How to Choose the Battery for Electric Bike
A rechargeable battery is one of the most important parts of an electric bike. The distance that you can travel on one charge will directly depend on the battery that you choose. Since there are quite a lot of different types of batteries, many questions arise about which one to buy. How to choose a battery for an electric bike? What type of batteries is more reliable? What is the difference between them? Let’s try to figure it out.
Types of batteries
There are a fairly large number of different types of batteries. Here are some of them:
- Lead Acid (SLA)
- Nickel Cadmium (NiCd)
- Nickel Metal Hydride (NiMh)
- Lithium-Ion (Li-ion)
- Lithium Polymer (Li-pol)
- Lithium Iron Phosphate (LiFePO4)
Each of these types has its advantages and disadvantages.
Lead Acid (SLA)
Despite its low cost, this type of battery is not really suited for use on an electric bike since it’s quite heavy. In addition, the charging speed of this type also leaves much to be desired.
Due to the specifics of operation in an electric bike, it is quite difficult to maintain the necessary charge levels, which causes fast battery failure.
Nickel Cadmium (NiCd)
These batteries have a larger capacity than lead batteries, which is a very important quality. Their disadvantage is the cadmium content, which is very difficult and expensive to process.
Therefore, such batteries are not widespread and it is not worth using them due to great harm to the environment. In addition, they have a “memory effect”, which means that these batteries must be fully discharged, otherwise, they will quickly begin to lose capacity.
Nickel Metal Hydride (NiMh)
These batteries appeared as an alternative to nickel-cadmium ones and eliminated its main flaw, - environmental damage. In addition, they have on average 30% more capacity than the latter.
The disadvantage of this type is a small number of charge-discharge cycles (about 500 cycles).
A very common and probably the most advanced type of battery at the moment. They are used heavily everywhere: in electronics, as power sources for phones and laptops, in electric and marine vehicles, even your toothbrush might have one.
They are unpretentious enough to charge mode. Their term of operation is often determined by the life of the contained chemical composition, therefore, with careful handling, they will work from 3 to 4 years. Today they are the most capacious batteries available.
Their main disadvantage is the high price.
Lithium Polymer (Li-pol)
These batteries are comparable in performance to lithium-ion but they are cheaper, lightweight, able to give a higher current.
Despite their advantages, they have a big drawback - low fire safety. They are subject to spontaneous combustion. They also do not have a hard case, which complicates this problem.
In addition, this type of battery is not designed to work in conditions of increased vibration, which makes it not a really good fit for an electric bike.
Lithium Iron Phosphate (LiFePO4)
These are one of the most advanced batteries from the lithium class. They surpass their predecessors in all major parameters such as the number of charge-discharge cycles, a wide range of operating temperatures and the absence of a “memory effect”.
In addition, they are thermally and chemically stable, which increases safety, but have a greater weight due to the lower cell voltage. A similar lithium-ion battery will always be 30% lighter.
Tips to keep your batteries healthy
Of course, each of the types of batteries has its own advantages and disadvantages.
For example, if you do not plan to travel far, then perhaps a cheap lead battery is suitable for you.
If you plan to travel long distances, then you should look towards a group of expensive but energy-intensive and lightweight lithium batteries. Whichever of them you choose, familiarize yourself in detail with the features of their operation and charge modes.
Here are some simple rules to extend your battery life:
- Do not leave the batteries discharged for a long period of time. Nickel-cadmium and nickel-metal hydride batteries require a full charge/discharge cycle to avoid loss of capacity. A group of lithium-ion batteries doesn’t require this. But none of them will survive a long-term idle time in the discharged state.
- Observe the temperature regime for each battery type.
- Spend some money on a good specialized charging device for the type of battery you need. It will cost you less than having to completely replace the battery every year or so.
Choosing a battery capacity
After determining the type of battery, you need to decide what capacity it should have. The total distance will directly depend on both the capacity and the voltage of the battery itself. In fact, the energy stored in the battery is calculated as the product of its capacity, (which is measured in ampere-hours) and its voltage.
That is, if there are two batteries of 24 and 36 V, each of 10 ampere-hours, then the energy stored in a 24 V battery will be 30% less than in a 36 V one. Of course, in general, you need to focus on the operating voltage of your electric drive and choose components in strict accordance with its requirements.
Another important aspect that you should pay attention to is the location of the battery. It can be placed both on the rear and on the front rack, as well as in the space of the triangle of the frame.
The rear racks battery location may be reasonable if the motor-wheel is installed in front. Then you get a more uniform distribution of the weight of the bike.
The location of the battery in the front is justified by reducing the length of the wires to the drive if it’s installed in the front. But this reduces controllability and moves the weight balance more to the front wheel.
Very often you can see the installation of the battery in the space of the triangle frame. This arrangement most evenly distributes the weight on the bicycle frame. Unfortunately, the disadvantage of this method is that it really complicates battery maintenance. The battery replacement can take much longer time in this configuration.
It’ll take you only a couple of hours to learn the basic characteristics of different types of batteries. In my opinion, this time is really well spent, because this knowledge will allow you to choose the battery that will be suitable for your bike and your situation. After you buy the battery, keep in mind those basic tips that we discussed earlier to extend the battery life to its maximum.