When electric bicycles are slowly becoming more and more common in the market, there are still many doubts about the charging method of lithium batteries of electric bicycles. So, after receiving the e-bike, how to charge and maintain the lithium battery?
How to charge a new battery.
Regarding the "activation" of lithium batteries, basically all sales staff will tell you this: "The battery should be fully charged for 12 hours for the first three charges", which is obviously a continuation of the statement from nickel batteries. Therefore, it is not difficult to see that this claim was misrepresented in the first place. The charging and discharging characteristics of lithium batteries and nickel batteries are very different, and I can tell you very clearly that all the serious formal technical documents I have reviewed emphasize that overcharge and over discharge will do huge damage to lithium batteries, especially liquid lithium batteries.
So, does the battery need to be activated? The answer is yes, the battery needs to be activated! However, this process is done by the manufacturer and has nothing to do with the buyer, and the user does not have the ability to complete the process. The real activation process of the lithium battery is as follows: the lithium ion battery shell is infused with the electrolyte--sealing--formation, that is, constant voltage charging, and then discharging. After several cycles, the electrodes are fully soaked in the electrolyte and fully activated until the capacity reaches As long as it is required, this is the content of the activation process, that is to say, the lithium-ion battery is already activated in the hands of the user after leaving the factory. The battery will go through a period of time from the appearance to the sale of the car, and then across the sea to the hands of users. In this way, the electrode material of the battery is "passivated". It is recommended in the manual that the battery used for the first time should be charged and discharged three times in order to quickly eliminate the passivation of the electrode material and achieve the highest efficiency. But this process does not take 12 hours, the time should be full. Batteries can also eliminate passivation over a period of normal use. Therefore, the so-called "activation" process is simple and does not require special methods and equipment.
Lithium batteries or chargers will automatically stop charging when the battery is fully charged, and there is no so-called "trickle" charging that lasts for more than 10 hours for nickel battery chargers. That is to say, if your lithium battery is fully charged, it will be a waste to put it on the charger. It is also difficult for us to guarantee that the characteristics of the protection circuit during the charging and discharging process of the battery will never change and the quality will be foolproof, so your battery will be at the edge of danger for a long time. That's one of our arguments against long charging. On some machines, if the charger is not removed after charging for a certain period of time, the system will not only stop charging, but will start a discharge-charge cycle. Perhaps the manufacturers of this practice have their own purposes, but obviously it is not good for the life of the battery. At the same time, long charging takes a long time, often at night, and I believe that no one wants to think about worrying things in real life in their sweet dreams. Moreover, compared to nickel batteries, lithium batteries are very delicate, and their ability to withstand fluctuations in charge and discharge is much less, so this brings additional dangers.
When should charging be started during normal use?
Because the number of charging and discharging is limited, the user should recharge the lithium battery as much as possible. I found an experimental table about the charge-discharge cycle of lithium-ion batteries, and the data about the cycle life are listed as follows: cycle life (10% DOD): > 1000 times, cycle life (100% DOD): > 200 times. DOD means depth of discharge. It can be seen from this data that the number of rechargeable times is related to the depth of discharge, and the cycle life at 10% DOD is much longer than that at 100% DOD. Of course, if it is converted to the relative total capacity of actual charging: 10%*1000=100, 100%*200=200. Therefore, the full charge and discharge of the latter is better. Under normal circumstances, the user should reserve the charge according to the principle of recharging the battery after the power is exhausted, but if your battery is expected to be impossible to use all day long the next day, you should start charging in time. Of course, if you are willing to carry an extra charger to commute, it is another matter.
I believe that most consumers have heard that the life of lithium batteries is "500" times, 500 times of charge and discharge. After this number of times, the battery has reached the stage of "end of life". In order to prolong the life of the battery, many consumers charge the battery only when the battery is completely exhausted. Does this really prolong the life of the battery? The answer is negative.
In fact, there is a wrong concept here, which is easily misunderstood by consumers. The life of a lithium battery is "500 times", which refers not to the number of times of charging, but a cycle of charging and discharging. For example, charge 40% of the battery first time, then charge it 20% after using it for a while, and then charged 30% use it again after the next use. Then 20% next time. In the middle of the 20%, that is, when 10% of the power has just been replenished, a total of one charging cycle is completed, and then the next cycle.
A lithium battery was only half charged on the first day and then fully charged again. If it's still the same the next day, that's half of the charge, for a total of two charges, which counts as one charge cycle, not two. Therefore, it may usually take several charges to complete a cycle. Each time a charge cycle is completed, the charge decreases a bit. However, the reduction is very small, and a high-quality battery will still retain 80% of its original charge after many cycles. Assuming that the power of a complete discharge is Q, and the cycle of a battery is 500 times, then the total power it provides in its life is 500Q. If we charge half of the power, let the number of charging times be A, and simply solve, 1 /2Q*A=500Q, A should be 1000 times. So for battery life, we can measure it in cycles, but never in charging times.
The principle of recharging the battery when the remaining power is exhausted is not for you to go to extremes. There is a saying that is as widely circulated as long charging, that is, "try to use up the battery of the machine as much as possible, it is best to use automatic shutdown". This practice is actually just a practice on nickel batteries, the purpose is to avoid the memory effect, and unfortunately it has also been passed down on lithium batteries. There have been cases in which the user continued to use the machine without charging after the warning that the battery power of the machine was too low until it was automatically shut down. As a result, the machine in this example did not respond during subsequent charging and booting, and had to be sent to customer service for overhaul. This is actually because the battery voltage is too low due to over-discharge, so that it does not have normal charging and power-on conditions.
Correct approach to lithium batteries.
To sum up, the most important tips for charging and discharging lithium batteries in use are:
1) Charge according to the standard time and procedure, even for the first three times;
2) When there is a prompt that the power of the machine is too low, you should try to start charging in time;
3) The activation of the lithium battery does not require any special method, and the lithium battery will be activated naturally in the normal use of the machine. If you insist on using the circulating "first three 12-hour long charge activation" method, it won't actually work. Therefore, all the pursuit of 12-hour long charging and the use of lithium batteries for automatic shutdown are wrong. If you have done it wrongly in the past, please correct it in time, it may not be too late.