Don't buy a universal charger for your laptop
Don't buy a universal charger for your laptop, it may end up damaging your laptop, so that it does not charge again. Instead have a spare original-brand charger that you store separately. If you are travelling, pack it e.g. in a different bag so you don't lose it at the same time as the charger you're using.
Update 2016-07-08: I now have an OEM charger and the flashing of the keyboard backlight has stopped, and charging seems to work. Last night, with the universal charger, it both flashed and refused to charge which made the OS shut down the laptop. However with the new OEM charger, no flashing and it seems to charge just fine. It could have been as simple as the universal charger not having enough juice to drive the laptop and charge it, when the battery is close to empty. In that case there was maybe no risk for damaging the laptop. However the OEM charger is only rated at 3.42A and the T'nB universal charger at 4.7A, so the universal charger should have no problem. Still something goes wrong.
Longer story
Last week I lost a charger for my Acer laptop at the Vivatech fair in Paris. Totally my own fault, just forgot it in the wall socket and it was never retrieved. I still needed my laptop so what to do on a Sunday in Paris? I went to fnac and got me a universal charger, that should work with Acer. Before buying it I searched the Internet for info on universal chargers and to my dismay I read that they have a history of destroying laptops, such as the charging circuitry part.
I bought one anyway and at first it seemed fine.
But I thought about it, and remembered that I did buy a universal charger for my previous laptop too, a Dell. And that worked fine. I had to change the battery shortly afterwards because the computer did not run without the power cable plugged in. So I bought a new battery. That did not work either. Oh my! I realised that it is quite likely that it was the universal power charger that put my previous laptop out of commission.
With my current laptop, I have noticed that the backlight of the keyboard has started flasing in pulses and the battery does not charge. An original charger should arrive tomorrow. I hope I have not destroyed one more laptop...