[01010111]

Hello! This looks like it's very nearly the perfect music player for me, however, I would really like to get away from dedicated internal batteries (even though they are convenient). Where it runs on a 3.7v battery, it seems like it could potentially be run on rechargeable AA/AAA batteries. They normally output 1.2v, so, 3 of those batteries gets you very close to the 3.7v internal battery.

I am very much a novice when it comes to these kinds of mods, but I am tempted to take on this project if it's possible to modify the battery charging stuff via firmware. My background is coding in python, basic soldering skills, and some experience with tinkercad. Is this a pie-in-the-sky dream, or is this in the realm of possibility?

I'll likely pick this up either way, but if it's at all possible to mod it to run on AA/AAA batteries then this is a no brainer.

---

It looks like it's not managed via firmware, but it looks like the controller board would accept that voltage? It looks like the low battery voltage indicator might not work correctly though
https://www.mouser.com/ds/2/268/22090a-52174.pdf

I don't think I'd trust it to charge my AA/AAA batteries, but that should theoretically be okay? I'd probably just remove the batteries when connecting to a computer.

[emily]

One problem you may run into here is that 3.7V is a *nominal* voltage; these batteries are usually charged up to 4.something volts. Tangara considers 4.2V to be "full" and 3.5V to be "critical". You'd have an easier time starting with another shape of lithium battery that also outputs around 3.7 nominal volts, maybe an 18650 or similar?

An alternative route you could take, depending on *why* you're doing this (do you just want the battery to be easily swappable?), is to make an alternative back half for the case that's easier to remove so you can just unplug the battery and plug in a different one.

[jacqueline]

Hi! You'll want to refer to the datasheet for the charge controller Tangara uses: https://ww1.microchip.com/downloads/en/D...02090E.pdf

Of note:
- Try not to exceed around 4V2 on the Vbat pin; it's unclear what the actual max voltage here is from a quick skim (maybe 5 volts?) but certainly keeping within the LiPo's expected range should be safe
- Below a Vbat of 3V3/3V4ish you'll lose regulation. Much below that and you'll start getting brownouts. This is not that big a deal for our LiPo bc by that voltage we've used most of the useful capacity anyway, but it might be different for whatever cells you're using
- You can use the NTC pin to disable charging complete as if there was a temperature fault. You probably want to do this, rather than trying to charge non-LiPo/Lion cells with the built in charge controller.

In general though I really would caution against having too much fun with the battery part of your device without having a good understanding of how battery systems in general work; the worst case with these things tends to be "you start a fire", which ideally we want to avoid.

[01010111]

Based on what I understand, it sounds like it "should" theoretically work, but I might have more limited battery life. It also might not drain the batteries enough to get a full charge cycle. Where all the testing and design recommendations for that controller are between 3v and 4.2v, using three 1.2v AA batteries should be within the charge it needs to operate. I was hoping to get up to at least a 4.5v tolerance so I could just use any random AA batteries I can find, but that sounds like a bad idea.

Disabling the charging completely is probably the wise thing to do in this application. I'll do some testing with the batteries I'm using. They claim to be able to maintain a more consistent voltage than traditional alkaline batteries, which should be good for this application.