The cheapo 650VA APC BACK-UPS I have was rated at 5.4 minutes at full load (650W).
So even if it only has 10% of capacity it should cover 5 minutes at 50W. (My requirements are to cover ~150W for a few seconds at most.)
Given the comments from above I'd qualify my "anything really" to be "anything from scan.co.uk really" as I'd trust all of the brands they stock as reliable and not some random shit that will self combust.
The cheapo 650VA APC BACK-UPS I have was rated at 5.4 minutes at full load (650W).
So even if it only has 10% of capacity it should cover 5 minutes at 50W. (My requirements are to cover ~150W for a few seconds at most.)
Given the comments from above I'd qualify my "anything really" to be "anything from scan.co.uk really" as I'd trust all of the brands they stock as reliable and not some random shit that will self combust.