The open-circuit voltage (OCV) of batteries is a crucial characteristic parameter which reflects many aspects of a battery's performance, such as capacity, state of charge (SOC) and state of health (SOH). In order to improve and better the applicability of Li-NiCoMn lithium-ion batteries in electric vehicles, a series of charge and discharge experiments were carried out in constant current mode. The battery capability of Li-NiCoMn lithium-ion batteries had been obtained from the experiment results with multiple different type models. Based on the analysis on the charge and discharge curves, the battery capacity as well as SOC can be deduced according to the corresponding OCV. The results of charge and discharge tests indicate that Li-NiCoMn lithium-ion batteries have heavy load charge and discharge performance.