All Things You Need to Know about Charging a Lithium Battery

Compared with lead-acid batteries, lithium batteries can provide higher voltage, greater battery density, better load performance, lighter quality and longer life. Therefore, people are gradually replacing lead-acid batteries with lithium batteries. However, the charging performance of the two is different, so the chargers required are also different. The quality of the charger directly affects the performance, life and safety of the battery, so it is necessary to let people know about lithium battery chargers. This article mainly expounds the lithium battery charger from the following 8 points.

Conventional Lithium Battery Charging Method

1. Constant Current Charging(CC)

According to the size of the charging current, CC can be divided into fast charging, standard charging and trickle charging. During the entire charging process, it is generally used to adjust the charging voltage of the power supply or change the resistance value in series with the battery to keep the charging current of the battery unchanged.

The advantage of this method is that it is simple to control and is suitable for charging battery packs with multiple batteries in series.
The disadvantage is that the acceptable charging capacity of the lithium battery will gradually decrease as the charging progresses. Excessive charging current in the late stage of charging will cause air bubbles inside the battery and cause damage to the battery.
Therefore, constant current charging is often used as a link in the stage charging.

2.Constant Voltage Charging(CV)

Constant voltage charging means that the charging voltage remains constant throughout the charging process, and the size of the charging current is automatically adjusted as the battery state changes. As the charging progresses, the charging current gradually decreases.
Compared with constant current charging, this charging process is closer to the optimal charging curve, with simple control and low cost.

The disadvantage is that the charging time is long, and the battery charging current is too large in the early stage of charging, which directly affects the life and quality of the lithium battery.

Therefore, the constant voltage charging method is rarely used alone, and only when the charging power supply voltage is low and the current is high.

3. Constant Current and Constant Voltage Charging(CC-CV)

The CC-CV charging method is a hybrid approach that combines the two previously mentioned charging methods. It uses CC charging in the first charging stage, and when the voltage reaches the maximum safe threshold value, the charging process shifts tothe CV charging method. The charging process is complete when the current levels off or when full battery capacity is reached. The charging time is mainly defined by the constant current value (CC mode), while the capacity utilization is predominantly influenced by the constant voltage value (CV mode).

CC-CV charging was initially used to charge lead-acid batteries and, later, to charge Li-ion batteries. Li-ion batteries require a much longer CC mode.

The CC-CV charging method is more efficient than either the CC or CV methods individually, and as such it is used as the reference for comparison with the latest charging methods.

The main challenge with CC-CV charging is defining suitable constant values for each mode. The suitable current value will provide a balance between charging performance and battery safety. Having a current that is too high or too low can cause negative effects as previously discussed.

4. Intermittent Charging Method
The intermittent charging method of lithium batteries includes the intermittent charging method of variable current and the intermittent charging method of variable voltage.
Compared with lead-acid batteries, lithium ions batteries is more suitable for CCCV charging method. In addition, Li-ion batteries require a much longer CC mode. The CC-CV charging method is more efficient than either the CC or CV methods individually. Thus we’d better choose CC-CV charger for a lithium battery pack when we choose battery charger.

The Most Suitable Charging Process for Lithium-ion Batteries

The most suitable charging process for lithium-ion batteries can be divided into four stages: trickle charging, constant current charging, constant voltage charging, and charging termination.

Stage 1: Trickle charging
Trickle charging is used to precharge (restorative charging) the fully discharged battery cell first. When the battery voltage is lower than about 3V, first use a constant current of up to 0. 1C to charge the battery.

Stage 2: Constant current charging
When the battery voltage rises above the trickle charging threshold, increase the charging current for constant current charging. The current of constant current charging is between 0. 2C and 1. 0C. The current during constant current charging does not require very accurate, and quasi-constant current is also possible. In the design of linear chargers, the current often rises as the battery voltage rises to minimize the heat dissipation problem on the transmission transistor. Constant current charging greater than 1C does not shorten the entire charging cycle time, so this approach is not advisable. When charging at a higher current, the battery voltage will rise more quickly due to the overvoltage of the electrode reaction and the voltage rise on the internal impedance of the battery. The constant current charging stage will become shorter, but since the time of the following constant voltage charging stage will increase accordingly, the total charging cycle time will not be shortened.

