2021 Yukon Denali - Correction, the "40w pulling the battery down" was misread of clamp meter

[tagexpcom]

***I apologize for posting a completely wrong battery draw reading***
It's actually 2-3w.


I recently bought a used 2021 Yukon Denali with middle package. I drive once a week. Noticed the battery seemed really low and started measuring it at 12.0v - 12.1v. Thought it was weak (used car and all) and installed a new battery.

But still showing 12.0v after just a few days from the last drive.

I manually charged it to 12.8v and put a clamp meter on the negative and it's been pulling 3.3a = ~40watts for the last 3 hrs. If this continues it will be low within a day.

Saw a youtube suggesting that 0.4a (400ma) is more normal but I don't know. Is 3a (40w) draw normal for a 2021 with everything (seemingly) off?

 

[B-train]

Shouldn't be. Generally the computers should all go to sleep, at the latest, after the RAP (retained accessory power) says nobody is still here (usually 15-30min).

I think you have a module/ecm staying awake for no reason.

 

[tagexpcom]

@B-train - thank you for replaying... got me to thinking about what could be on with the vehicle off.

Turn off the wi-fi hotspot but that didn't seem to help.

 

[Chad G 1979]

You dont happen to keep your key fobs nearby the vehicle when at home do you? I thought i read that if they are close they can keep waking up the vehicle. But dont know how true that is as i have one about 10 feet away at most on inside of door to house from garage and have not had any issues.

 

[tagexpcom]

You dont happen to keep your key fobs nearby the vehicle when at home do you? I thought i read that if they are close they can keep waking up the vehicle. But dont know how true that is as i have one about 10 feet away at most on inside of door to house from garage and have not had any issues.

Thank you for the thought - but no, the fobs are 50ft away in the house.

 

[Silverado4x4]

The computers dont all go to sleep it is always monitoring the vehicle. The alternator only charges the battery when it needs to so what your seeing as 12v is pretty normal sometimes you will see it drop below 12v when the alternator doesnt need to charge the battery at all while your driving.

 

[Steve Smith]

I recently bought a used 2021 Yukon Denali with middle package. I drive once a week. Noticed the battery seemed really low and started measuring it at 12.0v - 12.1v. Thought it was weak (used car and all) and installed a new battery.

But still showing 12.0v after just a few days from the last drive.

I manually charged it to 12.8v and put a clamp meter on the negative and it's been pulling 3.3a = ~40watts for the last 3 hrs. If this continues it will be low within a day.

Saw a youtube suggesting that 0.4a (400ma) is more normal but I don't know. Is 3a (40w) draw normal for a 2021 with everything (seemingly) off?

Unhook all of the wires going to the alternator, and remeasure the current. It sounds like you might have a shorted rectifier diode in your alternator.

 

[tagexpcom]

Folks, I was completely wrong in my initial post. I was misreading the clamp meter!
The actual draw is ~2-3w. 2.5w/12.2v = 200ma or 0.2a. I understand that 0.2a (200ma) is more in range with what's expected.

False alarm on my part - I apologize.

However, after a week this does draw the battery down toward 12.0v which is pretty low - but perhaps this is nothing to worry about? Interested in opinions.

 

[DuraYuk]

Have you had a no start condition?

 

[tagexpcom]

Have you had a no start condition?

No

 

[DuraYuk]

No

Rule of thumb is 100mili amps needs to be looked at. But every car is different. And the tolerance range is different. Your denali has tons of modules that stay awake.

If it were mine unless I was actually seeing issues like a no start I wouldn't be bothered to be looking so deep.

 

[Fless]

I'd put an ammeter wired inline with the negative battery terminal and let everything go to sleep (just don't start it or turn anything on with this setup; the meter can't take a lot of current). Very few clamp meters are accurate at these low draw values. It's best to measure directly in Amps or milliamps.

I'd venture a guess that your "totally asleep" draw is less than 50mA. If it's much more than that, I would dig deeper.

 

[tagexpcom]

Once I discovered my clamp meters are way inaccurate I started measuring overall voltage drop over the week.

It's 12.4v -> 12.1v (~0.4v drop in 7 days). This is ~30% discharge of the 80ah battery and my calculations yield ~140ma (0.14a) average battery drain over the 7 days based on 30% discharge.

Interestingly, I see this same pattern on my 2004 Cadillac SRX - e.g. 12.3v -> 11.9v after 7 days of sitting - e.g. a 0.4v drop.

So I'm thinking that the Yukon is in a similar range of battery drop as my old car which I've been driving weekly for several years - and so I'm making a mountain out of mole hill.

It's weird - after buying this used rig, for A LOT of $, I find I'm overly alert about things as I don't have a history with the vehicle and it's been 19yrs since my last purchase. So far (7 weeks and 1,500miles) it's all looking great so I'm looking forward to relaxing a bit soon