A charging cycle is a fundamental concept in the world of rechargeable batteries, and yet we find that it's often misunderstood.
It's not just about plugging in your device and watching the battery percentage climb.
A charging cycle is the process of using a battery's full capacity, but not necessarily all at once.
For example, if you use 75% of your phone's battery today and then recharge it fully, and tomorrow you use another 25%, you've completed one full charging cycle over those two days.
Understanding charging cycles is really important because every rechargeable battery has a limited number of them before it starts to lose its ability to hold a charge.
This is known as battery degradation.
In this blog post, we're going to demystify the concept of charging cycles, explain how they differ from cycle life, and explore how they impact various devices, from your smartphone to your electric vehicle. We're even going to provide practical tips to help you maximize the lifespan of your batteries and save money in the long run.
What Is a Charging Cycle?
We just covered this, but let’s get a quick, clean definition out of the way:
A charging cycle is the process of using a battery's full capacity, but not necessarily all at once. For example, if you use 75% of your phone's battery today and then recharge it fully, and tomorrow you use another 25%, you've completed one full charging cycle over those two days.
Charging Cycle vs. Cycle Life: What's the Difference?
While often used interchangeably, "charging cycle" and "cycle life" are two distinct but related concepts.
A charging cycle is the process of using and recharging a battery's full capacity.
Cycle life, on the other hand, refers to the total number of charging cycles a battery can endure before its capacity drops to a certain level, typically 80% of its original capacity.
Think of it like this: a charging cycle is a single event, while cycle life is the total number of those events a battery can handle before it's considered "worn out."
For example, a smartphone battery might have a cycle life of 500 cycles. This means that after 500 full charge and discharge cycles, the battery will only be able to hold about 80% of the charge it could when it was new. This is why an older phone's battery seems to die so much faster than a new one's.
How Charging Cycles Work Across Different Battery Types
The way charging cycles affect a battery depends heavily on its chemistry, so let’s start with that. Here's a look at how charging cycles work for some of the most common battery types:
Lithium-Ion (Li-ion) Batteries
Found in most of your personal electronics like smartphones, laptops, and tablets, Li-ion batteries are known for their high energy density and long cycle life.
A typical Li-ion battery can handle 300 to 500 charge cycles before its capacity degrades significantly. These batteries don't have the dreaded "memory effect," either, so you don't need to fully discharge them before recharging.
In fact, it's better to perform shallow discharges and recharges to prolong their life. For more information on this popular type, check out our full guide on Li-ion batteries.
Lead-Acid Batteries
Common in cars, boats, and uninterruptible power supply (UPS) systems, lead-acid batteries have a much shorter cycle life than their lithium-ion counterparts, typically around 200 to 300 cycles.
On top of that, they are also more susceptible to damage from deep discharges. This is a problem because regularly discharging a lead-acid battery below 50% of its capacity can significantly shorten its lifespan.
Nickel-Metal Hydride (NiMH) and Nickel-Cadmium (NiCd) Batteries
Once common in portable electronics, NiMH and NiCd batteries have largely been replaced by Li-ion.
NiCd batteries, in particular, suffer from the aforementioned "memory effect," where they "forget" that they have additional capacity if they are repeatedly recharged after being only partially discharged.
To get the most out of a NiCd battery, it's best to fully discharge it before recharging. NiMH batteries are less prone to the memory effect but still benefit from occasional full discharges.
3 Common Questions About Charging Cycles
Alright, you now know the fundamentals, so let’s move onto some of the common questions we’ve received about charging cycles over the past few decades.
1. What counts as a charge cycle on an iPhone?
Apple defines a charge cycle in the same way we described it earlier.
You complete one charge cycle when you've used (discharged) an amount that equals 100% of your battery's capacity. It's not about the number of times you plug in your phone but about the total amount of energy you've used.
2. What does 500 battery cycles mean?
If a battery is rated for 500 cycles, it means that it can be fully charged and discharged 500 times before its capacity drops to a certain level, usually 80% of its original capacity.
But here’s the important part: after 500 cycles, the battery will still work. It’s just that it won't hold a charge for as long as it did when it was new.
3. How long is 1000 charging cycles?
The length of time it takes to complete 1000 charging cycles depends on how you use your device.
If you use your device a lot and go through a full charge cycle every single day, it will take you about 1000 days, or a little under three years, to reach 1000 cycles.
If you use your device less frequently, it will take longer.
4 Practical Applications and Examples
To better understand how charging cycles work in the real world, let's look at a few examples:
Smartphones
A modern smartphone battery is typically rated for 300-500 charge cycles. If you're a heavy user who drains your battery every day, you might start to notice a decline in battery life after about a year and a half. To prolong your phone's battery life, try to keep it charged between 20% and 80%.
Laptops
Laptop batteries are also typically rated for 300-500 cycles. If you frequently use your laptop on battery power, you'll likely need to replace the battery every few years. If you primarily use yours plugged in, your laptop battery will last much longer.
Electric Vehicles (EVs)
Not surprisingly, EV batteries are much larger and more complex than the batteries in your personal electronics. They are typically rated for 1,000 to 2,000 charge cycles.
And because EV batteries are so large, a single charge cycle can last for hundreds of miles. In fact, most EV owners will never need to replace their cars’ batteries.
Power Tools
The batteries in cordless power tools are designed for high-power output and are often subjected to heavy use. They typically have a cycle life of 300-500 cycles. To get the most out of your power tool batteries, be sure to use the correct charger and avoid exposing them to extreme temperatures.