Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Hey gang!
Building this was such a fun project! I love it, but I want to lower the profile, and reduce battery waste. I was digging through my stuff, and I found a replacement battery for an ipod nano 3. It's 3.7V (within voltage range), and 370 mAh, and about the size of an NFC sticker! Awesome! I got inspired by John Park's Atari controller video https://www.youtube.com/watch?v=h8Sy8gepqk4&list=PLjF7R1fz_OOVvPjQU_KXsLPVB0pG_kdxW, and wanted to wire up something similar for my TV-B-Gone.

IMG_3075.JPG (37.6 KiB) Viewed 754 times

So here's my question:
The TV-B-Gone's got two power points: positive and negative. If my battery's got a white cable - I'm assuming it's ground - where would I put that for the TV-B-Gone? i.e. Where's ground on the TV-B-Gone? If it doesn't have ground, why not? With only 3.7V, could I *gasp* ignore the ground on the ipod battery? Is there any good resource for the do's and don'ts of powering home-brew stuff with a lipo battery? How do I incorporate the USB Micro-B breakout?

All of this is down-right inspiring. This is a very special and beautiful type of fun.

Thanks so much for all your help and suggestions!

in_finem

Posts: 4
Joined: Sun Dec 03, 2017 10:29 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

If my battery's got a white cable - I'm assuming it's ground - where would I put that for the TV-B-Gone?

Don't assume. If the terminals are not marked, ,measure the battery with a multimeter to make sure which terminal is positive and which is negative.
The negative battery terminal goes to the point marked "-" on the TV-B-Gone. The positive battery terminal should connect to the point marked "+".

All the parts on the TV-B-Gone should be able to handle the increased voltage. The TV-B-Gone should work well with a 3.7v LiPo.

Posts: 69809
Joined: Sat Feb 07, 2009 10:11 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Thanks for the quick response! I've validated via multimeter that red's positive and black's negative, but how would I approach the ground problem? If I wanted to add a USB charging breakout, how could I? How does one ground a portable device so it can charge with something like a USB adapter? Thanks again for all the help!

in_finem

Posts: 4
Joined: Sun Dec 03, 2017 10:29 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Simply connect the MicroLiPo charger to the battery according the the instructions and wire the TV-B-Gone in parallel. All the negatives go to negative and all the positives go to positive.

Posts: 69809
Joined: Sat Feb 07, 2009 10:11 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Awesome! Thanks so much for the help!

in_finem

Posts: 4
Joined: Sun Dec 03, 2017 10:29 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

No problem. Happy hacking! :)

Posts: 69809
Joined: Sat Feb 07, 2009 10:11 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Alright! Any time I get help, I think it's important to provide an update. I've included pics of the semi-final result. I haven't secured anything beyond the charging port - I want to give it a field test first. Shoutout to adafruit_support_bill: thanks for taking the time to help out a novice! I'm very happy with the result!

I swapped the AA batteries for a gen-3 ipod nano's battery pack to slim down the design and make it a little less conspicuous.
IMG_3081.JPG (38.64 KiB) Viewed 610 times

Here's a view of the charging port opposite from the LEDs.
IMG_3082.JPG (29.96 KiB) Viewed 610 times

Cables are a little nasty, but on the plus side, it looks like I'm grabbing a mint while hitting the killswitch, it keeps running with a closed lid, and the debug LED stays hidden!
IMG_3083.JPG (39.57 KiB) Viewed 610 times

in_finem

Posts: 4
Joined: Sun Dec 03, 2017 10:29 am

Re: Upgrading from 2 AAs to 3.7V 370mAh lipo battery

Nice looking stealth TVBG build. Thanks for the follow-up!