2007 Prius Parasitic Bat Drain Different

With any battery drain scenario you need to hook up your DVOM and set it to amps to see the flow of current it is drawing. Then you start removing fuses to see if you can pinpoint the circuit in which the draw is affected. You can go another way is to disconnect a wiring loom and see what that affects or does not affect. Its a process but a tedious one. Sooner or later you will get results as to the circuits affect the readouts. Its a good idea to document the reads and look them up on a wiring schematic to see what components are in that chain. Oh one last thing...check the 12v battery to make sure it is not getting weak overnight....that would make all your checking one big waste of time. If unsure..replace the AGM battery

 

We can talk about systems that can drain the 12v when car is sitting for a while later.

But first, I submit something must be wrong with your 12v... Is it an Optima? They often resell defective batteries as brand new. You should be seeing 14volts when car is in ready mode and our general rule is 12.8v is minimum when car is off, which you're just under after topping off?

Are you using a smart charger with significant amps? If you're only using a trickle charger than the answer is you never fully charged the brand new battery. A normal voltage reading after a full charge should be up in the 13v range and then gradually dropping down into 12.8v or above after days or weeks without use and not connected.

 

I saw a camper van on youtube that had an OEM kill switch on the negative terminal of the battery and I immediately wanted one. So if you could find a good aftermarket one please post the link here.

And now that we know your new battery has been fully charged with a good charger let's focus on what's draining it down...

The car not being at 14v when car is in ready mode is the symptom that's most odd to me... The charge sent to the 12v by the hybrid battery is known for being a very weak low amp charge, which is why I suggest people give their Prius 12v a full charge with a good charger in the darkest coldest part of the winter.

I'm not sure what could be draining your 12v system but it appears to be doing so both when power is on and power is off. Maybe you could look at your car through the lens of a thermal camera and see if there's anything that's running hot?

 

I observe many different charging voltages on the 'temporary' volt meter I have connected to my Prius for more than a few years via the console 12 V plug. I haven't observed 14.x V when running for a long time and the only time I observe it is when I haven't had a chance to externally charge the 12 V in many weeks. In fact, when I see 14.x V, it prompts to do an external charge.

I most often see 13.2, 13.5, and 13.8 V in normal day-to-day use. So I don't think that's an issue.

Assuming we are talking about an SKS-equipped car, it might cause your car to wake up, but only if they actually walked up to within about 2-3 feet of one of the front doors or the hatch. In any case, it should quiesce reasonably quickly after that event and unless he is constantly walking past your car all night I don't think that's it.

If you do have SKS, you could try pressing the 'Key' button below the steering wheel into the 'in' position to disable the SKS. You would then need to lock your car with the button on the remote.

The only other thing you might try is seeing if you can film a timelapse of your ammeter overnight to see if you can catch the current jumping up from 20 mA and see what that current is, for how long, and when. That might help answer some of the unknowns.

 

There are devices for monitoring battery voltage.

You can connect it to the 12V battery terminals and monitor the battery status.

It is important to understand that this device will not indicate a specific leak location. Current leakage is cut off only by successively removing fuses for different systems.

 

The problem is that when the battery is disconnected, the trunk door closes magically and cannot be opened without 12V power supply.

 

Have you turned off the key fob activation overnight to see if that is the problem? There is a button below the wheel at the bottom of the dash. This is too easy, but worth trying. If not here is my idea.
It is a pain but maybe worth it. Pull a few fuses, maybe 3 or 4 overnight and check the battery voltage in the morning. Sooner or later you should find where the current drain is going by elimination.

 

Yeah... But I've spent so many years climbing into the back of Prius to release the hatch latch when a 12v is dead, I barely even remember that as a problem.

 

Have you turned off the key fob activation overnight to see if that is the problem? There is a button below the wheel at the bottom of the dash. This is too easy, but worth trying. If not here is my idea.
It is a pain but maybe worth it. Pull a few fuses, maybe 3 or 4 overnight and check the battery voltage in the morning. Sooner or later you should find where the current drain is going by elimination.
That is really great advice! thanks so much! I'll try that.

This could get really frustrating, you will end up several mornings with a dead battery. Do you have a jump start pack or cables to jump from another car?

 

With the information you provided 1) new battery with good capacity 2) only 20 ma parasitic draw 3) but it discharges overnight we can assume it discharges overnight is correct but 1) good capacity or 2) only 20 ma is incorrect.

The sks key theory does not hold water either. I have left a fob in the car for several days and never had a problem.

Repeated replacement batteries had to load test as low capacity or the store would not replace them. I would load test your current battery.

So the odds are there is unusual parasitic draw.

First I would ask how the 20ma draw was measured. If it was a dc clamp meter it is very likely not accurate enough to depend on. On the other hand, disconnecting the negative battery cable and inserting a ma/amp meter in series is accurate even with a $5 harbor freight meter.

The usual suspects in excessive parasitic draw are aftermarket accessories such as gps, audio equipment and or an obd2 module plugged in. Hatches not shutting properly (they have a two stage switch) can draw current even if the hatch light has been disabled. On rare occasions a Toyota module may be faulty and is the worse case scenario.

 

Okay...would you not start pulling fuses to see where the 20 mili amp draw is coming from as a curiosity ? Even disconnecting whole looms would answer your question if that circuit had anything to do with the draw if the draw went to zero.
If it were me I would start with the ECM - disconnect wires to it or the fuses which powers it. What have you got to lose by trying?

 

20-30 ma is normal and a decent battery with normal capacity would still Ready the car after three weeks or longer. No need to look for a 20ma draw.