USB Phone World Posting Page
Thursday, October 20, 2011
Actually, the internal resistances have great influence on laptop battery in specifications, standby time, running temperature and so on. With time goes by, resistance value comes to be higher and higher while the output power of batteries will be reduced to some extent.
Different type of laptop battery has got different internal resistances with different electrochemical properties. Usually, we can indicate it by milliohm that is also related to the output electric current and output power value.
In the process of charging and discharging, the internal resistances will produce enough heat inside the lithium-ion batteries. However, it is not determined by a certain value but a relative magnitude. Therefore, what we need to care about it not the pure resistance but the relationship of output voltage, current and power capacity as well.
Now, let’s see some popular measurement methods to calculate the internal resistances.
DC discharge resistance test method – According to the physical equation, the test device will have a powerful DC current value and voltage as well. Therefore, we can learn about the internal resistance by U(volt)/I(mAh). The result is very accurate with difference within 0.1%.
Exchange impedance measurement of pressure dropping – Actually, the internal resistances are those of resources, we can apply a fixed frequency and current by kHz and mAh. Then we can take sample and handle by rectification, filtering and other ways. The process of measuring is very short to be of around millisecond.
In some cases, although the electric quantity of laptop battery if large enough, high internal resistances have prevented it from running smoothly. Once the resistance value comes to increase, it is really hard to reduce by ourselves even if with good usage methods. Therefore, the most effective way for us is to control and handle it before it has reached a dangerous level. Compared to wrong battery indicating information, higher internal resistances have more dangerous influence on the performance. That is to say, we need to calculate and judge if it is within a safety range. Those batteries that haven’t been used for a long period will also have very large internal contamination. Of course, if the value is too short is also dangerous as it is possible to cause short circuit. Please try to learn and use these ways to calculate your battery and take good care of it to have longer lifespan and better performance.
by: USB Phone World