Stage 3: Constant voltage charging
When the battery voltage rises to 4. 2V, the constant current charging ends and the constant voltage charging stage begins. In order to achieve the best performance, the voltage regulation tolerance should be better than +1%

Stage 4: Termination of charging
Unlike nickel batteries, continuous trickle charging of lithium-ion batteries is not recommended. Continuous trickle charging will cause the lithium metal to have a plate plating effect. This will make the battery unstable and may cause sudden automatic and rapid disintegration.

What is the difference between lithium battery and lead-acid battery charging?

For Lithium Battery:
Lithium batteries have high requirements for chargers and they require protection circuits, so lithium battery chargers usually have high control precision and chargers can charge lithium batteries with CC-CV charging method.
Lithium battery charging control is to first charge according to a constant current, and then when the battery voltage rises to 4. 2V, the voltage will no longer rise and the charger detects the current, if the current is less than a certain value, the battery will end charging.

For Lead-acid battery:

Lead-acid batteries are relatively durable and do not require high charging circuits. Occasionally overcharging and over-discharging will not cause damage to the battery, and the structure of the charger is relatively simple.

Lead-acid batteries are usually charged in three stages, namely constant current, constant voltage, and trickle current. The charger’s light-emitting diode is red to indicate that it is in the constant current or constant voltage stage, and it turns green to indicate that it is in the trickle stage. Usually, the battery can only be fully charged for a few hours after the green light turns on.

Lead-acid Battery Charging Method:
1.Pulse charging is simple and economical.
The charging current of this method is large and the charging speed is fast. The disadvantage is that when the voltage of the power grid fluctuates, the charging current also fluctuates.

2.Constant current charging
In order to prevent the internal temperature rise of the lead-acid battery from being too high and the loss of electrolyte is too large, the charging current is adjusted relatively small, and the charging time is required for a long time. On the other hand, if the charging time is too long, overcharge will occur. In order to prevent damage to the battery due to overcharge, an overcharge detection or timing circuit needs to be set up.

3.Constant voltage charging.
Both theory and practice have proved that constant voltage charging is safe when the charging voltage is lower than the upper limit of the charging voltage. Even if the charging time is very long, there is no danger. If necessary, the battery can still work in a floating state.

Can lithium battery chargers be universal?

No way. This is because,

1. Lead-acid battery chargers are generally set to two-stage or three-stage charging mode, and the voltage level of lithium batteries and lead-acid batteries does not match.

2.There are also many kinds of lithium batteries, and the battery performance and battery protection board parameters may be different. Therefore, lithium batteries are not like lead-acid batteries, and there are universal battery chargers. Generally speaking, lithium batteries are equipped with a dedicated charger when they leave the factory. In order to protect the lithium battery, it is best to use the corresponding dedicated charger.

3.Fast charging stations are only suitable for lead-acid, not lithium batteries

4.The materials of lithium-ion batteries and lead-acid are inconsistent, so lead-acid battery chargers and lithium battery chargers cannot be used interchangeably.

In summary, if you use a lead-acid charger to charge the lithium battery, it will cause the lithium battery to be overcharged, which is detrimental to the lithium battery. If it is light, the battery will end its life early, and if it is heavy, it will cause a safety accident. If the lead-acid battery is charged with a lithium battery charger, it will cause the lead-acid battery to be dissatisfied and affect the battery life.

How to choose the right lithium battery charger?

A lithium battery charger is a charger specially used to charge lithium-ion batteries. Lithium-ion batteries have high requirements for chargers and require protection circuits, so lithium-ion battery chargers usually have high control precision and can charge lithium-ion batteries with constant current and constant voltage.

As far as the current research report shows, most lithium battery accidents are caused by chargers. Therefore, the choice of lithium battery charger is very critical, so how to choose the right lithium battery charger?

1.Voltage adaptation principle

Take the choice of phosphoric acid battery charger as an example:

——If your lithium battery voltage is 48V, you cannot choose a lithium battery charger with an input voltage larger than 54. 75V, nor can you choose other types of battery chargers with an input voltage smaller than 54. 75V. You can only choose a lithium battery charger with an input voltage of 54. 75V.

——If your lithium battery voltage is 60V, you can only choose a lithium iron phosphate battery charger with an input voltage of 69. 35V. You cannot choose a charger with an input voltage of less than or greater than 69. 35V, let alone a charger for other types of batteries.

——If your lithium battery voltage is 72V, you can only choose a lithium iron phosphate battery charger with an input voltage of 83. 95V. You cannot choose a charger with an input voltage of less than 83. 95V.

