The 12 Volt Battery

[Ikelos]

Hi all, a question to put my mind at rest, after a spell in hospital I am not allowed to drive for 8 weeks, am I right in thinking that if the Battery in the boot should go flat, can I just disconnect it and charge it up like any other car Battery, and that it will not upset any electronics, apart from stopping the clock................thank you.

[Grumpy Cabbie]

You're not far off. Maybe you're best just getting someone to fire the car up for ten minutes every couple of weeks instead - if you're able to arrange that.

To get more out of the 12v Battery you're best switching off the keyless entry system (details in handbook I believe) as the constant scanning for your key does reduce 12v Battery life considerably if the car is sat.

[Ikelos]

Thanks GC for that, I will sort one of them out..................

[Black Knight]

Basically you're right. The 12V system runs the accessories mostly and the hybrid system works as the starter for the engine as well as EV mode driving.

You can charge the 12V system like any other 12V system. Never tried it but my understanding though is that even if the 12V system is flat you can still start by using the hybrid Battery which will then bring up the 12V system. I wouldn't swear to this though.

[Grumpy Cabbie]

Heard that too. If you press and hold the start button for 15 seconds it will fire up off the HV Battery, but I've never tried it myself and I'm not entirely sure it works if the 12v is completely flat.

[timberwolf]

<snip>

Never tried it but my understanding though is that even if the 12V system is flat you can still start by using the hybrid battery which will then bring up the 12V system. I wouldn't swear to this though.

The Hybrid Battery is isolated by open relays when the Prius is switched off. To connect the Hybrid Battery, the Prius has to boot up various computers (ECUs) and once the computers are operating they close the relays. If the 12V Aux Battery is dead, then you ain't going anywhere, even though there is lots of energy safely stored in the Hybrid battery it isn't accessible.

Letting the 12V Aux battery go flat is not a good idea as it shortens the life of the battery (apparently it's to do with the chemistry of lead acid batteries).

[johalareewi]

Hi all, a question to put my mind at rest, after a spell in hospital I am not allowed to drive for 8 weeks, am I right in thinking that if the battery in the boot should go flat, can I just disconnect it and charge it up like any other car battery, and that it will not upset any electronics, apart from stopping the clock................thank you.

If the Battery should go flat, you won't be able to disconnect it to charge it up because you won't be able to open the rear hatch to get to the Battery (unless you cimb over the back and use the manual door release).

However, there is a jump terminal under the bonnet which you can use to start the car. Read up in the owners handbook.

Chances are, the 12v Battery will be fine over 8 weeks but it is handy to know how to jump start a Prius just in case.

[Ikelos]

Thank you all so much for the replies, good of you all to take the trouble.......................

[johalareewi]

Have just read in the manual (page 59) that if the entry system isn't used for 5 days (I assume they mean SKS), it is switched off to preserve Battery life.