Battery drain - what is causing it?

[DenisM]

When I first took delivery, I charged the dual battery set up several times following low readings and used the "recondition" function on a Victron 15A smart charger. It's operating normally now. That was 18m ago. The vehicle doesn't do many kms at the moment so I charge it once a week to maintain it.

 

[TheDocAUS]

When I first took delivery, I charged the dual battery set up several times following low readings and used the "recondition" function on a Victron 15A smart charger. It's operating normally now. That was 18m ago. The vehicle doesn't do many kms at the moment so I charge it once a week to maintain it.

A good practice as a smart charger maintains and charges the battery(s) better than an alternator.

A solar panel with the CTEK CTEK250SE does a good job as well, if there is sun around.

 

[Dschubba]

Further to last post.
I got a Victron ip65 25A, gave the battery a full recharge and sulphation condition. Then I had to go away for a week. I had installed the BLM voltage monitors, so here’s the pictures.

It’s interesting to see how the ctech 120 keeps topping up the main battery, then just preserves itself once it gets to 12V. At that point you can see the main battery voltage dive fast, and towards the end was in a real death spiral at .5V a day loss.

The car screen display is what showed when I turned the key on. I videoed the ctech 120 module during the start and I can see it used the auxiliary battery as main battery failed to start it. (Thanks Rok instructions guide)

Also of note was that when I started the car the voltage shot straight up to 14.9v. That would indicate to me that the battery has a high internal resistance.

So to summarise the main battery wouldn’t last 7 days after being given a full charge with the car being locked and untouched.

For interest what’s the consensus for how long you should be able to leave the car without charging it?

Thanks
Sean

 

[TheDocAUS]

Thanks great information.

When I went away for 2 weeks recently, both batteries were is good condition upon my return, but not fully charged. This was because of the CTEK250SE and solar panel topping everything up.

I suspect both batteries would be fully charged in summer, however, the shorter winter days means less solar charge going in. The car was not driven on 26 May onwards. The voltage drops on 24 and 25 May are the car being started and driven.

It seems clear the main battery was benefiting a great deal during the day from the solar panel. The aux which was fully charged to begin with was allowed to supply power and drop voltage (you can see this in the 7 day graph), but on 1&2 June was recharged again and the pattern of supplying power to the main battery repeats. On 2 June both batteries were being charged in a similar way until the aux battery was topped up (see 1 Day graph below).

A bit of difference between our graphs, ignoring my graph is for 2 weeks (first 2 graphs).

NOTE: My graphs use different colours between my first screenshot and 2nd and 3rd screenshots- the app picked up a battery box as I walked around.

2 weeks ( I had the graphs mixed up below - main is really aux battery I mislabeled them early on)

@Dschubba

7 days

1 day, being 2 June were both batteries were charged

 

[ADVAW8S]

I went away and my car was dropped off at dealer for work. It was not driven around. I have a single battery. Left with the screen saying 98% charge. Picked up 11 days later, battery was at 93%. The work done was software update, new safari window seals, coolant pipe and coolant reservoir replaced. Limited engine needed to run.

 

[Tenac]

I went away and my car was dropped off at dealer for work. It was not driven around. I have a single battery. Left with the screen saying 98% charge. Picked up 11 days later, battery was at 93%. The work done was software update, new safari window seals, coolant pipe and coolant reservoir replaced. Limited engine needed to run.

I've been out in travel past 4 weeks got home on Thursday my dual battery system read 92% and is now back at 98%, I didn't drive it very far.

 

[stegelkamp]

Hi everyone,

Since I also have the battery drain problem with my MY23, I would like to share my experiences.



First of all, the IG has never let me down, even with an empty battery. Even though the SOC in the head unit regularly drops to 50%.

This happens sporadically, sometimes yes, sometimes no! Very spooky.

Even the charging current according to the head unit is then very limited and is usually below 3A.

My dealer has no advice, but is in close contact with Ineos, but they all seem to be helpless.



A few days ago, I removed the CTEK and replaced it with a Redarc ALPHA 50 R. The goal here was to support a solar panel and get more information about the AUX battery.

It took a while, but now everything is working. Thanks again to the community for lots of tips.



The main battery is still losing SOC. However, I have noticed the following several times now



- Car is locked

- No doors open

- No key nearby

- I constantly hear a high-pitched beeping sound from a control unit

-> When this occurs, the SOC has also dropped significantly. SLEEP mode does not seem to work here, but the question is which control unit



Well, okay:

with the Redarc Alpha, the batteries are now truly separated and are not “leveled.” This is clearly shown by the Redarc RedVision, and the DUAL battery always has 100% SOC (I calibrated the app).

If the SOC of the main battery drops to, say, 61%, I can finally see that the BMC is doing its job. The charging current of the main battery is immediately more than 35A, and after a good 15 minutes of driving, the SOC is at 68%.

I have observed this several times. It works as I would expect. This was NEVER the case with the CTEK. But the CTEK also works differently.



