I have developed a robust, powerful and feature rich battery power supply board for the Raspberry Pi which I believe will work equally well with the Banana Pi family of boards (e.g. M3/M4), therefore I hope you don’t mind if I provide some information about it.
We are in the pre-launch phase for our Kickstarter campaign at https://www.kickstarter.com/projects/pascal-h/the-red-reactor-when-power-really-matters . We designed this board as part of creating a portable internet radio and found that existing boards did not provide all the features we needed, or could not reliably supply enough current and steady voltage for the whole system when dealing with peaky demands from the Pi, display, amplifier etc.
Whilst a simple power bank might seem like the obvious solution, they typically fail to either deliver enough power (so you have under-voltage issues causing crashes), can’t provide power whilst being charged (or if they do, causing the battery charging to be permanently on thus reducing battery life), don’t give you access to battery voltage for a safe shutdown, don’t have adequate voltage regulation (which will cause crashes when heavily loaded - as they’re designed for charging batteries, not match peaky power demands), won’t restart unless the load is removed first, and don’t have a way of connecting your own external power button nor read the charging status in software.
The Red Reactor board delivers a very stable 5.1v, with an I2C interface for battery voltage and current for safe shutdown on low battery or when you detect that the external supply has failed (uses 3v3 from the Pi for this), and drives a GPIO to provide the ON button state information with a separate open drain pull down interface for a long-press RESET function. We will be providing one version with pogo-pins to sit directly underneath the Pi, and a version of the board where you can easily wire these connections, and use your own ON button which can also be used for other functions in your software (short press, long press etc) and/or drive it from an RTC alarm.
The circuit design ensures that the 18650 batteries are not under load whilst being charged, allowing the charging cycle to complete accurately, whilst the board only consumes 10uA when off (compared to some designs with CPU’s that consume many mA’s monitoring the ON button!), ensuring maximum battery life. But at the same time, our extreme testing shows a super steady 5.1v output when delivering over 4 Amps, where we used 1 board driving a Pi4, display, USB hub with keyboard, mouse, webcam, and at the same time it was charging the battery of another board connected to a Pi3, also with a display and both running a heavy graphics test case.
If you would like more information and register to be notified when the campaign goes live, please check out https://www.theredreactor.com for details, including pictures and a video of the extreme testing. We’d love to get your support to achieve our goal and also benefit the Banana Pi community! Of course, feel free to ask questions too. Thank you!