Overview
The 4x18650 battery shield V8 turns four rechargeable 18650 cells into a portable power station for your projects: a regulated 5V output capable of ~3A peaks, a 3V output for low-voltage loads, USB charging, and built-in cell protection — all on one board with the cell holders included. It's the practical way to unplug an ESP32, Arduino, or Pico project from the wall: mobile robots, field data loggers, camera rigs, sensor nodes, and bench testing during power cuts.
The four cells sit in parallel, so capacity adds up: four 3,000 mAh cells behave like one 12,000 mAh battery. Charge the pack over the shield's USB input, flip the output on, and draw 5V from the USB-A port or the header pins. No wiring is required beyond plugging in your load.
At a Glance
Cells
4x 18650 (parallel)
Protection
Over-charge/discharge
Ports
USB-A out + pin headers
Specifications
| Parameter |
Value |
| Battery Slots |
4x 18650 Li-ion, wired in parallel (1S4P) |
| 5V Output |
Rated ~2.2A continuous, ~3A peak (USB-A port and 5V header pads) |
| 3V Output |
3V / 1A on header pads |
| Charge Input |
USB (micro-USB or Type-C depending on batch), ~600-800 mA charge current |
| Protection |
Over-charge, over-discharge, over-current (built-in IC) |
| Indicators |
Charge / power LEDs |
| Control |
Output switch/button (varies by batch) |
| Cell Type |
Standard flat-top or button-top 18650 (unprotected fit best) |
| Use While Charging |
Supported for light loads (basic pass-through) |
Setup & Power Guide
1. Insert cells — polarity is everything
Match each cell's + end to the + marking in its holder. Because the slots are parallel, one backwards cell short-circuits against the others and can damage the board and cells immediately. Double-check all four before powering anything.
2. Charge the pack
Connect a 5V USB adapter to the shield's charge input. At ~0.6-0.8A shared across four cells, a full charge of high-capacity cells takes many hours (often overnight) — that's normal for this class of board. The LED indicates charge status.
3. Power your project
| Load |
Connect Via |
| Dev board with USB port (ESP32, Arduino, Pico, Pi Zero) |
USB-A output with a short USB cable — simplest and safest |
| Bare 5V loads |
5V + GND header pads (to VIN/5V pin of your board) |
| 3V-class loads (LEDs, small sensors) |
3V + GND header pads |
Warning: Use matched cells — same model, capacity, and age, at similar charge levels — when filling multiple parallel slots. Mixing old and new cells makes them charge/discharge each other and shortens pack life. Quality cells only; recycled laptop pulls of unknown health are a fire risk in any holder.
Note: When powering a dev board through its 5V/VIN pin from the headers, don't simultaneously plug that board's own USB into a computer unless you know its power-OR circuitry — when in doubt, use the shield's USB-A port instead.
Tip: Estimating runtime: pack mAh x 3.7V x 0.85 (converter efficiency) / load watts. Example: 4x3,000 mAh = 44 Wh x 0.85 ≈ 37 Wh; an ESP32 project averaging 0.5 W runs roughly 3 days.
Frequently Asked Questions
Do I need all four cells installed?
No — it runs on one, two, three, or four cells since they're parallel. More cells = more capacity and less voltage sag under load. Whatever you install, keep them matched.
Can it really deliver 3A at 5V?
Treat 3A as peak and ~2.2A as the comfortable continuous rating. Sustained 3A stresses the boost converter and sags tired cells. A Raspberry Pi 4 under load is borderline; ESP32/Arduino/Pico projects are easy territory.
Can I use it while it charges, like a UPS?
Light pass-through use generally works, but the shared ~0.7A charge budget means a hungry load charges slowly or not at all, and cheap pass-through isn't seamless switchover. For genuine UPS behavior, use a dedicated UPS module.
Protected or unprotected cells?
The shield has its own protection IC, and its holders are sized for standard 65 mm cells — so unprotected flat-tops fit best. Longer protected cells (~69 mm) can be a forced fit or not fit at all.
Why does my board reboot when Wi-Fi transmits?
Voltage sag from tired or mismatched cells during current spikes. Fresh matched cells, shorter/thicker output cabling, and a 470-1000 µF capacitor across the dev board's 5V input all help.
How do I know when the pack is empty?
The protection circuit cuts output around 2.5-3V per cell — your project simply loses power. For graceful shutdowns, have your microcontroller watch the pack voltage through a voltage divider into an ADC pin and save state below ~3.3V.
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