When it comes to Fitbit's range of fitness trackers, none are more powerful than the Fitbit Charge 2. It heralds a host of new features including guided breathing, interchangeable bands, a larger screen and new data tracking with VO2 Max.

While the Alta HR keeps things simple and the Blaze has its watch-like abilities, the Charge 2 is harder to categorise.

It's definitely not a smartwatch, but it does a lot more than many other fitness trackers. Fitbit rolled into 2017 following a big streak. Dropping the Fitbit Alta, Fitbit Alta HR and Blaze earlier in 2016, it then went on to launch sequels to classic models with the Fitbit Charge 2 and the Fitbit Flex 2.

Wareable verdict: Fitbit Charge 3 review

We gave our initial verdict after a few weeks with the tracker, but now we've spent a bit more time with it, here's our verdict on the Fitbit Charge 2.

Design and comfort





The Charge 2 retains a very Fitbit-esque look. Taking cues from its predecessor, as well as the Fitbit Alta and a little from Surge, it's actually much sleeker than the others, with a larger black and white OLED screen that's four times bigger than on the old Charge devices.

It's also more fashionable looking with a polished silver body that's similar to the one on the Alta HR. It has the same clasp system as the Charge/Charge HR, but while this keeps it firmly in place, it's a bit fiddly and often requires a bit of extra force to slip the band through.

The display definitely feels big enough and sits better than the Surge does on the wrist. The overall design is pleasing, perhaps because the display is larger than Alta's but still smaller than the Surge (and even the Fitbit Blaze), which means you get to see a little more information without it being uncomfortably big.



Early verdict: The Fitbit Ionic review



For a device which requires so little user interaction, it's surprisingly complex to use. Metrics are scrolled by tapping on the touchscreen. You can then cycle through modes by pressing the side button, and then move through exercises by swiping down on the screen.

To access a mode, you need to long-press the button. You can tell that Fitbit knows things are convoluted, as hints on how to use the device appear on the screen during the first few hours of use. It takes a little getting used to.

It is a little annoying that you can't scroll back, and instead must keep tapping to get back round to a previous screen that you might have missed. There aren't a lot of screens to go through but it's still a hassle if you're in a rush.

The sensitivity of the display is also little questionable at times. It's as if you need to be in a certain position for an arm turn to register, and it doesn't always illuminate the screen when it should.



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The heart rate monitor on the back protrudes a bit, but after using the Charge 2 for quite a while we haven't noticed it as much as we thought it would. It might need a bit of adjusting to find the sweet spot, but once it's there it's perfectly comfortable. Just behind the wrist bone is perfect for getting a read on the heart rate.

Read next: Fitbit Flex 2 review



Wearing it for more than just fitness is also definitely an option, as the band can be switched out for nicer materials if you feel so inclined.

The $29.95 Classic band comes in black, plum, blue and teal, and there are special editions including black with gunmetal body, or lavender and rose gold, which are pricier at $179.95.

Like the Alta, the Charge 2 will also get Luxe leather accessory band options, in brown, blush pink and indigo, which cost $69.95.

A gripe that's stood out over the longer term is the lack of waterproofing. In fact, we're still quite surprised Fitbit didn't include it on the Charge 2, with the Flex 2 offering a waterproof design.

The Charge 2 is water resistant, meaning it's fine dealing with sweat and rain, but Fitbit doesn't recommend taking it in the shower, which is annoying. Given how much the Charge 2 does, we feel like we should be able to take it into the pool too.

Activity tracking

Long pressing the side button starts tracking specific workouts manually and you'll get a detailed summary in the app afterwards. The Charge 2 is also equipped with SmartTrack, which automatically recognises running, cycling and more. Sleep is also auto-detected along with floors climbed, active minutes and hourly activity.



Sleep tracking has been given the biggest overhaul since launch with the arrival of Sleep Stages and Sleep Insights, which provide more in-depth tracking and tips respectively. We've found tracking to be accurate, though not always perfect at nailing our wake-up times.

Put up against the Beddit 3, a dedicated tracker, we've found that the scores have often been similar within under five minutes. Occasionally Fitbit has struggled picking up the actual time we woke up – especially if we stayed in bed for a while - mistaking restless sleep for actually being awake.

However it's been pretty good at recording bathroom breaks and the times we've fallen asleep, and is substantial enough for a basic overview of each night's sleep.

With Stages, Fitbit is now using our heart rate data to calculate our stages of sleep, but it's those insights we like best as Fitbit gets to know you over time and starts delivering feedback that's more personal and useful.

As for step tracking, you certainly couldn't accuse the Charge 2 of being stingy. Testing the accuracy of step trackers isn't easy, but we've definitely noticed the Charge 2 overcounting.

We first noticed this when testing it over long distances against the Garmin Fenix 3, but in our longer term testing we also found it has a tendency to over-estimate.

