In the case of electric vehicles, due to the charging current limitation of lithium battery at low temperatures (below -20℃), it has been proposed to heat the battery pack up to a suitable temperature range before charging through a liquid-heating plate with PTC. However, in the low state of charge (SOC), there is a question which one could take the place of battery pack to supply power for PTC when heating. So that off-board charger has been considered to supply power for PTC detailed in this paper. In order to control the current charging to the battery pack as less as possible at low temperatures, three control strategy models are established and compared: First, BMS controls the charging request current value which is send to off-board charger as a signal, and equals to the working current of PTC. Second, BMS controls the charging request voltage value which is slightly lower than the battery pack voltage. Third, when the communication between BMS and off-board charger has been established and power-on flow has been finished, BMS disconnects the pack from the charger, and keeps the high voltage connection between the PTC and the charger. The function of the three control models have been verified by simulation test and vehicle test. The results shows: the first two models can supply the power for the PTC successfully. However, the last one can’t keep the PTC working properly due to a power-down fault judged by the off-board charger which is not mentioned and requested in Chinese national standard (GB/T 27930-2015) about fast-charge requirement. As a result, compared to the other control strategy models, model-2 is much better in controlling the charging current to the battery pack.