Actions To Be Taken When Batteries Are Depleted

WARNING: This page is about a different car, the 2002 Toyota Prius. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The following phenomena indicate that the auxiliary battery is depleted:

No display appears on the instrument panel when you turn the ignition switch to the ON position.
The hybrid system does not start.
The headlights are dark.
The sound from the horn is weak.

Actions to be taken when the auxiliary battery is depleted:
1. Move the shift lever to the P position, and engage the parking brake.
2. Remove the ignition key plate from the ignition switch.
3. Using a booster cable, connect the 12 V battery of the rescue vehicle and auxiliary battery of the stalled vehicle. See Fig 1.
  WARNING: Never use a quick charger.
  
  Fig 1: Connecting Jumper Cables
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. Start the engine of the rescue vehicle and run the engine at a speed slightly higher than the idling speed for 5 minutes to charge the auxiliary battery of the stalled vehicle.
5. Turn the ignition switch of the stalled vehicle to the START position to start the hybrid system.
  If the hybrid system fails to start and the master and HV battery warning lights come on, the HV battery, may have been discharged. See Fig 2.
  
  CAUTION: If the auxiliary battery needs to be replaced, replace it only with a 12 V battery specially designed for the PRIUS.
  
  Fig 2: Identifying Master And HV Warning Lights
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
6. Disconnect the booster cable in the reverse order of the connection procedure.
Actions to be taken when HV battery is depleted.
NOTE: Leaving a vehicle alone for 2 to 3 months may cause electric discharge from HV battery. When this happens, replace the HV battery.