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This toaster-looking gadget boosts your phone’s battery in seconds
(www.theverge.com)
This is a most excellent place for technology news and articles.
90's, definitely.
Which 80's models mobiles are you thinking of, exactly?
The Motorola DynaTAC. They had a big Ni-Cd battery that is also the back of the case. You would need often need two batteries to get through a whole day, so they were made to be easily swapped.