Thread: Odd battery drain issue

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

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.

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?

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.

Originally Posted by 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?

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.

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.

I searched on the 48V MHEV, these may help to understand
2020 Land Rover Discovery Sport Mild-Hybrid Technology (MHEV) - YouTube

And

48-Volt Mild-Hybrid System Explained

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

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

2020 Land Rover Discovery Sport Mild-Hybrid Technology (MHEV) - YouTube

And

48-Volt Mild-Hybrid System Explained

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