Adafruit PowerBoost & LiPo Chargers: Portable Power Solutions

Powering portable projects has always been the trickiest part of embedded design. I’ve built countless battery-powered gadgets over the years, and the difference between a reliable power system and a frustrating one usually comes down to the charging and boost converter hardware. That’s where Adafruit’s PowerBoost lineup and LiPo charger modules shine—they solve the real problems that crop up when you’re trying to run 5V electronics from lithium batteries.

This guide covers the entire Adafruit PowerBoost family, standalone LiPo charger boards, and solar charger options. Whether you’re building a portable Raspberry Pi, a wearable project, or an off-grid sensor node, you’ll find the right power solution here.

Understanding the Adafruit PowerBoost Family

The PowerBoost series combines DC-DC boost conversion with battery management in compact packages. All models use the TPS61090 boost converter from Texas Instruments—a synchronous converter with 90%+ efficiency, 2A internal switch, and 700kHz switching frequency that keeps external components small.

PowerBoost Model Comparison

Feature	PowerBoost 500 Basic	PowerBoost 500C	PowerBoost 1000C
Output Current	500mA+ (1A capable)	500mA+ (1A capable)	1000mA+
Output Voltage	5.2V	5.2V	5.2V
Built-in Charger	No	Yes (500mA)	Yes (1000mA)
Load Sharing	No	No	Yes
Input Voltage	1.8V-5.5V	3.0V-4.2V (LiPo)	3.0V-4.2V (LiPo)
Low Battery LED	Yes (3.2V)	Yes (3.2V)	Yes (3.2V)
Enable Pin	Yes	Yes	Yes
LBO Pin	Yes	Yes	Yes
Quiescent Current	5mA enabled, 20µA disabled	5mA enabled, 20µA disabled	5mA enabled, 20µA disabled
Price	~$10	~$15	~$20

The 5.2V output voltage deserves special attention. Adafruit deliberately set this slightly above 5.0V to compensate for voltage drop in USB cables and connectors. This prevents brownouts when powering current-hungry boards like the Raspberry Pi through long cables.

PowerBoost 1000C: The Premium Choice

The PowerBoost 1000C represents the most capable option for demanding portable projects. Its MCP73871 battery management IC provides something the 500C lacks: true load sharing. This means the board automatically switches between USB power and battery power without interrupting your project—essential for UPS (uninterruptible power supply) applications.

PowerBoost 1000C Specifications

Parameter	Value
Boost Converter IC	TPS61090
Charger IC	MCP73871
Max Output Current	1000mA continuous
Peak Current	~2.5A (limited)
Charge Current	1000mA max
Input (USB)	5V via Micro-USB
Battery Input	3.0-4.2V (LiPo/Li-Ion)
Output Voltage	5.2V nominal
Efficiency	90%+ typical
Switching Frequency	700kHz
Board Dimensions	36mm x 22mm

PowerBoost 1000C Pinout Reference

Pin	Function	Description
USB	Charge Input	5V from Micro-USB, charges battery
BAT	Battery	Direct connection to JST battery connector
VS	Load Share Output	~5V when USB connected, battery voltage otherwise
GND	Ground	Common ground for all signals
5V	Boost Output	Regulated 5.2V output
EN	Enable	Pull LOW to disable boost output
LBO	Low Battery Out	Goes LOW when battery below 3.2V

One important note about the PowerBoost 1000C: you must always have a LiPo battery connected. The board can’t operate from USB power alone because it relies on the battery to handle current spikes during boost conversion.

PowerBoost 500C: Compact Charging Solution

The PowerBoost 500C offers integrated charging without the complexity of load sharing. It uses a simpler MicroLipo charger circuit alongside the TPS61090 boost converter. This makes it smaller and cheaper than the 1000C, though with some tradeoffs.

PowerBoost 500C vs 1000C Key Differences

Feature	PowerBoost 500C	PowerBoost 1000C
Charge Rate	500mA	1000mA
Load Sharing	No	Yes
UPS Capability	Limited	Full
iOS Resistors	500mA	1000mA
Simultaneous Charge/Boost	Yes (with drain)	Yes (balanced)

The 500C can charge and boost simultaneously, but if your project draws more than about 300mA continuously, the battery will slowly drain since the 500mA charge rate can’t keep up with the discharge rate through the boost converter. For low-power projects like Arduino-based sensors, this limitation rarely matters.

PowerBoost 500 Basic: Maximum Flexibility

The PowerBoost 500 Basic strips away the charging circuit entirely, leaving just the boost converter. This creates interesting possibilities: you can power it from any source between 1.8V and 5.5V, not just lithium batteries. Two AA alkalines, a pair of NiMH cells, or a single LiPo—all work fine.

