The oldest bag phones i remember had a fuse in the lighter plug, circia
1993, all other electronics was in the "bag". The first cell phones that i remember having anything electronic beyond a fuse / resistor / some diodes was about 1998 Motorola / Nextel car adapters with some widget in the lighter plug.-- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
Here's another lead, someone describing making and using an external battery pack (4xAA alkaline cells) to charge a LiIon battery in a mini-disc player:
And another example, this one from 4/17/2000:
Best, James Arthur
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