What are the 3 stages of lithium battery charging?

Introduction

Lithium batteries have 3 stages of charging, usually divided into these three stages:

1.Constant Current Pre-charge Mode

2.Constant Current Regulation Mode

3.Constant Voltage Regulation Mode

Sounds similar to Lead-acid battery? Something different. That's why we need to buy a new charger for lithium batteries. Moreover, what exactly is "quick charge" and how can it make your battery be charged faster?

What is the principle of lithium battery charging?

Lithium batteries are divided into an anode (the negative pole) and a cathode (the positive pole). The cathode is a lithium compound. The anode is mainly made of graphite, and both are immersed in the electrolyte. Whether it is discharging or charging, it is actually a process in which lithium ions move between the anode and cathode of the battery, and electrical energy and chemical energy are converted to each other. During charging, due to the effect of the electric field, lithium ions move from the positive pole to the negative pole and store energy; during discharge, lithium ions move from the negative to the positive under the action of a chemical reaction, at which time a current is supplied to the power supply.

The speed at which lithium batteries are charged is actually the rate at which electrical energy is converted into chemical energy, which is called "power" (P).

Formula: P(Power) = I(current) * U(Voltage)

The larger the current or voltage, the greater the power, and the lithium battery should be charged faster. However, due to the limitations of the lithium battery itself, charging under the condition of Undervoltage or overvoltage will cause damage to the battery. Therefore, the charging method of the lithium battery is special and usually divided into three stages:

Pre-charge Mode

Definition: When the phone is completely empty, the charger first charges the lithium battery with a constant current with a small current to make it slowly reactivate.In the pre-charge phase, the battery is charged at a low-rate (typical of 1/10 the Constant Current Regulation Mode) when the battery cell voltage is below 3.0 V. This provides recovery of the passivating layer which might be dissolved after prolonged storage in deep discharge state, also prevents overheating at 1C charge when partial copper decomposition appears on anode-shorted cells on over-discharge. When the battery cell voltage reaches 3.0 V, the charger will increase the constant current and gradually increase the voltage, which is the main stage of lithium battery charging.

Battery charger operation modes

Constant Current Regulation Mode (CC)

Definition: Replaces ≈80% of the battery's state of charge at the fastest possible rate.

This is a constant-current stage. This stage typically leaves the batteries at around 80% of their capacity. It accomplishes this by maintaining a constant relatively high current. The current is held constant against the rising internal resistance to charge current by raising the battery voltage. Therefore, if you want to increase the charging speed, it is the best way to optimize it is at the next stage: Constant Current Regulation Mode.

Fast charge battery refers to a battery that can be filled with 80% or 100% in a short time.

Normally high discharge rate (C-rate) batteries can be fast-charged. For example, when the charging voltage is 5V and charging with 1C, it can be fully charged in 1 hour. If it is a 1000mAh battery, 1C means the charging current is 1A; for a 2000mAh battery, 1C means the charging current is 2A, and so on.

Lithium battery - Normal battery vs Grepow fast-charging battery

Learn more about Grepow fast charge battery: Click Here

As you can see from the chart, the period of the Constant Current charging stage of the normal battery is much longer than Grepow fast-charging battery.

Constant Voltage Regulation Mode (CV)

Definition: Voltage is held constant in order to prevent damage and keep batteries at a full charge, replenishes the remaining 20% of charge.The battery is typically charged at a constant current of 0.5 C or less until the battery voltage reaches 4.1 or 4.2 V (depending on the exact electrochemistry, around the 80% fulfilled of the battery). When the battery voltage reaches 4.1 or 4.2 V, the charger switches to a “Constant Voltage” stage to eliminate overcharging.

P.S.: Superior battery chargers manage the transition from constant current to constant voltage smoothly to ensure maximum capacity is reached without risking damage to the battery.

Maintaining a constant voltage gradually reduces the current until it reaches around 0.1 C, at which point charging is terminated. If the charger is left connected to the battery, a periodic ‘top-up’ charge is applied to counteract battery self-discharge. The top-up charge is typically initiated when the open-circuit voltage of the battery drops to less than 3.9V to 4V, and terminates when the full-charge voltage of 4.1V to 4.2V is again attained.

Can I charge my lithium battery with a lead-acid charger?

Different types of lithium batteries and lead-acid batteries are not recommended for use together, because the load characteristics and capabilities of the battery are different, which will lead to abnormal conditions and safety issues. As I mentioned before, the charger of lead-acid battery is generally set to two-stage or three-stage charging mode, the charge is not matched for lithium and lead-acid battery due to different voltage levels. Batteries with completely different performances should not be used in parallel. Even if diodes are added, self-discharge between the batteries can be prevented, but a good parallel discharge effect is not obtained.

Related article: Can lithium batteries and lead acid batteries be used together?

Learn more about battery

Keep an eye on Grepow’s official blog, and we’ll regularly update industry-related articles to keep you up-to-date on the battery industry.

Grepow: https://www.grepow.com/

Grepow Blog: https://www.grepow.com/blog.html