Odd battery drain issue

[Toiny]

Hi All,

I'm new to LR - but have a 2020 P400 Defender. I've tried looking through the various other forums including this one and Youtube videos etc but have yet to find an answer.

A few weeks after purchasing the vehicle I started experiencing low battery warnings. I looked it up and schooled myself of this being an expected issue with modern Land Rovers, fair enough.

The car is 3 years old, so I decided to have the battery replaced regardless. Now, here is one possible explanation to my woes below. When the person who replaced the battery was pulling out the old / putting in the new battery they knocked the battery sensor plug and pulled out one of the wires (green/yellow trace). I took the car the next day to an auto electrician to repair and reset the BMS. I wonder if this caused an issue with the BMS, running the car with one of the wires disconnected.

A few days later, same issue - battery low. Yes I've done some small trips, and long trips (40+ minutes). I also have a Noco battery charger if needed.

I decided to install a Bluetooth battery monitor to track the voltage. Took the car for a drive and noticed that the battery is discharging whilst driving, and reading around 12.3v.

Next experiment:
Ignition on - drivers door open: voltage - 14.3v (awesome - its charging with the engine on)
Ignition on - drivers door closed: Voltage - immediately drops down to 12.6 and continues to drop to 12.3 and battery draining.

Seems so strange that the vehicle doesn't charge while driving.

I've read on here, and other forums that battery issues have been resolved with software updates (my cars software is still from 2021 as the previous owner never had it updated). Or wondering if I should try installing a new BMS, reset it and go from there. The door open vs close thing however, has totally stumped me.

[Eric SDV6SE]

Smart alternator will only charge if the system demands it. The BMS needs to be reset and to be "told" that it has a new battery. There are a lot of systems to power up when the door opens, cars getting ready to go basically. There was an issue with the later L663, mine (MY23.5) had a recall just the other month with the . Definitely get the software updated. Most likely the "old" battery was still fine, if you still have it, put it on the charger, it may recover.

I don't driving it around for 1 day, with the wire disconnected would cause harm, the car just ran on battery, not being charged by the alternator.

The alternators in the L663 are also smart and more complicated, especially with the mild hybrid systems.

I'd suggest a good long drive (2-3 hours) whilst monitoring the battery, it "should" charge once it drops below around 12.3-12.4V and the system demands more load.

As a last resort, take it to a LR dealer and have them check it out, your average auto sparky would have limited knowledge on these vehicles.

This thread is D3/D4 related, but Tim from Traxide is the guru
Lithium batteries and smart alternators (https://www.aulro.com/afvb/l663-defender/291608-lithium-batteries-smart-alternators.html)

[Toiny]

Thanks Eric,

You're right the smart alternator is behaving as it should. Last night I went for quite a long drive and the voltage was sitting at 13.1v, got home and double locked the car.

To my surprise today, around 1/2pm I hope in the car and I'm greeted with a low battery warning.

I checked the battery monitor and it appears as though even double locking and placing my key in a Faraday box, the battery has a consistent drain over night. Something is slowly chewing power. Anyway, turn the car on and she's driving with 14+v charging as it should be.

I've attached the graph showing slow voltage drop over 19 or so hours.

Hoping software updates solve this.

[Eric SDV6SE]

Parasitic drain, do you have any accessories like a phone charger, radar, brake controller etc? Something is definitely drawing a decent current to drain the battery. Do you have the centre console phone charger and left the phone on there?

[jwb]

The MHEV system in our cars is not like the previous alternators however smart they might be.
It has a starter generator in place of an alternator which both starts the engine in stop start mode and harvests kinetic energy under braking to feed back into the battery.
There's a 48V lithium in there as well as it's own DCDC to 12v in the mix but it's beyond my understanding.
It does appear to work like an alternator though as my DCDC aux battery charger is happy with it.
Can't help you with parasitic drain but just spent several days camping and didn't have a problem with battery drain by leaving a door cracked so the pivi didn't keep waking up and mainly using the back door which doesn't activate the pivi.

[Toiny]

Parasitic drain, do you have any accessories like a phone charger, radar, brake controller etc? Something is definitely drawing a decent current to drain the battery. Do you have the centre console phone charger and left the phone on there?

Zero accessories or after market things on the vehicle apart from the Bluetooth battery monitor but I highly doubt that is drawing so much current.

Also I've unplugged all USB cables inside, no phone left in there, no camera or brake controller, everything off.

[Toiny]

Again, battery drained overnight.

I'll try to do a process of elimination but hopefully in the next few weeks when JLR update firmware/software and replace the dead TCU battery it resolves itself.

[Eric SDV6SE]

I searched on the 48V MHEV, these may help to understand
2020 Land Rover Discovery Sport Mild-Hybrid Technology (MHEV) - YouTube (https://www.youtube.com/watch?v=FmgXkLZJPOY)

And

48-Volt Mild-Hybrid System Explained (https://www.autoweek.com/news/a36331077/48-volt-hybrid-system-explained/)

Re your issue, could be a failing BiSG, or am issue with the 48v system?

