Dalius decided to upgrade his graphing calculator, a TI-86. He has been complaining that the calculator has been draining the batteries too fast.

Normally it runs on four 1.5 V AAA batteries (6V total). It drains four Ni-MH rechargeable batteries (4.8 V) even faster because of lower voltage.

Dalius took 3.6V Li-ion battery, an USB Li-ion charger and a step-up module from Ebay and was able to fit everything into the battery bay.