12v Battery Is Discharging, Re-Charge Now !

I was watching this video.

It explains how to isolate a particular circuit that is drawing amp WITHOUT removing fuses and without connecting amp meter to a battery in series. I think this may be the easiest and safest way to test the current draw on my car.

Here is another video that describes the problem of removing fuses in modern computerized cars like Prius. Watch at 4:40 explains that removing a fuse in modern computerized cars can "wake up" the other modules causing a problem in amp draw test.

One concern I have is that those test for "parasitic draw" on the 12v battery is for something that draws more than 50mA which causes the 12v battery that cranks the engine at starting to die overnight. However, here what I want to check is a much smaller amount of draw than that. So, regular "parasitic draw" tests may not work. And even if it does isolate a circuit, I may not be able to pinpoint the exact component which is drawing amp. Also, obviously, something like a random emission check that comes on a few hours after the car is shut down would be missed, but any continuous draw should be identified.

 

When I did the test I was seeing milliamperes around 16~18, with spikes to around 40.

What about one of those clamp meters? Are they sensitive enough? Very pricey? Out-of-my depth btw.

 

Was your 12v battery drained in days, weeks, or months?

 

Wasn't drained. I believe that test was back when the car was still daily-driver for my wife, in her work.

But now, and doubly so with Covid, the car has a LOT of downtime. But I don't do torture tests like you guys lol: just keep in on a charger 'round the clock.

 

You mean this one? Power Probe

Well, it is cheaper than Fluke 87V multimeter. BTW, after I started measuring my 12v battery and found out that my 3 different el-cheapo multimeters show different measurements, I wanted a better tool, but I didn't want to spend $400. Ended up buying used Fluke 87 multimeter on eBay very cheap, but still 3 times more than what I paid for a Craftsman.

 

There's a load tester in that menagerie IIRC?

The Suaoki?

 

Suoaki is another el-cheapo tool I bought for the battery maintenance. It is a 4A smart charger. You must be thinking of this load tester.

 

For me it was Logo (I was in 7th grade), TRS-80 Basic (High School), Pascal, C, Ada, Fortran, x86 ASM, Perl, C++, C#, Python, Lua...
(or something like that), but it's pretty much all C++ now.
I've been a professional game programmer for about 25 years.

 

I haven't posted in a while due to needing to drive the car, which put a stop to my measurements. However, I've recently measured another 2-week period of non-driving. Unfortunately I didn't measure every day.

5/16: 12.70v
5/17:
5/18: 12.57v
5/19
5/20
5/21
5/22
5/23: 12.46v (End of Week 1)
5/24
5/25: 12.37v
5/26
5/27
5/28
5/29: 12.22v
5/30 (End of Week 2)
6/1: 12.16v
6/2: 12.10v (and after driving for 2hrs, 27miles, it went up to 13.01v)

so, it drained 0.6v in 16 days, averaging a drain of 0.038v per day.

I ran a linear regression, r = -0.9948, which is pretty highly correlated (granted I only have 7 data points)

Scatter plot with linear regression:


You can make your own graph here: Correlation Coefficient Calculator

 

agreed, that is not a pretty chart.

and i don't see a reduction in decrease after sks shuts off in 5 days

 

I have not had my car not charged for longer than 1 week at a time, but it seems from a fresh charge-up with an external wall charger, ~13v drops most in the first two days. Then the resting voltage seems to settle somewhat after that up to 1 full week. The lowest I have let my 12v battery drop was 12.3v.

 

When you charge with your wall charger do you remove the engine cover for the negative pole or do you just use the poles on the battery. I realize the manual seems to indicate removing the engine cover but it adds a complexity that, if not required, is somewhat time consuming

 

I haven't been following the safety precaution written on the manual. I just connect directly to the (+) and (-) posts of the 12v battery using alligator clips. I think connecting to the engine block is safer to prevent any hydrogen gas emitted from the battery ignited by the spark, but I think the possibility of that happening is low, I think. If you want to be safe and quick, then installing a quick connector that comes with most of the charger is the way to go. I am actually thinking to install "on-board charger" with 120v plug-in port so I don't even have to open the hood to charge-up the 12v battery.

 

I use a ground point right by the dipstick.

 

Do you mean circled bolt or near it?

 

Yes, in the circled area, but I clamp on to the smaller bolt that attaches the braided cable, which attaches to the chassis at the other end.

 

Thanks. Good to know. That is certainly easier than removing the engine cover each time. Although, I am not sure if the alligator clip cord that came with my charger is long enough to connect to the battery post and the ground point in the photo. I will try it next time, but as I said, I am planning to install an on-board charger with a plug-in port on my PRIME.

 

You're welcome! When you asked about the exact location, I was a little worried I was doing something wrong because I think you have had a lot more experience with the Prime than I do. And I haven't seen any others on any of the 12 volt charging threads on here refer to using that ground point. When I 1st got my charger I was concerned that the negative clip wouldn't reach this point with the positive connected to the battery, but all I had to do was peel the positive and negative charger wires apart for a longer length of the cable and it reached fine. Good luck with your on-board charger!

 

If you look under the engine cover, don't have to remove the cover, under the the left-most edge you can see the bottom of the bracket in this picture which you can attach the negative (-) to