed a battery that wouldn't do that. This was a prototype array which would become the basis for the Two-X design. When subjected to those conditions, its voltage drops much less, indeed, enough less to keep it out of dangerous nosedive territory.
Keep in mind, just because we couldn't nosedive the Two-X in our tests doesn't mean it's impossible. The board still contains this design flaw, and higher-still loading (than we could produce in our nerdy tests) can still trigger it.
Things that contribute to the loading include: Extreme speed, accelerating hard, steep hills, being heavy, rough terrain, low tire pressure, larger tire, air resistance, or any mechanical friction (worn bearings/motor, etc.). While the Two-X pushes the nosedive chances much lower, it's still possible to nosedive one by increasing any combination of those things by enough (especially when the batteries are low, getting old, or in extreme temperatures).
The Two-X has over twice the current-sourcing capability of the original. It thus effortlessly exhibits unprecedented voltage stability even in demanding conditions. And this does drastically lower the chances of a nosedive.
But we're not daring you to try. The real goal is for everyone to not break ribs wrists and collarbones. And we're doing it! Please be intelligent about that stuff when you ride. We wish you all the safest riding.
Q: Please explain footpad-related nosedives?
A: This is not the jurisdiction of Two-X, but we are including it anyway for riders who may not yet be aware. Because our M.O. is to stop nosediving.
Foot-sensor nosediving is a very real thing that affects riders who haven't yet been through the process of learning how the foot sensors work. So, go through that process! It turns out, that's usually all it takes to effectively eliminate these nosedives for good.
So, what's the connection between footpads and nosediving?: To avoid sailing off down the street when you bail off, the board has two pressure sensors, one on each side of the front foot pad. These sensors are pretty damn flaky, actually, kinda unreliable, which is why there are two of them, for redundancy. Get to know these sensors. If you power on your board and push the foot sensor, the headlight will brighten briefly. Learn where they work and where they don't.
While at speed, if ever the left and the right front foot pad sensors both stay un-triggered continuously for a half second, then the board decides that you bailed. And to avoid shooting off down the road by itself, it cuts power. If in fact you are still on the board, riding, but just have your foot or weight off the sensors somehow ... then you're gonna nosedive.
Conclusion: Pay attention when you place your feet when getting on your board. Back foot? Doesn't matter at all, you can do yoga with it for all I care. Front foot? Just make damn sure that front foot is planted centered sideways across both sensors.
6. COMPATIBILITY WITH OTHER PRODUCTS
Q: What about my bomb-ass Dunlop tire? Will it interfere?
A: The housings have more clearance than the stock footpads, from the tire. By a little bit.
Q: Can the Two-X be installed on a Onewheel XR?
A: No, the Two-X is specifically for the original Onewheel or Onewheel+, and can not be made to work on an XR.
Q: Is it true the girl who coded this website and the inventor of the Two-X are totally falling in love?
A: > Maybe.
Aw, that is so cute! It is true you totally ran my onewheel into a disabled homeless crackhead last night ;).
Q: Will I be able to use other Onewheel add-ons along with the Two-X?
A: That depends on whether they interfere with each other. For example, you can use Flight Fins, because they attach up top in an area Two-X doesn't require, but you can't use Float Plates, because they attach underneath the footpads.
Basically, Two-X wants the area underneath the footpads, and probably is incompatible with other products which attach there. Products that attach to the outside of the rails are probably OK, just get a good look at the attachment points and the space used to judge whether there are interferences.
Products that use the charging port should be fine, the Two-X doesn't need that. Charge-N-Ride setups should work seamlessly with Two-X. Though you probably won't need to use it as often, just for seriously long trips.
Q: Will Two-X work with my extra macho Beast Rails?
A: The Two-X beta units were hit and miss, as to whether they might fit on Beast Rails. But any Two-X unit manufactured after September 2018 will definitely fit.
Q: Will my board fit in my stand, with Two-X installed?
A: Depends on the stand. Usually not though.
Fortunately, most stand designs can be easily modified to work perfectly with the Two-X. Search through the forum, this is a common subject of discussion in there.
7. CHARGE-X CABLE
Q: What is Charge-X?
A: Charge-X is a simple cable that allows you to combine the current from two chargers (you supply) in order to charge up twice as fast.
It also contains protection circuitry to ensure your board and your chargers can not be damaged electrically.
Q: What boards and chargers are the Charge-X compatible with?
A: The updated 2nd version of the Charge-X design is compatible with V1, Plus, and XR Onewheels. Works on any compatible board, with or without the Two-X system installed.
Pint is not compatible. Don't try to adapt a Charge-X to use on your Pint, as you could possibly explode it.
Use any charger that works to charge your board, as long as its output is under 4A. You can use Future Motion chargers like the one that came with your board, or third-party chargers having equal output voltage ratings.
