Not able to capture draw that kills the battery
As a mobile guy, how are you supposed to get to the bottom of something like this?
(I understand that you can't, but explaining it to your customers can be difficult.)
They put a brand new battery in it, put it across the ammeter and it's pulling just barely 20mA.
I sit there staring at for about an hour, but I got to get moving. I leave the ammeter in glitch-mode to record whatever the highest current it sees might be.
3 days later, the battery is dead and the highest draw was 70mA.
I tell the customer all they can do is start unplugging modules and letting it sit. Usually the OnStar or VCIM is the culprit, but this car has had both of those removed already. They want to put a BCM in it.
Bcm is a common problem but radio is also.. A new battery does not mean its still not the problem? IS THE ALTERNATOR WARM WITH THE ENGINE COLD? BAD DIODES? I start with how much each module is as a complete job etc: part, labor, programming, and present the evidence.. Let them make the decision with no guarantees of it fixing anything.. You didnt break it, build it, or buy it..
Oh, I did all of the traditional stuff. Alternator pulled completely out of circuit, BCM unplugged. VCIM unplugged. AirRide module disconnected. ABS fuses out. Radio removed. Cluster removed. RKE module removed. Door lock fuses pulled. PCM disconnected. The battery has been replaced multiple times.
That sounds like a nice case study.. I hope you find it my man, sorry I was no help..
If you were to leave the car in the same geographical location…. Unhook one of the battery cables, then come back 3 days later and hook it back up, would the battery still be charged?
I would be breaking out the infrared camera. looking at the fuse boxes.
I would also use the infrared camera, but I would point it at the bcm and radio after it sits overnight. If they are using power they should be hotter. Its a place to start that does not take a lot of labor investment.
What is “dead?” 11.5V? 3V? Slow crank no fire? I agree with the suggestions of an infrared camera …after an overnight cold soak. Have you tried to verify the test results with a different measuring device? For example a different ammeter or a scope with a shunt. Of course neither one will tell you what is draining the battery. The scope with shunt will tell you when the drain occurs, for how…
Something is fishy here. 70mA ain’t gunna kill a good battery in 3 days.
70ma isnt going to kill a new battery in 3 days. Battery is probably junk…
Or it’s acting like the battery is dead but it isn’t 🤔
I have seen an increased number of batteries in the last 6 months from parts stores failing . I know enough from your other posts to know your very sharp with electrical. I am guessing it’s not a loose or failed cell internally draining other cells in battery . I like holding onto a smaller battery that fits most anything to rule out the cars battery . We have a very expensive battery tester -…
Just a couple of thoughts Jeff: (I realize your question is more about what approach should be taken with a customer versus the technical question at hand on what is wrong with this particular vehicle) - When you came back and saw the 70ma max, did you catch what the average was? If the average was in the 60's versus 10 or 20ma, it would say a lot about how long it was up near 70ma or if it…
Long ago I had a similar situation on a GM truck and my buddy Dave DeCourcey RIP offered some help. He connected a Tech 2 to the vehicle and powered it via the auxiliary power port from another battery (isolating it from the vehicle battery). He set up a screen that counted network pings and we left it overnight. If I remember correctly the following AM we had a weak battery and no more pings…
70 will not kill the battery that fast as everyone is stating…. that being said, does this vehicle have a battery current sensor? And have to load/voltage drop tested the battery cables? I read the battery is down to 7 volts? A gentleman shared the pico draw with a shunt…. that is where I would go next. Or a battery maintainer with a GOOD infared camera. That is generally how I find mine if the…