2. Current adaptation principle

The current of the charger should be adapted to the lithium battery. Don’t covet fast charging. Use a high-current charger to charge a small-current battery, because a high-current charger will cause the internal resistance of the battery to increase and damage the protection board, thereby reducing the service life of the lithium battery.

3.Charging interface adaptation principle

Common lithium battery charging interfaces are Pin header interface, three horizontal interface, three vertical interface, round head interface, Giant interface, and two plugs. The plug type must match the charging interface of your device.

In addition to the above points, we must also have an understanding of our own batteries. Consult a professional before buying a charger, rather than just buying a charger to charge the battery. If the battery is damaged due to the charger problem in the end, it is very much worth the loss.

How to choose a good quality lithium battery charger?

1. The charging speed of the charger

Common chargers use constant current charging, and the charging speed is mainly related to the current provided by the charger. The greater the charging current, the faster the charging speed. The length of charging time is not only related to the charging speed, but also depends on the capacity of the lithium battery

It should be noted that the greater the charging current, the higher the quality requirements for the internal system design of the charger and lithium battery. Under normal circumstances, the greater the charging current, the more heat may be generated during the charging process, and the greater the damage to the performance of the battery. Poor-quality chargers and batteries are prone to safety performance problems such as leakage when charging quickly at high currents.

2.The charging efficiency of the charger

Not all of the energy input to the lithium battery during charging is converted into the energy stored in the battery, and some of it is used for side reactions inside the battery and converted into heat during charging, so the charging efficiency is always less than 100%.

When charging, the charging current should be controlled within a certain range. If the charging current is too large or too small, the charging efficiency will be reduced. For high-current fast chargers, the charging method of lithium battery chargers also needs to be specially designed in order to improve the charging efficiency.

3.The charging termination control method of the charger
Small-current chargers generally use time control. The greater the current provided by the charger, the more complex the charging termination control method, and the higher the cost and price. For users, they must make choices based on their actual situation.

If the battery capacity used is not very high, or the charging speed is not particularly important, you can choose an ordinary charger; if it is necessary to choose a fast charger with a higher price, it is best to learn more about the performance of the charger and lithium battery.
4. Judge the quality of the charger
A good electric vehicle charger adopts positive and negative pulse technology, which can effectively prevent, suppress, and eliminate the vulcanization and polarization of the battery. It can keep the capacity of the new battery stable for a long time; restore the capacity of the old battery that has been polarized and the capacity has decreased, and effectively extend the battery life by 2 to 3 times. It has intelligent timing protection function, automatic temperature compensation function, instantaneous impact protection of power grid, super moisture-proof and corrosion-resistant and other functions.

5. Charging cable
The same is true for the charging cable, it is best to choose the original or set of charging cable. If it is a similar charging cable, it should be marked on it to avoid confusion.

What should we pay attention to when charging lithium batteries?

①The charging cannot be exposed to the sun in high temperature weather, and cannot be charged immediately after driving.

High temperature will cause the battery capacity to decline. Try to choose a cool and ventilated environment for charging. A too sultry environment is not conducive to the state of charging, and it will destroy the battery and reduce the life of the charger. Although it is winter, it is still necessary to stay away from open flames and high-temperature heat sources.

②the battery is prompted to be too low while driving and should be charged in time.

After the battery is discharged, the vulcanization process begins. Timely charging can remove the less serious vulcanization. If the charging is not timely, these vulcanization crystals will accumulate and gradually form thick crystals.

Charge with an adapted lithium battery charger.

If the charger is lost or damaged, please find the appropriate dealer to purchase it. Do not use lead-acid chargers or other forms of chargers for charging.

④ Overcharge is prohibited.

Lithium batteries have no memory effect, and each charge is about 5-8 hours. Users should pay attention to estimating the time when charging.

⑤ For lithium battery packs, try to implement on-demand charging as much as possible.

Avoiding the battery from undervoltage every time and recharging later can extend the service life of the battery and keep the battery in a shallow cycle state.

⑥ Disconnect the battery from the vehicle if it is not used for a long time.

Lithium battery electric vehicles should be disconnected from the battery and the vehicle when they are not in use for a long time to avoid self-discharge of the battery.

⑦Lithium batteries are not allowed to be stored empty.

If the electric vehicle is not in use for a short time, please charge the battery to more than 50% for storage, and the battery must be replenished every month.

