Lithium polymer (LiPo) batteries are the lifeblood of many radio-controlled (RC) vehicles, powering everything from high-speed cars to agile airplanes. However, these batteries can be quite expensive, and getting the most out of their lifespan is crucial. In this article, we’ll explore a simple yet very effective method to extend the cycle life of your LiPo batteries by adjusting how you charge them. A video version of this article is at the end of the article.

Understanding LiPo Battery Lifespan

The lifespan of a LiPo battery is typically measured in charge cycles. One charge cycle is the process of charging a battery from 20% to 100% and then discharging it back to 20%. One charge cycle can also be from 70% to 100% state of charge. However, LiPo batteries do not like being charged to their maximum voltage of 4.2V per cell. (Or 4.35V for high voltage variants) This is also true of voltages on the lower end of the range. Prolonged exposure to these maximum voltages can significantly shorten their lifespan.
Here’s one battery that has a much different voltage curve as it actually may not be a true LiPo. Zeee LiPo Battery Load Tests.

The Simple Hack: Charging to a Lower Peak Voltage

The key to extending the cycle life of your LiPo batteries is to avoid charging them to the maximum voltage. Instead, aim to charge your batteries to a slightly lower voltage. Here’s how you can do it:

1. Set Your Charger to a Lower Voltage: Most modern chargers allow you to set the maximum charge voltage. Instead of charging to the full 4.20V per cell, set your charger to terminate the charge at around 4.10V to 4.15V per cell. This small reduction in voltage can have a substantial impact on the lifespan of your battery.
2. Benefits of Lower Voltage Charging:
   • Increased Cycle Life: Charging to 4.10V per cell can effectively double the number of charge cycles your battery can handle. For instance, if your battery would get 200 cycles when charged to 4.2V, charging to 4.10V can extend this to around 400 cycles.
   • Reduced Stress on the Battery: Lower voltage charging reduces the stress on the battery cells, which helps in maintaining their health over a longer period.
3. Performance Trade-Offs: It’s important to note that charging to a lower voltage does come with some performance trade-offs. You may experience a slight reduction in maximum performance. You will also experience a shorter duration of run time as you will be missing out on some capacity of the battery. For example, a battery charged to 4.10V per cell will not provide as much power as one charged to 4.2V. This means your RC vehicle might not reach the same top speeds or run as long on a single charge. However, this trade-off is worth it for the significant increase in battery lifespan if you make this your #1 goal.

Implementing the Cycle Life Hack

To implement this hack, follow these steps:

1. Access Your Charger Settings: Most computerized chargers have a setting that allows you to adjust the maximum charge voltage. Refer to your charger’s manual to find this setting.
2. Set the Desired Voltage: Adjust the maximum charge voltage to between 4.10V and 4.19V per cell. The exact voltage you choose within this range can depend on your preference for balancing battery lifespan and performance.
3. Charge as Usual: Start the charging process as usual. Your charger will automatically stop when the battery reaches the set voltage.

Practical Considerations

When applying this method, consider the following:

• Application: Use this charging method for batteries in vehicles where maximum performance is not critical. For instance, use it in bashing or casual flying sessions rather than a top speed run vehicle.
• Battery Size: If you’re concerned about losing runtime due to the lower charge voltage, consider using a battery with a higher capacity. This way, you can maintain a longer runtime while still benefiting from the increased cycle life.

Conclusion

Maximizing the lifespan of your LiPo batteries doesn’t have to be complicated. By simply charging to a slightly lower voltage, you can significantly extend the number of charge cycles your batteries can handle. While there are some performance trade-offs, the benefits of longer battery life and reduced costs over time make this method highly effective.

https://www.youtube.com/watch?v=ObxcKJ_E-14

Before we dive into this article, I need to address something upfront—we recently tested a Zeee battery pack, and the response was, well, mixed. While Zeee clearly has a strong fan base, many viewers didn’t agree with the results of that test. Some even questioned whether the data truly reflected the battery’s performance. So, after going back to the drawing board (and the budget), I decided to retest a fresh set of batteries to give this another shot.

That brings us to today’s article. When choosing a battery for your RC vehicle, one of the most talked-about specs is the C rating. But what does it actually mean? And how do you know if it’s telling the truth about a battery’s capabilities? In this article, we’ll break down the idea of a “true C rating” by putting the Zeee 5200mAh 120C LiPo pack through a full performance test. Along the way, we’ll explore not just what the numbers say on paper, but how the battery really performs under load—and what that means for you.

What is the C Rating?

The C rating of a battery essentially represents how much current a battery can safely discharge relative to its capacity. For example, a 120C-rated battery with a capacity of 5200mAh can theoretically deliver a peak current of 624A (120 * 5.2). However, the “true C rating” is determined through rigorous testing. We expect the manufacture to do this accurately and market the batteries accordingly and truthfully. Unfortunately this does not happen. Let’s explore further.

