Battery

[Andy2809]

Has anyone had this problem: Corolla is 5 months old, was listening to the radio for 20 minutes with the engine off, no other electronics, radio stopped and then car wouldn’t start. Breakdown guy charged it and then car started. Surprised it went flat so quickly. 

[Catlover]

Common one, you need the engine on. What you did was switch the car on into aux  odd, which does give power to the radio as well as other things, BUT it’s purely taking power from the 12v Battery and acting like a drain on the Battery and nothing going back in.           
So what you need to do is switch the car onto Ready mode, that is put foot on brake and press the power on button. You will see Ready light up. It is what you do when the next went to drive off, but in this case you still sat still. This means you 12v Battery is being refilled from the big hybrid battery. The car computer will not allow the hybrid battery to go flat, so as it depletes the computer turns on the car engine to charge up the hybrid battery so it can feed the 12v battery.               
So you now thinking that is going to cost a lot of petrol. No. The engine will run for a couple of minutes and shut off again. This will be repeated maybe three or four times in the next hour (that is if you are still sat there for an hour), so uses little petrol. In the warmer weather just make sure you turn off all other accessories, ie heater, wipers……. Just have the radio on.           
As you get to winter it is all the more important that you adopt this procedure of being in ready mode when stationary  and using the radio etc.  The 12v battery is relatively small in power it doesn’t have an engine to crank as in a non hybrid Toyota car, so doesn’t need to be big……. Saves cost, weight and space.           What I explained is the official Toyota method. Lots of users have been caught out during last winter, what with not using the car regularly due to covid, and the cold weather. There are many posts on here so do a search and read more, but the method is as above.

[Stopeter44]

17 minutes ago, Catlover said:

What you need to do is switch the car on to Ready mode, that is put foot on brake and press the power on button. You will see Ready light up. It is what you do when you next want to drive off, but in this case you still sat still. This means your 12v battery is being refilled from the big hybrid battery.

The car computer will not allow the hybrid battery to go flat, so as it (the 12v battery) depletes the computer turns on the car engine to charge up the hybrid battery so it can feed the 12v battery.  

@Catlover Excuse my editing, but that is a top class tip! I could have easily fallen in to the same predicament. 

[Andy2809]

Thank you so much for this info, much appreciated!