Ignition-off Battery Draw

axel1

axel1

Member
Hi all!

Woke up this morning to a dead battery. First deep freeze of the year so that definitely wasn't helping things. Normally I'd suspect the battery but it's only six months old and hasn't seen a winter yet. A test at Advanced auto confirmed that it was A-OK.

Started poking around a decided to measure the current draw with the truck powered off. Disconnected all aftermarket accessories and probed the current from the battery terminal to the main power lead and got an initial burst of 500-600mA and a stable 160-180mA after that. Now, that seems exceedingly high from my point of view.

Curious if anyone else has measured the ignition-off current from their battery. If this is actually normal than so be it, but I'd like to know if I need to start poking around the factory fuses to see if something's drawing more than it should be.

Looking around, I couldn't find a thread on 5th gen current draw but please direct me if I'm wrong.

Cheers!
 
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I think it should be about half of what you are getting.

Weird that it would spike how long did you leave it on and did it spike again to 500mA?
 
I think there is something screwy with our electrical systems. My current battery is about to crap the bed. Sometimes it cranks right up and sometimes it acts like it’s dead and eventually starts.

This is the third battery I’ve had since I bought it (‘12 model) in 2016.
 
I have a Limited with PTS and proximity key so my data may be different from yours since the prox key system draws additional current. I also have a Maestro RR module for the radio, dash cam with park recording and a remote start with Drone that draws current talking with cell towers.

I will have an initial 130ma current draw when hooking up the meter. After waiting 35 minutes the truck goes to sleep and the draw is around 60ma.

Ideally you want under 50ma.
 
Typically I'd expect somewhere between 50-100mA tops which is why I'm asking.

I'm using a multimeter inline with the main battery line so the initial current spike is likely everything powering on for the first time when it gets connected. It only lasts for maybe ten seconds tops before going to ~150mA and staying there. I left it for about three minutes and it stayed there so I'm assuming that's the actual sleep current.

I've got everything aftermarket disconnected including the remote start (unless there's another 12v tap I can't find - it was very poorly installed by the previous owner).

We'll see if she starts tomorrow morning. I ran it a decent amount today so it should be relatively charged up. If it wasn't so damn cold I'd be more inclined to do some fuse pulling to further narrow things down but I value the tips of my fingers too much.
 
Measure the voltage drop using the voltmeter across each fuse until you find the one that is NOT reading zero !!...you can convert the millivoltage to milliamps using a chart that you can Google !!...just make sure that all the cars modules are "sleeping" ...maybe 20-30 minutes...and if you leave the drivers door open to check the fuses there manually lock the door !!
 
rwrobs777 said:
Measure the voltage drop using the voltmeter across each fuse until you find the one that is NOT reading zero !!...you can convert the millivoltage to milliamps using a chart that you can Google !!...just make sure that all the cars modules are "sleeping" ...maybe 20-30 minutes...and if you leave the drivers door open to check the fuses there manually lock the door !!
Click to expand...

Say what?

So you want him to check mV on one fuse and convert that to mA to find his draw. But this is only reading one circuit?
 
Dillusion said:
Say what?

So you want him to check mV on one fuse and convert that to mA to find his draw. But this is only reading one circuit?
Click to expand...

assuming your goal is to find which circuit has the parasitic loss, then measureing voltage drop across each is a great way to quickly do it


for overall you can just put your multimeter in series with one of your battery cables to get the overall amperage, but if you want to know what circuit is pulling that amperage you have to check each one individually and voltage drop is quicker than pulling fuses to check amperage
 
Dillusion said:
I must be having a major brain fart moment on how to convert mV to mA.
Click to expand...

Ohm's law, super easy. V=IR. Voltage is proportional to current and resistance. Of course, you'd have to know the resistance across the fuse which is likely on the order of 1/10th of an ohm or less.

The idea is more that any fuse that has a slight voltage drop between the two terminals is one that's drawing current from the battery. It's more of a quick test than an accurate measurement.
 
I figure we were talking mA, which is damn small already, here already we would want something accurate.

Guess people troubleshoot "in the ballpark" now days.

Not to mention there is more than just the fuse resistance. Guess I don't see the point in doing it this way.
 
Copied this from my old post in this section:

remembered I had a Telematics transmitter from AAA insurance plugged into the OBD II connector. Unplugged it and the current went down to 125ma.
 
5ht gen current draw

My current draw (all items off) is also 500mA, dropping to ~120mA after a few seconds. It was unpowered (unlocked) for 48 hrs before i took the measurements. Had advance auto parts hook it up to their battery tester and it showed bad battery as i suspected. Just installed new battery and verified that the 500mA/125mA was the same with new battery. Note I have a 2018 with 50,000 miles, its an SR5, 4WD, totally stock.
 
Frank w said:
My current draw (all items off) is also 500mA, dropping to ~120mA after a few seconds. It was unpowered (unlocked) for 48 hrs before i took the measurements. Had advance auto parts hook it up to their battery tester and it showed bad battery as i suspected. Just installed new battery and verified that the 500mA/125mA was the same with new battery. Note I have a 2018 with 50,000 miles, its an SR5, 4WD, totally stock.
Click to expand...

You have to allow enough time for the ECU to go to sleep to measure the true parasitic standby current.

Here’s what I get for my 18 ORP. No remote start. Removed the OBDII interface dongle, it draws power even with the ignition off.

Hooked up the DVM in series with negative battery post wiring.

After getting out of the drivers seat, did not arm the alarm, and closing the door the dome lights etc are on for 30 seconds or so while it draws about 600mA.

Then it drops to about 135 mA and stays there for about 20 minutes.

Then the ECUs go into sleep mode and it drops to about 12mA and stays there.

I saw somewhere in a Toyota service manual that typical is 50 mA or less.
 
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