Powering a Portable Consumer Medical Device
The client sold a small device which ran on batteries (4 X "AAA" Ni-MH rechargeable) or could be run from an AC line adaptor. The insertion of the AC adaptor into the device automatically disconnected the electronics of the device from the batteries. It was necessary to remove the four "AAA" batteries from the device and charge them in an external charger. Some people using the device had difficulty removing and properly re-installing the batteries after charging (the batteries were difficult to extract). Additionally, the device required that the batteries be inserted in a very specific positive/negative configuration which consumers often overlooked.
The solution to the problem involved the following three steps:
I began by swapping two wires in the AC power adaptor receptacle. This change resulted in the receptacle being disconnected from the device electronics and connected, instead, to the internal battery circuit when the AC adapter plug was inserted.
The battery compartment was altered by the removal of three slip-out bars which connected the four individual batteries in series.
A four "AAA" battery pack with welded internal connectors was designed to fit into the device’s battery compartment. This battery pack can be charged within the device via the AC adapter so that the battery does not have to be removed.