When I got my CE, I was somewhat disappointed to find out that it would not run off of USB power with the battery removed. Additionally, the performance is negatively impacted by having the charger connected, so having the calculator continuously charging is bad in multiple ways. Recently this came up again in a discussion, so I decided to try powering the calculator directly from the contacts intended for the Lithium-ion cell. The Li-ion battery provides 3.7V, so I initially connected the 3.3V supply of an Arduino Uno, but this was not a high enough voltage to power the calculator. I then connected the 5V supply, and the calculator turned on and worked as expected.

Since having the calculator connected with alligator clip jumpers is less-than-ideal, I plan to make a dummy battery and cover that will facilitate powering the calculator directly from a computer or USB charger.



Here is a comparison of power consumption between the CE and SE at default screen brightness:

Code:

This sounds like a great project, jonbush; good luck! Please let me know if it would be useful to have a custom battery cover with space for a USB port 3D printed, and I suspect that geekboy and/or myself would be very happy to assist.

Before you do that, an even more elegant solution would be a replacement battery cover with some circuit mimicking battery presence and allowing existing usb port to power the calculator- not sure if it is possible but someone knowledgeable in such things here should confirm

This would at least avoid bulk of the usb cable etc under the calculator and I would actually worry about 5v going into ports expecting 3.7v -but as i say I don't know those things for sure.

Alternative to my solution above would be reusing the existing battery and cover and adding some switch switching battery off but the mimicking its presence so that usb keeps powering the calculator without constantly charging the battery

I wonder if the existing extra charging ports at the bottom of the calculator may help in finding even better solutions