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Why the battery life of the electric scooter drops in winter?

Into the winter, the temperature drops, a variety of electric products also began to out range decline problem, even if fully charged, the range is much lower than before. The uninformed consumer may suspect being pitted, only to buy a few months, the range has shrunk so much, many businesses cry foul. So why exactly does this happen? In fact, this is a common problem of all batteries.

Temperature effects

First of all, most electric mobility tools use the model 18650 lithium battery, where 18 means the diameter of 18mm, 65 means the length of 65mm, 0 means a cylindrical battery.

18650 battery

The internal structure of lithium battery is mainly composed of positive electrode, negative electrode and electrolyte between positive and negative electrode. The principle of battery discharge is that the negative electrode precipitates lithium ions through a chemical reaction, and then moves to the positive electrode through the dielectric, when the positive electrode is in the lithium-rich state and the negative electrode is in the lithium-poor state, and in the process of lithium ion activity, the resulting electron movement generates current.

 

18650 inner structure
18650 inner structure

And in the case of lower temperature, this charging and discharging process will become slower. Therefore the current of discharge becomes smaller, and the capacity of the battery becomes smaller. The marked working temperature of lithium battery is 0-40℃, but in fact, when the temperature is lower than 25℃, there will be a certain degree of performance reduction: the battery capacity decreases, the discharge speed becomes slower, the battery output power becomes smaller, etc.

The figure below shows the temperature capacity curve of lead-acid battery and lithium battery, you can see that the capacity of lithium battery can reach 100% at 25℃, while below 25℃, the capacity curve has a downward trend. Since Li-ion battery can reach the maximum capacity value at 25℃, so this is the reason why the temperature is set to 25℃ as the experimental temperature in various range tests.

Of course, the above table is only the data of a certain type of battery for reference only, in fact, the data will be different because of the material and process difference of lithium battery. But there is a relatively simple and crude way of calculation on the Internet, which is.

With 25 ℃ as the standard, the temperature drops by about 1% for every 1 ℃, the electric capacity drops by about 1%. In other words, you can run 25 kilometers in the summer (25 ~ 28 °) the car, in winter 5 ° conditions, taking into account only the battery factor, you may only run 20 kilometers at most.

The reduction in range caused by temperature is reversible, and the car's range will be restored when the temperature rises again. This shows that the electronic and human like, winter are not want to move ah.

Excessive temperature for the lithium battery itself is also affected, when the temperature is higher than 45 ℃ will disrupt the chemical balance in the battery, resulting in harmful side reactions, will also reduce the life of the lithium battery, reduce the capacity of the lithium battery. So in the normal use of the environment, the biggest factor affecting the operation of the lithium battery is the temperature. The same use of lithium battery cell phones in cold weather, the power will be used faster, but also due to the impact of temperature resulting in smaller battery capacity.

Charge and discharge times influence

Of course, besides temperature, one of the factors that affect the capacity of lithium battery is the number of charge and discharge. According to the experimental data on the Internet, 18650 lithium battery completes 50 cycles of charging and discharging at 25℃, and the discharge capacity remains at 96.6%. Taking 18650 model as an example, after the cycle times reach 400~500 times (one cycle is equal to the process of fully charging to fully discharging the battery), the battery capacity will generally drop by 10%-20%.

For example, if you have an electric car with a lithium battery that has a range of 25km, and you charge it once a day with a full charge and use it up, then for about a year and a half, the range will only be about 20km. However, this is calculated based on actual use, if you just use 50% of the charge every day, then it is equivalent to 2 days once a cycle, then it may be 3 years before the range drops 20%.

Li-ion battery capacity loss is due to the electrode in the battery with the charging and discharging process gradually loss, and temperature drop temporarily change the battery capacity is different, this is an irreversible process.

In addition to the electrode loss caused by charging and discharging, overcharging will also cause the electrode stripping. However, most lithium batteries now come with charge protection control, so even if the charging plug is always plugged in, the charging connection will be intelligently disconnected, so overcharging can basically be avoided.

Electric scooter battery maintenance

  1. When storing electronic devices with lithium batteries in winter, it is best to move them indoors to reduce the natural electric loss. Because the lithium battery charging temperature is slightly higher than the discharge temperature, so charging is best placed in the temperature of 0 ~ 25 degrees Celsius indoor, charging efficiency is higher.
  1. Do not place the lithium battery in the summer for a long time in a high temperature environment, will reduce the service life. 
  1. Long-term non-use of lithium batteries should also be charged regularly, it is best to keep the lithium battery power at about 30%.
  1. Li-ion battery is suitable for use with charging, and charging once ≠ one charge/discharge cycle, so it is not recommended to charge it only when it is completely out of charge, which is more harmful to the internal electrode of Li-ion battery.
  1. Use the rated voltage for charging, although too high charging voltage can speed up the charging speed, it will also damage the life of Li-ion battery.