It is fine to mix different brands of chargers, as long as each is compatible with the board, and under 4A. Do *not* use an FM Hypercharger with a Charge-X.
Q: What's the difference between version 1 and version 2 Charge-X cables?
A: The first version was only thoroughly tested on V1 and Plus boards. When you use it to charge an XR, it will charge it up to like 80% super fast, but then kinda just give up. So in version 2 we made it act right when charging an XR to the top.
Its performance on V1 or Plus is basically unchanged.
Q: How can I charge even faster?
A: Charging slows down significantly as the battery nears the top of its capacity. So you can save significant time by stopping the charge cycle once it has reached 90-95%. This is especially relevant with the XR.
Doing this is also good for your battery service life.
Q: How is Charge-X's claim of 20-minutes to charge a stock Plus any improvement over the 20 minutes advertised by FM?
A: The advertised charge time for a Plus is in fact only half the actual charge time.
Q: Does cell balancing still work when using Charge-X?
A: The built-in cell-balancing in your board will work normally, whenever you let it charge to full 100%.
Q: What does it mean when just one of the charger lights turns green?
A: If one charger turns green, it means you're basically full, you can grab and go at this point. If you wait around, eventually the other light will also turn green, but only a miniscule amount more energy will have been added to the battery in that time.
Q: How does the Charge-X with two stock chargers compare to the FM Hypercharger?
A: (This question is only relevant to XR, as there is no Hypercharger equivalent for V1/Plus).
The Charge-X with two stock XR chargers supplies 6.8A, outpacing the Hypercharger's 6.5A. This lasts for most of the charge, then when it's getting near the top they both start tapering off, until they're barely putting out 300mA at the very end. The Charge-X tapers off more gently than the Hypercharger, so even tho it gets to 80% faster, the Hypercharger will overtake it before reaching 100%.
Basically, they perform about the same.
The Charge-X rig is volumetrically smaller than gargantuan Hypercharger, and packs flatter, which can be nice for backpack portability.
Q: I can feel heat coming from the Charge-X connectors. Should I panic?
A: The metal connectors of the Charge-X serve as heat sinks for the active circuitry located within them. They can get pretty warm during use. This means they are shedding heat effectively and is a good thing.
But you should panic anyway - it's good exercise.
Q: Why would I buy this from you, when I can get four microphone splitter cables on Amazon for that price?
A: A decent bit of engineering went into the Charge-X. Do *not* try combining chargers without the proper circuit protections - you will fry stuff.
8. MOBILE APP
Q: Does the Two-X properly report its status in the app (temperature, odometer, voltage, cell voltages, range, gauge)?
A: Yes, yes, yes, yes*, sort of, and no :) Read on ...
Temperature: Is a determined value based on readings from sensors on the main pack as well as both satellite packs.
Odometer: Functions normally. Trip lengths will come out correct.
Voltage: Also correct.
Cell voltages: These are also accurate, though each of the readings now applies to two cells instead of one. * Except, FM took the cell voltage reporting out of their app, but some third-party apps will still show them tho).
Gauge: Unfortunately the stock fuel gauge doesn't seem to be able to adjust its concept of your battery capacity. Which means it can't adjust to a change in capacity like the Two-X brings.
When you charge up to full, the app will accurately show 100% remaining. But as you use it up, the percent will drop twice as fast as it should. So at some point it will hit bottom, or 1%, when you really have at least another 50% left. Beyond that it just stays there at 1%, being quite uninformative.
See question below about reading your voltage. Once you get good at this you can get by just fine.
Range: Similar issues to the gauge. The app thinks you have a much less gutsy battery than you have now. So it predicts you have half the remaining range than you really do. You simply will have to mentally multiply this number. What will you multiply it by? (Hint: Two-X)
Q: Will there be a Two-X app?
A: We are working with the developers of an existing third-party onewheel app to provide an option to accurately show the range with a Two-X installed.
In the meantime, remaining battery life may be estimated by monitoring the overall pack voltage as it discharges. The voltage number must be linearized to give an accurate percentage. More on this later.
Q: How can I use my battery voltage as a fuel gauge?
A: Get good at this, and you can know how much battery you have left even when the fuel gauge isn't accurate.
Become familiar with the following graph. Use the red line to estimate charge remaining based on your battery voltage.
The blue line is what the voltage really looks like during a ride. Not as clean.
But you can see that most of the curve is basically a straight shallow slope. Which means for a reading to be useful it has to be fairly accurate.
The battery voltage jumps around all over the place in response to how much current it is putting out. So to get a reading you can use it's good to minimize that effect. Try slowing to a constant 3MPH or so for 5 seconds before taking each reading.
Note the stark non-linearities at the very start and the last quarter of the scale. In particular, as the batteries approach dead, notice how the voltage drops at an ever-increasing rate. This makes it pretty easy to tell how close you are to the end by taking regular readings and noticing how fast it's dropping.
