This article was original posted on Electric Skateboard HQ as part of the body of work I'd written for them.

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If you want the TL;DR, see end of review

Update from Paxson (Editor):

On 10th July 2019, Unlimited announced the fusion between them and the Loaded. Hence born Unlimited X Loaded. You can read about the news and the changes on Unlimited after the update here.

The following post is written prior to the update, but almost all of it stays relevant.

The Rundown: Mellow Drive (April 2018)

Note: The version of the Mellow Drive I reviewed was from before their switch to paid software unlocks. I will not be covering that in this review.

The Mellow Drive. The swappable, flexible drive kit that started everything. Originally conceived as a Kickstarter project and funded on June 11th, 2015, it's famous for enabling the dream of turning any board electric. The dream was within reach!

The hardware engineering on the Mellow Drive is flawless. Heavy, durable construction can be consistently used to describe every facet of the physical product. It's impressive, really, how nice the drive unit itself feels in the hand. It's so hefty and solid in fact that I would say you can knock somebody out with it.

The battery packs are well engineered as well. 7S2P and each with its own BMS, they're water resistant up to IP65. I was given two batteries to test, and had no difficulty carrying one in a small backpack to swap out on rides. At under 99Wh, they fall below most airlines' safety regulations and so can be carried onto planes to double as a battery pack to charge your stuff (USB port is included on each pack).

The Mellow app provides a really nice interface for looking at vital information on the fly. Setup is easy. All you have to do is connect the app to the Drive. Software updates are also provided this way, and are pretty easy to apply. During troubleshooting sessions with Mellow, the level of access they were able to obtain through the app was astounding. It's really all a very, very nice setup.

The Rundown: Unlimited Eon R Kit

If the Mellow Drive is the ruling big brother from Germany, the Unlimited Eon is the underdog younger brother from Spain.

Where Mellow went for the one piece design, Unlimited went for the fully modular approach. The entire drive system is meant to fit on almost any setup you can think of. The hubs are designed to be installable on almost any truck, and the battery and ESC setup under almost any deck. The only limitations are drop decks and trucks with non-standard axles, such as the 10mm on Surf-Rodz.

Speaking of the battery and ESC setup, I'm quite impressed with their forward thinking approach. Each ESC runs FOC and comes in a pigtailed module that connects to each other via an external CANbus module. That same middleman module also allows the ESCs to connect to the battery modules, which are each 10s1p packs with their own BMS and rated IP65. What this means is you can have ultimate flexibility in your setup. Want to optimize for mileage? Run one ESC with two batteries. Want to optimize for board weight? Run one ESC with one battery and carry the extra one. Want power? Slap both batteries and ESCs on there my dude. It's also worth noting that the batteries come with USB ports for charging devices as well. Unlimited does provide a fast charger, although only a 3A fast charger as the internal PCB traces may burn at a higher amperage I'm told.

Unlimited does have an app, though it's only a very basic one for updating firmwares. I was not able to test it as I had to return my review unit before the app was released, but I was able to take a look at it after the fact and can only assume it works though the interface is extremely utilitarian.

The Matchup: Flexibility

Consider: any deck? or any deck and any truck? I'll take the latter please. The Unlimited hub system is really a game changing system. Easy to install on almost anything with no modifications and easy to remove after, I was able to put it in many ridiculous configurations and setups. At one point I even put it on a G|Bomb push pumping setup.

The Matchup: Cruise

Living in San Francisco means it's much easier to get from point A to point B using alternative transportation methods due to traffic and street layout. However, the frequent and frequently steep hills means that it takes a vehicle with decent power and good brakes to get up and down those hills to cross town. Unfortunately for Mellow, it sort of all starts to fall apart once you start maneuvering those hills. The max hill grade for the Mellow Drive is about 20%, or 11-12 degrees. I found this to be true most of the time, although many times the Drive would start beeping at me and slowing down going up a 9-10 degree hill, and I'm not even that heavy (125lb). The Unlimited kit would power up the same hills no problem, though even though it's rated for 36% grade hills (20 degree), it can't reasonably power up anything more than 25%.

Going downhill sucks as well on the Mellow Drive. Often times, I have to brake down a hill and stop at an intersection while still on the hill. The Mellow Drive does this thing where it will actually cut brakes once you drop below a certain ERPM. What this effectively means is that I will almost stop at an intersection then the brakes will suddenly let go and I'll start rolling again. It got to the point where I had to start relying on foot braking more than the actual brakes. The Unlimited R Kit didn't have these issues, though the brakes on both drive units were pretty weak so weren't that effective at stopping you anyways.

There's also a feature that stops the Mellow Drive from accelerating without a rider on it, although it doesn't always work. I've had the Drive shoot into traffic a couple times, as well as cut power while I was doing some heavy acceleration. I did bring the issue up to Mellow, and the response I got back after much troubleshooting was that I was likely too light and that it wasn't likely to be fixed. Welp.

Where the Mellow Drive really shines, though, is flat, wide open spaces where I can just crank the throttle all the way up and carve. There's no other feeling that can come close to carving at speed on a smooth, long road devoid of pedestrians, and the Mellow Drive simply delivers on that front. While testing, I found zen by going to Crissy Field, turning on Endless mode, and just carving without having to deal with a remote. While the R Kit does also have cruise control capabilities, it doesn’t feel as refined and sort of “jerks” into the mode when the button is held and vibrates when it’s activated while not moving, a side effect of unsensored motors. In comparison, the cruise mode on the Mellow simply feels a lot more refined.

