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Common sense of several rechargeable batteries

Introduction To Rechargeable Batteries

Types of rechargeable batteries 

Nickel-Cadmium Batteries (Ni-Cd)

Voltage: 1.2V

Service life: 500 times

Discharge temperature: -20 degrees to 60 degrees

Charging temperature: 0 degrees to 45 degrees

Remarks: Strong resistance to overcharge.

Ni-MH battery (Ni-Mh)

Voltage: 1.2V

Service life: 1000 times

Discharge temperature: -10 degrees to 45 degrees

Charging temperature: 10 degrees to 45 degrees

Note: The current maximum capacity is about 2100mAh.

Lithium-ion battery (Li-lon)

Voltage: 3.6V

Service life: 500 times

Discharge temperature: -20 degrees to 60 degrees

Charging temperature: 0 degrees to 45 degrees

Remarks: The weight is 30% to 40% lighter than that of Ni-MH batteries, and the capacity is more than 60% higher than that of Ni-MH batteries. But it is not resistant to overcharging. If overcharging, it will cause the temperature to be too high and damage the structure => an explosion.

Lithium polymer battery (Li-polymer)

Voltage: 3.7V

Service life: 500 times

Discharge temperature: -20 degrees to 60 degrees

Charging temperature: 0 degrees to 45 degrees

Remarks: The improved type of lithium battery does not have battery fluid, but uses polymer electrolyte instead, which can be made into various shapes and is more stable than a lithium battery.

Lead-acid battery (Sealed)

Voltage: 2V

Service life: 200 to 300 times

Discharge temperature: 0 degrees to 45 degrees

Charging temperature: 0 degrees to 45 degrees

Remarks: It is a general car battery (6 *2V connected in series to form 12V). The battery life without adding water is up to 10 years, but the volume and weight are the largest.

The Noun Explanation Of Battery Charging

Charge rate (C-rate)

C is the first letter of Capacity, which indicates the current magnitude when the battery is charged and discharged.

For example: when the rated capacity of the rechargeable battery is 1100mAh, it means that the discharge time at 1100mAh (1C) can last for 1 hour. For example, the discharge time at 200mA (0.2C) can be

Lasting 5 hours, charging can also be calculated according to this comparison.

Cut-off discharge voltage

Refers to when the battery is discharged, the voltage drops to the minimum working voltage value that the battery should not continue to discharge.

According to different battery types and discharge conditions, the requirements for the capacity and life of the battery are also different, so the specified termination voltage of battery discharge is also different.

Open circuit voltage (OCV)

When the battery is not discharging, the potential difference between the two poles of the battery is called the open circuit voltage.

The open circuit voltage of the battery will vary according to the material of the positive and negative electrodes of the battery and the electrolyte. If the materials of the positive and negative electrodes of the battery are exactly the same, no matter how big the battery is and how the geometry changes, the open circuit voltage will be the same.

Depth of discharge DOD

During the use of the battery, the capacity released by the battery as a percentage of its rated capacity is called the depth of discharge.

The depth of discharge has a deep relationship with the charging life of the secondary battery. The deeper the depth of discharge of the secondary battery, the shorter the charging life. Therefore, deep discharge should be avoided as much as possible in use.


If the battery exceeds the termination voltage value of battery discharge during the discharge process and continues to discharge, the internal pressure of the battery may increase, the reversibility of the positive and negative active materials will be damaged, and the capacity of the battery will be significantly reduced.


When the battery is charging, if it continues to be charged after it is fully charged, it may cause the internal pressure of the battery to rise, the battery to deform, and to leak at night, and the performance of the battery will also be significantly reduced and damaged.

Energy density

The electrical energy is released by the average unit volume or mass of a battery.

Generally, under the same volume, the energy density of lithium-ion batteries is 2.5 times that of nickel-cadmium batteries and 1.8 times that of nickel-metal hydride batteries. Smaller size and lighter weight.


Regardless of whether the battery is in use or not, due to various reasons, it will cause the phenomenon of power loss.

If calculated in units of one month, the self-discharge of lithium-ion batteries is about 1%-2%, and the self-discharge of nickel-metal hydride batteries is about 3%-5%.

Cycle life

When the rechargeable battery is repeatedly charged and discharged, the battery capacity will gradually decrease to 60%-80% of the initial capacity.

Memory effect

During the charging and discharging process of the battery, many small bubbles will be generated on the battery plate. Over time, these bubbles will reduce the area of the battery plate and indirectly affect the battery’s capacity.

Basic Requirements For Charging And Discharging Rechargeable Batteries

Does the new battery need to be charged for 8-12 hours?

Any battery has the characteristic of self-discharging, so when a new rechargeable battery arrives in your hands, the rechargeable battery may have been self-discharging for a period of time. This means that the chemical raw materials inside the rechargeable battery have not been used for a period of time, and appear in a “passivation” state, which cannot fully exert the chemical reaction and provide sufficient voltage. In this case, when using the rechargeable battery for the first time, be sure to fully charge the rechargeable battery to restore the voltage to its original level. In fact, if your rechargeable battery has not been used for a long time, this “passivation” phenomenon will also occur, and the situation will be more serious. It is best to charge and discharge the rechargeable battery 3 times, which will help the activation of the rechargeable battery. Allows the chemicals inside the rechargeable battery to work as intended (NiCd batteries). Sometimes when a newly purchased rechargeable battery is put into the charger, it will stop charging before it is fully charged. When you encounter this kind of problem, you just need to remove the rechargeable battery from the charger, and then put it in the charger to continue charging. This is normal for a new rechargeable battery, not a bad rechargeable battery you bought (NiMH, Li-ion). Generally speaking, the charging time should not be too long, a maximum of 12 hours is enough, and if it is overcharged, it will cause damage to the rechargeable battery.

How to calculate charging time?

Charging time (hours) = rechargeable battery capacity (mAh) / charging current (mA) * 1.5 factor

If you use a 1600mAh rechargeable battery and the charger charges with a 400mA current, the charging time is: 600/400*1.5=6 hours (Note: This method is not applicable to newly purchased or long-term unused rechargeable batteries)

Ni-MH rechargeable batteries and lithium-ion rechargeable batteries actually have a memory effect. Do they really need to be discharged?

In fact, the memory effect of nickel-metal hydride rechargeable batteries and lithium-ion rechargeable batteries is very slight, and it is not worth our attention to it.

(Please note that when you see this, do not use the discharge function of the charger to discharge nickel-hydrogen rechargeable batteries and lithium-ion rechargeable batteries, especially lithium-ion rechargeable batteries, due to their own material factors, the battery itself is not allowed to withstand Forced discharge of the charger. If you insist on discharging the lithium-ion rechargeable battery, it will eventually lead to battery damage.) In addition, if you use a nickel-cadmium rechargeable battery that needs to be discharged, it is recommended that you use the battery frequently or not. It is best to charge and discharge the nickel-cadmium rechargeable battery every two or three months, so as to ensure that the memory effect of the nickel-cadmium rechargeable battery has a minimal impact on the battery.