Park Assist after Flat 12V battery

[dickfineman]

Hi, hope someone can help with my problem: i let my 12V Battery run flat on my Prius Excel PHEV through non use over the cold weather, probably been about 3 weeks ! Charged Battery very quickly, all appeared fine. But when i moved car and parked etc, i knew it sounded really quiet...the parking sensors were not making their usual audible tone. So i checked in the menu and the PARKING ASSIST selection is off (should be lit green ) and will not let me select it. 

I've tried turning off and on etc but no luck. Any thoughts from anyone and thanks in advance.

Peter.

[dickfineman]

I just read in the pdf manual, in the INTELLIGENT CLEARANCE SONAR section that you have to initialise the system after a Battery inststall/charge. Could this apply to the PARK ASSIST SENSORS also since they are the same sensors but have a different detection range/area ? If this is true, it says to drive the car above 22mph for 5 seconds, to initialise only i havn't been out yet due to the snow. Hope this is correct ??

[kithmo]

Yes, driving it for a while initialises it, mine was the same when I picked it up from the dealers, they must have had the Battery disconnected.

[dickfineman]

Thanks for the assurance Kithmo, much appreciated. So after driving for a while, will i have to go into the menu on the MID and manually select PARKING ASSIST ( make it green ) or will the system auto select it and the sensors start working on their own ? Guess i'll find out...but so kind of you to get back !

Peter Hill.

[dickfineman]

Just to let people know, been out finally in the Prius and the PARK ASSIST kicked in by itself; sensors working fine. Also, the CLEARANCE SONAR warning light stopped flashing, so all fine again. Thanks again Kithmo.

 

[johalareewi]

If you have flattened the 12V Battery, you have probably shortened its life. :( 

[dickfineman]

16 hours ago, johalareewi said:

If you have flattened the 12V battery, you have probably shortened its life. :( 

Hi johalareewi, yea, i was silly to leave it so long without runnung the hybrid system ! I have already left it a couple of days to test and all is fine. From your info above, and from reading info regarding being a NEW Battery, a lot of experts online have said happening once shouldn't be a problem ? Thanks.

[PeteB]

I think it's worse if the Battery is fully discharged for more than a few hours, and day at most.

The 12V Battery in my 2002 Gen 1 Prius was flattened early on when I parked in a Robotic car park in London for about 6 hours.  You drove onto a big metal tray, which was whisked away by robot arms and put into a big pigeon hole.

They insisted the the car was left with the parking brake off and transmission in neutral.  The Gen 1 Prius has a big lever in the dash rather than the little joystick of later models, with P-R-N-D-B positions.  It was not possible to remove the ignition key unless the selector was in the P position, so I had to leave the key in the ACC position, that only supplied power to the radio and 12V socket.

Unfortunately, the Gen 1 Prius had a relatively high drain on the small 12V Battery when parked, and just leaving the key inserted (but off) increased this.  In ACC it was worse still.

So on return, it was dead.  Completely.  However, with the help of the parking attendant's jump starter, it easily fired up and got a good charge on the 2 hour drive home.

That 12V battery was still in the car when I sold it 9 years later!

[dickfineman]

Thanks PeteB, that's good to know...great testament to Toyota all those years ago and lasting 9 yrs ! Hopefully, mine will be ok with the knowledge that the 12V doesn't turn the engine, only supplies the metering and accessories and the HV Battery is continually topping up the 12V in READY mode. Thanks for the reply, much appreciated.

[PeteB]

44 minutes ago, dickfineman said:

...the 12V doesn't turn the engine, only supplies the metering and accessories...

plus the alarm and locking sensors, but the thing that can be the last straw if the Battery level is marginal is the brake hydraulic pump that works when you unlock the car or open the driver's door depending on the generation of the car.  It takes quite a bit of power.

I actually needed a new 12V Battery last year on my 2016 Gen 4 Prius.  I think it must have been faulty, or maybe mistreated before delivery.  But a few times as soon as I opened the door the pump continued making a horrible sound and didn't give then Battery a chance to recover enough to start the system.

Luckily, I keep one of the modern, compact jump starters in the driver's seat pocket, which gets me out of trouble.

One trick if leaving the car for a while, provided it is somewhere secure, is to lock the car with the emergency key (or by pressing the locking button on the open driver's door and closing it with the handle held in the opening position [making sure they key isn't inside, of course!]).  That means the alarm isn't on.  (On a Gen 4 Prius the menu option to disable the ultrasonic alarm feature doesn't cancel the whole alarm system).  If really paranoid, another option might be to go into the menus and disable the remote key function, which I suspect will reduce the power drain further.

Fortunately, my ever helpful dealer replaced the battery under warranty without hesitation.

[dickfineman]

Thanks PeteB, useful stuff much of which i didn't know !