Battery for handheld devices

T

thecomfychair

Active member
I'm building a Teensy-based handheld portable device (specifically an MP3/music player), and would love to hear people's opinions on the best way to power it.

Requirements:
  • Enough current to supply a T4.1 using the SD card slot, plus a TFT screen and external audio codec, for a least 10hrs minimum
  • Easy and safe to recharge on the go, probably via USB
  • Safe to travel with including using on international flights
  • Small enough to fit in a handheld device (ruling out most big powerbanks)
Nice to haves:
  • Battery charge level status, or at least a low-battery indicator
  • Pass-through charging ie charge while continuing to use the device
  • USB power (not direct DC) to avoid needing to cut jumpers on T4.1 for external battery - preserves ability to connect to PC for potential code changes, and possibly accessing SD card via USB for file transfer.
  • On/off switch (although this is probably unnecessary; I need to investigate how to power down the T4.1 properly)

Options I've considered so far:​


1. Flat power bank with integrated micro-USB cable, such as this one from Vida-IT:
1764761360430.jpeg

But I'm concerned about evolving rules around using powerbanks on planes, so this might not be a viable long-term solution.
Power bank models and form-factors keep changing too which would require hardware redesign if the battery needed to be replaced.

2. Rechargeable NiCd AA/AAA batteries with Adafruit's Powerboost 500c (1A versions weren't available from my local site at the time)
1764761629772.jpeg

I tried this but didn't seem to provide enough current to run the full setup (this was some time ago). Would also require taking a battery charger with me, although you can get USB AA/AAA battery chargers. Ideally would use AAAs to keep size down.


The obvious solution is to stick some sort of LiPo in it but those scare me slightly, and scare airlines and airport security more. I really would like to be able to travel with this without fear of losing it at Security or it melting a hole in my pocket mid-journey.

Are there any other solutions I'm missing?
Or a better way to implement the above ideas?
 
I've used the <PowerBoost 1000C Charger> from Adafruit successfully in several of my portable projects (hopefully, you will be able to get & use it in the future). This module will take care of boosting the output voltage from the LIPO battery to a clean 5.2VDC that the Teensy will just love. It'll also take care of managing the charge on the LIPO, & can even act as a 5VDC pass-thru when the USB input is connected & the LIPO is charging and/or fully charged. Charging from any USB phone charger is very convenient & the 1000C includes an signal to control the ON/OFF state of the output power (when the signal is gronded, turns things off). I use this <Adafruit cable adapter> to connect from the case of my projects directly to the microUSB port on the Teensy (also carrying USB data for programming, MIDI, & monitor, etc.), and I break the 5VDC line, connecting the panel side to the input of the 1000C, and the Teensy side to the output of the 1000C, with ground commonly connected to everything. One consideration is that the Low Battery Out (LBO) signal from the 1000C is a 5-volt level signal, so you'll need to add some way to drop this to a safe level (3.3VDC or less). I use cascaded BJT transistors as a level-shifter in all of my projects for this, & the simple circuit works very well. In my biggest project so far, my TeensyMIDIPolySynth (TMPS) (which also draws the most current, as it runs a 7" RA8875 display, one T4.1 & one T4.0, one Teensy Audio Shield & the USB host port on the T4.1 for connecting external MIDI keyboards, sequencers, etc.), I make use of the <Adafruit 2500maH LiPo battery> & I regularly get more than 12-hours of continuous operation on a single charge. This 1000C+2500maH LiPo combo is a real winner in most of my portable projects !! My TMPS is compact enough that I carry it onto the plane in my backpack. So far, I've not had any questions about it as it passes thru any security scanners, international or domestic.

Hope that helps . . .

Mark J Culross
KD5RXT
 
If you want to use batteries with the common 2 pin JST plug, I've used the Lipo Rider Plus from Seeed. You plug the battery into the JST plug. You get 5 volt, 2.4 amp power out of a USB A plug, and you can recharge the battery via a USB C plug using 5 volt and 2 amp charging:
If you are using a Teensy 4.0 (4.1 needs an adjustment due to being larger than the Teensy 4.0), you can use the Adafruit Teensy feather adapter. It charges the battery in the background if you have the Teensy plugged into USB. It charges the battery at 500 mAh:
Lets see, the largest JST battery that Adafruit sells is the 3.7 volt, 10,050 mAh battery (10 Ah):
I have bought this charger and battery output device for a single 18650 battery. It provides USB A output, along with solder connections for 5v and 3.3v outputs. It charges via micro-USB (I haven't actually used it at present):
 
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