The Charge 2 also misses some stair climbs. This is an ongoing problem with other wearables that claim to count stairs, and the Charge 2 also struggles sometimes.



As mentioned, the Charge 2 has heart-rate tracking built in, so you won't have to worry about choosing between two variants. The heart-rate tracking uses Fitbit's PurePulse tech for continuous monitoring whether you're exercising or not.

There's no onboard GPS, and the Charge 2 relies on connecting up with your phone using the ConnectedGPS feature to get pace and distance stats. All these features can be found on the other Fitbits in some form – but the VO2 Max and guided breathing training are new.

VO2 Max

VO2 Max in the Fitbit app is labeled as Cardio Fitness Level. Wearing your Charge 2 to sleep to ensures the tracker measures your resting heart rate. Then it takes your user profile – age, height, weight and fitness data – to give you a score which is matched up against other people in your age group and gender.

You also get bar charts of your fat burn, cardio and peak heart rate zones which makes for the most complete picture of your ticker's data of any Fitbit to date.

The data is slightly hidden, and can only be accessed via the heart rate tab on the Fitbit app dashboard.

Unlike the resting heart rate, Cardio Fitness Level isn't tracked over time, and is displayed as a single figure which you should see rising over time. Why Fitbit didn't opt to plot Cardio Fitness Level we're not sure.

VO2 Max is properly calculated with a fairly hardcore test in a sports science lab, so the Fitbit Charge 2 is always going to offer something of an estimate. It clocked us at 49 – close to the Jabra Sport Pulse (47) and Garmin Fenix 3 (48), and while it does appear at the higher end of the scale, there are no complaints here.

We also let someone else borrow our Fitbit for a day, which caused the score to change, which at least demonstrates a degree of sensitivity in the data.

The Cardio Fitness Level feature is one of our favourite additions to the Fitbit Charge 2. It's a proper fitness metric that's new to the company's ecosystem – and one that we hope to see evolve over time to become even more useful.

Guided breathing

Breathing in deeply isn't a new concept for calming down. Thus Fitbit didn't invent the wheel – rather it's giving us a nice little tool to help us remember, which is why the guided breathing has been a surprising but welcome feature. At Wareable we've already noticed a growing trend of mindfulness apps and wearables solely dedicated to managing stress.

Read this: The science behind Fitbit and Apple's mindfulness push

Fitbit Charge 2 personalises its guided breathing exercise by taking your heart rate to find a good rhythm, making sure you're not inhaling too deeply or exhaling too quickly.

This is actually the debut of some serious new tech for Fitbit, and is the first time heart rate variability has been used on its devices. You can also complete a two minute or five minute session for a moment of relaxation, or use it to cool down after a workout.

After taking your heart rate, the Charge 2 readies you to breathe in time with a pulsing circle that's animated on the screen.

When we first used it to wind down after a workout, we felt like we were doing it wrong – inhaling too deeply and practically holding our breath. The second time we used it was to 'relax' and de-stress. This worked better and were able to breathe in time with the animation.

We've used it many times since in our longer-term test both for post-workouts and we like it. The Charge 2 has been able to accurately find the correct rhythm, allowing us to follow the pattern on the little screen.

It's oddly comforting watching the animations, and after continuously using it, two minutes flies by pretty quickly. We're also fans of the fact that there are no metrics making sure you're doing it correctly; it's there if you want it, but if you don't, that's ok.

Heart rate training





All eyes will be on the accuracy of the PurePulse heart rate sensor, but disappointingly it's still somewhat of a mixed bag on the Charge 2.



The good news is resting heart rate, which was tracked with aplomb and matched up to our Garmin Vivosmart HR data. We found the Blaze often tracked RHR too high, so this is an improvement over previous versions.

Generally, we found data from long steady runs to be useable – but the sensor took around 10 minutes to lock onto our heart rate when compared to a chest strap.

We also found that while generally accurate during steady and prolonged periods, it had a tendency to under-report current heart rate, often up to 5bpm. And when it comes to HIIT, the Charge 2 is more miss than hit. We undertook a couple of high intensity sessions and ran into a few problems with the Charge 2.

Interval woe: Fitbit Charge 2 and Garmin Fenix 3 with chest strap



First is the lag time, which often meant that as we reached 180bpm on the first interval the Charge 2 was stuck at 115. This usually improved as the session got underway, but often the Charge 2 was almost an interval behind.

However heart rate discrepancies with a chest strap were more apparent on the screen read out than the summary – like the Fitbit algorithm made sense of the data after the event. Often long sessions ended up being only 3bpm out from a chest strap, despite a stream of nonsense displayed live on the device during the workout.

Since this, Fitbit has issued an update to improve some issues in the device, including the GPS, which was spitting out some clear discrepancies beforehand.

In our longer term testing this has definitely improved, but as with the Blaze, it's still clear we have here is a device far better suited to everyday lifestyle use than for hardcore fitness fans.

