Hi,
Why not upgrade the battery to a cheap cellphone battery, like this one:
??
Should be more than enough to fuel the arduboy for days worth of fun!
If not upgrade, why not create an extension pack where these kinds of batteries can be inserted (from the back or so)?
Arduboy was designed to be creditcard sized and as thin as possible to fit easily into your pocket.
Making an extension pack is not really worthwhile. It would be pretty expensive to make and 1000 mAh isn’t that much. It would be more convenient and cheaper to use a powerbank. A single 18650 cell powerbank has rougly a capacity of 2200mAh that’s more than twice the capacity of your suggested battery.
Credit card sized power bank and some double sided tape.
Anything is possible! If you’re using the Arduboy for more than 6 hours between charge that is pretty impressive!
One thing I have thought of in regards to a power bank is maybe if you had a game that detected if it was being charged and gave the user points for charging it up? 
Is it currently possible for the game to detect charging?
You can use the ADC to read the processor supply voltage (Vcc) compared to the internal reference voltage. I won’t be very accurate unless you calibrate it for your particular unit. You would have to experiment to see if you can relate the voltage with whether the battery is charging or discharging.
No, adding a wire isn’t required. You can compare Vcc against the internal reference.
In software? 
Yes. You use Vcc as the ADC reference and then read the 1.1V bandgap using the ADC. Since the bandgap is fixed and stable, you can compute the reference voltage (which is Vcc).
The problem is: Although the bandgap is relatively stable, it’s not very precise. You would probably have to calibrate it on a per unit basis, and store the calibration values in EEPROM, in order to be able to calculate an accurate battery voltage reading.
Is there one out there? I’ll have to look
You don’t really need a battery measuring tool.
Charge them at 4.00-4.20V, and display empty symbol at 3,40V (cutoff is 3.30V).
The curve doesn’t go linear, as the Li/Li-ion voltage curve is more S-curved:
Alternatively, they have 1.5V Lithium AA or AAA batteries. If not equip the device with decent batteries, why not equip it with an extension port, where the batteries would fit in?
This is just going to be DAMN useful (because then I can calculate how many juice my battery have left) and hen do proper charge cycles
Wanna write something like that with me?
Should have bumped into this thread before even using it…
As I said, it may have to be calibrated on a per unit basis.
And what do you plan to do, load a sketch each time you want to check the battery level or build it into each game?
Right plug it into your computer, flash the battery check program onto the Arduboy … wait a while … wonder why the battery always reads 100%?
It probably will be a separate sketch (because it might be too big to fit into any of my games)
I am tinkering around the Presudo-random generator (because it read from PINs)
Speaking of games… @Eried probably didn’t look at my pull request for adding 2 games (of mine) to his collection
It wasn’t like you will kill the Arduboy by just uploading another sketch. (but there is this write limit of 10,000 times)
Maybe we forgot that there is a voltage stabilizer…
Maybe you forgot that when you plug the arduboy in, it will start charging. If you are close enough to a computer to flash the Arduboy to see how much battery is left, why not leave it in for a short while to charge the battery?
It just seems like a really pointless exercise.
Or maybe we DO have something tiny that we can put inside our void loop() in anything we created (that take up 0 RAM and 1% ROM)
And then things start to make sense…
Like cellphone-you don’t need to quit the current software to see the battery presentage (although on some models you might need to temporarily “quit”)
