Selecting a good battery directly determines the distance you can travel on a single charge and the efficiency of the battery. With the same size and weight, different batteries can work quite differently depending on the type and structure. All batteries have characteristics such as capacity, voltage, size, weight, time of charge, and total battery life.
Voltage: most e-bike kits are rated for a specific voltage range. A typical 36V e-bike needs a battery that delivers power between 42V to 30V. A 36V pack, at 42V is fully 100% charged and holding as much energy as it can and at 30V it should shut down and stop giving power before causing permanent damage. More on BMS (Battery Monitoring System) in a bit. The common " 36V" number is an average operating voltage or sometimes called nominal voltage. Voltage - measured in volts (V) which used to describe how fast electrons move, more voltage = more speed !
Capacity is the amount of energy that can be stored in the battery. It is the main characteristic of any battery. The unit of measurement is the ampere-hour (Ah) . This value is a measure of how many fixed number of Amps a battery can sustain for 1 hour ( C rate ). Or, double the amps for half the time. Or half the amps for two hours. etc.
The battery has a certain number of discharge-charge cycles, after which the capacity starts to fall proportionally. If the battery is discharged by, say, 10% and recharged, it is considered that one cycle has been spent.
Actual battery life is determined by the number of cycles and depends on the operating conditions of the battery. The longer the battery is discharged, the less possible cycles it can be expected from it.
Lead (gel) batteries
Li-ion battery (Li-ion)
The most popular and optimal type of battery for an e-bike today. Lithium battery has the best combination of total weight and capacity. Specific capacity of lithium-ion batteries is the highest among all existing types and it is their main advantage. Lithium-ion batteries do not have the so-called memory effect.
The disadvantages of this type include sensitivity to the temperature conditions and the inability to quickly charging. The lithium-ion battery is also sensitive to overheating and requires control of the discharge mode. Ageing and loss of capacity over time. The number of cycles is about 400, which is two and a half times more than the lead-acid battery.
Lithium ion batteries for electric bicycles must be specifically designed due to the presence of a battery management system (BMS) within the pack. This piece of circuitry must be set appropriately to control the amount of current draw required by the motor and to limit excessive discharge capacity.The BMS is also important for balancing cell charge between the individual cells within the battery to maintain battery life over time.
Relatively new but already popular type of battery. The advantages of this batteries include frost resistance (works in frost up to -30 degrees without loss of capacity) and is able to charge quickly. This type of battery has the largest number of full cycles, which is about 1000. Less susceptible to aging than the usual li-ion. Also devoid of memory effect. The disadvantages of LiFePo4 batteries include low specific capacity and high cost.
- How not to destroy the battery?
First, pay attention to the battery's on/off system. Famous manufacturers use the so-called "sleep mode" in their batteries. You activate the battery mainly by pressing a button or turning on the e-bike on the control display . Once you turn off e-bike, the battery will «sleep» on its own after a few hours - so the power from the BMS system will turn off also. If you are driving on, you need to press the button again to activate the battery.
- How to store the battery in winter?
Storing the battery during the winter is very easy. Basically, it is enough to charge the battery by 50% and store it in a chilly place. It is better to store the battery outside of e-bike to prevent unwanted activation.
- Batteries heat up during charging, something wrong?
No, it's okay, all types of batteries heat up during charging. And the chargers too.
- What is the memory effect?
The memory effect happens when the battery is recharged without being completely discharged before. The battery remembers its last remaining capacity before its next charge. Therefore, when you charge the batteries before they are fully discharged, the battery usage time will decrease. Batteries used by most of our products (Li-Ion, Li-Pol) have no or very small memory effect.
- What does self-discharge mean?
If the battery is not used after it has been fully charged, it will gradually lose energy. The self-discharge value for Li-ion and Li-Po batteries is very low and fluctuates by a maximum of about 5% per month at room temperature. It is good to check the battery once a month, and if its capacity has fallen below 50%, charge it by about 70%.The suggestion that deep discharge prolongs battery life is a total nonsense!
We'll help you to make your perfect choice!
Is there anything you haven't read here?
and we'll be happy to tell you everything you're interested in!