eBike Battery Tech: Unpicking the myths from the reality – Singletrack World Magazine

Nov 02, 2024

There are a lot of myths and misinformation and general lack of understanding about what it is that lies at the heart of every eBike – the battery.

With the help of Giant Bicycles we thought it was a useful exercise to get into the tech and the reality of battery technology.

I spent some time last year in the company of Giant Bicycles tech experts and ebike designers at their Utah eBike launch camp. Part of the deal with the launch was that we learned all about the technology behind the batteries they used. Not just the battery itself but the individual cells that make up the batteries inside every Giant ebike. It was all pretty eye-opening, revealing a world of intricate engineering and design that goes into the ebike experience.

Batteries are made up of cells, and understanding this fundamental aspect is crucial for anyone interested in electric biking. The ubiquitous AA battery, often found in household devices, is not actually a battery in the traditional sense. It’s a single cell that outputs 1.5 volts. When you bundle more than one together—whether in a flashlight, remote, or game controller—you effectively create a battery. Similarly, the Giant ebike batteries are constructed from individual cells, but these cells differ significantly from the standard batteries you might find in everyday electronics.

Lithium-Ion or LIon cells are commonplace now, present in devices such as our phones, laptops, tablets, and even electric cars. However, it’s important to note that there are several different types of LiOn cells, each with unique characteristics and applications. Giant, for instance, opts for a specific type known as Lithium Cobalt Manganese. This selection is particularly noteworthy, as it combines the benefits of high energy density with stable performance and safety.

The technology behind these cells ensures that Giant ebikes are not only powerful but also capable of handling the demanding conditions of various terrains and riding styles. The combination of innovative cell chemistry and advanced battery management systems allows for optimal energy use and performance, making the riding experience not just enjoyable but also reliable. This deep dive into battery technology provided insight into how Giant is pushing the boundaries of electric biking, making their ebikes a leading choice for enthusiasts and casual riders alike.

Understanding the nuances of battery composition can significantly enhance one’s appreciation for the ride. The performance, longevity, and environmental considerations tied to these technologies contribute to the overall value proposition of the ebike. As technology evolves, so do the possibilities for ebike options, making this exploration of battery technology all the more fascinating.

There are many types of lithium-ion batteries for manufacturers to choose from, each boasting unique characteristics and price points. Some excel in high energy density (compact size for a given capacity) and long lifespan, while others focus more on cost. Longer-lasting, higher-density cells come at a price.

At Giant, Liv, and Momentum, they use Lithium Cobalt Manganese batteries. This specific type offers a combination of two crucial benefits – Extended battery lifespan and high energy density.

While Giant prioritises Lithium Cobalt Manganese for its advantages, the E-Bike market utilises four other Lithium-Ion variations. This diversity translates to a range of battery qualities and performances across different brands. Giant have prioritised optimised power and long-lasting performance.

Individual rechargeable cells have a distinct and universal labelling format. You may have seen these referred to in manuals or online. For example the 18650 LiOn cells are partcilularly common.

The ’18’ refers to the physical diameter of the cell in mm and the ‘650’ refers to the length of the cell, in this case that means a diameter of 18mm and length of 65mm. The capacity of the battery is directly linked to the volume of the cell, so a cell with a higher physical volume will store more energy, but also and crucially a cell with a wider diameter will be able to discharge a higher current too. So, there’s obvious advantages to having large capacity cells. Not only can they store more energy but they can release it quicker too – which translates to higher power output.

So, the standard cell designation is 18650. Tesla developed their own cells which they designated the 21700. That translates to a cell with a diameter of 21mm and 70mm length. If you remember your maths from high school you can calculate the volume of a Tesla cell as 14.7 cm3. Compare that with the standard cell volume of 11.7cm3 and you see there’s a big increase in capacity. This extra capacity and diameter is why Tesla car batteries can provide enough ‘poke’ to accelerate the car from 0-60mph in under 4 seconds. There’s literally a 25% performance improvement between 18600 and 21700 cells.

Giant use cells manufactured by Panasonic who have been in the battery game for a very long time. The physical size of these cells exceed that even of Tesla. They are designated 22700, which means they have a diameter 5% larger than Tesla cells and therefore also a corresponding performance increase over them too.

The performance boost you get from a wider diameter cell is not just in its output. A wider diameter of cell means it can take a higher charge. This measn these batteries can take a higher charge current and ergo a faster recharge time.

These cells can take a hammering when it comes to recharging and Giant claim they can be recharged twice as often as standard batteries made from 18650 cells, which means the lifespan of your battery should easily last many years. Longer lasting cells means less waste and recycling although Giant also work with a recycling partner for batteries that have reached the end of their useable life. Which raises an often asked question.

The reality is that batteries will slowly degrade over time. Anyone with a smartphone will recognise the phenomena where you phone battery lasts progressively shorter as it ages. But the real world life of a LiOn battery isn’t one where one day it will simply stop working. all other battery tech faults aside a LiOn battery will simply slowly degrade and will hold less energy per charge as it ages. Battery aging is linked not to time but to the number of recharge cycles it is put through. Also, it’s important to understand that the industry standard for the lifespan of a battery is not until it simply won’t hold any charge at all but rather the point at which it will hold a maximum of 80% of its original capacity.

So, lifespan of say 2300 charge cycles claimed by Giant for their batteries means that after 2300 charge cycles it will likely only hold 80% of it’s original charge. If you find you are rarely ever getting back from a ride with less than 20% ‘in the tank’ then this kind of means your battery will serve you just fine for much longer than 2300 charges.

To summarise. A quoted lifespan of 2300 charge cycles does not mean your ebike’s battery is useless after that number of charges. It means your range will be 80% of what it was when the battery was new. Your ebike and battery will happily still function after 2300 charges. It’s up to you to decide if at 80% capacity you need to replace the battery. This 2300 quoted charges is to an industry standard “end of life” of 50%. This doesn’t mean the battery is dead after that it’s just that the battery industry has deemed 50% to be the metric they use for practical reasons.

We’ve all seen videos and pictures of electric cars on fire and how really difficult they are to put out. We’ve all probably read stories of LiOn batteries exploding and how they are not allowed in the hold of planes for this reason. Does this mean LiOn batteries are quietly sitting there acting like bombs waiting to go off?

Well, no. Of course not. The truth is that if you short circuit a LiOn cell it will suddenly discharge all of it’s energy through the short circuit. If that short is a thin bit of wire then that wire will get really hot really quickly and this is what can start a fire. Fuses are the things that aim to stop that from happening and we are all familiar with those. eBike batteries will all have extensive fuse circuits built in to prevent this kind of situation with a battery fault. The stories of LiOn batteries bursting into flames tend to come from cheap devices or cheap eBike batteries from nameless brands. Quality eBike batteries like the Giant batteries go through a lot of rigourous testing and quality control and the reality is that batteries that come with quality bike brands are safe and come with a variety of safety features that go far beyond the simple fuse. Internal thermal cutouts will stop the charge to the battery or even individual cells if the temperature reaches a critical point.

Giant’s cells each come encased in a fireproof shell to further minimise the chances of a ‘thermal event’. Here’s the list of safety features that come with Giant’s batteries.

Which does bring us to one big charging safety tip. Use the charger that comes with your bike. Don’t be tempted to buy yourself a cheap spare or try to use a charger from another brand. Each of the major bike brands tend to match the charging charateristics of their chargers to their specific battery configuration. Maximum charging safety comes from a combination of the features in side the battery AND the charger.