Classification of rechargeable batteries

There are many types of rechargeable batteries, but they require high energy density, light weight, and large discharge current when used on model aircraft. At present, nickel-cadmium batteries, nickel-metal hydride batteries and lithium-ion batteries are mainly used. The internal resistance of the rechargeable battery is low, so be careful not to short circuit when using it, otherwise it may cause burns and fire.

The main feature of nickel-cadmium batteries (Ni-Cd) is excellent high-current discharge performance, which meets the short-term high-power requirements of aircraft models. An important performance indicator of a rechargeable battery is the discharge rate. The so-called discharge rate refers to the ratio of the maximum continuous discharge current of the battery to its capacity C. C stands for the number of hours required to discharge one ampere. Usually, a number is added before the capacity C. For example, the discharge rate of a Grignard 1800mah battery is 10 C, which means that its maximum continuous discharge capacity is 18A. It can be seen that the discharge rate is an important indicator to measure the rapid discharge performance of the battery. Due to the difference in production process and structure, the discharge rate of different brands of batteries is often different. The domestic nickel battery is generally 6C~12C, and the imported battery is usually higher, especially the special power battery for model aircraft, which can often reach about 20C. The first thing to choose a battery is to choose a battery with a high discharge rate.

However, the energy density of nickel batteries is small, and there is a memory effect. Waste batteries are relatively polluting to the environment and will be eliminated soon. Currently, they are only used in occasions with extremely large current output. Nickel-metal hydride battery (NiMH) is an environmentally friendly rechargeable battery. Its performance and charging method are the same as those of nickel-battery. The battery is only inferior to the nickel battery in terms of high-current discharge performance, generally around 7C.

Nickel battery and nickel metal hydride battery have the same series of models, commonly used mainly are SC type, A type, AA type (No. 5), AAA type (No. 7) and so on. In addition, there will be some special models of batteries, which are usually lengthened or shortened models derived from standard battery model specifications. The battery cells (battery cores) are sometimes directly marked by the size of the battery, such as 18650 and 1848, which mark a single battery with a diameter of 18 mm and a length of 65 mm and 8 mm respectively. The motors and receivers in model airplanes use power supplies. Their voltages are generally above 5v, and the power packs are generally above 9~12v. This requires multiple batteries to be connected in series, which are generally connected by spot welding with nickel sheets. Amateur production can use copper tin soldering, but pay attention to the short soldering time to avoid damage to the battery.

Lithium-ion polymer batteries (Li-Poly) are currently the mainstream of rechargeable batteries. It has been widely used in handheld electronic products such as mobile phones. The monomer voltage of lithium ion polymer is as high as 3.6v, the energy density is high, the weight is light, and there is no memory effect. However, the charging and discharging requirements of lithium-ion batteries are relatively high, and it is difficult to achieve high-current discharge, otherwise it is very easy to damage the battery. The discharge capacity of lithium-ion polymer batteries for aircraft models has reached more than 10C. At the same time, the safety of lithium-ion polymer batteries is no longer a problem, but special charge and discharge protection circuits are required for protection. There are many packaging forms of lithium-ion polymer batteries, most of which are flat cuboids, and each battery has a dedicated protection circuit, which will automatically protect when the discharge voltage is lower than a certain time or the discharge current is higher than a certain time. Many battery protection circuits It also has a charging protection function. Lithium-ion polymer batteries use aluminum-plastic flexible packaging in structure, which is different from the metal shell of lithium-ion batteries (Li-ion) in the early liquid batteries. Once a safety hazard occurs, liquid batteries are prone to explosion, while polymer batteries are the most Only angry.