Hi since 2020 when I bought the car used 2008 V8 LR3 I have been experiencing what a lot of folks are experiencing, dying batteries, battery dead after sitting for 10 days, or almost dead resulting in car's inability to start.

What it isn't caused by:

1. bad battery (instant nope, replaced many times)
2. bad alternator (nope, already replaced)
3. bad starter (nope, already replaced)
4. bad negative or positive lead connections (already cleaned up all the grounds and connections between alternator to battery to starter, plus replaced negative and positive leads with new ones)
5. hood switch (replaced)
6. tailgate switch (replaced)
7. brake switch (replaced)
8. instrument cluster (replaced, a local Shop in Seattle had identified that to prevent car from sleeping, but it resolved one power draw issue there is still another)
9. existing codes pointing to a faulty component (checked no faults)
10. EAS relay replaced
11. rain sensor replaced

There are no codes and no dash light indications that anything is wrong (car runs perfectly fine with fully charged battery). What is happening is simply that the car wakes up intermittently from sleep because of a faulty component and much more frequently then spec when parked over night. This is resulting in the battery draining that way, or maybe the car never goes into deep sleep in the first place, again causing existing systems to draw power at a higher rate then when sleeping.

I have not found any forum with a list of components that causes this issue that most commonly are replaced, maybe a user here can provide a list of most likely to least likely.

What i will do next is do the fuse power draw hunting exercise by:

1. open doors, latch the locks and lock the car so car thinks all doors are locked, including the hood and hood switch (also remove fob from car so it doesn't think it is near)
2. let car sleep and connect amp meter in line with negative ground (one questions is it 30min or more like 4 hours before car goes to deep sleep?)
3. instead of 2 decided to by a AC/DC Amp Clamp meter so I don't have to worry about blowing out my multimeter, and will measure current flowing that way
4. look at power draw, and in the engine bay pull fuses one at a time, pull relays one at a time and see differences (avoid body control module fuse since that will wake car when inserted again)
5. repeat but in cabin fuse box
6. isolate circuit that has draw higher than 70mA (I think that is the default draw in sleep, another question?)
7. Isolate components on circuit and replace

Any other ideas on approach?

 

Hi, did you figure out your battery drain issue? I have same thing. Highly random however. Battery died 8 hours into 10 hour trip. Swapped Alternator. No issues during two 10 hour road trips. No issue during normal driving for next 2 weeks. Yesterday, 2 hours into a 3 hour drive home, battery died. Put in new battery. Drove home, 5 minute drive. This morning, battery is dead. I do have the Gap tool. Will start my investigations today. It is cold however, minus 3F, which may complicate things.

 

How confident are you in the quality of the new alternator you installed?

 

I did not resolve it. It is simply any ECU in the car (there are about 60) could cause the BMC (body management computer) to prevent the car from sleeping, or going into deep sleep. What I did is hook up a solar charger to the battery and installed two solar panels, and replaced the battery with a lithium ion. This way during the day it recharges the battery, next day it always has enough charge to start. It is a brute force solution by ignoring the battery drain entirely. If you have a GAP tool and any equipment has an obvious internal error, then replacing it could also fix the issue. The problem in my case there weren't any obvious issues or codes and I have already replaced the brake switch, rear hatch switch, the odometer control panel, battery negative cable, battery positive cable and other things that may have helped in my case. It didn't drain the battery in a day to begin with, but after 7 days it typically was enough to kill it.

It seems like in your case the battery might not be charged, hook up a voltage meter on the battery and make sure it generates ~14.4Volt or something like it. One other thing I did is clean the connections between battery and car body, alternator and battery to make sure all the grounds are clean (and after install coated them with corrosion prevent compound).

I did some initial hunting of parasitic current draw with the following AMP meter, but my current draw when i tested was actually within spec so I didn't get it into a state where it was draining the battery during the 2-3 test cases that I did (override hood switch with hood open, car locked, key far away from the car), AMP meter over positive battery lead. Once you see a battery current draw out of spec you can start pulling fuses to see on which circuit these occur, though I never got to that part.

The following AMP DC clamp meter is the only one that will work.

 

Thanks.

1. Pretty confident the Alternator is decent quality, intentionally purchased from FCP Euro, because lifetime warranty, and actually was pleased with the price. Bosch. It was however a reman unit, so of course there is always some 'risk' there. But when I left Batteries Plus, with new Battery fitted, tested, fully charged, I only drove 5 minutes back to house, into garage. Next morning, dead battery. Can a bad Alternator drain a Battery even when vehicle is not running? (I am useless at electricity - this project has motivated me to learn more).

2. I charged up the Battery last night. No issues getting it fully charged.

3. I have started to research 'parasitic battery drain' issues and diagnostic process.

4. I do have the GAP tool.

5. I do have several electrical issues (according to GAP tool) which I will try to take care of before testing every fuse / relay / circuit, etc.

6. Will probably do a hard reset.

7. As I said earlier, I am useless at electrics, and up until now have been the proud owner of the (free) Harbor Freight multi-meters. I have decided to 'adult', and have purchased a decent meter.

8. Will be a bit chilly here in Madison until next week, probably won't do much until it warms up a bit.

P.s. I do have an additional LR3 that I recently picked up, same year, 2008, (but SE vs my HSE) - So I can easily do some swapping / testing using the other car, if necessary.

Cheers, Simon