Cell Count (1S / 2S / 3S)

The single most important match. A 1S charger tops a cell to 4.2V; a 2S charger to 8.4V; 3S to 12.6V. Never charge a multi-cell pack on a single-cell board. For 2+ cells in series, use a 2S charger (TP5100) or a balance charger (iMAX B6).

Charge Current

Charge a cell at roughly 0.5–1C. A 1000mAh cell likes ~0.5–1A; a tiny 150mAh wearable cell needs a low 100–150mA. Too much current cooks small cells; too little means slow charging. Pick a module whose current suits your battery size.

Built-in Protection

Bare cells (18650, pouch) need over-charge, over-discharge, over-current and short-circuit protection. Buy the “with protection” TP4056 (DW01+FS8205), or use a cell that already has a protection PCB. Protected boards are worth every penny.

Charge Only vs Charge + Boost

A plain charger outputs the raw 3.0–4.2V cell voltage. To run a 5V device (or make a power bank) you need a boost converter. Charge-plus-boost boards and battery shields combine both, giving a stable 5V while charging.

Input Type & Load Sharing

USB-C is the modern default; solar and DC jacks suit off-grid builds. If your project runs while charging, look for load sharing (like the bq24074) so the input powers the load directly and the battery isn’t constantly cycling.

Where the TP4056 stops at one cell, the TP5100 keeps going. This switch-mode buck charger handles both single-cell (4.2V) and 2-cell series (8.4V) packs at up to 2A, taking a wide 5–18V DC input. That makes it the go-to for 2S 18650 packs, small e-bike/tool packs and higher-capacity builds that a 1A linear charger would take all day to fill. Being a buck converter it runs far cooler than a linear charger at 2A, and it includes input over-current/under-voltage, over-temperature, reverse-battery and short-circuit protection.

For multi-cell RC packs, a bare charger board won’t cut it — you need balancing, and the SKYRC iMAX B6AC V2 is the classic choice. It charges and balances 1–6S LiPo/LiHV/Li-ion/LiFe packs (plus NiMH/NiCd and Pb) at up to 6A/50W, keeping every cell within millivolts of the others for safety and longevity. The “AC” V2 has the power supply built in, so unlike the DC-only B6 you just plug it into the wall. A backlit LCD walks you through charge, discharge, storage and balance modes with per-cell voltage readouts. It’s overkill for a single 18650, but essential for drone, car and airplane packs.

Small cells hate being charged too fast, and that’s exactly where the SparkFun Adjustable LiPo Charger shines. Built around the MCP73831, it lets you dial the charge current from 15mA up to 500mA with onboard switches — so a delicate 100mAh wearable cell gets a gentle 50mA while a bigger cell can take the full 500mA. It accepts a battery via JST, PTH pins or an onboard 2450 coin-cell holder, and powers from micro-USB or input pins. It’s a quality, US-designed board with clear documentation — ideal when you want control rather than a fixed 1A.

When space is the enemy — think keychains, badges and tiny wearables — the Adafruit Micro-Lipo is the smallest tidy charger around at just 30×12.5mm. It defaults to a safe 100mA (great for the smallest cells) and flips to 500mA with a slide switch when you’re charging a bigger battery. Plug in via micro-USB, connect the cell to the JST port, and the red/green LEDs tell you charging vs. done. It runs a proper three-stage CC/CV charge and comes assembled with a JST cable. It’s single-purpose and low-current, but nothing beats it for slipping a charger into a cramped project.

A plain TP4056 charges a cell but can’t power a 5V device — this board fixes that by pairing the TP4056 charger with an integrated DC boost converter that lifts the cell’s 3.7V up to a steady 5V output. That makes it the fastest route to a DIY power bank or a 5V-powered Arduino/ESP project running off a single 18650: charge over USB, draw regulated 5V out, with charge/discharge and reverse-polarity protection built in. LEDs show charging and full. It’s not the highest-current option, but for “charge a cell and get 5V out of one little board,” it’s exactly right.

For a self-contained solar node, the DFRobot Solar Power Manager 5V is a tidy, purpose-built board. It uses a CN3165 with a constant-voltage MPPT algorithm to squeeze maximum charge from a 5V panel, topping a 3.7V cell at up to 900mA from solar or USB. Unlike a bare charger, it also provides a switchable, regulated 5V 1A output to run your microcontroller, with full over-charge/over-discharge/over-current, reverse and output protection. It even ships with a heatsink and standoffs. If you’re building a solar-powered weather station or outdoor sensor, this is a cleaner solution than stitching a TP4056 to a boost board.

Powering a Raspberry Pi from batteries safely means charging and running the board at the same time — and switching to battery the instant mains drops without rebooting. The Waveshare UPS Module 3S does exactly that: it charges a 3-cell (3S) Li-ion pack while delivering a stiff 5V at up to 5A to your Pi, and seamlessly switches to battery on power loss. It packs multi-cell protection (over-charge/discharge, over-current, short-circuit, reverse) plus balance charging, so a Pi 4/5 stays up through outages. For always-on Pi projects — NAS, cameras, home servers — it’s the reliable choice.

Part charger, part power supply, the Dual 18650 Battery Shield V8 is the easiest way to run an ESP32, ESP8266, Arduino or Pi Zero from cells. Drop two 18650s into the holders, charge them over micro-USB, and draw a regulated 5V (up to 3A) and 3V from the onboard USB-A port and header pins. Two cells in parallel means longer runtime, and the header layout plugs straight into breadboards. It won’t fast-charge (600–800mA input) and it’s a parallel holder, not a balancer, but as a grab-and-go battery base for maker projects it’s superb value.

Charging one 3.7V cell?

Get the TP4056 Type-C (with protection) — cheap, reliable and endlessly documented. It’s the right answer for 90% of single-cell projects.

Going solar or always-on?

Choose the Adafruit bq24074 for USB/DC/solar input with load sharing, or the DFRobot Solar Manager 5V for a built-in regulated 5V rail.

Charging a 2-cell pack?

Use the TP5100 for fast 1S/2S charging at up to 2A. For RC packs of 3–6 cells that need balancing, step up to the iMAX B6AC V2.

Need 5V out / a power bank?

Pick the TP4056 + Boost board for a single-cell 5V rail, or the Dual 18650 Shield V8 to power dev boards from two cells.

Backing up a Raspberry Pi?

The Waveshare UPS Module 3S charges while powering the Pi at 5V/5A and switches to battery instantly on an outage.

Tiny or wearable build?

The Adafruit Micro-Lipo squeezes into cramped spaces, and the SparkFun Adjustable lets you dial a gentle current for small cells.