Parasitic current draw.

I don't have access to the exact information that you are asking for.

Are you aware that a failing battery will "self discharge" when not in use at a rather rapid rate ?

 

One of the battery drain suspects is the brake power back up box. It a box full of caps that hold enough charge that if you lose power you should have enough to do some braking. Its the vertical box metal box that's right next to the 12 volt battery. The box could have some corrosion or the caps have dried out and are now esr'ing.

But almost everyone who comes on here thinking they have a phantom power draw usually just have a bad 12 volt battery that has become sulphated or they do not drive enough to properly charge that battery. You have to drive a significant distance to charge the 12 volt battery.
Like 10-15 miles a day hopping around town for 20 mins wont do it.

Almost everyone who comes on here does not own a modern battery charger with recondition mode that they put on there battery regularly to see how it does. .

Hope your not saying the dealer tested the battery as the dealer is incapable of testing a 12 volt battery based on what i see here.
if you own a DC voltmeter theirs a simple test you can do to see how capable the battery is.

A healthy 12 volt battery should be at 12.6 volts at the front jump points with the car off.

 

I remember someone on here saying it should be no more than 30 milliamps with everything turned off.

 

On a 3rd gen I measured 16~18 milliamperes with spikes (every 5 seconds or so) to around 40~45.

 

Just got to love people who have never even owned a Prius Gen 2 hijacking every thread that mentions "battery" and offer often irrelevant information that derails a thread. I have seen pages and pages of irrelevant and often semantic nonsense clutter up a thread. Sheesh! Interestingly, they never seem to have the direct answers to the question(s) asked, but rather just go off on their own hobby horse. Anyway, I digress, sorry about that.

Mendel's Gen 3 information (in this particular case) is pretty close. I would guess that the spikes would be the SKS waking to check if there is a fob nearby. On a Gen 3, I believe this SKS activity will automatically shut down after a number of no-fobs hits (or is it after a time period, I have no idea) to reduce the quiescent draw. In the Gen 2, there is a "Key" button below the steering column that, when pressed in, disables the SKS function to achieve this same objective. Another press toggles the button to the out position to re-enable the SKS function.

To put into perspective what is the effect of the quiescent current draw and out of interest I conducted a little experiment when required to isolate for COVID-19 and after reading of so many 12 V battery woes.

By way of background

• The car is a non-SKS Prius with a 6-year-old 55 Ah AGM battery that is in very good condition.
• The car had the hatch open, but all interior lights were switched off.
• The "Door Open LED" was illuminated.
• This battery has had a lot of love.
• The battery was still connected to the car.

The experiment parameters were reasonably simple.

1. Charge up the battery to full.
2. Bleed off the surface charge, then let it sit for 30 min.
3. Measure the voltage across the terminals.
4. Measure the battery again after 3 weeks.

Results:

Initial reading 13.1 V
After 3 weeks 12.9 V

This is obviously not a double-blind study nor even a statement that every battery/Prius combo should act this way. It is, however, an observation and documentation of something that really happened.

Is it a placebo effect? No, because I really expected that the battery would drop more, so I was pleasantly surprised.

Leeming effect? No, I never read of any other similar experiment, so I had no preconceived ideas at what outcome to expect.

Result of hope or any other psychological effects. No, I went into this out of interest and with no preconceived idea to the outcome.

Is it anecdotal? Sure, but hey, I think it is useful. YMMV.

I hope others find this as interesting as I did.

 

When I get a chance later today, I will measure draw on my 12V in my 2006 Gen2. And then get back with the info for this posting.

 

@Don Holtz

On my 2007 Prius:

I used a Fluke 115 with heavy gauge alligator clips leads.
I connected one alligator to the 12v battery positive terminal clamp. The other lead was connected to about 20' of doubled up 16ga speaker wire that I terminated at the underhood jump point. Once it was all connected, I unplugged the large and small car harness plugs at the positive terminal assembly so all current would pass through the meter.

With my meter outside the car, trunk closed, interior lights in off position, hood closed. After few moments, it was showing 70-80 ma and after several minutes, the meter was oscillating between 21 and 24 milliamps. If I did it with the trunk open, it was in the 500-700 range.

 

Yeah I had hatch closed, leads connected between neg cable (connected to battery post) and ground. Ran leads out hatch threshold, closed hatch on them. Waited about 20 minutes, fob away, other end of the house.

 

And we have seen hundreds of posts from members here complaining about other members......which sometimes stirs up really nasty feelings......as opposed to people who offer a few well meaning comments and cause no real trouble at all.

If you were REALLY sorry, you would CUT THE CRAP.

Even the rest of your post contained a LOT more useless information that all of the other well meaning posts combined.

Pot.....kettle.......BLACK.

 

Rule of thumb. Others have since provided more specific information. I would think if you are seeing more than 30 milliamps consistently you would want to investigate further, otherwise maybe not.

 

What measurement did you get?

 

Don, I also have a 2005. I've measured by undoing the positive cable at the battery, and letting the current flow through the meter. 16 to 18ma is the magic number. Open the hatch, with all lights switched off, and it will be just a tad under 500ma.

 

This actually sounds about right. Look to see if the iPod accessory can be made to power off when the car is IG-OFF. Otherwise, you are stuck with it. It is, in and of itself, reasonably insignificant.

Maybe, but I'm not so sure. In the Gen 2, the SKS does not fully quiesce, so there is an SKS disable button (marked 'Key') below the steering wheel that you can press in to disable the SKS exactly for this reason. The owner's manual advises disabling the SKS any time the car is not being driven for an extended period.

 

Interesting. I'll be watching to see how this turns out.