How long is the charging time of NiMH battery? It is a doubt for many people, because NiMH batteries cannot be judged by the voltage to determine whether the battery is fully charged or not. NiMH batteries are different from lithium batteries, which represent the signal that lithium batteries are fully charged when they reach the specified voltage, and the conditions required to fully charge NiMH batteries with different degrees of newness are different, which is one of the characteristics of NiMH batteries.
How long does it take to charge a NiMH battery?
For newly purchased NiMH batteries, the first charge time is slightly longer to ensure the battery is recycled. Because the intelligent NiMH battery charger is judged by the -△V signal to determine whether the NiMH battery is full or not, the newly purchased NiMH battery may not have the -△V signal detected during the first charge because it has been stored for a certain period of time, so the charger is constantly replenished with a small current until the charging time set by the charger is stopped, theoretically speaking. At this time, the NiMH battery is actually overcharged, but this will not have much effect on the NiMH battery because the NiMH battery will convert the excess power into heat energy and consume it. So, when a newly purchased NiMH battery is charged for the first time, the battery will be hotter.
How long it takes to fill the NiMH battery depends on the capacity of the battery and the power consumption of the charger, in addition, it also needs to see whether the NiMH battery is in a normal state, when the NiMH battery is stored for more than half a month, the battery may enter a dull state, of course, the better the quality of the NiMH battery this time will be longer, the dull state of the battery using the intelligent NiMH battery charger is of little practical significance, there is no -△V signal when the Chargers are usually time forced to stop charging, generally ranging from 5-10 hours, the normal state of NiMH batteries using fast chargers, the fastest 2 hours can be filled. Individual ultra-fast chargers may be full in 1 hour, but NiMH batteries are not suitable for ultra-fast charging, as overheating will evaporate the water inside the battery and shorten the life of the battery.
How to determine how long it takes to charge NiMH batteries?
1) The nominal capacity of the battery, the larger the capacity, the longer the charging time required.
2) Charge several batteries at the same time. When charging a part of NiMH battery, the charging time of two and four sections is different, charging two sections is twice as fast as charging four sections.
3) the size of the current that the charger can output, high current is fast, low current is slow.
(4) the battery has no remaining, if completely dead, the charging time is longer, if there is still remaining power, the charging time is shorter.
NiMH battery charging has a formula: the capacity of the battery (mAh) ÷ charging current (mAh) & TImes;1.2~1.5 = the time required for the battery to be fully charged (hours).
The size of the charging current varies due to different chargers. Charging time is generally indicated in the charger's manual, full of four 2300mah batteries, standard charging takes 10 to 20 hours, fast charging takes 6 to 8 hours, and rapid charging takes 1 to 2 hours. The normal charging time is mainly related to the charging current of the charger used, under normal circumstances, NiMH battery chargers can automatically stop when full. For example, if the battery is charged with a 1000mA charger, it can be fully charged in one hour.
Notes on charging NiMH batteries.
The operating time of NiMH batteries (number of charges and discharges) depends mainly on the operating conditions. The operating time decreases with increasing depth and discharge rate. The operating time depends on the charging rate and the control method. Depending on the NiMH battery type, operating mode and operating conditions, the battery can provide 500-1000 discharge cycles at 80% depth of discharge and a service life of 3-5 years. To ensure reliable operation of NiMH batteries during the warranty period, follow the recommendations and manufacturer's instructions. Attention should be paid to the temperature environment. Avoid over-discharge (below 1V) and short circuits. NiMH batteries should be used according to their purpose. Do not directly solder unused batteries.
NiMH batteries are more sensitive to overcharging than NiCd. Overcharging can cause thermal acceleration. Charging is usually performed at a current of IC=0.1°C for 15 hours. Current Ic = compensating charge occurs at 0.01-0.03°C for more than 30 hours.
NiMH batteries with many active electrodes can be accelerated (4-5 hours) and charged quickly (1 hour). If such a charge exists, the process is controlled by temperature change ΔT and voltage ΔU and other parameters. For example, laptops and cell phones currently use mainly Li-ion and Li-polymer batteries, but fast charging is used to power NiMH batteries for laptops, cell phones and power tools. The first step of fast charging (1C or higher) is to charge at 0.1C for final charging, and it is also recommended to use a charging method with compensated charging at 0.05-0.02C. Information on how to charge NiMH batteries is usually included in the manufacturer's instructions.
Due to the release of oxygen at the anode, the amount of power delivered during charging (Q3) is greater than the discharge capacity (Cp). In this case, the return capacity (100Cp/Q3) is 75-80% and 85-90% for disk and cylindrical NiMH batteries, respectively.
Charge and discharge control: To avoid overcharging of NiMH rechargeable batteries, the following charge monitoring methods can be used in conjunction with appropriate sensors installed in the rechargeable battery or charger.
A method to terminate charging at absolute temperature (Tmax): The battery temperature is continuously monitored during charging and rapid charging is stopped when the maximum value is reached.
A method of terminating the charge relative to the rate of change of temperature ΔT/ΔT: when using this method, the slope of the battery temperature curve is continuously monitored during charging and charging stops when this parameter is above a certain set value. When the battery is fully charged, the oxygen cycle begins, the temperature starts to rise and the voltage decreases.
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