The Matchup: Performance

There's no question the R Kit is simply way more performant than the Mellow Drive. Off the line, the R Kit can put out more torque and so wins straight up. The R Kit hub motors are pretty strong and though it is unsensored (mandating kick pushing off the line to get started), the R Kit takes off faster once the ESC catches.

Now, you must allow me to rant a little bit as I'm passionate about this subject. Personally, I'm not a fan of unsensored motors for eskate. In a city like San Francisco (and this is true for any dense urban environment as well), having the ability to accelerate from standstill without having to kickpush is a godsend. Often times, it's hard to achieve an acceptable speed kickpushing uphill for the ESC to discover the stator position, which means you can't accelerate. Sensored motors solve this problem handily and I don't quite understand why they still aren't considered standard.

Unsensored motors aside, riding hard on the highest speed modes finds that the R Kit lasts longer (though not that much longer) than the Mellow on one battery. This makes sense since the R Kit technically has six more cells than the Mellow Drive. There is a caveat to this though, which is the fact that we're comparing two physical batteries for the R Kit to one physical battery for the Mellow. If you want to swap batteries for the R Kit and carry extra batteries with you, you will need to carry two physical batteries vs. the one battery for the Mellow Drive.

The Matchup: Remote

Now we must discuss a huge sticking point for most electric skateboards: the remote. The Mellow Drive remote is… not too great. While it does have a rock solid connection, the remote is largely ruined by its form factor and ergonomics. The slide mechanism, while novel, is not great in practice. It often sticks and yields less than ideal control, and while Mellow has done throttle control smoothing to try and remedy the issue, it just doesn't induce confidence.

It's also often hard to see what mode you're in in direct sunlight. The mode indicators are hard to read, and there's no speed indication, an unfortunate omission.

On the other hand, the Unlimited remote is ergonomic and fits quite well in my small hands. It uses a more traditional thumbwheel with nub based approach, and really is quite well designed. Again, rock solid connection here, and the integrated display is quite readable in direct sunlight. This isn't to say that I don't take issue with some aspects of the design, however. The battery indicator on the remote showing the R Kit's battery status never quite reached full. At first I thought it might be a pack balancing issue, but I was not able to fix it even if I charged the batteries separately. Navigating settings was also a slight bit difficult due to a combination of slightly questionable English translations and settings bugs, chief amongst which was I wasn't able to get the measurement units settings to persist across remote restarts. This was supposed to be fixed in an upcoming update, though I never saw the update. There is also a cruise control button on the remote, though I found it funny that it would just vibrate the motors if you pressed it while standing still.

The Verdict

In the end, it depends on what you're after. I can't speak to the durability of the R Kit, but I've heard good things about how much the Mellow Drive can take a beating. I can't speak to the effectiveness of the friction mount system employed by Unlimited in their hub motor mounting system, but I have never had an issue while using my review unit. If you're looking for power, Unlimited might be a good bet. If you're looking to just cruise on mostly flat terrain, Endless Mode on the Mellow Drive is very enticing.

TL;DR

I've included a pared down version of my notes that I took while reviewing the two drive kits. Use them as a tl;dr of the above.

As of September 2019

Mellow Notes:

• Sensored but no standing start, cites safety but is major inconvenience

• No-rider safety braking system works most of the time but not all the time, board shoots into traffic

• Braking doesn't work without weight, and cuts off once drive senses you're adequately slow. Weird when going down hill and reaching bottom. when board rolls away you have to chase it instead of just braking

• Push start is a bit unforgiving. You can only kick it once, kick it twice and you'll likely lose your balance

• Remote slide mechanism is a bit "tacky", not a completely smooth as I'd hoped, otherwise pretty effective Remote

• Onboarding UX is excellent. UX in general is excellent for the most part, including in app. Too many manufacturers forget about the UX part

• Batteries feel solid this time around, unlikely to fall out

• Doesn't run for very long on top power mode

Unlimited R Kit Notes:

• Unsensored, must push above certain erpm to start, big dislike

• Lightweight and properly powerful

• Pretty small and nice remote

• Hub motors were mountable on any truck I tried, very solidly built and clever securing mechanism. Super innovative

• Custom built ESC they call "MESC", R kit links dual MESCs together via CANbus, passthrough charging multiple packs at once. Very clever.

• UX was a bit confusing and felt unpolished

• App launched as of 12/07/18, feels super unfinished, was not able to test if functional

• Unable to use faster charger than 3A because charging traces may burn internally

• Batteries last an ok distance on top power mode, 8-9 miles

Note On Unlimited Kit Availability

While Unlimited kits have been shipping, the R kit is currently unavailable for purchase. Unlimited states the following: "We are currently manufacturing a big batch of product that we are hoping to have available during spring to summer."

Update by Paxson (Editor):

Along with the announcement of Unlimited X Loaded, Unlimited Kits are now available for purchase. Finally, the wait is over.

Check out Unlimited X Loaded here.