1. What to do if a lithium battery won't charge?
Lithium batteries have a self-discharge characteristic. If they are not used for a long time and are not charged in between, self-discharge will deplete the battery, resulting in a low voltage and preventing it from charging. So, what should you do if a lithium battery won't charge? Let's take a look.
1. It should be noted that lithium batteries will enter a dormant state after being left unused for a period of time.
2. Self-discharge will deplete the battery's power, at which point the capacity will be lower than normal, resulting in the battery being too low to be charged.
3. However, lithium batteries are easy to activate. They can be activated and restored to normal capacity after 3-5 normal charge-discharge cycles.
4. Due to the inherent characteristics of lithium batteries, they have virtually no memory effect. Therefore, no special methods or equipment are required to activate a new lithium battery in a user's mobile phone.
5. Not only is this true in theory, but from my own experience, the best approach is to use the standard charging method from the beginning – this "natural activation" method.
II. What are the reasons why a lithium battery won't charge?
There are many types of lithium batteries. Some are composed of spherical cells like the 18650, while others are composed of polymer cells. If we divide them into two main categories, they are lithium metal batteries and lithium-ion batteries. Charging methods generally include constant current charging, constant voltage charging, and pulse charging, with different methods used at different stages. If a battery cannot be charged, there are essentially a few possibilities:
1. The lithium battery is in an over-discharged state.
In other words, the lithium battery has been discharged to a very low level, entering a deep discharge state, with its charge almost completely depleted, reaching as low as the lithium battery's cutoff voltage. At this point, activation methods can be used, but this is not always effective.
2. There is a problem with the charger or charging cable.
First, check if the charger is faulty. The method is simple: just measure the output voltage or connect a load with the corresponding voltage and observe. If there is a problem with the wiring, then you will have to put in more effort, since it involves circuit hardware issues. If necessary, you may have to disassemble and analyze it.
3. Lithium batteries will fail after prolonged use.
The likelihood of this happening is relatively small, but it cannot be ruled out entirely. You should be familiar with your own batteries and know how long you should use them before replacing them.
4. Problems with the battery charging IC or BMS system.
Problems with the battery management system caused by factors such as cell imbalance can lead to misjudgments by the management IC, resulting in the inability to detect voltage or current.
III. Correct Charging and Precautions for Lithium Batteries
(I) Correct charging method for lithium batteries
1. Charging
The safe operating voltage range for lithium batteries is 2.8~4.2V. Below or above this range, the lithium ions in the battery become very unstable, potentially causing accidents. To ensure the battery operates within this safe range, a dedicated charger is required. These chargers automatically adjust the charging method based on the battery's current state.
2. Activate
Before a lithium charger starts charging, it supplies a small current to the battery while simultaneously detecting changes in battery voltage, and gradually increases the current until it reaches the set value. This process can be considered an activation or test charging.
3. Constant current transformer charging
The charger charges the battery with a constant current. As the battery voltage increases, the charger simultaneously increases the charging voltage to speed up the charging process.
4. Variable current constant voltage charging
When the battery reaches the 4.2V cutoff voltage, it has only been charged to about 70% (not fully charged). At this point, the charger continues to charge the battery with a constant voltage and a gradually decreasing current, stopping charging only when the current is less than 0.1A and the charger detects that the battery voltage is still rising.
(II) Precautions for Properly Charging Lithium Batteries
1. Avoid charging at excessively high temperatures.
If lithium batteries are used in environments exceeding the specified operating temperature (above 35°C), the battery capacity will continuously decrease, meaning the battery's power supply time will not be as long as usual. Charging devices at such temperatures will cause even greater damage to the battery. Even storing batteries in warm environments will inevitably cause some damage to their quality. Therefore, maintaining a suitable operating temperature is a good way to extend the lifespan of lithium batteries.
2. Avoid charging at excessively low temperatures.
If you use lithium batteries in low-temperature environments, i.e., below 4°C, you will also find that the battery life is reduced, and some original lithium batteries in mobile phones may not even charge in low-temperature environments. But don't worry too much, this is only a temporary situation. Unlike use in high-temperature environments, once the temperature rises, the molecules in the battery are heated and immediately recover their previous capacity.
3. Frequent use
Life is about movement. To maximize the performance of a lithium-ion battery, it needs to be used frequently to keep the electrons inside constantly flowing. If you don't use your lithium battery often, remember to complete a full charging cycle each month and perform a charge calibration, i.e., a deep discharge followed by a deep charge.
