The HTC One X comes with an 1800mAh battery that's unfortunately sealed within the chassis of the phone - meaning no chance of being able to swap it out in the event of a power-outage on the go.

The original power problems with our first review sample stemmed from a problem with the GPS chip - basically a server problem meant the phone was constantly asking for positioning data, and that ate the battery faster than a whippet in a mutton factory (or something).

Since then, there have been a few updates to the software, adding tweaks to make elements like auto-brightness a little dimmer and generally improve battery life.

HTC One X review

When we test any mobile phone we obviously run it through many tests and try to work out what the main selling points of it will be. With the HTC One X, we found there to be so many plus points that we really had to run the device hard to test it all out, leading to a quicker battery run-through than usual.

We gave the One X a power user test to start: we downloaded three movies from HTC Watch, played a number of Tegra 3 compatible games, watched said movies and went for a run with the GPS turned on - plus messed around with most of the features.

This is very atypical usage - but we believe that if a phone has something worth doing, then the battery should hold up. Under these conditions, the handset lasted until 7PM before conking out completely - although the power saver mode for the last 15% worked pretty well to hold on.

The reason for this is the screen - it's sucking a huge amount of power, because the graphical processing power needed to fire all those new pixels is really taxing the device. It's also a new type of technology for the firm, and it seems that HTC hasn't quite worked out how to optimise it yet.

Playing powerful games predictably drained a lot of power too - for instance, playing RipTide for 15 minutes caused the One X to heat up quite a bit and drained 4-5% of the overall battery power, which is more than a little worrying.

HTC One X review

Calling seemed to take the same level of power as well, as did movie watching for extended periods. If you're not going to use the phone very much, then you'll likely sail through a day on a single charge, but given that this is an awesome powerhouse of a device we're disappointed that the battery is the one thing that's really letting it down.

We're a pretty fair bunch here, so we decided to put together a little video testing the HTC One X against the HTC One S, Nokia Lumia 800, iPhone 4S and the Samsung Galaxy S2 running Gingerbread (note - the iPhone is running a movie using FlexPlayer, as we couldn't get our test movie to play through the standard video app):

As you can see, the HTC One X didn't do terribly well in the test (which saw screens at maximum brightness, all phones on Wi-Fi with an identical 3G SIM card in and running push email, Facebook and Twitter updates) - 41% in 90 mins is a big old drop.

It's interesting to note that the HTC One S did so much better, given it's got the same operating system and many of the same processes - plus it doesn't pack the Tegra 3 CPU with the power saving core.

In short, it's an easy one to work out: the combination of that large HD screen, with the multitude of pixels needing power to work, and the Tegra 3 processor are sucking the life out of the battery at a fairly accelerated rate.

You've got two choices: use the One X sparingly (such as not turning the screen on too much, keeping app frivolity to a minimum) and you'll get two days' usage out of the phone. It's really rather good on standby.

But use the phone for many internet browsing sessions, regular photography, movie watching or game playing (you know, all the things the One X is awesome for) and you'll definitely need a charger in your bag for the multiple times you'll be losing juice.

UPDATE: We've been using the HTC One X for a while now, and with the new firmware updates there is a slight improvement. It's not enough to say it's up to average use, but there's definitely less to to grumble about.

Connections

The HTC One X comes jam packed with every top-end connection we can think of - be it Wi-Fi 802.11n (the fastest kind) to Bluetooth 4.0, it's all present and correct under the hood.

The addition of Bluetooth 4.0 is particularly exciting, as it means the One X will be able to take advantage of a number of cool accessories coming onto the market soon.

This means personal area networks, allowing easy connection to a range of sensors and devices within proximity, will be easy to achieve and will make the One X the centre of your connected world. If you want to find out more, check out our 'What is Bluetooth?' feature that explains it all.

There's also a first from the Taiwanese brand in the shape of NFC, brought in to take advantage of Google's Android Beam service. Right now it's a pretty rudimentary offering - all you can realistically do is tap the One X against another Ice Cream Sandwich-enabled phone (with an NFC chip inside, obviously) and share things like Map directions, YouTube videos and contact details.

You have to activate the service on both devices and then tap to make the connection, and in truth it's a little cumbersome and not as cool as this video would have you believe. However, once NFC becomes mainstream in the next year, you'll be able to take advantage of contactless payments and a wider gamut of connectivity options, so stay tuned for that.

We've already mentioned the DLNA software that's built right into the HTC One X - for those of you unfamiliar with the term, this means you can connect the device up to a internet-enabled Smart TV or computer and stream content from your phone easily across.

The fact it's within the media player is a really nice touch, as it means you don't need to jump out to another application as you have to with the Samsung Galaxy S2 at times.

HTC One X review

In terms of wired connections, the HTC One X will also let you connect up to a TV using a MHL lead, which is sadly not supplied in the box. This mini HDMI connection uses the same microUSB port that powers your phone, which makes it really easy to mirror the content on the tiny HD screen on a much larger one.