[Eric SDV6SE]

I searched on the 48V MHEV, these may help to understand

2020 Land Rover Discovery Sport Mild-Hybrid Technology (MHEV) - YouTube (https://www.youtube.com/watch?v=FmgXkLZJPOY)

And

48-Volt Mild-Hybrid System Explained (https://www.autoweek.com/news/a36331077/48-volt-hybrid-system-explained/)

Re your issue, could be a failing BiSG, or am issue with the 48v system?

[jwb]

BSIG problem just notified (https://www.aulro.com/afvb/l663-defender/297408-bsig-problem-just-notified.html)

Ask about this at your dealer

[Eric SDV6SE]

Yes, but the OP's is a 2020 model, the BSIG recall was for 23-24 MY. That's not to say it isn't a BiSG issue, worth checking out.

[Toiny]

I thought I'd post an update for anyone curious.

My battery drain issues are now sorted. Basically what happened was:


Car went to JLR for service. They tried to complete a recall and update software. In the process they fried the NFSM module (Sensors and cameras).
Battery was draining to almost flat overnight since.
Now the challenge for me was that a) I only just received the car and b) I replaced the battery after the service so I didn't know if any issues were pre-existing.
The bricked module effectively left an open circuit draining the battery.
Yesterday JLR replaced the module finally and the battery drain is gone and back to spec.


Super frustrating to think of the damage that has been done to the battery over 3 months with constant draw even though I've had it on a charger every night.

[Grappler]

I have just started to get regular Low Battery warnings. The Defender D300 is 2 years old

The advise from the dealer was to go for a longer drives and keep the vehicle locked and alarm armed when parked up.

I normally didnt bother arming the alarm as it is locked in a shed

Hopefully this will help. The BSIG issue is not applicable to my VIN

Im reluctant to trickle charge . Is it OK to use a smart charger (CteK) via the terminal posts under the bonnet?

By contrast my 2012 Defender is still starting on its factory fitted battery (getting close to 13 y)!

[one_iota]

.....

Im reluctant to trickle charge . Is it OK to use a smart charger (CteK) via the terminal posts under the bonnet?



They are greedy!

Mine is also 2 years old.

It goes for a long drive every second week to our place in the bush. In the city it is rarely used and I keep it double locked and the key in a Faraday pouch as the Defender is close to where I keep the keys. I have a bluetooth battery monitor fitted to keep an eye on voltage. If it gets below 12.4 volts as a result of opening the doors to get stuff and the occasional short trip I put it on a decent quality smart charger (22amp) connected to the posts under the bonnet. I've been doing this for 2 years and have only had a low battery warning twice whilst away from a charging opportunity. It takes about an hour to get the battery back to full charge

It might be worth having the battery tested to see if its losing its capacity.

My 2008 is constantly attached to a charger to keep both batteries in good form.

[drivesafe]

Hi folks and long drives only solve low battery issues if you drive long drives virtually every day.

The problems caused by low use and lots of short drives can NOT be resolved by the occasional long drive.

Also Note, you are not Robinson Crusoe. This a common problem with most new vehicles, particularly when they are the second drive, not the primary drive vehicle.

First off, while better than nothing at all, but Mahn, your one hour charge actually does not full charge the battery.

All lead acid batteries Sulphate when not used regularly and decent driving is done when they are used.

That hour hour charge will top up the battery capacity that can be charged, but your battery may well only have anything from 80% down to 20% available and that’s all you are charging.

To fully charge a lead acid battery and to reverse the effects of Sulphation, your need to have your charger run for around 12+ hours straight.

And you may need to do this every night for at least a week to get your battery back to full health.

Here are to links that will explain how to check your battery, and how the Maintenance cycling works and how to do it for the best results.


Scroll down the page till you get to “LOAD TEST”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-10.html


Scroll down the page till you get to “Battery Maintenance”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-8.html

[one_iota]

......And you may need to do this every night for at least a week to get your battery back to full health.



Good guidance as usual thanks Tim.

The Ctek charger has a recondition mode. Does this help dealing with the sulphation issue?

[drivesafe]

Good guidance as usual thanks Tim.

The Ctek charger has a recondition mode. Does this help dealing with the sulphation issue?

Many AGM batteries do not take kindly to RECONDITION charging.

I will leave this one to your personal decision but I NEVER use a Recondition cycle on any AGM.

They are fine with any Wet or Flooded type battery.

[Grappler]

Since getting in the habit of arming the Defender when not being driven I havent has any low battery warnings

The powerfuluk YT episode https://www.youtube.com/watch?v=SMj7XBJ48WM explains the power draw in different door opening and arming scenarios, very well

Yesterday I installed update OS 4.2.1 that came over the air It included "Improved protection of 12v battery hardware during long cranking events"