The eternal and everlasting TI-86 graphing calculator is a great calculator: first made back in 1997, and still used by students today. But its battery life kinda sucks. So [Dalius] decided to bring his TI-86 into the 21st century.
If you’re not familiar, the TI-86 runs off of 4 AAA batteries, preferably alkaline. If you use rechargeable NiMH they don’t last very long since they have a lower voltage per cell, which means it ends up draining even faster to a voltage level the TI-86 cannot operate at.
Luckily, this means if you get rid of the batteries, there is some decent real estate available inside the calculator. [Dalius] was able to fit a 3.6V 900mAh lithium ion battery, a step-up module, and a USB Li-ion charger all into the compartment, complete with a micro USB port sticking out the side. Isn’t technological progress wonderful? Now you can recharge it just like your cellphone.
For other fun calculator projects, check out our recent Hacklet dedicated to all things calculator!