Overview
This holder turns two AA cells into a tidy, switchable power pack. The cells sit in a closed black box (67 × 31 × 17 mm), a built-in switch turns the output on and off, and red and black flying leads bring the power out to your circuit — no soldering to battery tabs and no loose cells rolling around the bench.
What comes out of the leads depends on what you put in. Two alkaline AAs give about 3 V, two NiMH rechargeables about 2.4 V, and two lithium primary cells about 3 V with a higher open-circuit voltage when new. That makes this pack a natural fit for low-power 3 V projects: a Raspberry Pi Pico through its VSYS pin, low-voltage sensors and LEDs, or a small boost converter that steps the pack up to 5 V for an Arduino or ESP32.
The holder itself is just contacts, a switch, and wire: it has no regulator, no fuse, and no reverse-polarity protection, and it does not charge batteries. This manual shows how to check polarity and voltage before first use and how to connect the pack safely to each of the common boards.
At a Glance
Specifications
| Parameter | Value |
| Cell format | 2 × AA (alkaline, NiMH, or lithium primary) — not included |
| Cell arrangement | Two cells in series (typical for two-lead holders — confirm with a meter) |
| Output, alkaline | About 3.0 V nominal, a little higher when fresh |
| Output, NiMH rechargeable | About 2.4 V nominal |
| Output, lithium primary | About 3.0 V nominal; up to about 3.6 V open-circuit when new |
| Do not fit | 14500 lithium-ion cells (3.6–3.7 V each, about 7.4 V total) |
| Switch | Built-in on/off switch |
| Leads | Red and black flying leads |
| Body dimensions | 67 × 31 × 17 mm (supplier drawing) |
| Enclosure | Black box with cover |
| Current rating | Not published — best for light loads well under 1 A |
| Protection | None: no fuse, regulator, charging, or reverse-polarity protection |
Wiring Guide
Check the pack before it meets a board. Fit two cells following the + and − marks in each bay, switch on, and measure across the bare lead ends with a multimeter: the red lead should read positive, and the voltage should match two cells in series (about 3 V for alkaline). Only then connect it — reversed or unexpected voltage is the fastest way to lose a board.
Arduino (Through a 5 V Boost Converter)
A 5 V Arduino cannot run from 3 V directly: the pack is below the 5V pin’s level and far below the 7–12 V the VIN input expects. A small boost converter such as the MT3608 bridges the gap.
| From | To | Notes |
|---|---|---|
| Holder red (+) | Boost converter VIN+ | Keep the holder switched off while wiring |
| Holder black (−) | Boost converter VIN− | Common ground |
| Boost converter OUT+ | Arduino 5V pin | Set the output to 5.0 V with a multimeter first |
| Boost converter OUT− | Arduino GND | Common ground |
ESP32 (Through a 5 V Boost Converter)
An ESP32 module needs a steady supply of about 3.0–3.6 V and pulls short bursts of several hundred milliamps when Wi-Fi transmits. Two AAs sag below that under load, so feeding the 3V3 pin directly leads to brownout resets. Boost to 5 V and let the dev board’s regulator do its job.
| From | To | Notes |
|---|---|---|
| Holder red (+) | Boost converter VIN+ | Keep the holder switched off while wiring |
| Holder black (−) | Boost converter VIN− | Common ground |
| Boost converter OUT+ (5.0 V) | ESP32 5V / VIN pin | The onboard regulator makes 3.3 V |
| Boost converter OUT− | ESP32 GND | Common ground |
Raspberry Pi (Not Recommended)
A Raspberry Pi computer needs a stable 5 V supply with amps in reserve. Two AA cells cannot provide that, even through a boost converter.
| Board | Works? | Use Instead |
|---|---|---|
| Raspberry Pi 4 or 5 | No | The official 5 V USB-C supply for your model, or a suitable power bank |
| Raspberry Pi Zero family | No | A 5 V USB supply or power bank |
| Raspberry Pi Pico | Yes | See the Pico tab — it runs happily from this pack |
Raspberry Pi Pico (Direct to VSYS)
The Pico’s VSYS input accepts 1.8 V to 5.5 V, so two AA cells can power it directly — alkaline or NiMH.
| Holder Lead | Pico Pin | Notes |
|---|---|---|
| Red (+) | VSYS (pin 39) | Direct connection for battery-only use |
| Black (−) | GND (pin 38) | Common ground |
| Red (+) through a Schottky diode | VSYS (pin 39) | Use this instead if USB may be plugged in while the pack is connected |
