Key off parasitic battery drain? - Toyota Sienna Forum - siennachat.com
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post #1 of 7 (permalink) Old 04-19-2017, 07:24 PM Thread Starter
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Key off parasitic battery drain?

Has anyone recently, or could anyone now, check how many mA their car draws when off with all doors closed? I've been having trouble with the battery draining if the car is not driven for a few days. When I hook up the mulitmeter in series with the battery I get and initial mA read of about 350ish, which drops down to a steady 214 mA after about a minute. Is this consistent with other Siennas out there? Mine is an 2004 LE.

I've read a generic recommendation that anything above 50mA is excessive, though wanted to double check this. As a side note, nearly all of the draw is through the ECU-B circuit.

Thanks.
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post #2 of 7 (permalink) Old 04-20-2017, 07:51 AM
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Re: Key off parasitic battery drain?

I'm not sure if there is anything different between our model years that would affect the measurements, but here is what I found when looking at the exact same issue (on my 2010 LE)

"Resting" Amps (amps drawn after all doors have been closed for a few minutes): 10mA but would change a bit and occasionally peak to 940mA briefly. You are getting a steady 214mA draw, which doesn't sound right to me.

Other interesting data I found:

key light only, all other interior bulbs removed: 350mA
All interior lights on: 3A
1 front door open: 890mA
2 front doors open: 1.27A
Amp draw while locking doors via remote: 5.37A
Amp draw while unlocking doors via remote: 9.45A
1 sliding door opening: mostly 7A, but peaks to 16A
1 sliding door closing: mostly 6A, but peaks to 11A

Also note that if any of the rear overhead lights are manually set to the "ON" position, they will NEVER time-out or turn off until you push that light again... I've had the kids leave one of the rear overhead lights on overnight and that is enough to drain the battery enough that the van won't start. (The combination of no light timeout plus a weak reserve rating on the stock battery sucks.) It's been on my todo list now to figure out a way to add a timeout to the rear cabin overhead lights, but haven't had time...

Last edited by mralexsays; 04-20-2017 at 07:57 AM. Reason: Added model/year
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post #3 of 7 (permalink) Old 04-20-2017, 08:28 AM
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Re: Key off parasitic battery drain?

Power draw drops down in steps on cars. The provision for 'key off operation of power windows', etc., means that the body ECU is still awake for at least 10 minutes after shut down. I found from a little research that a steady state draw of 75 ma is considered max after everything goes to sleep. But about 5 hours after shutdown, the Evap monitors run, so that will rise substantially during that test, and then everything should go back to sleep.

One thing to be aware of when attempting a draw test. Your milliameter needs to be in series with the battery, but you cannot break the connection to the ECU to insert it there without glitching the test. Simply lifting the negative battery terminal, no matter how fast you do it, will depower the ECU for a few seconds, and that will change everything! It's tricky to do, but you must maintain connection of the meter to the clamp and the terminal as you lift the terminal, so that there is always a current flow.

Current: '15 Sienna Limited Premium (FWD), '14 Subaru Outback, '13 Honda CRV AWD.

Past: '08 Sienna LE (FWD), '02 Subaru Outback, '02 Honda Odyssey EX
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post #4 of 7 (permalink) Old 04-20-2017, 05:54 PM Thread Starter
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Re: Key off parasitic battery drain?

Quote:
Originally Posted by mralexsays View Post
I'm not sure if there is anything different between our model years that would affect the measurements, but here is what I found when looking at the exact same issue (on my 2010 LE)

"Resting" Amps (amps drawn after all doors have been closed for a few minutes): 10mA but would change a bit and occasionally peak to 940mA briefly. You are getting a steady 214mA draw, which doesn't sound right to me.

Other interesting data I found:

key light only, all other interior bulbs removed: 350mA
All interior lights on: 3A
1 front door open: 890mA
2 front doors open: 1.27A
Amp draw while locking doors via remote: 5.37A
Amp draw while unlocking doors via remote: 9.45A
1 sliding door opening: mostly 7A, but peaks to 16A
1 sliding door closing: mostly 6A, but peaks to 11A

Also note that if any of the rear overhead lights are manually set to the "ON" position, they will NEVER time-out or turn off until you push that light again... I've had the kids leave one of the rear overhead lights on overnight and that is enough to drain the battery enough that the van won't start. (The combination of no light timeout plus a weak reserve rating on the stock battery sucks.) It's been on my todo list now to figure out a way to add a timeout to the rear cabin overhead lights, but haven't had time...
Thanks for all the information. The fact that your Sienna only pulls around 10mA confirms my suspicion that I have a parasitic drain somewhere related to the ECU-B. Now for the fun part . . .
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post #5 of 7 (permalink) Old 04-20-2017, 06:01 PM Thread Starter
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Re: Key off parasitic battery drain?

