calculate the charging time of a rechargeable battery

Charging common sense

A reasonable charge to extend battery life, and rough random charging a great influence on the battery life. Mentioned above, the present lithium battery are basically in accordance with each product individually packaged, is not universal. As a result, each product also provides its own charging equipment, are not universal. You need only when use according to the corresponding instructions. Therefore, this article with the introduction of the batteries is mainly refers to the nickel cadmium battery and nickel metal hydride batteries.

Which has two kinds of nickel batteries and nickel-metal hydride batteries charging ways, called “quick charge” and “slow”. Fast charge and slow charge are important concepts of charging. Only understand the rapid and slow filling, can correctly grasp the charging.

First, fast charging and slow charging are relative concepts. Once someone asked, my charger charging current is 200 ma, is a quick charge? The answer is not absolute. Should answer is that for some of the battery, is fast charge, and for some batteries, just slow to charge. So how do we distinguish between fast and slow filling?

capacity per AA battery

For example, an AA nimh battery capacity is 1200 mah, and another 1600 mah. We refer to a battery of electric capacity of 1 c, 1 c is a logical concept, the same is not equal to 1 c.

When charging, when the charging current is less than 0.1 C, which we call a trickle charge. As the name implies, is the current is very small. In general, a trickle charge without damage to the battery life situation for a full charge. But using a trickle lithium battery charging time is too long, so rarely used alone, but used in combination with other charging ways.

When the charging current between 0.1 C to 0.2 C, we call it slow filling. Charging current greater than 0.2C, less than 0.8C is fast charging. When the charging current is greater than 0.8 C, we call it a super-fast charging.

Because of 1 c is a logical concept, not an absolute value, so the translated at 1 c of quick charge and the charge is also a relative slow. Mentioned in the above example 200 ma is 1200 mah battery charging current slow filling, 700 mah battery quick charge.

Understand the concept of fast and slow filling filling, we also need to know the status of the charger, to properly charge the battery. Chargers on the market at present is mainly divided into constant current charger and automatic charger.

rechargeable battery charger

Constant current charger

Constant current charger are on the market the most common charger. We start from nickel cadmium battery using constant current charger. Constant current charger usually adopt slow charging current, simple to use, you only need to charge batteries in the battery compartment. It is important to note that the lithium battery charging time of calculation must be accurate.

Lithium battery charging time has a simple formula: h = 1.5 C/charging current. For example: to 1200 mah battery, charger, charging current is 150 ma, time of 1800 mah / 150 ma is equal to 12 hours. In many cases, of course, is unable to calculate the accurate time. We can choose the nearest half an hour for timing. For example: the charger current is 160 ma, give a 1400 mah battery, time of 2100 mah / 160 ma about 13 hours, not minutes.

The constant current charger has simple structure, stable operation. This is a very good way to recharge, little effect on battery life. But it also has its limitations. First, you need to calculate time. In addition, with the capacity of nickel metal hydride batteries is more and more big, the constant current lithium battery charging time required is getting longer and longer, to use a certain amount of inconvenience. Therefore, fast automatic charger gradually became popular in recent years.

fast automatic charger

Fast automatic charger

In the past two years, the rapid automatic charger more and more popular. Has the characteristics of fast charging, safe. But some are skeptical, because quick charge is essentially to recharge with fast charging flow, these people afraid will affect the service life of batteries. So actual situation how?

Make sure first that the large current charging the battery life. In many cases, we had to use quick charge even super-fast charging. Charging current sometimes can reach 2 c or higher. High current is not battery killer. What really affect battery life are produced by the large current charging high quantity of heat.

When we recharge the battery, be sure to use a slightly higher than the nominal battery voltage of the voltage, the battery itself can have counter electromotive force on the charging current. Therefore, the part of the current are freely used to offset counter electromotive force and translated into heat. Charging current is larger, the more electrical energy into heat energy, the temperature at which the charge is also higher. High temperature is bad for rechargeable batteries. In the slow speed constant current charger, due to the slow charge, the heat generated by the under control, therefore do not need special measures. But in the fast automatic charger using fast charging current will produce a higher temperature. Therefore, currently on the market of fast automatic charger used various methods to reduce the temperature in the process of charging. Usually using the cosine method, namely the current is not large at a constant current charging, but current strength changes with current strength like a cosine wave. This change can alleviate the accumulation of heat, thus the temperature control in a certain range.  

Use quick charger is another problem, if at the end of the lithium battery charging time forget stop charging, the damage to the battery than slow constant current charger too much damage. Therefore, in order to solve the problem of overcharge, quick charger usually use judging slope method to judge the battery voltage is close to full. The charger using the control circuit, or IC chips to finish the task. Fast when the battery is full of, the control circuit will automatically switch to a trickle charge mode, a trickle charge the battery. The benefits of using a trickle charging is obvious. As mentioned earlier, a trickle charge for a full charge. Second, don’t have to worry about being overcharged. So, the greatest benefit of using this charger is not computing time. The specific method of use, please refer to the respective manuals, prevent wrong operation.

fast charger

Ultra-high speed charger is a branch of quick charger. Range of application of this kind of charger is limited, its design, structure, process is very complex, so the price is quite expensive.

In some special occasions, people need to recharge the battery in a short time, it will need to use the ultra-high-speed charger. For ultra-high speed charger takes a lot of charging current, some even use 2 c – 3 c charging current, hot question is extremely serious, and only a cosine wave charging is not enough, so a lot of this kind of charger is inserted in a cosine wave after using this method of discharge time is short. This method can reduce the counter electromotive force due to the charging current consumption caused by the accumulation of heat, so as to further control the temperature.


rechargeable battery discharge

We also know that when the memory effect gradually accumulate, the actual use of your battery capacity will significantly decline. In order to reduce the negative impact of memory effect, an effective way is to discharge. In general, as a result of the nickel cadmium battery memory effect is more noticeable, suggested after repeated charge discharge time, use 5 to 10 times. Ni-mh battery has a good memory effect, repeatedly charging use 20-30 times. Release.

Sells on the market some high-end charger bring discharge function, but most mid-range charger without discharge function. This time what should we do? After discharge principle, we can also try to give the battery discharge.

We already know that the nickel cadmium battery and the nominal voltage of 1.2 V nimh batteries, but in fact the battery voltage is a variable values, as the power is enough, at around 1.2 V. General fluctuations between 1 V to 1.4 V. Different brands of batteries due to process different, have different voltage fluctuation.

The battery discharge is the battery voltage drops slowly with small discharge current, between the moment – 1 V to 0.9 V, should stop discharge. It is not recommended to put the battery discharge below 0.9 V. This can lead to excessive battery discharge and irreversible damage. Said a rechargeable battery wasn’t on the home appliances remote control, because the remote control using electric current is very big. Small, long time used on the remote control is easy to cause excessive discharge. After the battery discharge correctly, you will be surprised to find that the battery capacity has been restored to its original level. Therefore, it is best to discharge the battery when it is found to be decreasing in capacity.

Herself to a simple battery discharge method is to pick a flashlamp as load, but must use electric meter monitor voltage change, prevent the discharge.

battery depth of discharge


On the choice of the charger, it is fast or slow filling filling constant current charger, basically see the use of their priority. Used to go on the use of digital cameras and other equipment such as friends, should choose the quick charger to meet the lithium battery charging time requirements, you can even buy ultra-high-speed charger, and only use the walkman devices such as friends can use constant current charger. Fit for purpose

To master the correct charging and discharging after knowledge, you can better use rechargeable batteries. Please don’t insist on quick charge.

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