How to connect lipo batteries in series?

Lithium Polymer (LiPo) batteries are widely used in RC vehicles, drones, robotics, and portable electronics due to their high energy density and lightweight design.

Series connection increases the total voltage while keeping the capacity (mAh) unchanged, but it demands strict adherence to safety rules to prevent fires, explosions, or battery damage. Below is a step-by-step guide to help you master this process safely and effectively.

What Is Series Connection for LiPo Batteries

Voltage Addition: When LiPo batteries are connected in series, the total voltage equals the sum of the individual battery voltages. Most LiPo batteries are "single-cell" ,3.7V nominal voltage; 4.2V fully charged.

Capacity Remains Unchanged: Unlike parallel connection (which increases capacity), series connection does not affect the total mAh. If you connect two 2000mAh LiPo batteries in series, the total capacity remains 2000mAh.

Key Requirement: All batteries in the series must be identical—same brand, model, capacity, voltage, and age. Mismatched batteries will cause uneven charging/discharging, leading to overheating, swelling, or permanent damage.

How to Connect LiPo Batteries in Series

Step 1: Prepare the Batteries

Check Battery Condition: Inspect each battery for damage—swelling, leaking, or torn insulation are red flags. Do NOT use damaged batteries.

Charge Batteries to Equal SOC: Use a LiPo balance charger to charge all batteries to the same SOC (e.g., 80%). This prevents voltage differences that can cause current flow between batteries during connection.

Disconnect Existing Loads: If the batteries are connected to a device (e.g., a drone), disconnect the device first to avoid short circuits during wiring.

Step 2: Identify Positive (+) and Negative (-) Poles

Every LiPo battery has two main wires:

Red Wire: Positive (+) terminal.

Black Wire: Negative (-) terminal.

Step 3: Connect the Batteries in Series

The core rule of series connection is: Connect the negative (-) terminal of one battery to the positive (+) terminal of the next battery.

For three or more batteries, repeat this process: Connect Battery 2’s black (-) wire to Battery 3’s red (+) wire, and so on.

Step 4: Create the "Input" and "Output" Terminals

After connecting the batteries in series, you’ll need two wires to connect the series pack to your device:

Total Positive Terminal: Use the red (+) wire of the first battery in the series.

Total Negative Terminal: Use the black (-) wire of the last battery in the series.

Strip the ends of these two wires, solder on XT60/XT90 connectors

Step 5: Test the Series Pack with a Multimeter

Before using the series pack, verify its voltage to ensure the connection is correct:

If the voltage is lower than expected, the connection is loose or broken—recheck the soldered joints. If the voltage is zero or the multimeter shows an error, you may have reversed the poles

Common Mistakes to Avoid

Using Mismatched Batteries: Mixing batteries with different capacities or ages causes one battery to overwork.

Poor Soldering: Cold solder joints (loose, dull-looking) create resistance, which generates heat and can melt the insulation. Always ensure solder joints are smooth and tight.

Ignoring Balance Charging: Even in series, LiPo batteries need balance charging to ensure each cell charges to the same voltage. Unbalanced cells will degrade faster and pose a safety risk.

Skipping the Multimeter Test: Assuming the connection is correct without testing can lead to device damage or battery failure. Always verify the voltage before use.

Conclusion

Connecting LiPo batteries in series is a practical way to boost voltage for high-power devices, but it requires precision and safety awareness.

By using identical batteries, following the step-by-step wiring process, and adhering to safety rules, you can create a reliable series pack that powers your projects effectively.

Whether you’re powering a hobby project or an industrial device, following this guide will help you get the most out of your HV LiPo batteries while keeping safety a top priority. If you have questions about specific battery models or chargers, feel free to reach out to our team: levin@cebattery.com, we’re here to help!

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