The difference between the charge battery and the ordinary battery battery of the robot is that there are two differences in the end voltage of the two. First, the internal resistance of the rechargeable battery is much lower than that of the ordinary battery. For example, the short-circuit current of a section 5 ordinary battery is measured by a digital multimeter, and its value is generally below 3A and measure a section 5 nickel and cadmium. The short-circuit current of Ni MH battery is generally above 4A, and it is precisely because of this, we can measure the instantaneous short circuit current by measuring the instantaneous short-circuit current when judging the real and false nickel cadmium and nickel hydrogen charging batteries. Second, the discharge characteristics of Ni Cd and Ni MH rechargeable batteries are different from those of ordinary batteries, especially when discharge terminates. In the discharge process, the end voltage of the ordinary battery is gradually reduced with the increase of the discharge amount, which is gradually reduced by the 1.5V. There is no sudden change in the end voltage, while nickel cadmium and nickel hydrogen battery are different, and the end voltage of the battery is almost not changed with the amount of discharge in the discharge process, but once the discharge is completed. The terminal voltage drops from about 1.2V to 1.0V, and the discharge current also decreases. The continued discharge below the 1.0V of the terminal voltage is called over discharge, which will damage the battery and affect the life span.
In the rechargeable batteries we use at present, they can be divided into four types, nickel cadmium battery (NiCd), nickel hydrogen battery (NiMH), lead acid battery (PbSO4) and lithium ion battery (Li+), respectively. Here are a brief introduction to the four types of rechargeable batteries:

　　(1) lead-acid battery: it is an earlier rechargeable battery, that is, commonly used vehicle battery. There are two kinds of common lead-acid batteries and valve pull sealed lead-acid batteries. The former is gradually replaced by the latter because of its inconvenient use and serious pollution to the environment. The emergency lights we use are generally of such batteries, with a normal cycle life of 1000~1200 times.
             (2) nickel cadmium battery: it is also an earlier battery. That is the popular Walkman rechargeable battery. The nominal voltage of a single battery is 1.25V, and its capacity is represented by the current capacity (mA) multiplied by an hour (H). If the capacity of a battery is 500MA, it means that the battery can discharge with a current of 500MA for an hour) for normal 5 battery (AA type) between 450~800MA, the normal cycle charge is more than 500 times, but if the use is not correct, it will greatly shorten the use of the number of times. Nickel cadmium battery has a phenomenon called "memory effect". When people charge the Ni Cd battery without discharging, the battery will automatically "remember" the point without discharging completely. When the next charge reaches this point, it will show the same characteristics as the discharge of the battery. So although the battery has not been fully discharged, but at the same time the capacity is reduced, this is the so-called "memory effect", which essentially produces a tree like crystalline structure in the electrode, a "memory effect" that is unique to nickel cadmium batteries. It will seriously affect the capacity of the battery and reduce the use time of the battery, so the nickel cadmium should be thoroughly discharged before charging the battery to recharge it after the discharge, and do not recharge the battery again and again when using this kind of battery. Most of the cheap charging current of the market will be charged automatically. Very small, the battery is filled with at least 15 hours, and no discharge function, damage to the battery is larger. The charger, which has a good part of function, enters the preprocessing stage when it is confirmed that it can be quickly charged. In this stage, the charger discharge the battery completely to fully discharge each cell to reduce the battery voltage to about 1.0V to eliminate the "memory efficiency" of the nickel cadmium battery. After the pretreatment of nickel cadmium battery, it enters the fast charging stage directly. After the fast charging is completed, it will take 2-3 hours to switch to trickle charge. 
            (3) Ni MH battery: it is a newly developed rechargeable battery. Its performance is similar to that of Ni Cd battery, but its energy density is even higher. The number 5 NiMH battery is between 1000mah and 1300mAh. In addition, it does not have a "memory effect" and no pollution to the environment. So it is called a "green battery", and of course the price is higher.
            (4) lithium-ion battery: it is also the latest development of the battery, the biggest advantage is that the energy density is higher, but its price is very high, generally used in high gear electronic products, but in discharge, do not exceed the discharge voltage, and can not be greater than discharge current discharge.
            In order to use all kinds of rechargeable batteries correctly and make full use of the battery life, the correct charging of the battery is very critical. If the charging method is not correct, it will greatly shorten the life of the battery.