APC Universal Notebook Battery 70

The UNB sits between a laptop’s mains adapter and the laptop – something that’s achieved with a long, stiff three-way cable. One end of the cable plugs into the UNB, the other two plug into the mains adapter and the laptop via the appropriate power tip adaptor. The arrangement is a little ungainly and the three-way cable needs to be tied neatly together to stop it getting tangled, but it does at least mean that the UNB will work with any laptop power socket position.

The UNB charges when connected to the laptop mains adapter, but the laptop doesn’t need to be plugged in at the same time. When away from the mains, the laptop draws power from the UNB first, then from its internal battery – so you can put the UNB away once it’s been drained. The only catch is that the laptop thinks that it’s still running on mains power when plugged into the UNB, so you’ll need to manually activate the appropriate power profile to eke the most out of it.

Our test laptop with an Intel Core Duo low-voltage U2500 processor lasted for two hours and 34 minutes when running a set of application benchmarks on battery power. When plugged into the UNB, it ran lasted for five hours and 25 minutes – an additional two hours and 51 minutes. Just over double the battery life is good, but not great – but bear in mind that our application benchmarks work the laptop much harder than an ordinary user might and you can add an hour to both scores for typical daily use.

So if you're looking to extend your laptop's battery life and want a flexible extra battery, the UNB is certainly worth considering. It doesn't cost much more than a typical laptop battery and the provision of an on-board USB port means that it can recharge other mobile devices too.