A vehicle power system includes a traction battery, an electric machine configured to receive power from the traction battery, switching circuitry connected between the traction battery and electric machine, and including pairs of switches connected in parallel, and a capacitor connected with and between the pairs such that the capacitor shares a common terminal with each of the switches of the pairs, and a controller configured to responsive to a temperature of the traction battery being less than a first threshold, activate the switches of each of the pairs in complementary fashion at a switching frequency corresponding to a resonant frequency defined by a capacitance of the capacitor and an inductance of the traction battery to cause AC current to circulate between the traction battery and switching circuitry to generate heat within the traction battery, and responsive to the temperature exceeding a second threshold, deactivate the switches.