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How Safe Are Lithium Bicycle Batteries?

Lithium Batteries for E-Bikes

Lithium is a high performance type of battery, need to have special care taken in their production and use to insure a high level of safety. Here we’ll go over some common issues and questions related to lithium batteries in general, and also discuss some of the specific differences between types of lithium batteries and also how these issues relate to electric bikes and conversion kits. Some of the biggest issues surrounding lithium battery safety are the production process and quality control of the original battery manufacturer, the source and quality of the raw chemical materials, the electronic Battery Management System (BMS), how the internal battery cells are protected from shock, vibration, and weather, and issues relating to overheating. As lithium batteries have become extremely popular, many people have raised questions about certain safety topics. It’s a good idea to share questions and comments on these subjects and have these topics openly discussed.

Since most bicycle companies are not battery companies, it’s important that you know some basic information about the origin and manufacturing of the lithium battery when you’re considering buying an electric bike or kit. Some electric bike sellers may be completely transparent about the name and even contact information of the manufacturer of the battery in their system. Other sellers may not offer any information, and may not even know any information themselves regarding where their lithium battery came from. Most reputable sellers, however, will have some basic information available to the public regarding the specifications, production methods, and safety standards of their lithium battery. Please note that if a certain electric bike dealer won’t divulge detailed contact information about their battery supplier or manufacturer in addition to battery specification information this should not be taken as defensiveness or misdirection as it is a common practice in many industries whereby companies protect themselves from competition by keeping their supply chain relationships private.

The production process of lithium batteries is arguably as complex and important as the materials in the batteries themselves. There are many steps in this production process and a factory with a long history, good machinery, and high production volume will have an easier time producing a high-quality, safe battery than a start-up factory or a shop that does only small production batches. This is because quality control tolerances are easier to dial in as production volume and the size of the manufacturing operation increase. An example of one of many specific detailed steps that must be done well is the application of a polymer compound separator. Many lithium battery manufactures have relied on simpler liquid compound processes that can leak and be very dangerous if a battery cell is damaged. Our manufacturer uses a hardened compound process which adds significant stability and safety to the cells. Ukko builds its wildly popular Big Lithium battery using the same high-end lithium nickel-cobalt-manganese polymer cells its supplier manufactures for electric wheelchair distributors and full electric bike producers. A big Lithium battery is made up of many smaller batteries called “cells” inside the outer battery casing. Ultimately it is the quality standard by which these individual cells are produced that determines the performance, reliability, stability, and safety of the actual battery.

The cells in the Ukko lithium batteries are specifically chosen from one of the largest volume (50,000 unit per month) production lines inside our cell supplier’s factory. Basically this means that the cells in your Hill Topper electric bike conversion kit are manufactured to the same safety and stability standards required by the other large customers of our cell manufacturer who produce electric wheelchairs, medical equipment, and high-end full electric bikes. There’s a big difference between this type of cell production and small-scale project-based manufacturing. In other words, a world-class electric wheelchair producer is not going to be satisfied with a lithium battery wrapped up in duct tape selling on e-Bay from a small-scale production run, and neither are we, so we have our battery custom built from the same cells that already meet these high standards of other large companies.

As we are making sure our customers are getting the same high-grade cells that are sought after by large producers of
electric bikes
, our cell manufacturer is using the same philosophy one step higher up the production chain. Japan is world famous for its leading role in the lithium battery industry, and has experts and companies that specialize in the highest quality niches of all levels of production. Since finished lithium batteries can be only as good as the quality of the raw chemical materials they’re built from, it’s imperative that the Japanese world leaders in
lithium battery

production also produce the world’s purest lithium battery chemical compounds to insure a steady supply. Though often more expensive than the lower-grade lithium chemical compounds that can be sourced from China and other areas, our cell manufacturer sources its raw materials from Japanese suppliers, the best in the world. This pays off in overall higher quality control, cell stability, and safety in the end products.

Whether you’re a die-hard lithium battery researcher and hobbyist, or a newcomer to the world of electric bike kits just getting an overview of the basic considerations, you should be interested in the electrical circuit inside the battery itself called the Battery Management System, or BMS. The BMS is a green printed circuit board (PCB) that looks like a small chunk of the inside of a computer (about 2″ x 4″) and is actually permanently built inside the battery. You’ll never have to interact with this little computer board inside your battery, but it’s important you know about its basic functions. The general purpose of the BMS inside each Ukko lithium battery is to make sure the your battery displays a charge level indication, monitor each individual cell and make sure it never gets charged up to high, drained down too low, or discharges its energy too quickly. A BMS on a given battery may have all these functions, one or two, or even additional features. Since all lithium batteries are more unstable that other standard battery types, any big lithium battery should have a BMS as opposed to just relying on the electrical charges in the chemicals of the cells to regulate themselves. Without a BMS, it’s possible that the battery will have poorer overall performance and an overall shorter life span than if it’s cells were individually looked after by a computerized BMS. Also, without a BMS it’s possible for one or two cells to become overcharged compared to the others, heat up, and catch on fire, destroying the whole battery. Make sure any lithium battery that you buy that’s big enough to run an electric bike comes with a BMS.

What to Look For When Buying a Safe Electric Bike Battery

electric bike lithium battery is the casing that protects all the cells and BMS from shocks, vibration, and weather. Some lithium “batteries” are sold with nothing more than some plastic shrink wrap or tape covering up the individual cells and BMS computer board. This is okay if the battery is to be used on some kind of stationary system in a safe, dry place, but to safely operate in the harsh environment of a bouncing bike frame, a lithium battery must be protected from shock and water. This should be a straight forward cost consideration when shopping for a lithium bike battery. You may find a good deal on an ‘unprotected’ battery but you must then remember to factor in some extra money, and probably a lot of time and energy, to get that battery into some kind of shock-proof, weather-proof container. All Ukko lithium batteries come standard with a heavy duty, weather sealed case that protects the internal cells and BMS from the shocks, vibrations, and splashes that are the norm that any piece of bike equipment needs to handle.

Overheating is a simple but very important issue concerning all batteries, and lithium batteries in particular. All batteries are designed to work in a specific temperature range, and their performance drops when too cold or too hot. In the case of most lithium batteries they can be thought of as very similar to a person in terms of comfort with temperature, with special attention paid to high temperatures. Hill Topper lithium batteries will function with full performance anywhere from 30’F (-1’C) – 90’F (32’C), and have full overcharge protection and heat dissipation features. These safety features will protect the battery during any normal operation, however the user should understand that the hotter the battery gets, the more they are leaning on these safety features to protect them. For example, it would be a bad option to charge the battery while leaving it in direct sunlight on a hot day, since all of these factors increase the temperature of the battery and doing them all at the same time may push the battery temperature well over 100’F if there was not good air flow in the area. Ultimately, if a lithium battery gets extremely cold it will just not work very well, but if it gets extremely hot it will be closer to the point of catching fire, which can clearly be dangerous. The Hill Topper batteries are safety tested to much higher temperatures than they will ever be exposed to even on a hot day while charging, but it is important to note that in general overheating pushes the safety features of the battery much harder than does getting the battery too cold.

There are many more common features and important issues relating to the safe operation of lithium batteries and the more one researches and discusses these topics the better. In general, the basics of production process, raw material sources, shock and weather protection, and overheating issues will give you a good comprehensive picture of pertinent safety considerations regarding electric bike and conversion kit lithium batteries.