Parasitic drain / Battery Monitoring

[TimVZ]

I've got some weird electrical stuff going on, so I figured (1) I may as well document it here as I go and (2) it's likely that I'll get some good input from all of you.

We've had our 2015 LR4 HSE for at least 4 years and it has almost always given the low battery, start engine warning. Side note, the auxiliary battery was dead when we bought it and the previous owner said, "My dealer said it doesn't do anything except make the ECO function work. I don't like that anyway, so I never replaced it." I took him for his word on that. I removed the battery so it didn't leak/explode/whatever and thought maybe it was "stealing" power from the primary battery which would cause the low battery warning. No issues (that I could tell) and ECO never worked, but I was fine with that as well.

Battery low continued even after good charges and clearing battery memory/resetting with ODB scanner. I then had battery replaced and all was well for... a few weeks. We never had an issue with the vehicle starting, so attributed it to something odd with the auxiliary battery being gone/missing. A couple years went past and this battery started failing on a regular and tested bad by part store. Replaced battery again.

Good for a couple of weeks again and then low battery warnings started again. I then had TCM (shifter) fail to shift and my research shows those are touchy/sensitive to voltage issues and low batteries. hmm... (I sent TCM to Xemodex to be repaired. I have that back and it works, but I also have another used one that I have rigged with a zip tie to pull the shift lock mechanism. I'm going to keep using that until I get to the bottom of the power issues.)

LR4 sat for 5 days and battery was dead. Started to realize I've got a parasitic drain somewhere, so I started testing a few things with multimeter. Disconnected negative cable and tested amp draw between cable and negative post. The vehicle is drawing over 0.5 amps with everything off. yikes...

I pulled the plug on the BMS on the negative cable and tested battery voltage. On the battery I had 12.9v and on one of the pins of the BMS I only had 6.64v. Is this normal? It doesn't seem like it is. I found this post (older model and BMS is different).

https://www.landroverworld.org/threads/2012-lr4-electrical-power-loss.45637/#post-252484

Mine looks like this and if I put multimeter on the top pin inside the plug is when I read 6.64v.

Next steps:
1) Ordered a new Exide EK151
2) Test all fuses
3) Do I need a new negative cable end and BMS?
4) Anyone worked through a parasitic drain and have a good approach to narrow and pin it down?

 

[powershift]

#1 Check alternator voltage

 

[itsaguything]

LR4 sat for 5 days and battery was dead. Started to realize I've got a parasitic drain somewhere, so I started testing a few things with multimeter. Disconnected negative cable and tested amp draw between cable and negative post. The vehicle is drawing over 0.5 amps with everything off. yikes...

The vehicle takes 20 minutes to shutdown completely. If you touch doors, etc., restart the clock. Is that .5A reading after the shutdown period?

 

[DylanM]

I had a similar issue and it turned out to be a faulty starter motor causing the parasitic drain. If yours tests okay, another thing to check are the ground wires, particularly the one in the wheel well (which can corrode and disconnect).

 

[TimVZ]

2026-01-12 update

Auxiliary battery has been ordered and should arrive tomorrow. Exide EK151. Further research and chat says that could be a contributor to the electrical issues we've been experiencing as the auxiliary battery "covers" the difference in voltage at times? Not sure I totally buy that, but I also figure that I need to get the LR4 back to spec and how it was designed to be used.

Voltage tests without the auxiliary battery this past weekend show the following:
Engine running - no lights, no heat, no fan, no heated seats
--- 15.08v

Engine running - lights, windshield heat, heated seats, fans on high, radio
--- 15.61v

Engine running - turned everything electrical back off
--- 15.68v

Immediately after engine shut off
--- 13.58v

20 minutes later
--- 13.38v

Disconnected battery
--- 13.37v

Waited over 1 hour with battery disconnected, doors closed, hood closed (ran wires out to test amperage after the 1 hr)
--- 1.0 mA of draw

This would seem to make sense... as the battery was disconnected for more than an hour, what could possibly be drawing any power. The only connection to complete the circuit would be the multimeter.