The Zeee 5200mAh 120C LiPo Battery: A Quick Overview

This 4S LiPo battery has a nominal voltage of 14.8V. It comes in a durable hard case for protection. It features a balance tap with a convenient plastic cover that makes connecting the battery easier, which is a small but useful detail. What sets this battery apart is its claimed C rating of 120C (624A), which suggests it should be capable of handling high current loads. However, as we’ll see, the true performance can differ.

Testing Methodology

We tested the Zeee battery using three main methods: a 105A load test, a C rating test, and an internal resistance test. Each test focused on a different aspect of the battery’s true C rating.

1. 105A Load Test: In this test, the battery was loaded at a constant 105A to see how it performed under high discharge conditions. The battery’s voltage was monitored as it sagged under load, and the current followed this decrease, which is typical of most batteries as they begin to run out of charge. The goal was to measure how long the battery could maintain high current output before reaching a low voltage cutoff.
2. Ultimate C Rating Test: This test aimed to push the battery to its thermal limits by gradually decreasing the current after each test while monitoring temperature. Current is held constant during the duration of the test. The test was stopped if the temperature exceeded 58°C, which is considered the upper limit for safe operation. Ultimately, the aim is to determine how much current the battery can deliver while maintaining safe operating temperatures.
3. Internal Resistance Test: By measuring the internal resistance of the battery, an estimated C rating can be calculated. A higher internal resistance indicates higher energy losses within the battery, reducing its efficiency and performance under load. This test helps estimate the battery’s true C rating by evaluating how it could behave under realistic conditions.

The Results: Breaking Down the True C Rating

Test 1: 105A Load Test

The 105A test results showed that the Zeee battery performed similar to the last test, with the voltage sagging in a predictable manner as the load increased. The key observation here was the voltage drop and how quickly the battery approached the low voltage cutoff. The test revealed that while the battery could maintain 105A for a short duration, its performance would drop significantly as the voltage sagged. This is important because it highlights that while the battery is rated for a high C value, its practical performance under high loads does not align with the theoretical ratings. In the below image you can see the results of each of the 4 4s 5200mAh Zeee batteries that we tested.

Test 2: Ultimate C Rating Test

In the ultimate C rating test, the results did not improve—in fact, the Zeee batteries once again showed significant underperformance. During an 80A discharge, temperatures rose rapidly, exceeding the safe limit of 58°C. Reducing the load to 70A produced the same result, with temperatures still surpassing the safety threshold. Even at 65A, there was some improvement, but the battery continued to exceed the maximum safe temperature. At 60A, the battery delivered its best performance. However, it still exceeded 58°C in the final seconds—another failure. Based on this, the battery’s effective C rating appears to be just under 12C, with a continuous discharge capability closer to 57–58A. These are some wild results and the lowest values ever tested for a battery greater than 5000mAh.

Test 3: Internal Resistance Test

The internal resistance test offered a final piece of insight into the Zeee battery’s capabilities. Measurements taken across multiple cells revealed relatively high resistance levels—an indicator that the battery struggles to deliver high current efficiently. Averaging the internal resistance across all 8 cells from the two new Zeee packs resulted in a value of 7.55 mΩ. We then used this figure to estimate the battery’s true C rating, which closely aligned with the results from the previous performance tests. You can do the same thing at home using the calculator found on my Patron site which is downloadable if you become a member. Based on internal resistance, the calculated maximum continuous discharge current was 66A—remarkably close to the real-world limit observed during testing, which was just under 60A.

The Takeaway: Why the “True C Rating” Matters

The “true C rating” is crucial for users who want to ensure that their battery can handle the demands of their RC applications. Manufacturers often claim high C ratings for their products, but they sometimes inflate these numbers, which don’t reflect real-world performance. Through testing, we’ve shown that the Zeee 5200mAh 120C battery, while advertised as a 120C pack, realistically performs more like a 60C battery.

If you’re looking for a battery that can deliver high currents over longer periods without overheating, understanding the true C rating is essential. This ensures that you choose a battery that can handle the loads of your RC vehicle without compromising on safety or performance.

By conducting tests like these, RC enthusiasts can make more informed decisions about which batteries to use, ensuring they get the performance they expect from their gear.

Conclusion

The Zeee 5200mAh 120C battery test illustrates an important point: While marketing labels may claim high performance, real-world tests often reveal a different story. The true C rating helps you better understand the limits of your battery, ensuring you get the best performance possible for your RC applications. Whether you’re racing, bashing, or flying, knowing your battery’s true capabilities can make all the difference in achieving optimal performance.