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Choose the battery and solar panel from the energy use of your complete ESP32 build—not from a generic current figure or a panel’s advertised wattage. Measure the device across its real workload, decide how long it must run without sun, match the battery to a compatible solar charger, and size the panel for the site’s least-sunny conditions.
What size battery and solar panel do you need?
There is no defensible universal battery capacity or panel wattage for an ESP32 project. The right sizes depend on the exact board and peripherals, how often it wakes and transmits, how long it must run without sun, and the installation’s sunlight, shade, orientation, and temperature.
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Use two separate checks: average energy use determines battery capacity and solar harvest, while peak current determines whether the battery and regulator can handle startup and radio bursts. A system can have plenty of stored energy yet still reset if its power path cannot supply a short current peak.
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Measure every operating state
Measure current in the assembled device during boot, computation, sensor operation, Wi-Fi or Bluetooth activity, and sleep. Include the regulator, development-board LEDs and USB interface, sensors, pull resistors, and any always-on voltage divider or indicator. The current drawn by the ESP32 chip alone does not represent the complete build.
#1 Best Overall
- Solar-powered : With 5W solar panel built in battery slot.Can accommodate up to 4 18650 batteries.(Not included Battery)
- Easy to install : No chargers, outlets, or hassle, this solar-powered Meshtastic node ensures reliable off-grid communication whenever you need it.
- 360 ° adjustable bracket: The 360 ° rotating bracket ensures the maximum sunlight angle and allows for the installation of solar panels anywhere, fully absorbing sunlight and keeping your solar panels fully charged at all times.
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- Suitable for: IoT enthusiasts who enjoy DIY.
For a repeating workload, calculate average current by weighting each state by the time spent in it: Iavg = (I1 × t1 + I2 × t2 + …) / (t1 + t2 + …). Multiply by the supply voltage and the hours in a day to estimate daily energy in watt-hours: Wh/day = V × Iavg × 24. If the load voltage differs from the battery voltage, use watt-hours as the common unit and allow for conversion losses.
Use vendor figures only as context
Espressif’s ESP-IDF v5.2 power-consumption example reports 8.14 μA in deep sleep, about 23.88 mA in the demonstrated active measurement, and 6.37 mW for its example cycle. These are observations for that example, not guaranteed values for another module, firmware, radio schedule, or development board.
Rank #2
- ACEBOTT Smart Camera Solar Robot Car Kit: An educational kit for STEM beginners (kids) based on ESP32, built with omnidirectional Mecanum wheels, using high-quality metal gear servos, equipped with HD cameras, solar panels and ultrasonic infrared sensors, and programmed with Arduino, designed to help them learn how to build and program a fully functional robot, improve logical thinking and electromechanical skills, suitable for experimental projects or school training for teenagers and adults.
- Solar Science Fun: This smart robot building kit is equipped with a solar panel to support solar energy to charge the battery (Note: The kit does not include batteries, thank you for your understanding). Children explore renewable energy and energy-saving solutions by building a smart car powered by solar energy! At the same time, solar energy can be converted into battery capacity to achieve long-term endurance of the car and reduce the frequency of your charging.
- HD Video Real-time Transmission: This camera robot car is equipped with a high-definition camera, which can achieve real-time HD video transmission and real-time FPV experience through the WiFi hotspot of the ESP32 development board, allowing you to watch videos in real time on your smartphone. (Note: This kit does not contain batteries, please understand.)
- All-round control: The Robot Car Kit is equipped with advanced 6cm omnidirectional Mecanum wheels (omnidirectional wheels or lion wheels), which can easily achieve 360° movement in any direction, support multiple movement modes (forward, sideways, diagonal, rotation), and can complete difficult actions such as left and right drifting, and easily cross any position, including narrow bends, narrow alleys, and intricate roads. Built-in Wi-Fi and Bluetooth, enabling web page and APP control.
