Do you know to protect your electric skateboard battery?

October 16, 2019

It's never a bad thing to know more about something you're not familiar with, especially for battery. It's widely used yet not cheap, especially in skateboard.

How does the battery discharge happen?

The chemical reactions in the battery causes a build-up of electrons at the anode. This results in an electrical difference between the anode and the cathode. The electrons want to rearrange themselves to get rid of this difference(Like water in U tube want to be the same). But they do this in a certain way. Electrons repel each other and try to go to a place with fewer electrons.

In a battery, the only place to go is to the cathode. But, the electrolyte keeps the electrons from going straight from the anode to the cathode within the battery. When the circuit is closed (a wire connects the cathode and the anode), the electrons will be able to get to the cathode. In the following picture, the electrons go through the wire, lighting the light bulb along the way. This is one way of describing how electrical potential causes electrons to flow through the circuit.

However, these electrochemical processes change the chemicals in anode and cathode to make them stop supplying electrons. So there is a limited amount of power available in a battery.

Battery discharge process

When you recharge a battery, you change the direction of the flow of electrons using another power source, such as solar panels. The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and can again provide full power.

Whats the battery discharge rate C”?

A. The rate of discharge is how fast you are pulling power from a battery

B. The unit is “C”, short for Capacity,  and discharge rate is divided into time rate and multiple rate:

Time rate: the discharge rate is expressed as the discharge time, that is, the time when a certain current is exiled to the specified termination voltage. For example, when the rated capacity of a battery is 20 hours, that is when C20 is 12AH or C20=12AH, the battery shall discharge at the current of 12/20 = 0.6a, and the battery shall be qualified if it reaches 20H continuously. The lower subscript of C represents the discharge rate which is Cn

 Multiple rates: For a 12AH (C 20) battery, the current (12/20) *0.1= 0.06a is used to discharge the battery. The front mark of C represents the discharge rate, namely NC

Usually, the discharge rate information will be marked in the battery pack. The picture shows it on the label. The ‘C’ rating of the battery is 20C. This means the battery can peak output at 20X its capacity. So battery peakoutput=3000mah( Capacity)*20C=60Ah for this battery

Battery

 Is the discharge rate bigger better? No!

Too higher discharge rate will cause too many discharge current→ higher possibilities for overheat→shorter Life & reduce the reliability of electronics.

 

What's self-discharge and over-discharge?

A. Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes. Self-discharge decreases the life of batteries and causes them to initially have less than a full charge when actually put to use.

B. Battery is a gradual failure of the product because the use of various raw materials' performance is gradually aging. If the battery is in a long-term storage state after charging, it will enter the self-discharge process, Self-discharge is permanent and cannot be reversed.

Time: The energy loss is asymptotical, meaning that the self-discharge is highest right after charge and then tapers off. Nickel-based batteries lose 10–15 percent of their capacity in the first 24 hours after charge, then 10–15 percent per month.

Temperature: When the ambient temperature increases, the self-discharge process will be accelerated, lead-acid battery example below: temperature of 20° C, the self-discharge is roughly 3% per month and can theoretically be stored of 12 months without a recharge. With a warm temperature of 30°C, the self-discharge increases and recharge will be needed after 6 months. Letting the battery drop below 60 percent SoC for some time causes sulfation (Lead-acid should never drop below 60% SoC. Charge more often when warm)

Self-discharge increases with age, cycling, and elevated temperature. Discard a battery if the self-discharge reaches 30 percent in 24 hours.

Generally speaking, the battery temperature should be kept at 20-35 ℃ as far as possible. Too high or too low temperature, are adverse to battery storage life.

 ( Remark: the  information is from https://batteryuniversity.com/learn/article/elevating_self_discharge)

Over-Discharge

When the voltage drops to a specified value and still discharge which may cause damage to the electrode active material, lose the reaction ability(cause the battery hard recharge)and shorten the battery life.

Battery charge

How to protect your electric skateboard battery.

  • Environmental requirements:

    Electric skateboard should be charged or stored at room temperature. Excessively high or low-temperature environments are to be avoided.

    Charge and store your electric skateboard in a DRY place. Moisture or high humidity air, will enter your e-board's battery compartment or battery compartment. Into battery will loss of electrolyte and irreversible chemical reaction to reduce battery life, also a risk of electric shock if moisture is present when you plug in your power supply.

  • Charging frequency and capacity

    When a battery self-discharged the actual capacity ≤60%, it will reduce battery life, so please keep your eboard battery well charged, charging it regularly. If you will be going through periods of not riding your board, it is advisable to charge it once every 3-4 weeks.

    Help prolong battery life by not fully charging or fully discharging the battery.

  • Choose a suitable charger

It’s important to use the right battery chargers. Using a charger with a higher or much lower voltage rating is a bad idea. It will damage your cells and can cause over or undercharging.

Significantly reducing the working cycle or even causing them to stop altogether. 
Use the charger the manufacturer has supplied or one that meets the right specifications.

  • Choose battery with BMS and higher output current battery  

Choose BMS for your battery and also choose suitable C rate battery, Each battery has its own current output limit, beyond which the battery will lose power, example: the maximum output of the battery can only be 50A, while the maximum current of the ESC&motor is more than 50A with an untruely spec-marked battery, it will cause battery power off, So choosing a battery with a larger continuous output current will be better, just like: the eboard required is 30A, it is better to choose a battery that can continuously output more than 50A.

 




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