Boombox conversion

Problem:

D cells are expensive and the device shuts off no longer playing music after only a few hours. Likely the electrical engineer didn't set the device's cutoff voltage to an appropriate level...ie. 0.8v per cell. I observed the cells were at 1.2v when the boombox stops playing indicating that capacity is being thrown away!!!

So....

D cells: 10 in series @ 1.5v = 15v

AC input: 18v

Lithium ion: 4 in series @ 4.2v = 16.8v

Thus, four of my many free lithium ion batteries do the trick + an aluminium spacer.

I salvaged these cells from "dead" laptop batteries (1 or 2 out of every 6 cells is typically dead and the rest are usually just fine)

The stock setup is to use 10 D cells in series all packed in two columns of 5.

A wire on the bottom and two pieces of cheap pipe insulation did the trick.

Now time to make a REAL switch! I measured a 50mA drainage current from the cells flowing through likely some kind of solid state switch. Ie. batteries will die inside the device even when it is turned off!!! So I solved this problem with a switch on the back.

Problem solved!!! Hurray!!!