Best Way To Open Car When The 12V Battery Is Dead?

Interesting problem. There is no doubt that the incandescent hatch light will run the battery down overnight. Its not a matter if the battery is new or not.

First thing to do is to avoid the drain. The rear hatch light is marginal at best so I just removed the bulb after a drain incident. The rear hatch is the most common since the hatch is easy to leave partially open while it looks closed. I believe the map lights will stay on as well if they are manually turned on. When operated by the door switch they will time out and turn off.

As far as an accessible outside jump point, I might consider a fused trailer harness wired into the battery and left under the bumper. Then a mating connector would allow a jump pack to be connected. Obviously this setup would be prewired with great care to avoid a polarity problem.

[Update: Verified manual key works without power]

Finally if there is excessive off state current draw, one way to find it is to temporarily wire a meter in series with a battery lead. Using the amp mode and connections on the meter. Ensure all lights are off and the keyfob is away from the car. Breaking the battery connection and inserting the meter will restart all the computers so it takes a few minutes to see the off state current. Normally you would expect to see less than 30 ma. All of this is a little advanced, another approach is to simply measure the 12v voltage in the evening and again in the morning (off in both cases). Hopefully its not below 12v after it sits for hours.

Measuring off state current:

 

I was thinking of the plug-in pigtail that comes with many 12V battery tenders. Though this may be too short to reach outside (I was thinking of running it through the rear hatch seal), and really needs to be fused inside the car in case the insulation gets cut where it goes through. So the trailer harness idea is likely better.

This is news to me, I had understood the key to work purely mechanically at the front door. Then use the (very inconvenient) inside manual release to open the hatch. Or pop open the hood to reach the front jump point.

Some folks do experience phantom drains that must be tracked down. Aftermarket accessories are sometimes the cause, but not always.

During these reduced-travel pandemic times, many people are also experiencing dead batteries from insufficient run time to replace the charge continually lost to the always-on electrical housekeeping listening for remote controls, etc. Using a battery tender occasionally, helps out.

If interior lights keep getting left on, and you don't want to delete the offenders (lamps, not kids), consider replacing the factory incandescent lamps with low current LED models. For this to help, select LED lamps for low current, not for bright stadium lighting as some people prefer. This won't solve the problem of lights being left on, but will greatly extend the amount time you have to discover them before the battery goes dead.

 

Just checked on my Prius v and the manual key will work to open the driver's door without power. I disconnected the battery negative at the chassis with a 10mm socket. Rotate the key 90 degrees clockwise and the lock disengages. Then open the hood and jump it. No outside jump points needed.

If you do have power the manual key will energize the power door lock with an audible click.

If yours doesn't work that way, I would see the guy who changed the locks.

 

What panel are you talking about? As mentioned above I disconnected the battery and the manual key still unlocked the driver's door. I could feel the mechanical resistance as it was opening the lock.

 

Now that you are past 5 posts, try again.

 

It's possible that the shop that did the lock work before left part of the linkage disconnected. The mechanical key cylinder should have a link that mechanically unlocks the door, and a link that electrically signals the actuator (so that the alarm won't go off when it sees the door mechanically opened).

If somehow yours has been left only connected to the electrical switch, it would behave as you describe.

 

Hmm. I do not have a v to go look at. I do have a Gen 3 liftback, very similar car, and the mechanical key definitely mechanically unlocks the driver door. You also have rjparker, who indeed has a v, also telling you the mechanical key mechanically unlocks the driver door, and will do so with the battery disconnected.

Who replaced the actuators in 2015, and were they Toyota actuators or aftermarket?

Experience with aftermarket replacement actuators shows that they can be bad in surprising ways, such as completely missing some of their internal parts. This old thread documents that in the specific case of some Gen 1 Prius actuators. Those were built without one of the electrical switches inside (so they would work normally with the power lock, but would trigger the alarm if you used the mechanical key; the car would think you were forcing the door.)

They weren't one-off defects; if you follow that thread, they came from more than one eBay seller, and when the sellers were informed of the issue and how to test for it on the bench, at least one reported back that every unit in their inventory had the same problem, and at least one completely delisted the product from their store after finding that.

The disassembly photo of that one showing what's missing inside is an SVG, which PriusChat won't display, so it shows as a broken image where linked above. It was also reposted as an attachment here.

If you look at that photo (different generation, remember), you can see it has two different linkage 'arms', one in each case half. Both of them would engage mechanically with the latch assembly (and one also took the end of the Bowden cable from the inside lock button).

If, after double checking very carefully, you do not find a missing or disengaged external linkage in your door, it could be possible that you also have an, um, 'incomplete' actuator, where instead of missing an internal electrical part like the example above, it might be missing an internal mechanical one.

 

FWIW.
One could try hooking a the positive cable of a battery charger to the point on the starter where the 12V battery cable attaches.
Then ground the other charger cable to the frame.

Just might supply power to open the doors.
I have not tested this option.

Good luck.

 

There is no starter to connect to on a Prius.

The hybrid motor-generators have the role of starting the engine, and they are both high voltage AC motors with no accessible terminals.

 

There are some images available here. I haven't succeeded (so far) in finding any with the case opened.

The part for my 2010 (non v) liftback is a different part number, but a recognizably similar part. And I can definitely confirm the mechanical key mechanically unlocks that door, power or no. Just as rjparker confirms for the v.

That one's easier to find inside images of:



You can see there is some mechanical linkage involved from the part twisted by the key cylinder.

I'm not sure what you'll find if you take yours apart.

But after all, you did post a forum question about the best way to get into your car when the mechanical key won't mechanically open it. It's possible you have the question because your latch isn't working quite the way other owners' latches work.

 

Some of this post talks like 12v battery runs the starter. My understanding that the traction battery charges the 12v battery and when your 12v battery is dead, you just need enough power to the 12v via a jump to close the relays to get the traction battery available to run the starter and get the gas engine going. And, this means that once you get the car going, the traction battery will be in the loop to keep car going, run starter as needed, and continue to charge 12v battery whether gas engine is running or not, so only thing not to do is shut off power too soon after the jump so 12v battery doesn't go so dead again that you are again unable to get relays to close (more likely the nuisance would be not enough power to unlock doors to get back in car).

And I curse Toyota for the pathetic itty-bitty tab for jumping in the fuse box. 90% of US sold booster cables won't fit. I know you can buy alligator clip or something to adapt, but our first discovery that our cables would not fit was when we needed to jump our 2009 Prius, dead in the garage. After that we bought 1 pair with little extensions on the jaws that do manage to grab the little tab.

 

Sometimes it is just reversing the jaws that will cause a good contact. Some jumpers have insulation on one jaw.