Maximizing LiPo Battery Cycle Life

Introduction: Maximizing LiPo Battery Lifespan

In this blog, we are going to examine a simple technique to maximize the lifespan of a battery pack by increasing the number of charge cycles achievable in a lithium-based battery. If you are like me, there are some sacrifices to be made, and it can be challenging for individuals like myself who want to optimize battery performance, particularly in terms of runtime.

Now, let’s get into the details. Essentially, the focus of this blog is on working with charge cycles, and the way to achieve extended cycles is by not fully charging our battery packs to 4.20 volts (for regular lithium polymer batteries) or 4.35 volts (for high-voltage batteries).

The Dangers of LiPo Battery Maximum Voltage

We already know that if we charge a battery to 4.20 volts and store it at this voltage, we risk damaging a regular lithium polymer battery pack. Batteries do not thrive at their maximum voltage, and we are concerned with maximizing their lifespan. What batteries prefer is to be closer to the storage voltage of a lithium polymer battery, which is the key point we’ll focus on. The key takeaway is that batteries do not perform well when they are at either extreme of the voltage range; we will focus specifically on the high end of this range today. As for the low-voltage side, we will exclude that from the discussion here.

Maintaining LiPo Battery Minimum Charge Levels

What we want to ensure is that we always maintain at least 15 percent state of charge in the battery pack, with 20 percent being more ideal. We will not let the charge go below this level for the purposes of our discussion. This state of charge corresponds to the voltage levels shown on the chart. 

Managing Charge Cycles with a Computerized Charger

Now, regarding charge cycles, if you have a computerized charger, the process becomes significantly easier. The goal is to stop charging before reaching the peak voltage for a lithium polymer battery, which is 4.20 volts for regular batteries or 4.35 volts for high-voltage variants. Many modern chargers allow you to set a specific voltage to which the battery will charge, automatically stopping at that point. This is the simplest way to manage the charge process.

For this method, my recommendation is to set the maximum charge voltage between 4.10 volts and 4.19 volts.

Trade-offs Between Capacity, Performance, and Cycle Life of LiPo Battery

If you prefer, you can set it below 4.10 volts. However, this introduces a trade-off between battery capacity, performance, and cycle count. Below, I’ll provide a formula for calculating the cycle life of a battery pack based on these settings.

Charging to 4.10 volts as the maximum voltage will result in a cycle life equivalent to 0.5 cycles, where a full cycle ranges from 15 to 20 percent charge up to 100 percent. If you reduce the voltage to 4.10 volts, you can refer to the chart to see the capacity and state of charge your battery will hold. Essentially, you’ll be sacrificing some capacity, meaning you won’t get as much runtime, which may be a downside for some. However, you could mitigate this by purchasing a larger capacity battery pack in the future.

Performance Trade-offs Above 4.10 Volts

The second downside is that performance above 4.10 to 4.20 volts per cell will also be limited. This performance loss means your motor will not reach as high an RPM, limiting the potential top speed of your radio control vehicle. For me, I don’t mind sacrificing this when using my vehicles for casual bashing or flying a radio-controlled airplane, as I’m not focused on maximizing performance or runtime in those cases. This method, however, will be ideal for extending the lifespan of my radio-controlled vehicles, especially the batteries themselves. 

Not only do I plan to use this technique for my radio control equipment, but I am also adopting it for other electronic devices like my cell phones and laptops.

Choosing the Right LiPo Battery Charge Voltage for Cycle Life

You don’t have to stick to the 4.10 volts threshold; you can select any voltage within the recommended range. For example, if you choose 4.15 volts, your cycle life will equate to about 0.71 cycles.

Let’s put this in perspective: if you choose to charge only to 4.10 volts, it’s like using 0.5 charge cycles, essentially doubling the lifespan of your battery in terms of charge cycles. A well-maintained lithium polymer battery pack can typically last between 200 to 500 cycles. If you are diligent about proper care—such as keeping the battery at a reasonable temperature, avoiding excessive power draw, and charging at rates between 1C and 2C—you can maximize the cycle count. Conversely, if you abuse the battery, you may see less than 200 cycles.

How to Double the Lifespan of Your Battery

Let’s say that you get 200 cycles from a pack, and you charge it to 4.10 volts every time. By using this technique, you could effectively double the lifespan, meaning you would get 400 cycles. For a high-quality battery that is well-maintained, you could potentially get up to 500 cycles. By applying this method, you could see as many as 1,000 cycles from a top-tier battery.

This is a substantial increase in battery life. If you prefer more performance and higher runtime and are willing to charge to 4.15 volts, you will achieve about 770 cycles, as mentioned earlier. 

Conclusion: Maximizing LiPo Battery Life for Cost-Effectiveness

To summarize, the key takeaway is that by using this method to limit the voltage, we can significantly extend the life of our battery packs. Since batteries are expensive, maximizing their lifespan is a valuable strategy. If you don’t mind sacrificing some runtime or performance, this approach can make a noticeable difference. If you want to avoid sacrificing capacity, you can always opt for a larger battery pack, as long as it fits within the physical constraints of your device and doesn’t add too much weight.

As I mentioned earlier, this is an easy technique that we can all implement, provided we’re willing to make a few sacrifices in performance for the benefit of longevity.

Check out the full video here