What should we pay attention to when using a lithium battery charger?

Before charging the lithium-ion battery, first confirm whether the status of the lithium-ion charger is normal. To judge whether the charger is good or bad, you can connect the charger to 220V alternating current and check whether the green light is on. The green light is always on to indicate normal, and the rest (the light is not on, the light flashes, the red light is on, etc. ) indicates that the charger is damaged.

1. The charging voltage and current of the lithium battery charger should be the same as that of an electric vehicle. You cannot use a 60V battery charger to charge a 48V battery.
2. Pay attention when charging, first plug in the battery socket, and then turn on the power supply

3. Lead-acid battery chargers cannot be used to charge lithium batteries, and lithium battery chargers cannot be used to charge lead-acid batteries.

4. When charging, stay away from flammable and explosive items.

5. If you are charging an electric vehicle, the lithium battery charger should be attached to the car, not placed at home to charge.

6. If it is an electric vehicle charger, it is not recommended to carry it with the car. Damage to the charger caused by long-term bumps should be avoided.

7. It is strictly forbidden to disassemble the lithium battery charger for maintenance without permission, because there is a high voltage inside and there is a risk of electric shock, especially in the case of wet hands.

8. If you do not use the lithium battery charger for a long time, keep the charger in a cool and dry place to avoid moisture damage to the lithium battery.

9. When charging, since the charger emits heat when charging, it is necessary to ensure ventilation around the charger.

10.When charging, the charger displays a red light; if the charging is complete, a green light is displayed. If the light flashes or the light is not on, the charger is broken and must be replaced in time.

11. If the charger is found to be abnormal during the charging process, the power plug should be unplugged immediately, and the battery and charger should be sent to the purchase place to find out the cause.

Q&A 1: What voltage should I charge a 12V lithium battery?

Our experts point out that the charging time depends on the specific charger in your system. Lithium-ion batteries have low internal resistance, so they will absorb all the current transmitted in the current charging cycle. For example, if you have a 50-amp charger and a 100-amp-hour battery, divide 100 amps by 50 amps to get 2 hours of charging time.

Another example is if you have five 100 Ah (amp-hour) batteries, a total of 500 Ah and a 100 amp charger. It takes about 5 hours from battery depletion to 100% charging, taking into account enough time to balance the charging cycle. We do not recommend that you exceed this charging rate because it will cause the battery cycle life to be shortened. In case of emergency, the battery can be charged at a faster speed if needed, but we do not recommend that you develop the habit of emergency charging the battery.

Q&A 2: How do I know if my lithium battery is charging correctly?

The Green LED illuminates to indicate the charger is powered on. The Red LED indicates the battery is charging. The LED will turn Green when the battery is fully charged and on float charge.

Q&A 3: What is the right way to charge a lithium battery?

①First insert the corresponding charger output plug into the battery charging socket, then insert the charger plug into the jack, and observe the indicator light for charging determination.

②Generally, after the charger indicator light turns green, it will be recharged for about 1-2 hours, and the charging work will be stopped.

  1. Regardless of whether the lithium battery is used or not, the ”shelf life” is 3 years, and it decays quickly after about 400-500 times. It depends on whether you use it for 3 years or charge it first.
  2. In addition to being afraid of low battery power, lithium batteries are also afraid of overheating, especially when charging. If your mobile phone case has poor heat dissipation and generates heat while charging, it is best to take off the case while charging.
  3. Shallow charging and shallow discharge are the most ideal, that is, the charging and discharging do not reach the maximum capacity of the battery 100%, that is, the charging is not full, and the discharge is not finished. Ordinary charging is carried out when the battery is 10%-90%, and it can be taken out after it is fully charged. Don’t use the phone for a long time during the charging process, which can make it last the longest.
  4. It is not recommended to play with mobile phones while charging. Even if you want to play while charging, it should be safer at half power (that is, about 50%). If the temperature inside the battery is relatively high at full power, the heat generated when playing with the phone will become larger, and the battery temperature will have a certain impact on life.

Q&A 4: How do you know if my lithium battery is fully charged?

There are two criteria for judging whether the lithium battery charging has reached saturation: one is that the current is 0. 01C, and the other is that the total duration does not exceed eight hours. In other words, if the lithium battery charging process still fails to reach 0. 01C after eight hours, it will be regarded as an unqualified product.