The Asus ZenFone Max Pro M2 has a tough act to follow. The previous model, the ZenFone Max Pro M1, was a huge hit in India last year, with sales of more than one million units in less than six months.

Unsurprisingly, Asus has not changed the M1's winning formula. The M2 retains its predecessor's key selling points - a massive 5,000mAh battery, stock Android interface and competitive pricing ($349).

The most obvious change is its physical appearance.

Gone is the M1's bland metal backing. The M2 has a glossy and reflective plastic backing that could easily be mistaken for glass.

This glass-like backing makes the phone look more premium, but it is susceptible to fingerprints and other smudges.

Switching to a plastic body has helped Asus reduce the M1's hefty 180g weight by a fraction. But the new model - at 175g - is still heavier than the average smartphone because of its large battery.

The display has also been tweaked. Like many recent smartphones, its screen has narrow bezels with a small notch to accommodate the front camera. There is no option in the settings to hide the notch.

It is a decent IPS LCD screen with good viewing angles, though I had problems using the screen under the sun because it is not bright enough.

Besides the display and the backing, the M2 is physically similar to the previous version. Even the location of the ports (it has a 3.5mm audio jack and a micro-USB port), the power and volume buttons, as well as the SIM slot, remain identical to the M1.

It has a rear fingerprint sensor. Compared with more expensive smartphones, the M2 is a fraction slower at detecting my finger and unlocking the phone. But it is still faster than its face-unlock feature, which is sluggish and occasionally requires a few attempts to work.

Because I have multiple USB-C devices, it would have been convenient if the M2 uses a USB-C port for charging instead of the old-school micro-USB port. The bigger issue here, though, is its slow charging speed (about three hours for a full charge) given its large battery.

Another sign of its budget origin - the M2, like the previous model, supports only the older and slower 802.11n standard, not the prevailing 802.11ac protocol. It should not matter for most users unless they often download large files.

Even affordable smartphones have dual cameras and the M2 is no different - with a secondary depth-sensing camera to enable bokeh, or out-of-focus effect.

The amount of background blur can be adjusted before taking the photo, using the camera app.

This app is clunky and it would sometimes take too long to process the photo. Asus says the M2 uses artificial intelligence to detect scenes such as greenery and food and adjusts the camera accordingly, but this feature does not seem to be available yet.

Photos taken in bright daylight turn out sharp with good colour accuracy. The results are less impressive at night, with plenty of noise and blown-out highlights even when using its night mode.

It is powered by a Qualcomm Snapdragon 660 chip, which is faster than the M1's Snapdragon 636 chip.

This mid-range processor runs the game, PUBG Mobile, smoothly at medium graphics settings. The phone also does not feel overly warm after a gaming session.

Its stock Android 8.1 interface is clean and feels responsive, aided by 6GB of RAM. It does have a few third-party apps, such as Facebook and Instagram, that cannot be entirely removed.

Thanks to its large battery, the M2 can go almost two days without charging. It would end up with about 55 per cent of battery life at the end of a day. In The Straits Times' video-loop battery test, it lasted 10 hours and 50 minutes.

•Verdict: An affordable mid-range smartphone that offers excellent battery stamina and decent performance.