If the Highlander appears to be dead, the small auxiliary battery is likely discharged. This small battery is needed to power the Hybrid controls that allow the vehicle to operate. Very little power is needed from this battery to operate the vehicle or to start it.

You can jump start the Highlander in a conventional manner by connecting jumper cables to the small aux. battery positive terminal and a ground point on the engine. The Highlander Hybrid will be capable of being started immediately upon connecting the jumper cables -no need to wait for the battery to charge.

Note that the large Hybrid battery can not be jumped as the voltage of this battery is 288 volts DC which is obviously too high to be getting anywhere near. However, this battery will not fully discharge. The hybrid battery is carefully monitored and protected from deep discharge. In the very unlikely circumstance that the Hybrid battery ever did discharge to the extent that it did not have enough power to start the engine, the only option is to have it towed to the dealer.