Lithium-ion (Li +) cells compared with other chemical types of batteries Laptop Battery to be more vulnerable, for illegal operations with very small tolerance. Therefore, the lithium battery charging circuit more complex and demanding high-accuracy current and voltage settings. If you can not meet these accuracy requirements, the battery charger may not be completely filled, thus reducing battery life or affect battery performance.
In view of the Li + battery charger these requirements, the design of the charger completely tested and working within the framework of the entire sub-test is very important. However, the conventional load (ie, Li + battery) test Li + Battery Charger will be very time-consuming, but also in the laboratory and production environment is also difficult to achieve. To simplify the testing process, this paper presents a battery simulation circuits, can speed up the test speed, and without the battery case with the actual realization of lithium-ion battery dell Inspiron 1520 battery charger test.
CC-CV charge
Lithium-ion battery charging process of the first phase of moderate accuracy of the constant current (CC) charging, and then in the second phase of the transition to high-precision constant voltage (CV) charging.
Figure 1 for use in lithium-ion battery charger CC-CV IC (MAX1737) of the VI characteristic curve. This type of IC is the consumer products of all lithium-ion battery charger core. Figure can be clearly seen CC (2.6V to 4.2V battery voltage) and CV (4.2V) area.
Figure 1. MAX1737's VI curve is the standard Li + battery charger characteristic curves
Battery falls below 2.6V, the need to adopt a different charging technology dell laptop battery. If you attempt to discharge to 2.6V below the battery, charger required to provide a lower charge current ( "conditioning current"), will charge the battery voltage to 2.6V. This is the lithium-ion battery over-discharge must be taken when the security mechanism. VBATT <2.6V, by force if fast charging, would short-circuit the battery into an unrecoverable state.
CC to CV transition point of the critical phase of the tolerance of ± 40mV. The reason why such a demanding tolerance, because if the CV is too low, the battery will not be completely filled; while CV is too high, it will shorten the battery life. Means to detect the termination of charging the battery to reach full capacity, the charger must be disconnected or shut down. In the CV stage, when the detected charging current to quickly charge or maximum charge current flow of a certain percentage (usually "10%) when the termination charge.
Li + Battery Charger Parametric Test
Li + Battery Charger design usually consists of two basic parts: the digital part (control state machine) and analog parts, including those with high-precision dell 4834T battery analog part ( "1%) benchmark, can be precisely controlled current / voltage source. Pairs of lithium-ion battery charger (not only refers to IC) completely testing is a very difficult and time-consuming work, not just limited to current or voltage value tested.
Test, should be carried out throughout the scope of work of the charger segmented detection: including CC stage, the switch from CC to CV, charge termination. As noted above, the ideal test is the load on conventional charger: the Li + battery. However, due to charging process takes one hour or even longer, the use of lithium batteries is very time-consuming testing. Depending on the different test conditions: for example, large-capacity rechargeable battery + slow, small-capacity battery + Fast Charge as well as other possible combinations, the test time is not the same.
In addition, the charging process can not guarantee dell 2834T battery not to damage the battery under the premise of increased charge current, because the battery charge current by the maximum charge rate (ie, fast-charge current) constraints. For consumer products commonly used in batteries, very few provisions of current is greater than 1C (in 1 hour the battery fully discharge current). Therefore, in most cases to complete the charge cycle, the time required often exceeds two hours. If you need to repeat the test, you need to fully discharge the battery - this process is only slightly shorter than the charge. Or, must be able to have fully discharged the battery at any time.
Also you can use a simulated ideal alternative to a true load battery load test. Simulation should verify the circuit's DC response and dynamic stability. However, the use of power measurement standards used in simulation of the load to the battery is very difficult. Unlike most power supplies used in load testing is different from the battery can not be simply treated as a fixed resistance or exposure to current. As noted above, the scope of work must be carried out within the entire sub-tests. The following description of the Li + battery charger test circuit fully meet these dell Latitude LS battery requirements.
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