close-circle
Close

2 cell power bank

A project log for R8-D8 - a distant relative of R2-D2

a 12cm radius, 3d printed R2-D2 with some motors, servos and blinky stuff that follows lines, persons or just drives around via bluetooth

davedarko 06/18/2017 at 11:435 Comments

next maker faire this thing needs to roll around and move the head and stuff. SO I needed a power bank. I wanted it to be a 2 cell battery, that is also balance charged. https://learn.adafruit.com/multi-cell-lipo-charging/fast-multi-cell-charger my schematics are a bit different, but the general concept is the same. Micro USB is all the rage to charge stuff, but mounting can be quite a challenge, so I went with a USB B plug. I've used two classic TP4056 modules with onboard protection (TE420) and a voltmeter. Bye bye weekend, but totally worth it!

Discussions

Radomir Dopieralski wrote 06/18/2017 at 19:49 point

I like the simple hack for charging them with 1S lipo chargers. Finding chips that can charge 2S lipos is a so much of a challenge, that I simple switched to 1S lipos everywhere.

  Are you sure? yes | no

davedarko wrote 06/18/2017 at 20:35 point

one of the batteries seems to charge very slowly and gets very warm. it might just be a dead battery, since I'm recycling etc. but I need to check the schematics again, to be sure. I'm at 7.7V for the last 2-3 hours. meh. 

  Are you sure? yes | no

Ted Yapo wrote 06/18/2017 at 16:56 point

What is the capacity / which cells did you use?

  Are you sure? yes | no

davedarko wrote 06/18/2017 at 17:20 point

each have 2150mAh - Coslight LiPo CA603696. They're from a netbook that I had, I think it was the msi "macbook air" clone. 

  Are you sure? yes | no

davedarko wrote 06/19/2017 at 15:11 point

seems like they're too big for the TP4056, I thought it checks the voltage to know when to stop, but it seems more likely that it thinks that my batteries are 1000mAh instead of 2150mAh. weird. weid. weird. it stops charging at 3.8V

  Are you sure? yes | no