Headlights left on, 12v battery dies

This has actually happened to us twice with the last time draining the battery. It has not happened before. Usually I thought the light automatically shut off unless we had the power on. Maybe Coastal Tech can add it to their products.

 

This may sound harsh, but how about driving the car?

By driving the car, I mean be aware of traffic around you and the systems of the car at all times.

Maybe a checklist would help--something to glance at habitually as she leaves the car?

It's always best to turn the headlights off by the switch, for a couple of reasons. The automatic shutoff system is a failsafe, not intended to be used as a standard thing.

 

You can use a time-delay relay, or even a standard relay, in series with the light switch. Wire the 12 volts from the accessory jack to the coil side of the relay. That way the lights can be on only when the Prius is powered up. When you turn off the Prius, the 12V from the accessory jack will go off, which in turn will shut off the light relay. I prefer solid state relays, but any type will do as long as it can handle the current.

Tom

 

Turn them on and off using the switch. The advantage of leaving the lights on all the time is most likely marginal and turning them off will increase your mpgs.

 

OK, the dumb question of the day...

What happens when the 12v battery dies? Does the car not start at all?

 

<div class='quotetop'>QUOTE(LynneM @ Jul 16 2007, 09:48 AM) [snapback]479603[/snapback]</div>

12v battery fires up the computer... no computer, no run. Also powers the keyless lock system, thus you have the little mechanical key in the fob.

 

Yeah I just had that problem. My battery was dead enough to prvent start up but still allowed the locks and MFD to operate. I got the carziest messages and warning lights. It started freaking me out at first.

 

<div class='quotetop'>QUOTE(LynneM @ Jul 16 2007, 10:48 AM) [snapback]479603[/snapback]</div>

In addition to what others have already said:

The rear hatch door won't open. Which means you can't get to the battery. Which means you must be able to access the post under the hood (see manual). Which means if you park in the garage head-first (like I did), you will need a pretty long jumper cable.

Also, the post under the hood only accepts the needle-nose type clamp since it sits in a very small well. Very difficult to get to and clamp on.

 

<div class='quotetop'>QUOTE(paulccullen @ Jul 16 2007, 12:15 PM) [snapback]479630[/snapback]</div>

Thanks! I'll continue the dumbness....

I think I was getting confused as to which battery you were discussing.....little rectangular thing that goes dead if you leave the headlights on in my current car (12v), vs. the big honkin' Ni-MH battery that stores the power used by the electric motor.

I'm assuming that the 12v battery does pretty much the same things it does in a non-hybrid, and is drained by the same sorts of things (headlights on, etc.). Is that the case?

Does the Ni-MH battery ever completely lose its charge? What happens in that case? Is the car capable of running solely on the gas engine until the Ni-MH battery charge is regenerated?

 

Long-time habit. I turn off my headlights with the 'stalk' switch thus avoiding the possibility of depleting the 12-volt battery. It *IS* possible, as previously noted, to deplete the 12-volt battery by exiting the passenger door. Considering the configuration of the front seats and console, it seems difficult to exit that way.

Not ever having had to 'jump' either Prius I've owned, I've not used the jump terminals under the hood. I have read that these terminals are rather small and are difficult to access using standard jumper cables. One other Prius owner has designed a supplementary set of cables designed to make it easier should the need arise.

Conclusion: Turn off the headlights with the switch.

 

<div class='quotetop'>QUOTE(LynneM @ Jul 16 2007, 01:45 PM) [snapback]479685[/snapback]</div>

Correct, the 12v battery runs the radios, lights, and that sort of thing. There are two differences with the Prius: the 12v battery is used to boot all of the computers, but it is not used for powering the starter, which is not a normal starter on the Prius.

The Ni-MH traction battery can lose its charge, but you have to work at it. Most commonly you have to do something stupid, such as leaving your Prius in neutral so that it can't charge, or driving on electric-only after the engine dies. If you do drain the traction battery, your Prius will need to be towed to a Toyota service center, where they have a special high voltage charger.

Tom

 

<div class='quotetop'>QUOTE(zenMachine @ Jul 16 2007, 01:34 PM) [snapback]479678[/snapback]</div>

This is such a mis-conseption. A normal jumper cable clamp can be easily used, it's meant to be clamped to the tab the extends upward out the the well, that's under the protective cover. It's quite a large tab that sticks up there.

 

Another common misconception is you can fully drain the traction battery. You can't. Unless something in the car fails. The car's sytems will shut down if the traction battery is drained too far. It is supposed to always leave enough to restart the ICE. Several times.

Yea, I know. Best laid plans of mice and men. Err, mice. sorry.

If you do manage to drain the traction battery enough, the car will be towed to a Toyota dealer, who will request the traction battery charger from the regional Toyota rep. I believe it comes with a tech. It can't be cheap!

 

<div class='quotetop'>QUOTE(Charles Suitt @ Jul 16 2007, 04:54 PM) [snapback]479878[/snapback]</div>

We learned the hard way on our 2004 Prius. My wife forgot to push the park button after she moved the Prius. The next morning it was dead when I tried to get into it.

After watching the tow truck driver try to figure out how to get into the (rear) battery compartment (I read the owner manual) to help and then try to jump off the (front) battery unsuccessfully. I (idea) told him to clamp some needle point vise grips (I had) onto the terminal then clamp onto the vise grips. I won't bore you with how hot it was with all the windows up and me in the drivers seat trying to start it while he wiggled the jumper cables for what seemed forever.

Anyway the vise grips worked very well. I have not checked the 2007 but but the 2004 did not have anything we could see his cables would reach and clamp onto.

I did remind my wife what the park button does on a Prius. :lol:

 

<div class='quotetop'>QUOTE(paulccullen @ Jul 15 2007, 08:18 AM) [snapback]479092[/snapback]</div>

Huh? I'm confused? Why would you get out via the passenger door anyways? It's kinda tricky to get there from the driver's side.

As for your second statement, that doesn't sound right either. If I turn off the power to the car w/the lights on, the headlights automatically shut off right when I *open* the driver's door. This behavior is identical to a 91 Camry I used to have. IIRC, my mom's 96 Camry does this too. Your car should already have this and basically have the device you're looking for.

IIRC, my former 02 Maxima would only turn the headlights off automatically after the the ingition was off and the lights have been on for 30 minutes.

 

<div class='quotetop'>QUOTE(mrg @ Jul 17 2007, 08:35 PM) [snapback]480624[/snapback]</div>

What does the Park button do that's special? I thought it goes into park when you press the Power button to turn the car off.

 

<div class='quotetop'>QUOTE(paulccullen @ Jul 15 2007, 08:18 AM) [snapback]479092[/snapback]</div>

Stop driving from the passenger side?