Charging Lithium Batteries: The Basics

Table of Contents

How to charge Lifpo4 battery?

  1. New lifepo4 battery charging
    Under normal circumstances, the life of a lifepo4 battery has already begun from the moment it leaves the factory, and it is in a low-capacity self-discharge state. After the lifepo4 battery is placed for a period of time, it will enter the dormant state. At this time, the capacity is lower than the normal value, and the use time is also shortened. The capacity loss caused by this self-discharge is reversible, that is to say, it can be recovered by charging the lifepo4 battery. Simply put, this process is like when the human body is not working, the energy consumption is at a low level, but there are still a small amount of cells and tissues working to ensure the normal operation of the human body.

Regarding the beginning of charging the lifepo4 battery, there is such a misinformation that the lifepo4 battery must be charged for more than 12 hours when it is activated, and it can be activated after repeated charging three times. In fact, overcharge and overdischarge will cause different degrees of damage to lifepo4 batteries, and this statement is also for traditional nickel lifepo4 batteries.

The lifepo4 battery is easy to activate. Generally, after 3-5 normal charge and discharge cycles, the lifepo4 battery can be activated to restore its normal capacity.

  1. When to charge the lifepo4 battery
    When to charge the lifepo4 battery? The number of charging and discharging times of the lifepo4 battery is limited, so the lifepo4 battery should be used up and recharged as much as possible.

Under normal circumstances, the lifepo4 battery should be used up and then recharged, but it should be implemented according to actual life needs. For example, the remaining power of the electric car tonight is insufficient to support the trip tomorrow, and the conditions for charging are not available the next day. At this time, it should be charged in time.

In fact, the principle of insisting on using up the remaining power of the lifepo4 battery and recharging does not refer to the extreme practice of using the lifepo4 battery completely. If the electric vehicle still does not charge until it cannot drive after the warning of low battery level appears, this situation may cause the voltage to be too low due to the over-discharge of the lifepo4 battery, resulting in damage to the life of the lifepo4 battery.

  1. Summary of lifepo4 battery charging
    The activation of the electric vehicle lifepo4 battery does not require any special method, according to the standard time and procedure to charge, even for the first three charges. In the normal use of the electric vehicle, the lifepo4 battery will be activated naturally; when the electric vehicle is prompted that the battery is too low, it should start charging in time.
Charging Lithium Batteries: The Basics

Do Lifpo4 battery packs need a dedicated charger?
Lifpo4 battery pack requires a dedicated charger.
The charging principle of lead-acid battery: the electrode of acid battery is lead and its oxide, and the electrolyte is sulfuric acid solution. When discharging, the positive electrode is mainly a lead-brocade-calcium alloy fence, which contains lead oxide as the active material, the negative electrode active material is lead, and the positive and negative electrodes are lead sulfate during charging.

The nominal voltage of Lifpo4 battery is 3.2V, and the charge cut-off voltage is 3.6V. The nominal voltage of ordinary lithium batteries is 3.6V, and the charge cut-off voltage is 4.2V. If you use an ordinary lithium battery charger to charge the Lifpo4 battery, the charging voltage will be a little high, which is harmful to the battery. A dedicated charger should be used to charge the Lifpo4 battery.

Lifpo4 batteries cannot be used with ordinary lithium battery chargers, because the nominal voltage of Lifpo4 batteries is 3.2 volts (generally used as 3V batteries). The full voltage of 3.65V cannot exceed 3.8V. If you use a 4.2V ordinary charger, the battery will be damaged.

Lifpo4 batteries and lithium batteries have different working principles, different charging and control modes, and mixing them is very dangerous. The best and safest charging method is to use the original charger. In addition, when choosing a Lifpo4 battery charger, a charger with an appropriate charging current should be selected, which can effectively protect the battery and improve the battery life.

Lifpo4 battery charging method is generally Lifpo4 battery charging upper limit voltage 3.7~4V, discharge lower limit voltage 2~2.5V, comprehensively considering discharge capacity, discharge median voltage, charging time, constant current capacity percentage, safety these five aspects, using constant current For the constant voltage charging scheme, for Lifpo4 battery pack, it is reasonable to set the charging limit voltage at 3.55~3.70V, the recommended value is 3.60~3.65V, and the discharge lower limit voltage is 2.2V~2.5V.

The charger of Lifpo4 battery pack is different from ordinary lithium battery. The highest end charge voltage for lithium batteries is 4.2 volts; Lifpo4 battery packs are 3.65 volts. When the Lifpo4 battery pack is charged, it is the cable connected to the balanced charging board. Generally, the overall charging is directly connected in series from both ends, and the charger voltage is greater than the battery pack voltage. The cable detects the voltage of each single cell, which is equivalent to connecting a voltage regulator tube in parallel. The charging voltage of the single cell will not exceed the voltage regulation value, while other cells continue to charge through the voltage regulator tube bypass charging.

