Phone backup battery is made!

Now that the tab welder is working, I was able to make up the little battery pack for power backup of my cordless phone.  After a little thinking about which ones should go up and which down to make the interconnects simple, making the pack from the old discarded Nimh cells went smoothly.

I first hot-melt glued the cells together so I’d have something solid to work on.  The welding of the tabs went without a hitch.  Since I’m cheap as an experiment, and since this pack is only expected to deliver 20mA or so, I cut some of my 1/4″ strip in half lengthwise and used that 1/8″ wide strip.  That worked out fine.  I cleverly arranged for the end connections to be fairly close together.  I welded tabs on, and then soldered to the tabs.  Some more hot-melt as a strain relief, and the pack was functional.

I plugged the pack into the cable I’d left hanging out of the phone and disconnected power to the phone.  I made a quick phone call.  The phone worked with the power removed (an additional valuable feature of this power-outage backup supply for a cordless phone!) and – the driver for the whole project – it remembered the time and date!

All I need to do is insulate the ends (with their shiny newly welded tabs) and then it will be done.  Woo hoo!