- Intelligent Perception: Accurate multi-way cruise allows the cart to easily plan the path and realize autonomous navigation; multi-direction ultrasonic obstacle avoidance allows flexible response in the face of obstacles; the new follow mode allows the car to always follow your steps. Allows children to control this car through the IR remote control and App, make you enjoy the fun and convenience of intelligent technology. Simply master all the actions of the car with just one touch.
Deep sleep shuts down the digital core and wireless peripherals; waking restarts the application. Include the energy for booting and reconnecting in the workload budget. A project that must remain connected or respond quickly may consume much more than a sensor that wakes briefly to report a reading.
Check supply capability separately
Espressif’s ESP32 hardware design guidance recommends a 3.3 V single supply with output current of at least 500 mA. This is a supply-design capability recommendation, not a claim that every ESP32 continuously draws 500 mA. Check the documentation for your exact board before choosing its input voltage; do not assume an arbitrary board connector accepts 3.3 V.
Rank #3
- Complete Outdoor Meshtastic Solution: Specifically designed for the ESP32 LoRa V4 (with L76K GNSS module and OLED display), this 5W solar enclosure offers a ready-to-deploy, weatherproof solution for your long-range wireless projects
- Solar Power with High Efficiency: Featuring a 24.3% high-efficiency monocrystalline solar panel, this kit continuously harvests energy to provide a stable 3.7V/5W output, significantly extending your device's runtime
- Extreme Weather Proof: Built with a rugged IP67 waterproof enclosure and tempered glass face, this kit is fearless of extreme weather. It can protects your sensitive LoRa V4 development baord from rain, dust, and harsh outdoor conditions, ensuring long-term stability for agricultural monitoring or disaster relief scenarios
- Strong Signal: Equipped with a dedicated 915MHz single LoRa antenna, optimizing signal strength and range for both LoRa meshtastic communication and device configuration. This professional setup enhances the performance of your Meshtastic repeater or node
- Flexible Battery System: Supports a flexible 1-4 x 18650 battery configuration (batteries not included), allowing you to customize capacity for days of extra-long battery life. Combined with Type-C charging backup, it offers unparalleled power flexibility for ESP32 LoRa development board, and other Meshcore devices
How to size the battery for no-sun autonomy
First decide how many hours or days the device must operate through poor or absent sunlight. Multiply its measured daily energy use by the required autonomy to find the energy the battery must provide to the load. Then account for regulator losses and other always-on loads, and leave a reserve appropriate to the climate and service expectations.
Do not assume all the capacity printed on a battery is usable. The usable amount depends on the allowed depth of discharge, cell-maker limits, discharge rate, temperature, aging, and the conversion path. Compare candidates by usable watt-hours under the expected conditions, rather than comparing milliamp-hour labels alone—especially when battery and regulated-load voltages differ.
Rank #4
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- 🏞️【Small Size for Flexible Builds】Each 89.5 x 89.5 mm small solar panel fits compact crafts, garden light repairs, model cars, and project boxes where space is limited.
- 🏞️【Built for Low-Power Solar Experiments】These solar cells are suitable for learning series or parallel layouts, comparing output, and building simple 5V solar panel projects.
- 🏞️【Match Before You Connect】Designed for low-current devices, each 1W solar panel should be used with the proper circuit, polarity, and sunlight conditions for better project results.
- Voltage range: Check nominal and full-to-empty voltage, including the number of cells in series, against the regulator’s input range.
- Discharge capability: Confirm the battery can supply both the continuous load and short peak current demands.
- Protection and temperature: Check overcharge, overdischarge, and overcurrent protection where required, along with operating and charging temperature limits.
- Practical constraints: Consider cycle life, size, mass, and enclosure or outdoor-environment requirements.
How to choose the battery charger and panel
Match the charger to the battery
Choose the charger and battery as a pair. Their chemistry, cell count, charge voltage and profile, charge current, temperature provisions, and protection must agree. “Lithium” is not a single charging profile: do not assume a charger for one lithium chemistry is suitable for another.