(1) Constant voltage charging method: During the charging process, the output voltage of the charging power supply remains constant. With the change of the state of charge of the Lifpo4 battery pack, the charging current is automatically adjusted. If the specified constant voltage value is appropriate, it can not only ensure the full charging of the power battery, but also minimize gas evolution and water loss.

(2) Constant current charging method: During the whole charging process, the charging current is kept constant by adjusting the output voltage. Keeping the charging current unchanged, the charging rate is relatively low. The constant current charging control method is simple, but because the acceptable current capacity of the lithium battery pack gradually decreases with the charging process, in the later stage of charging, the power battery receiving capacity decreases, and the charging current utilization rate is greatly reduced.

Yes, the car generator can only directly charge lithium batteries with a rated voltage of 12V.
The following symptoms will appear when the car generator is broken:

Can a car alternator charge a lithium battery?

  1. Dim headlights or dashboard lights: The alternator is part of the vehicle’s electrical system. Its main role is to provide power to operate the starter, ignition and all electronic accessories in the car. If the alternator starts to fail, the headlights or dashboard lights start to dim. Once the instrument lights or headlights are dimmed, this is a clear sign of a potential alternator failure;
  2. Warning light on: Most modern cars have a reminder when the alternator warning light flashes in a dashboard. Usually, the light is shaped like a battery, though, some might say, ALT (alternator) or GEN (generator). This light may only fire if multiple electrical components are being used;
  3. A system belt used for working with the alternator of the automobile generator belt. If the belt doesn’t turn freely, the excess friction can cause the belt to heat up, which produces a burning rubber smell. If you notice an electrical fire-like smell, this may indicate that the alternator pulley on that belt is slipping, causing poor generator output.

What is direct current and alternating current
Direct current, as the name implies, is that the magnitude and direction of the current will not change with time, such as: constant voltage power supply, constant current power supply. Alternating current, as the name implies, is that the magnitude and direction of the current will periodically change with time, such as the electricity generated by a generator.

What is the difference between direct current and alternating current

  1. Essential difference:
    In direct current, the magnitude and direction of the current are fixed within a specific time range. In alternating current, the magnitude and direction of the current will change periodically.
  2. Different transmission methods:
    Generally speaking, the transmission mode of direct current is better than alternating current, and alternating current can replace direct current. From the perspective of the development history of electricity, this is only a technical reason. Therefore, in daily life, the more common transmission method is alternating current.

Are Lifpo4 batteries AC or DC?
All battery power is direct current, alternating current is just produced by a generator.

There are many forms of generators, but their working principles are based on the law of electromagnetic induction and the law of electromagnetic force. Therefore, the general principle of its construction is to use appropriate magnetic and conductive materials to form magnetic circuits and circuits that conduct electromagnetic induction with each other to generate electromagnetic power and achieve the purpose of energy conversion.
The classification of generators can be summarized as follows:
Generators DC generators, alternators, synchronous generators, asynchronous generators (rarely used)
Alternators can also be divided into single-phase generators and three-phase generators.

How to understand the charging cycle of lithium batteries? Is lithium battery life related to the number of charges?

How to understand the charging cycle of lithium batteries? Is lithium battery life related to the number of charges? The lithium battery charging cycle is closely related to the life of the lithium battery. A charging cycle refers to the complete charging and discharging process of a lithium battery. If it is decomposed, a charging cycle consists of a full charge and a full discharge process. The life of a lithium battery is related to the number of completed charging cycles, and has nothing to do with the number of times the lithium battery is charged and discharged.

How to understand the charging cycle of lithium batteries?

A lithium battery is only half charged on the first day, and then fully charged; the next day, it is half charged, for a total of two charges, which can only be counted 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.

In other words, the lithium battery charging cycle is an expression of the lithium battery power, which means the process of the battery power from full to empty and then from empty to full. From the perspective of voltage in the existing battery design, a single lithium battery is used from no-load 4.2V (the capacity is the nominal capacity) to 2.75V (the capacity is zero at this time), and then a reverse process is completed to complete a charge cycle.

In fact, the life of a lithium battery is determined by the charging cycle. In daily life, it may usually take several charging cycles to complete a cycle, and the battery capacity will decrease a little after each charging cycle is completed, but the decrease in power is very small. High-quality batteries will still retain 80% of their original capacity after being charged for many cycles, and many lithium-ion battery-powered products are still used as usual after two or three years.

Is lithium battery life related to the number of charges?