 

[itsaguything]

Good work @TimVZ .
However, those reading you have taken when the engine is running does not represent the battery. They represent the output from the generator.

The disconnected battery reading immediately after charging is irrelevant. It represents the residual charging voltage. You really need to wait at least 6 hours to have an accurate battery voltage. Many shops wait overnight.

And I'm glad you confirmed the 1mA of drain, following the complete shutdown. The only outstanding bit is an indication of battery health. Get that reading 6 hours after any charging event.

Cheers!

 

[powershift]

The alternator sounds strong, maybe a little too strong as I thought 15V would be the limit. On my '12 I'd expect the battery to be dead if I just leave it while camping for a few days so I disconnect the negative cable. I don't think anything is wrong with it, the brains take power. Corvettes and new Defenders are no different.

If you have anything aftermarket electrically connected, try temporarily disconnecting the equipment. But 1ma draw is tiny so I wouldn't see that as a problem. Maybe keep reading the draw over time to see if it changes. A weak battery could also be the culprit even though the voltage is good after a charge.

 

[TimVZ]

@itsaguything - I realize that the reading while it is running isn't the actual battery voltage and is coming from the alternator. And that the reading immediately after engine shutoff isn't super valuable. I was just checking/writing down everything I could. Thanks though. I appreciate any/all advice.

Auxiliary battery has been installed. Ran for two weeks before I could finally get to my brother-in-laws shop to use his scanner. During that two week period battery low warning would appear only about 50% of the time when entering the vehicle. This is an improvement of the 100% of the time prior to auxiliary battery being re-installed.

Just this morning I was finally able to get to shop and performed the Service, battery replacement tasks via the ODB scanner. I did this for both primary and secondary batteries. We'll see what happens now.

I'm still not convinced that I don't have a draw somewhere. I ordered an amp clamp that I can put around the negative battery cable to monitor amp draw rather than disconnecting battery and then using multimeter between disconnected negative battery cable and negative battery terminal. This should show me real-time draw.

Question - Will keeping the hood open keep things "awake"? Do I need to trick it into thinking my hood is closed?

 

[itsaguything]

Opening/closing a door will wake it up. Complete shutdown can take up to 30 min.
Leaving a door open, rear hatch and the hood open, should not cause the vehicle to awake.
The second you close an open door...

FYI, I never bothered with the battery replacement procedure when I do the work. It corrects itself within the week. The shop always does though.

 

[TimVZ]

Today's update:

Got a multimeter with amp clamp and ability to switch between 20 amps and 2 amps max. (2nd one... first one didn't have enough precision as it was capable of up to 600 amps and no reset/zero/tare button).

Here are readings on the negative battery cable. Time is after engine shutoff, locking vehicle, and putting the key inside so it wasn't close enough to trigger anything. I had to unplug the hood sensor and then jumper it so the vehicle thought the hood was closed. Without that I couldn't lock the doors.
I don't know the exact time that the amperage dropped. I wasn't standing there watching it the whole time (it was 10 degrees and windy).

5 seconds - 9 amps
30 seconds - 6 amps
1 minute - 2.58 amps
4 minutes - 0.8 amps
9 minutes - 0.36 amps
24 minutes - 0.2 amps
46 minutes - 0.23 amps
64 minutes - 0.23 amps

The 0.23 amps / 230 milliamps seems a bit high. I'll start doing millivolt readings on fuses next to try to narrow down where the 230 milliamps are coming from.

Need it to warm up a bit to perform a BMS test. I saw the scanner I was using had a test for BMS, but needs to be above 10 degrees F to perform test. Anyone see this option on their GAP IID or iCarsoft unit? I think its time to buy my own instead of always needing to run over to my brother-in-law's shop and hoping he's there.