21. What the curves shown in this figure? Compare them and make assumptions about their nature
We see the dependence of the voltage on the capacity. 4 types of curves discharge differing discharge current are shown. The first curve corresponds to the discharge at C / 5, which is equal to 0.5 A. The curve has a maximum source voltage and the maximum voltage value for the entire discharge time. The second curve shows the dependence of the discharge at C/2, which corresponds to 1.3 A. The initial voltage and common voltage during discharge is less than C/5. The third curve corresponds to the category at 1C or 2.6 A. It has a performance worse than the first two. The fourth curve is the lowest voltage because the discharge current equal to 2C or 5.2 A. Based on the chart one can conclude that the voltage decreases with an increase in discharge current. It is not much impact on the capacity of the battery, although the maximum discharge capacity decrease.
22. Draw a typical curve of self-discharge nickel-cadmium batteries.
The nickel–cadmium battery (NiCd battery or NiCad battery) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. A NiCd battery has a terminal voltage during discharge of around 1.2 volts which decreases little until nearly the end of discharge. NiCd batteries are made in a wide range of sizes and capacities, from portable sealed types interchangeable with carbon-zinc dry cells, to large ventilated cells used for standby power and motive power. Compared with other types of rechargeable cells they offer good cycle life and performance at low temperatures with a fair capacity but their significant advantage is the ability to deliver practically their full rated capacity at high discharge rates (discharging in one hour or less). However, the materials are more costly than that of the lead acid battery, and the cells have high self-discharge rates.
Rated voltage of sealed Ni-Cd batteries - 1.2V;
nominal (standard) charge mode NiCd batteries - a current of 0.1 C for 16 h;
Nominal discharge nickel-cadmium battery mode - Current of 0.2 C to voltage 1 V.
S
elf-discharge
Causes: corrosion of the negative electrode; electrolyte drying; recrystallization of the active mass (memory effect).
23. Draw on the one graph any possible discharge curves of two batteries (aa type) with a capacity of 1500 mAh and 2500, respectively. The discharge current 1000 mA.
The validity of the battery is calculated by the following formula: duration (in hours) = battery capacity (in ampere-hours)/ current (amps). Capacitance element - a quantity of electricity which chemical current source gives during discharge C = I . (А . h, if the item is discharged current I (A) for (h)). 1=С/I=1500/1000=1.5h; 2=C/I=2500/1000=2.5h.
During testing performed discharge battery current setpoint value. Despite the fact that the battery voltage during discharge it decreases gradually, the current throughout the time the discharge was maintained at that same given value. In this test, the batteries were discharged DC 1000mA.
Rated voltage penlight AA format batteries is 1.5 V (volts), but in the process of battery discharge the voltage gradually decreases. When the voltage drops to a predetermined value, consider the battery discharged. These results are calculated in two versions of the final discharge voltage values. In a first embodiment, the battery consider working until the voltage on it drops to 1.3 V. At this voltage disables "smart" devices such as MP3-players, cameras, radios and so on. In the second embodiment, the battery consider working until the voltage on it is reduced to 1 V. Until this voltage still somehow able to operate lights on the "normal" light bulbs, moving primitive toys, toothbrushes and electro. In the chart below you can see how to can see how long worked for each of the batteries reduces stress on them over the battery discharge time as well. The greater the figure - the more energy comprises a battery, the longer it will work in a variety of devices.