PowerBoost 500 Basic Input Options

Power Source	Voltage Range	Typical Output Current
1x LiPo (3.7V nominal)	3.0-4.2V	1000mA+
2x AA Alkaline	2.0-3.2V	750mA+
2x NiMH	2.0-2.8V	750mA+
3x NiMH/Alkaline	3.0-4.8V	1000mA+
2x AA Lithium	2.4-3.6V	750mA+

Without an onboard charger, you’ll need a separate LiPo charger if using lithium batteries. The payoff is flexibility—you can use the Basic with disposable batteries for truly remote deployments where recharging isn’t practical.

Adafruit LiPo Charger Options

Sometimes you don’t need boost conversion at all—your project runs directly from 3.7V, or you’re combining a charger with a different power management solution. Adafruit offers several standalone LiPo charger boards for these situations.

LiPo Charger Comparison

Charger	Charge Rate	Input	Features	Price
Micro Lipo v2	100mA/500mA	USB-A plug	Ultra compact, switch selectable	~$7
Micro Lipo (MicroUSB)	100mA/500mA	Micro-USB	Cable-based charging	~$7
Mini Lipo (USB-C)	100mA/500mA	USB-C	Modern connector	~$8
BQ24074 Solar Charger	500mA/1000mA/1500mA	USB/DC/Solar	Multi-source, MPPT-like	~$15

All these chargers use the MCP73831 or similar ICs that implement proper CC-CV (Constant Current – Constant Voltage) charging profiles. They handle preconditioning for deeply discharged cells, constant-current fast charging, and trickle charging to maintain full capacity without overcharging.

MCP73831 Charging Stages

Stage	Condition	Current	Voltage
Preconditioning	Battery < 3.0V	~10% of max	Rising
Fast Charge (CC)	Battery 3.0-4.2V	Maximum set rate	Rising to 4.2V
Trickle (CV)	Battery at 4.2V	Decreasing	Held at 4.2V
Termination	Current < 10% threshold	Stopped	4.2V

Solar Charger with BQ24074

For off-grid projects, the Adafruit Universal USB/DC/Solar Charger (BQ24074) handles the unique challenges of solar panel input. Regular LiPo charger circuits struggle with solar because panel voltage collapses when you draw too much current—leading to oscillation between charging and not charging.

BQ24074 Solar Charger Specifications

Parameter	Value
Charger IC	BQ24074
Input Sources	USB, DC barrel, Solar panel
Input Voltage Range	5-10V
Charge Rates	500mA, 1000mA, 1500mA (jumper selectable)
Solar Optimization	Input DPM (Dynamic Power Management)
Load Output	Up to 4.4V (load sharing)
Battery Type	3.7V/4.2V LiPo/Li-Ion

The BQ24074 implements Input Dynamic Power Management (Input DPM)—when input voltage drops below about 4.5V, the charger automatically reduces charge current. This prevents the voltage collapse that plagues simpler chargers with solar panels. While not a true MPPT (Maximum Power Point Tracker), it achieves near-identical efficiency without the cost of a buck converter.

Recommended Solar Panel Specifications

Panel Type	Voltage	Notes
6V Panel	6-7V open circuit	Optimal, minimal heat loss
Small 5V Panels	5.5-6V open circuit	May droop too low under load
9V Panels	9-10V open circuit	Works but wastes power as heat
12V+ Panels	>10V	Not recommended, may damage charger

The charger is linear, not switching, so any voltage above the battery voltage plus dropout is dissipated as heat. A 6V panel keeps this loss minimal while providing enough headroom for reliable charging even in partial shade.

Wiring and Assembly Tips

Adding an On/Off Switch to PowerBoost

The PowerBoost boards don’t include power switches, but adding one is straightforward. The Enable (EN) pin controls the boost converter—tie it to ground to turn off the 5V output. Since EN just signals the converter, you can use a tiny slide switch; it carries microamps, not the full load current.

For a 3-pin SPDT switch:

• Connect center pin to EN
• Connect one outer pin to VS (enable)
• Connect other outer pin to GND (disable)

Some slide switches are “make before break” which can briefly short VS to GND during switching. To avoid this, use only EN and GND connections with a 2-pin switch, or cut off the third pin.

Battery Polarity Warning

Third-party LiPo batteries sometimes have JST connectors wired backwards compared to the Adafruit standard. Connecting a reversed-polarity battery will instantly destroy the charger or PowerBoost. Always verify polarity with a multimeter before first connection. Adafruit batteries are wired correctly; others should be checked.

USB Power Supply Requirements

The PowerBoost 1000C at full load plus charging can draw up to 1.8A from the USB port. Many USB ports and cheap adapters can’t deliver this reliably. Use a quality 2A+ USB adapter with thick cables. Voltage droop from thin cables causes erratic behavior—the MCP73871 charger chip won’t function properly if input voltage sags below about 4.5V.

Practical Applications

Portable Raspberry Pi

The PowerBoost 1000C pairs perfectly with Raspberry Pi projects. Connect the 5V output directly to the Pi’s 5V GPIO pins (not through USB for lowest resistance). The load sharing feature means you can keep the Pi running during USB charging—perfect for a portable computer or retro gaming handheld.

Runtime estimation: A 2500mAh battery provides roughly 2-3 hours for a Pi 3/4 depending on peripherals and CPU load.