The life of a lithium battery is generally 300-500 charging cycles. The life of a lithium battery is related to the total charging capacity of the battery, and has nothing to do with the number of charging times. Deep discharge and deep charge and shallow discharge and shallow charge have little difference in the impact of lithium battery life. In fact, shallow discharge and shallow charge are more beneficial for lithium batteries. Only when the power module of the product is calibrated for lithium batteries is it necessary to deep discharge and deep charge.

The life of the battery is based on the number of charge and discharge cycles of the battery, and the number of times is determined by the battery life. For the life of the battery, the life of the power lithium-ion battery can reach 2000 cycles. According to the life of the lithium battery, Generally, it has a life of about 500 to 800 charging cycles.

How to maintain the lithium battery?

  1. Lithium batteries that are not used for a long time should be stored in a cool and dry place. The half-charged state is the best. It is dangerous to store the battery at full power and the battery will be damaged. If the battery is stored without electricity, it will be destroyed. Every 3–6 months, check whether you need to recharge.
  2. Lithium batteries should be charged at any time. Don’t wait until the battery’s power is exhausted before charging. The best charging is to charge the mobile phone when the power of the mobile phone is lower than 20%.
  3. Try to avoid charging the mobile phone overnight. Although the lithium battery does not have a great impact on the long-term charging loss, the lithium battery has unsafe characteristics, and long-term charging will cause serious consequences.
  4. Do not use the mobile phone while the mobile phone is charging, it will have an adverse effect on the charging circuit and battery of the mobile phone, and there will also be unsafe factors.

Lifpo4 battery floating charge
Floating charging is a supply (discharge) working method of the battery pack. The system connects the battery pack and the power line to the load circuit in parallel. Its voltage is generally constant, only slightly higher than the terminal voltage of the battery pack. A small amount of current supplied by the power supply line compensates for the loss of the local action of the battery pack, so that it can always be kept in a fully charged state without overcharging.

Floating charge characteristics: The battery pack is a charging device that provides floating charge current to the battery pack in addition to supplying power to conventional loads. This mode of operation is called full float operation, or float operation for short.
Therefore, the battery pack can be charged and discharged as the power line voltage fluctuates up and down. When the load is light and the voltage of the power supply line is high, the battery pack is charged. When the load is heavy or the power supply is interrupted unexpectedly, the battery pack is discharged to share part or all of the load. In this way, the battery pack will play a role in voltage regulation, and is in a standby state.

There are two types of floating charging power supply modes: half floating charging and full floating charging. When part of the time (when the load is heavy), the floating charge is used for power supply, and the other part of the time (when the load is light) is powered by the battery pack alone. If the power supply line is connected to the battery bank in parallel with the floating charging power supply at all times, it is called the full floating charging working mode, or the continuous floating charging working mode.

The battery pack used in the floating charging mode generally has a longer life than the full charging and discharging mode, and can be replaced by a battery pack with a smaller capacity. This floating charging power supply mode is mostly used for power-off backup power supply in power plants and normal power supply for telephones in telephone offices.

What are the proper charging voltages for the 12V, 24V, and 48V lithium batteries?

Our Keheng Battery charging parameters consist of the following:

Bulk/absorb = 14.2V–14.6V.

Float = 13.6V or lower.

No equalization (or set it to 14.4V if possible).

No temperature compensation.

Absorption time is approximately 20 minutes per battery, if possible.

For a 12V system, we really want to emphasize reaching 14.2V – 14.6V for bulk and absorption and float to be 13.6V or lower.

For a 24V system, we suggest a bulk and absorption rate of 28.4V– 29.2V and float to 27.2V or lower. No equalization is required, but if it’s possible we suggest 28.8V. No temperature compensation is required either, and absorption time is approximately 20 minutes per battery if that is an option. 

For a 48V system, we recommend a bulk and absorption rate of 57.4V and floating it at 56.5V to 57V. Sometimes, one of the batteries may trigger a high voltage disconnect in your system. The battery’s internal BMS will help handle a high voltage disconnect. Our team wants to emphasize that, overall, there’s no harm in playing around with charge rates to optimize your system. 

How long does it take to charge lithium batteries?  

One of our most frequently asked questions is “how long does it take to charge lithium batteries?”

Our experts note charging time depends on the specific charger in your system. Lithium-ion batteries have low internal resistance, so they will take all the current delivered from the current charge cycle. For example, if you have a 50-amp charger and a single 100-amp hour battery, divide the 100 amps by 50 amps to come up with a 2-hour charging time. 

Another example is if you had five 100Ah (amp-hour) batteries for a total of 500Ah and a 100-amp charger. It would take about 5 hours of charging from empty to 100 percent while factoring in enough time to balance the charging cycle. We don’t recommend you exceed this charge rate as it can lead to a shortened battery cycle life. In an emergency, the battery can be charged at a quicker rate if needed, but we don’t recommend you make a habit of emergency charging your battery. 

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