A rule of thumb is, once the level drops below 50V during a ride, then you're going to be on that final descent and it's time to think about where you're going to plug in. Whenever the voltage is under 50.0V, you can judge your % left by memorizing the tail end of the curve above. You'll quickly get a feel for this with a little practice.
The tricky part is the shallow flat part of the curve, specifically the part between 50% (where the app % stops being useful) and 30%, where the curve starts being curved. Here's a trick for when you get a voltage reading between 50.9 and 51.3: Mentally remove the "5" and the "." from your voltage number, making a new number. Then subtract 3 from it, then multiply by 5.
Example: Billy has been riding for a while and wants to know how much battery he has left. He looks at the app and it shows "1%", so he knows he's somewhere between 1% and 50% left, but wants more information than that. He looks at the voltage, it is changing often, "51.4V", "50.8V", "50.2V", "50.6V". That's not helpful. So he aims for a flat spot in the road, and slows to 3MPH, and maintains that for 5 seconds, watching the voltage. "51.2V", "51.0V", "50.8V", "51.0V". Much better. His mental average of that is 51.0V. Chopping out the "5" and the "." from "51.0" leaves Billy with a new number "10". Our hero then uses his advanced brain to subtract 3, making 7, and then multiply by 5, giving 35% left. Billy smiles, knowing he will make it to the liquor store before it closes, and his daddy won't whoop him.
Q: What's next for Two-X?
A: We have a sizeable list of clever new ideas up our sleeve. At least one of them is actively being researched at the moment, though we have not announced anything yet.
Q: How do I take my Two-X upgraded Onewheel on a plane?
A: We have done extensive research into transporting lithium batteries. Ultimately the responsibility to comply with the rules is that of the traveler, of course. But we are happy to share some of what we've learned with you.
You must not check any of the batteries as below-deck luggage. By our interpretation this is legally possible but only with specific permission by the airline, which you'll have a snowball's chance in hell of getting. With the batteries removed, the board may be checked, and batteries carried on.
One limitation is that no more than two "batteries" may be transported by a passenger. Here, the official definition of a "battery" is any set of electrically-connected cells. Thus, the Two-X kit, as shipped, consists of two (not three) batteries (One for the main pack, and one for the assembly of both satellites).
Another distinction is based on the maximum energy capacity of the batteries. The entire Two-X kit, when connected together as in a typical installation, would count as one single battery, with too much max capacity to legally transport on a passenger flight. So, the main pack must be electrically disconnected from the satellite pair. And then it becomes two batteries, each having a legally transportable capacity.
So, remove the Two-X main pack so it is separate from the satellites/battery-box assembly. A smart way to pack them is inside a container that's been specifically designed for safe lithium transport, like this cheap one we found on amazon. This shows a level of self-motivated safety awareness that makes for very good optics from TSA's perspective, as well.
(note: the bag at that link fits the Two-X kit nicely, but likely not while attached to the battery box. If anyone finds a good size one for this, please share the link!)
Be careful that the overall basic appearance is one of a consumer product rather than a homemade device. Like, if wires are hanging out, etc. they could easily get spooked by that.
Now though this may not be necessary, your safest approach would be to contact the airline ahead of time and ask for pre-approval to carry on two compliant batteries (under 160Wh each). This shouldn't be a tall ask, we are told, airlines frequently grant this.
We are aware folks have flown without issue by carrying on (or even checking) the fully-connected battery box plus satellite pair, or even the entire board with all batteries installed. But these approaches are not compliant and so are risky, by our understanding. If some TSA agent decides to prove a point, you could easily get denied.
The actual danger a battery can present isn't due to its maximum energy capacity, but rather, its stored potential energy at that moment. So, to make them actually safer, you can run them down first to a low state of charge, somewhere between 20% and 30% remaining is recommended. When judging charge remaining for Two-X, this would correspond to a stable low-speed voltage level of around 50.3V
You may seek more advice by searching the larger online forums for discussions about flying with onewheels. It is a common concern in the community. You must adapt any such advice for the Two-X using the information given above.
Levels of understanding of the official rules vary widely from person to person, and policy details vary from one airport (or other facility) to the next. This, combined with the fact that many of the applicable rules have recently changed and/or are likely to soon change, means confusion is quite the norm, and it is ultimately hard to say for sure how any given situation will actually be handled.
So regardless what you do and how carefully you do it, we advise that you arrange yourself a backup plan in case your board or battery is denied. In other words, have a friend who is prepared to hold on to your equipment (so you can deal with it later) join you up to the security gate, just in case. So you don't miss your flight or lose your stuff.
Ultimately it is a lot more sure-fire and hassle-free to ship the batteries around by ground rather than try to fly with them.
(disclaimer) Please use this information as you see fit. We can't accept any responsibility for anyone's experience that didn't go well. We stand willing to modify or improve any of this information upon learning more details about the rules and from feedback we get.