This paper has proposed a multi-resolution energy strategy for battery management system (BMS) of unmanned ground vehicles (UGVs) in farming. On the basis of “Smart Farm” definition, battery energy consumption and management have been taken into consideration during the working process and system control. A battery energy controller has been proposed for the low-cost ($1000) UGVs designed by our lab for farming usage. Moreover, three levels of energy control loops have been developed, that is, motor control, path planning, and mission arrangement. In this way, an energy-efficient UGV can prolong its working time and also decrease the cost. The three closed-loop energy strategy of BMS provides not only separate working methods for the three levels, but also a weights way to adjust the influence of three levels on the performance of the UGV in different tasks.