The Tool Desk
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Best Value
- 【High Conversion Rate】This 20W solar panel with monocrystalline A+ solar cell has an excellent cell efficiency of 21%-30%. Designed to charge and maintain 12V rechargeable batteries like LiFePO₄, Lithium Ion, AGM, SLA, GEL, EFB, MF, etc. Keep batteries in charged for trailer, tractor, truck, boat, motorcycle, RV, car, lawn mower, water pump, gate opener, electric fence, etc
- 【Built to Last】 Low-iron tempered glass surface and corrosion-resistant aluminum frame, make this solar panel 100% waterproof and rustproof, and provide the prolonged lifespan up to 25 years. This 12V solar panel can withstand all weather conditions such as sandstorm, strong wind, thunderstorm, blizzard, hail, etc. It can withstand up to 2400Pa wind pressure and 5400Pa snow load
- 【Smart MPPT Controller】The charging efficiency of this upgraded 10A controller is 30% higher than other controllers on the market. Its intelligent three-stage charging design effectively prevents the battery from overcharging, over-voltage and short circuit. It takes no power from the battery. You will clearly know the charging status of the battery through the two indicator lights on the controller
- 【360° Adjustable Bracket & Plug-and-Play Installation】Comes with a fully 360° angle adjustable mounting bracket, which allows you to adjust the solar panel to the optimal sun-facing angle for maximum solar energy absorption and higher charging efficiency. Pre-drilled mounting holes and matched screws greatly simplify the installation process, no complicated tools or professional skills are required. All cable connections support plug-and-play, enabling quick and effortless installation and disassembly for both indoor and outdoor scenarios.
- 【Complete Accessories & Reliable After-Sales Service】Our SOLPERK Solar Panel kit includes 1*20W solar panel, 1*smart MPPT charge controller, 1*adjustable mounting bracket, 1*alligator clip, 1*O-ring and a full set of mounting accessories to meet your diverse installation and use needs. We offer 1-year professional after-sales service and lifetime technical support, with 7×24-hour online customer service to respond to your questions and solve problems within 24 hours, bringing you a worry-free shopping and using experience.
For examples of different charger capabilities, Texas Instruments’ BQ25798 documentation describes a buck-boost charger for one to four cells with solar input and MPPT; its listed capability includes charging up to 5 A, subject to device and implementation limits. TI’s BQ25185 documentation describes a one-cell charger with solar-input and power-path features, listed for up to 1 A. These are chip-level examples, not recommendations for every project; check the datasheet and the details of the implemented circuit.
Size the panel for the site, not its label
Estimate the energy the panel can realistically deliver in the low-sun season that matters for your project. Account for location, weather, seasonal changes, orientation, shading, installation, and conversion losses. Nominal peak watts alone do not establish daily energy yield.
Compare a panel’s operating voltage and current, as well as its open-circuit voltage, with the charger’s input limits and MPPT range. Also consider mounting area, shade exposure, and durability in the intended environment. A panel that appears large enough by its watt rating may still be a poor match if its voltage falls outside the charger’s useful range.
Analog Devices describes the LT8491 as a solar-capable buck-boost charger with automatic MPPT. This illustrates an available design feature; it does not determine the correct panel size for an unspecified load or site.
Do not connect a panel directly to a rechargeable battery unless the complete design includes a suitable charge controller for that battery chemistry. A generic USB charger should not be assumed to manage a solar input or provide the correct battery charge profile.
Quick Recap
How to verify the assembled system
- Measure the final build: Record its representative operating cycle, including startup, radio activity, peripherals, and sleep; separately note peak current.
- Set the no-sun requirement: Convert daily load energy and chosen autonomy into required usable battery energy, allowing for losses and reserve.
- Pair battery and charger: Verify chemistry, series-cell count, charging profile, current, temperature provisions, and protection.
- Match panel and charger: Check the panel’s electrical operating range against the charger input and MPPT or regulation range, then estimate harvest for the site’s relevant low-sun period.
- Test worst cases: In the final enclosure and installation position, check behavior at low battery, in weak or changing sun, during radio bursts, and when charging and load operation occur together.
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