I'm trying to work out a sensible powering solution for a wearable system I'm prototyping.
In a nutshell I will have at least two Arduino Nano 33 BLE (datasheet here: https://docs.arduino.cc/static/8386f6e2dbb41f3377e97835c61737db/ABX00030-datasheet.pdf) sending accelerometer data pretty continuously for about an hour at a time. Each will likely be worn on the back of a glove or on a wrist strap. This will be used in performance, and I would like if possible for the battery solution to be relatively inconspicuous and unobtrusive. In addition, because of the needs of performance, I would like to be able to swap batteries before a show.
Right now I'm thinking that the easiest, but not best, solution would be to find small and relatively flat USB power banks (possibly under clothing) and tun USB leads to the units. Not very elegant and possibly bulky.
I was thinking of using LiPo 3.7v batteries and attach small detachable connectors, but I'm reading conflicting opinions. Would that work?
I would imagine that many people have similar needs and have found reasonable solutions. Does anyone have any good suggestions or leads for me?
I like lipo batteries for little portable projects.
You can get them in a very wide variety of shapes, sizes and capacities.
I would use 3.7 1s cells for a 3.3 volt system.
For a 5 volt system my recommendation would be to use a 2s lipo, nominal 7.4 volts, and a step-down or "buck" regulator to give a solid 5 volts for your electronics.
Pololu has a number of these regulators, which I think are best bought from reputable sources, and even then I would spec it conservatively, like to handle 1.5 to 2x your expected load.
Stepping down has always worked better for me.
Do the charging as a separate matter, just charge up some packs and swap them in at the time of need.
Do the back of the envelope calculations to select the capacity of the lipo.
If you take good care of the batteries they can last many cycles. Do and don't all the stuff you are supposed to do or not do with the lipo chemistry!
You might want to dive a bit deep into the pros and cons of lipos, see
The Adafruit Feather series with radios would be an alternative. They have a built in LiPo charger and battery connector, and together with a small, flat LiPo cell, you have a very compact, self contained unit.
With careful programming and use of sleep or low power modes, it should be no problem to have one send accelerometer data for an hour.
Experiment with a few possibilities before settling on a final design.
Thank you. That's not really an option at this time; for one thing I already have four Arduino Nano 33 BLE, and for another, from what I see the Feather series does not have a built-in accelerometer unit. I appreciate the suggestion and will keep the option in mind for future projects.