Despite the move to VO2 Max, the device isn't up to the rigours of hardcore training or high intensity sessions.

Notifications

The Charge 2 isn't a smartwatch and it's not trying to hide this fact. While you'll get notifications, you can't reply to them or review them on the fitness tracker – they simply disappear.

Call, text and calendar notifications can all be displayed on the Charge 2 but your phone must be connected. Since our initial review, WhatsApp notifications have started working with the Charge 2, but other third-party notifications are still MIA from both iOS and Android for now.

Read next: Which Fitbit should you buy?

When receiving a call or text, the Charge 2 buzzes briefly then shows the phone number (and/or name) of the person calling. Texts show a clipped version if the message is long, and emojis can't be seen at all.

However a later update changed the way notifications appear, with the message now showing ahead of the contact. You'll also now see a + sign indicating you have more than one notification.

Other notifications you'll see include reminders to move, which debuted on the Fitbit Alta. It's the same concept where every hour you'll get a little message telling you to take 250 steps.

Fitbit Charge 2: App

If you've used a Fitbit before than you should be familiar with the app, which hasn't changed much for the Charge 2. You get your usual graphs and dashboard items along with settings for each device that's paired and you can still view leaderboards.

What's new can be found in the Challenges. Fitbit released the 'Adventures' Challenge for its entire lineup so it's not specific to the Charge 2, but we tried it out anyway since it was announced at the same time.

The idea of Adventures is pretty creative and fun. There are different step goals for various Adventure locations – for example, it takes 15,000 steps to 'walk' on the Yosemite Vernal Falls hike. That means every step you're taking at home, work, wherever is then matched up to the hike Fitbit has set up in the app.

You even get to see your steps mapped out with the app telling you how many more steps you need to go. You don't have to complete the whole thing immediately, though the app gives you a daily destination with points to meet based on your seven day step average.

Fitbit has also since launched Adventure Races, which lets you invite up to 30 friends to compete in the Yosemite National Park and New York City Marathon courses.

The step goals you meet on the 'trail' unlock a new panorama image that Fitbit's taken in real life, called 'Landmarks.'

The company noted that these are about the same amount of steps you'd need to take to actually reach the locations in real life.

After reaching one, moving your phone out in front of you will let you pan around the image. There are also 'Treasures' to discover, which are just bits of trivia, little health quizzes and motivation.

Adventure has been enjoyable and really easy to get into since all you need to do is press start. Sometimes you'll forget you've even begun the challenge so it would be nice if you could get notifications on the Charge 2 screen letting you know you have goals to meet.

But aside from that, we like seeing the map's route matching up to the usual steps you take each day. We'd definitely rather be hiking the actual steps in Yosemite, but this is fun too.

Battery

Fitbit says the Charge 2 battery will last up to five days depending on use. This was surprising, since it's the same battery life as the older Charges which had a much smaller screen. In comparison, the Alta HR gets about six days from our testing.



With every notification it's able to receive turned on, for fitness, continuous heart rate, sleep tracking and general daily usage, we've managed to get about six days of life out of the Charge 2. After charging it up for 15-20 minutes, it lasted another six days. Like the Alta battery life, that's better than expected.

It's nice to know that we'll get almost a week's worth of use from the Charge 2, but it'd be even better if there was a battery life indicator on the device itself.

The good news is that this is coming with a new update, currently rolling out. It's been annoying having to check the app when it feels like the information should be available directly on the screen, so we're pleased this is now changing.

Long-term view

We revisited the Fitbit Charge 2 back in December, but since then Fitbit has been padding it out with more updates and we've been living with the tracker to see how much it's improved.

It's still not perfect - HR tracking still falters at high intensity - but the Charge 2 has come on a long way since it first launched.

The biggest since we last visited the Charge 2 regards sleep, as Fitbit has rolled out its Sleep Stages and Insights features to the device, which gives users a more in-depth look at their sleep behaviour while also serving up useful tips to improve it.

We really like that Fitbit has built out the sleep aspect of the Charge 2 without having to refresh the hardware, and it makes the tracker much more capable.

We've also seen some tweaks to the UI to make notifications work better and generally make the Charge 2 feel more intuitive.

We've also seen the arrival of the Fitbit Alta HR since, but until the Fitbit smartwatch touches down later in the year, the Charge 2 is the most well-rounded of the Fitbit flock, and it's come on miles since we first got our hands on it.

We're starting to see new ideas in trackers like the Garmin Vivosmart 3, which uses heart rate variability to measure stress, but the Charge 2 still outpaces many rivals with VO2 Max and deeper sleep tracking.

And while we'd ideally like built-in GPS, the fact you can get it via your smartphone means it still has a leg-up over much of the competition (and its own tracker alternatives).

All things considered, we've bumped up the Charge 2's score by a star. There are still improvements we'd like to see in the Charge 3, but this is the most capable Fitbit tracker you can buy right now.