How to buy a 'real' UPS (battery back-up)

Like if this guide is helpful

In the 'good old days', a UPS would keep running until the batteries were exhausted - and this is what you might expect as the 'default' behaviour. However these days that's no longer the case - the typical modern "UPS" is a 'pretender' that is actually DESIGNED to cut the power off after a very short interval 'to protect the batteries' (some call this a 'green function', no doubt in response to the Advertising Department's wish to get onto the Global Warming band-wagon).
Why is this the case ? Well it means they are built with dirt cheap batteries which may be rated at eg 17AHr but will fail when called upon to deliver more than 10% of their rated capacity, rather than the traditional (and a lot more expensive) 'deep cycle' batteries that are capable of delivering at least 90% of their capacity every time.
So the typical (cheap)  modern 'pretend UPS' will only keep running for a few minutes after the mains power is lost, the idea being that this gives their 'clever' software time to 'shut down' your PC 'safely' - so if you want to buy a UPS and use it to run a tablet or some other kit during a real power-cut, you have another thought coming.
These 'pretend UPS' units are variously described as a 'Line Conditioning', 'Line Interactive' or sometimes 'Line Management' UPS - however these names mean little, as do the 'Technical' details (which, for many units, is just some thinly disguised meaningless advertising anyway). Don't expect the seller to know - most of these units are made in China and even when a printed 'manual' exists it will have been translated into Chinglish - and whilst it may have some very nice photo's that often include a 'Settings' window showing a 'Run Time' option box, it's only when you install the actual software that you discover the only value in 'Run Time' option pull down is 5 minutes (or less). Of course some 'management' software is so well written that it allows you to enter any value you like in 'Run Time' .. but  the unit will still shut down after a few minutes anyway.
About the only way to discover if you are gong to spend hundreds of ££'s for a "UPS" unit rated at  multiple kW Hr to power a 100w load only to have it cut off after 5 miniutes is to read the Customer Feedback for that model on Amazon !
The other option is, of course, to 'build your own' with a Charger, some deep cycle (eg Golf Buggy) batteries and an Inverter. Of course that won't include any fancy 'PC shut down' software, but then the idea is that it keeps you kit running until the mains power is restored not shut it down after 5 mins !

Have something to share, create your own guide... Write a guide
Explore more guides