Key features and specifications

Operates with 1 or 2x 18650 (4.2v) flat-top Lithium cells

  • Battery Protection provided by the board
  • A re-settable fuse protects against discharge between 2 cells
  • Circuit consumes less than 100uA when in stand-by

Accurate Over-Charge (4.2v), Over-Discharge and 6A Over-Current protection

  • Charging is limited to 1A to maximise battery life, trickle charge starts below 3v
  • Batteries not under load whilst charging ensures correct charging cycle completion

Direct soldered connection for high current usage, or standard 5v micro-USB supply

  • Enables seamless transition when external power is removed or enabled
  • LED’s for Charging, Charging complete, and Output ON and error conditions

Provides accurate battery voltage and current monitoring over I2C for software

  • INA219 SW library for measurement configuration and access at address 0x40
  • Shows charging / discharging current flow, use to indicate end of charging
  • Detect presence/absence of external power

ON/OFF Button Interface (external button required)

  • Triggers GPI Interrupt for SW detection of button press (e.g. short press, long press)
  • Choose your own button, easy to connect in, not tied to board location
  • Use for software safe shutdown control, system reset and your own functions
  • Or simply configure the OS to shutdown after n-seconds
  • Automatically disables voltage regulators after shutdown
  • A button press of approx. 7 seconds will pull the Reset (RUN) line low. This can be used in case SW becomes non-responsive, ensures system can easily be restarted

Separate 5V high current port for ancillary devices

  • Internal 500uF power supply capacitance for stable voltage output under load
  • Mounting holes for additional capacitance as needed

Dimensions

  • 78.7 x 56 mm x 29mm (incl. stand-offs and battery holder)
  • 4 Mounting holes designed to fit Raspberry Pi Model A+/B+/2B/3A+/3B+ and Pi 4 (all 40pin header models), and compatible Banana Pi / Orange Pi designs
  • 2 Mounting holes for Pi Zero with 2 landing zones for additional supports

Python Software examples for Battery Monitoring, Safe Shutdown, the Button/RESET interface, and a detailed technical manual (including installation instructions) are available on GitHub. Please take a look at our FAQ for any other questions you may have!

Red Reactor Battery Holder view
Red Reactor Bottom View and Feature Highlights
Red Reactor User Manual - click here
Click the image to view the User Manual

Performance testing

Test Setup
We have a set of extensive test setups which are used to verify all features

  • Tested with Raspberry Pi 4, Pi 3 Model A+ / B+, and Pi Zero
  • Driving a 4 inch SPI touch screen, Fan, USB Hub with Keyboard, Mouse and Webcam
  • Also driving a 5W audio amplifier with stereo speakers

Stand-by Power Consumption
We have measured standby current at a tiny 10.5 micro-Amps

  • That’s 700x lower than other on-the-market products. The Red Reactor will keep your batteries fresh even when the system is in stand-by!

Running extreme CPU stress testing
Using the Raspberry Pi 4 with all the ancillary equipment listed on the left, we also use the Vout port to charge another board, and drive an attached Raspberry Pi Model 3A+ also running a CPU stress test.
This used in excess of 4 Amps from the first board, switching seamlessly between external and battery power.

Production History

The initial design was developed in October 2020, with first boards fully tested by December 2020 using a Pi 4, Pi 3 Model A+ and B+, and a Pi Zero. These were then used extensively in the ReplayRadio project driving a Pi 3A+ together with a touch screen and audio amplifier. The board was updated with a few small tweaks (reducing the ON button press time for a Pi4 to be the same as the Pi3 and Pi Zero, a delayed OFF sequence that now supports re-boots, improved heat dissipation and EMC layout improvements).

We delayed our Kickstarter launch due to Covid and component supply problems, so it was great to be able to run a very successful campaign during autumn 2022. Having shipped to all our backers we are now busy shipping units ordered through our order form! Simply click the Buy Now button to check out the options.

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