Arduino Sensor Nodes

For lower-power Arduino projects, the PowerBoost 500C offers the best value. Most Arduino boards draw under 100mA, leaving plenty of margin for sensors and wireless modules. A 1200mAh battery can run a low-power sensor node for 10+ hours of active operation, or weeks in deep sleep mode with periodic wake-ups.

Solar-Powered Weather Station

Combine the BQ24074 solar charger with a 6V panel and 2000mAh+ battery for self-sustaining outdoor projects. The charger’s load output connects directly to your 3.3V microcontroller (add a regulator if needed). During daylight, solar power runs the project and charges the battery; at night, the battery takes over seamlessly.

LiPo Battery Safety Considerations

Lithium batteries demand respect. They store significant energy and can cause fires if mistreated. These practices apply to all LiPo charger applications:

Essential LiPo Safety Rules

Rule	Reason
Never charge unattended	Catch problems before they escalate
Use proper charger	Wrong voltage/current damages cells
Inspect before charging	Swollen/damaged batteries can ignite
Charge on fireproof surface	Contain potential fires
Don’t over-discharge	Below 3.0V causes permanent damage
Store at 3.7-3.85V per cell	Prevents degradation in storage
Keep away from heat	Temperatures above 60°C risk thermal runaway

The Adafruit chargers include proper termination circuits and won’t overcharge batteries, but they can’t protect against physical damage or extremely over-discharged cells. If a battery swells during charging, disconnect immediately and dispose of it properly.

Essential Resources and Downloads

Resource	URL	Description
PowerBoost 1000C Tutorial	learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost	Complete guide with schematics
PowerBoost 500C Tutorial	learn.adafruit.com/adafruit-powerboost-500-plus-charger	Setup and pinout details
BQ24074 Solar Charger Guide	learn.adafruit.com/adafruit-bq24074-universal-usb-dc-solar-charger-breakout	Solar optimization explained
TPS61090 Datasheet	ti.com/product/TPS61090	Boost converter specifications
MCP73871 Datasheet	microchip.com/MCP73871	Load-share charger IC
MCP73831 Datasheet	microchip.com/MCP73831	Basic charger IC
PowerBoost PCB Files	github.com/adafruit/Adafruit-PowerBoost-1000C	Open source hardware
Fritzing Library	github.com/adafruit/Fritzing-Library	Design files for all boards

Frequently Asked Questions

Can I use the PowerBoost 1000C without a battery connected?

No, the PowerBoost 1000C requires a LiPo battery to function. The battery acts as a buffer for current spikes during boost conversion. Without it, the board may oscillate or fail to start. If you need USB-powered-only operation, consider a simple buck/boost converter instead.

What size LiPo battery should I use with the PowerBoost 500C?

Match battery capacity to your charge rate and runtime needs. The 500C charges at 500mA maximum, so batteries under 500mAh charge faster than the standard 1C rate (which can stress smaller cells). For most projects, 1000-2500mAh batteries offer a good balance of runtime and reasonable 1-2 hour charge times.

Can I charge a LiPo battery and power a project simultaneously?

Yes, both the PowerBoost 500C and PowerBoost 1000C support simultaneous charging and boosting. The 1000C handles this better due to its load-sharing circuit—it prioritizes USB power for the load while charging the battery with the remainder. The 500C will slowly drain the battery if your project draws more than about 300mA while charging.

Why does the solar charger recommend 6V panels instead of 5V?

Solar panel voltage drops significantly under load. A “5V” panel might only deliver 4V when charging a battery, which falls below the minimum input voltage for reliable operation. A 6V panel maintains adequate voltage headroom even in partial shade. The BQ24074 solar charger accepts up to 10V input, so 6-7V panels are optimal—higher voltages work but waste power as heat.

How do I monitor battery voltage in my project?

All PowerBoost boards provide the BAT pin, which connects directly to the battery. Read this with an analog input on your microcontroller (through a voltage divider if your ADC reference is 3.3V). The LBO (Low Battery Output) pin provides a digital signal—it goes LOW when battery voltage drops below 3.2V, suitable for triggering a safe shutdown routine.

Choosing the Right Power Solution

Selecting between PowerBoost variants and standalone LiPo charger boards comes down to your project requirements. High-current projects like Raspberry Pi benefit from the PowerBoost 1000C‘s load sharing and 1A charge rate. Simpler Arduino projects work fine with the PowerBoost 500C or even the Basic model with a separate charger.

For solar applications, the BQ24074 charger handles variable panel output gracefully—something that frustrates users who try connecting panels directly to standard LiPo charger boards. The automatic current reduction prevents the charge/collapse oscillation that wastes energy and can stress both panels and batteries.

Whatever your application, these Adafruit power modules deliver reliable, well-documented solutions backed by open-source hardware designs. The pinouts are clearly labeled, the tutorials are thorough, and community support helps when you hit snags. That’s worth a lot when you’re debugging a portable project at midnight and need answers fast.