Why does a battery lose range? Natural degradation of lithium-ion cells and how to slow it down
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Did you buy an electric bike or scooter two or three seasons ago, and today the same charge level lasts for a significantly shorter ride? This isn't a malfunction and usually not a battery defect—it's a natural aging process of lithium-ion cells. It happens to every battery, regardless of brand. The difference lies in how quickly this process occurs and whether it can be slowed down.
In this article, we explain why cells lose capacity, which factors accelerate degradation the most, and what you can realistically do to maintain an acceptable range for longer.
Why every lithium-ion battery loses capacity
A lithium-ion cell (regardless of format — 18650 or 21700) stores energy by moving lithium ions between electrodes during charging and discharging. With each such cycle, microscopic changes occur in the electrode structure, which gradually limit the cell's ability to accept and release energy. This phenomenon affects all lithium-ion cells on the market — only the rate differs.
Cyclic aging vs. calendar aging
It's worth distinguishing between two independent mechanisms:
- Cyclic aging — progresses with the number of full charge and discharge cycles. The more cycles, the lower the available capacity.
- Calendar aging — progresses independently of use, solely with the passage of time. A battery loses some capacity even when unused, and the rate of this loss depends mainly on temperature and state of charge during storage.
In practice, both processes overlap. Therefore, a battery used rarely but stored in unfavorable conditions can lose range just as quickly as a battery used daily.
What most accelerates cell degradation
Not all factors have the same weight. Below are the most important ones, ranked by their impact.
| Factor | How it affects the cell | Practical recommendation |
|---|---|---|
| High temperature | Accelerates chemical reactions responsible for calendar aging — even at rest | Do not leave the battery in a sunny place or near a heat source |
| Depth of Discharge (DoD) | Regular discharge to 0% stresses the electrode structure more than partial cycles | Where possible, avoid frequent discharge below approx. 10–20% |
| Storage at full charge | High cell voltage at rest accelerates calendar aging | For longer storage (e.g., in winter), a level of approx. 40–60% is best |
| High charging/discharging current | Higher current load generates more heat and micro-damage in the cell structure | Do not overload cells beyond their nominal parameters |
| Time (calendar aging) | Progresses independently of use | Cannot be stopped, but can be slowed down by temperature and state of charge |
How to slow down degradation and maintain range longer
Charging and discharging
Daily topping up the battery to full, instead of discharging it to zero, is gentler on the cells. If your equipment allows, also avoid leaving the battery connected to the charger for many hours after charging is complete.
Off-season storage
The riding season in Poland and most of Europe ends in autumn. If the equipment goes into the garage or basement for several months, this period has a major impact on calendar aging. A battery stored at around 40–60% charge in a cool but frost-free place will lose capacity more slowly than one left at 0% or 100%, especially in a warm environment.
Cell quality matters from day one
The rate of degradation largely depends on what cells were used in the battery during assembly or replacement. Original branded cells (Samsung, LG, EVE) have repeatable parameters and better documented cycle life than anonymous substitutes. If you are planning to replace cells in a pack, it is also worth knowing the difference between new cells and disassembled cells — this directly affects how quickly you will see a drop in range.
When a drop in range signals cell replacement
If the range has noticeably dropped—e.g., by 20–30% compared to the first season—and the battery has already seen 2–3 years of regular use, this is usually a natural effect of aging, not a malfunction. In such a situation, the two options are to buy a new battery entirely or replace the cells in the existing pack, which is usually cheaper and allows you to keep the original casing and BMS. When choosing cells for such a replacement, our guide 18650 or 21700 — which to choose will be helpful, and for selecting the parameters of the entire pack — the article how to choose a battery for an electric bicycle.
FAQ — frequently asked questions about battery degradation
How many charging cycles does a lithium-ion cell withstand?
It depends on the cell model, operating conditions, and charging method. Branded cells (Samsung, LG, EVE) retain usable capacity for hundreds of full cycles under typical conditions, but the real number largely depends on the operating temperature, depth of discharge, and charger quality.
Can battery degradation be reversed?
No. The loss of capacity due to cell aging is an irreversible process. It can only be slowed down by maintaining proper temperature, state of charge during storage, and avoiding extreme current loads.
Do disassembled cells degrade faster than new ones?
It depends on their previous usage history, which is why their verification before sale (actual capacity, internal resistance) is crucial. You can find more about the differences between these two categories of cells in the article new cells vs. disassembled cells.
How to check the real capacity of a cell before replacement?
The most reliable method is to measure on a capacity tester (e.g., a full discharge and charge cycle counting mAh) or measure internal resistance as a supporting indicator. By purchasing new cells from a verified supplier, you avoid this problem — the parameters comply with the manufacturer's datasheet.
Do you have doubts whether your battery already requires cell replacement, or is it still a normal stage of use? Check out our offer of 18650 cells and 21700 cells, or contact us via the contact form — we will help you choose the right solution.