Quote:
Originally Posted by fibber2 View Post
Power draw drops down in steps on cars. The provision for 'key off operation of power windows', etc., means that the body ECU is still awake for at least 10 minutes after shut down. I found from a little research that a steady state draw of 75 ma is considered max after everything goes to sleep. But about 5 hours after shutdown, the Evap monitors run, so that will rise substantially during that test, and then everything should go back to sleep.

One thing to be aware of when attempting a draw test. Your milliameter needs to be in series with the battery, but you cannot break the connection to the ECU to insert it there without glitching the test. Simply lifting the negative battery terminal, no matter how fast you do it, will depower the ECU for a few seconds, and that will change everything! It's tricky to do, but you must maintain connection of the meter to the clamp and the terminal as you lift the terminal, so that there is always a current flow.
I noticed that when I hook up the meter after disconnecting the negative cable there is a surge (around 350mA) that then drops down after a minute or two to what I am assuming is the baseline draw (which, in my case, is just over 200 mA and apparently indicates a parasitic draw). This is the case even after the car has sat for many hours without having been driven.

Thanks for your thoughts.
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post #6 of 7 (permalink) Old 04-20-2017, 09:23 PM Thread Starter
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Re: Key off parasitic battery drain?

Update in case anyone is interested or having a similar problem: based off of some of the above recommendations I exercised a bit more patience and kept the meter hooked up in series for a bit longer. Draw started off at about 350mA, after about 30 seconds drops to just above 200mA, and after another minute or two it drops down to just above 10mA. So, my problem is thankfully not a parasitic draw but was a bad battery, which Costco swapped out. Lucky I caught it at 35 months. The warranty expired at 36 months. Typically one catches these things at 37 months. . .

Thanks again to those who shared their knowledge.
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post #7 of 7 (permalink) Old Today, 10:22 AM
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Re: Key off parasitic battery drain?

Quote:
Originally Posted by wdnmaclean View Post
So, my problem is thankfully not a parasitic draw but was a bad battery, which Costco swapped out.
This is *exactly* what happened to me!!!

Every time my 2005 Sienna sat around for a few days, it wouldn't start, and I'd need to jump it. I used a multimeter to test the battery (both off and running). That was my very basic mistake. This video here is what I watched: https://youtu.be/COJr7OB23Hw

So, thinking that the battery was totally fine, I then went on looking for a parasitic drain. The van would begin at about 1000 mA (1 amp) and then quickly drop and stay at 200-250 mA. I thought, "Oh, this is bad, because the recommendation is no more than 50 mA." So I discovered that after pulling the ECU-B fuse, it would drop to zero. Apparently, the ECU-B fuse is what is pulled when Toyotas are sitting in storage for long periods (like, before they go to the lot, etc). I drove the van again, and then it sat in the driveway for about 24 hours.

Then... IT WOULDN'T START AGAIN.

So I was scratching my head, thinking it could be starter solenoid contacts. My thinking was that the battery tried to send the voltage to the solenoid on the starter, but the contacts were too worn or dirty to send/receive enough voltage. So the battery needed to be at 100% in order to give enough power. If the battery was at anything less than that, then it's not enough to turn over the engine.

But I was wayyyyyyyyyy overthinking things. My dad insisted that I just take the battery out of the van and get them to do a load test on it (it's free). I insisted that the battery is fine since I checked it with a multimeter.

But in order to properly test batteries, they *need* to be tested with a LOAD TESTER. A load tester puts a load on the battery (separate from the car... you're disconnecting it from your car), and tests it that way. Otherwise, stuff like the alternator and whatnot is going to interfere with multimeter test, making up for what the battery is not able to do.

Well... the test at Canadian Tire showed that the CCA (cold cranks) on the battery were almost HALF what they were supposed to be. Guess what? The battery was also from 2008 (9 year old battery, lol). I replaced the battery, and popped back in that ECU-B fuse, and everything works as good as new. No more starting issues. And I still don't drive the van much (I'm at home with kids, so I sometimes I only use it once or twice a week).
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