Disposable batteries seem so 1990s. Sure, it’s nice to be able to spend a couple of bucks at the drugstore and get a flashlight or TV remote back in the game, but when the device is a daily driver, rechargeable batteries sure seem to make more financial sense. Unfortunately, what makes sense to the end user doesn’t always make sense to manufacturers, so rolling your own rechargeable calculator battery pack might be your best option.
This slick hack comes to us from [Magmabow], who uses a Casio FXCG50 calculator, a known battery hog. With regular use, it goes through a set of four alkaline AA batteries every couple of months, which adds up quickly. In search of a visually clean build, [Magmabow] based the build around the biggest LiPo pillow-pack he could find that would fit inside the empty battery compartment, and planned to tap into the calculator’s existing USB port for charging. A custom PCB provides charging control and boosts the nominal 3.7-volt output of the battery to the 5-ish volts the calculator wants to see. The PCB design is quite clever; it spans across the battery compartment, with its output feeding directly into the spring contacts normally used for the AAs. A 3D-printed insert keeps the LiPo and the PCB in place inside the battery compartment.
Almost no modifications to the calculator are needed, other than a couple of bodge wires to connect the battery pack to the calculator’s USB port. The downside is that the calculator’s battery status indicator won’t work anymore since the controller will just shut the 5-volt output down when the LiPo is discharged. It seems like there might be a simple fix for that, but implementing it on such a small PCB could be quite a challenge, in which case a calculator with a little more room to work with might be nice.
Or just get a ti nspire cx or cas that already has a USB rechargeable battery
Arm CPU, and like 64mb of ram etc
Yes it can run emulator
Yes it will run doom
Yes it can atleast run android 2.3
Or just get a regular smartphone and RDP into your home PC with 24-core CPU and 64 GB of RAM which is running Matlab.
But that ping and latency tho….
If you’re buying new yes. But the best calculator is the one you already have.
Alternatively, just use NiMH batteries.
There are Lipo-1.5 V AAs with USB-C charge.
I use them for my mouse and love them.
And AAAs and 9Vs as well. Even with less capacity than NiMH the seem to last longer, as they say longer above the voltage cutoff than NiMH.
Nah, LSD NiMH cells are the best for any device you aren’t using constantly or doesn’t draw much because they’ll hold charge for ages.
They are not suitable for devices without a low voltage cutout. The calculator I have will drain the batteries to almost nothing in 6 months just trying to retain the memory contents while it’s switched off. That will ruin your rechargeable batteries.
The 1.5V rechargeable lithium batteries should have a built in low voltage cutoff. They do have a high self discharge rate because of the voltage converter though.
I’m not sure how well the 1.5 lithium batteries are built, but technically there are some amazingly low power buck regulators nowadays. Under 1 µA quiescent current.
My Tuya Thermo/Hydro/Bluetooth sending thingy runs happily with two of those AA-Lions for over a year.
Single AA-Cell mouse runs about 4 to 5 months.
I’m fine with that.
I totally like the USB-C charging. Simplifies my desktop to only one USB-C cable, no more charger device flying around and collecting dust.
Yeah, this is the way to go. Tons of people still think rechargeables are as bad as they were in the 90s, but they’re great now. I honestly prefer them over built-in lithium batteries for most small applications.
Or buy an alkaline battery regeneration device.
I have Ti84 that i modded with 5v USB C Charger + 3.7v Battery. Works great.
Ironically, I use lipo cells out of discarded douche flutes for this purpose :D
How is that ironic?
IMO it would have been smarter to include a USB-C charge port and 3D print a replacement for the battery cover. This would make installation much easier as nothing needs to be soldered to the calculator’s PCB, and it would make it easier to sell this as a kit.
certainly would have been easier. when i do a hack like this i always agonize over the difficulty of soldering onto the existing connector, finding the right spot on the board, that sort of thing. but then in the rare occasions when i’ve done it, it’s just a little tedium and uncertainty, and then it’s over…i’ve got my two wires coming from the board and i never think about it again. my ‘ridiculously dodgy’ solder job seems to hold up just fine. so for a one-off hack, i think either decision is fine. but yeah as a kit you’d rather not ask every purchaser to embark on that voyage
It’s a neat little board he’s designed but I dread to think what the battery life is like on this, he’s replaced a bunch of alkaline AA cells which usually have a capacity of 2AH upwards for a capacity of around 12-18WH with a single, 1000mAH 3.7V Li-Ion with a ~4WH capacity.
To make that worse still, he’s boosting it up to 5.4V which definitely won’t be 100% efficient so that’ll shorten the life even further and he’s sacrificed the battery status indicator so he’s got no warning of the cell being cut off for over discharge.
He’d have been better off just carrying a spare pack of AA cells or if he absolutely had to have Li-Ion cells, he could have just used two (or maybe even three) 14500 Li-Ion cells in the original AA cell slots and a buck/boost regulator in the fourth slot to bring it to 6V.
OR, you could use rechargeable AA/AAA batteries. My remotes and mice have long since been “converted”…
Any recent similar modifications for HP calculataors?