Charge Lithium Battery in Parallel
2021-07-27 14:07:00 Pageview: 930
Lithium Battery in parallel aims at increasing capacity. Thus, for lithium batteries in parallel and single lithium battery, charge design features are different. This difference is mostly reflected by charge current design and consistency of battery in parallel.
Lithium batteries in parallel are characterize by unchangeable voltage, single battery capacity sum, decreased internal resistance and longer use time. According to parallel theory, main current equals each branch current sum. Hence in order to attain same charge efficiency as single battery cell, charge current of paralleled Lithium Battery Pack should be the product of battery cell number and single cell current, which is reasonable under Ohm’s Law: I=U/R formula. However, battery internal resistance after parallel also changes. Based on parallel internal resistance formula, total resistance of two lithium batteries in parallel equals the ratio of resistance product to resistance sum. Because parallel resistance decreases as number of batteries in parallel increases, a charge current less than battery cell current sum can fulfill charge efficiency of lithium batteries in parallel.
Uniformity problem of battery in parallel should be paid attention to because failure to charge or overcharge might happen to lithium batteries in parallel with poor consistency. Therefore, mixture of different brands, different capacities or new and old lithium batteries should be avoided. Battery uniformity requires battery cell voltage differential 10mV, resistance differential 5mΩ, capacity differential 20mA.
Actually, after parallel, a protection chip will protect lithium battery charge. Lithium battery manufacturers have considered change features of lithium batteries in parallel and have designed charge as per the above requirement. So all users need do is to charge lithium batteries under instruction and avoid damages arising from incorrect battery charge method.
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