My assumption is therefore:

- The BMC had “incorrect” values because both batteries were “leveled” and were essentially shifting the load back and forth.

- This means that the Smart alternator can now work properly.

- The IGN/D+ signal is now connected to the Redarc, which was not the case with the CTEK ex works.

- There are probably several factors at play here. Power consumption when parked, recharging the battery, etc.



It's all very strange.

 

[Dschubba]

After a day in the dealers, I got a call and they said they had load tested the battery and it was ok and that the drain was probably due to the UHF radio install.
I suggested that with 210AH of battery capacity and 24 hours on a Victron 25A smart charger of course it will pass a load test, and that the radio was wired to be controlled by those roof switches and would be completely isolated with the switches in the off position. Nevertheless it should last longer than a week.
So lots of to and fro, and in the end they have agreed to change the main battery out as I think the most likely scenario is sulfation causing the battery to die.
Of course no batteries in stock so waiting to hear back so a new battery can be installed…
Apart from that cars going great.

 

[Tom109]

My Gren-indicated SoC has dropped to the mid-80’s for the past six months. It never indicates more that 2-3A charge. I finally decided to throw it on a wall charger on 21-June, drove it on 22-June, then parked it until 3-July. In that time it had dropped to 91%, and each day of use picked up ~5% until it hit 100% July 5th. It seems to be back where it was the first year of ownership.

 

[Eric]

My Gren-indicated SoC has dropped to the mid-80’s for the past six months. It never indicates more that 2-3A charge. I finally decided to throw it on a wall charger on 21-June, drove it on 22-June, then parked it until 3-July. In that time it had dropped to 91%, and each day of use picked up ~5% until it hit 100% July 5th. It seems to be back where it was the first year of ownership.

Yep, that's exactly how mine behaves, I just now accept the smart alternator is smarter than me. Even if fully charged by a smart charger, but I end up doing a few days of short journeys the alternator let's it drop to mid 80's when parked up. If the day and night ambient temperature is high, it holds it at 90°

 

[matt_grenadier]

I too had a battery drain the last days. Last drive for 1u30 on Sunday night, then the next drive Wednesday morning, and i got a 'battery low warning', with the battery at 48%.

Don't know what happened, never had this before.

I do always notice the main infotainment system stays on for a long time after the engine is off, en the doors are closed and locked, which i always find strange, but that is normal it seems.

 

[Jonny72]

Helpful thread. Mine fluctuates between 0% and 43%. It’s a 2025 1924, Diesel which I picked up 3 months ago. It was my daily, but noticed a significant drop in charge 3 weeks ago. I called the dealer straight away, and last week I decided to park it up last week and use another car as don’t want it to let me down by not starting.

 

[Skydance]

Helpful thread. Mine fluctuates between 0% and 43%. It’s a 2025 1924, Diesel which I picked up 3 months ago. It was my daily, but noticed a significant drop in charge 3 weeks ago. I called the dealer straight away, and last week I decided to park it up last week and use another car as don’t want it to let me down by not starting.

Have you checked that the power switches on the overhead panel are left switched on overnight?

 

[Skydance]

I too had a battery drain the last days. Last drive for 1u30 on Sunday night, then the next drive Wednesday morning, and i got a 'battery low warning', with the battery at 48%.

Don't know what happened, never had this before.

I do always notice the main infotainment system stays on for a long time after the engine is off, en the doors are closed and locked, which i always find strange, but that is normal it seems.

The infotainment system after driving, turning car off, open car door, infotainment system turns off immediately. HVAC usually times out approx 20 seconds after switch off.

If you open door but not switch on the car. right side Infotainment screen will turn on. Infotainment then turns off approx 20 seconds later after door is locked or if the car isn’t started.

This should be the new procedure after the software update back in earlier this year.

 

[Jean Mercier]

I too had a battery drain the last days. Last drive for 1u30 on Sunday night, then the next drive Wednesday morning, and i got a 'battery low warning', with the battery at 48%.

Don't know what happened, never had this before.

I do always notice the main infotainment system stays on for a long time after the engine is off, en the doors are closed and locked, which i always find strange, but that is normal it seems.

I agree completely with @Skydance , infotainment turns off immediately. I had a "head unit" software update in January this year.

 

[onuraiu]

I'm having also issues, I’ll try to be short and concrete.

All power switched in the ceiling are turned off all the time during this.

I got the car in the end of 2024. Sometimes when car was stationary for few days I notice when starting car that battery indicator came on either yellow or red. Meaning starter battery low to some point. As I actually didn’t had any problems I ignored it.

In the end of May 2025 I installed 415W solar panel and Victron 100/20 controller. At first I connected Victron to aux battery, but then I discovered that Ineos engineers have done some magic and aux battery is only used to charge main battery via CTEC Smarpass (actually this forum was big help to discover that). Ok then I connected my victron to the main battery.

All seemed well. No matter how much car was stationary, main battery was always full. Victron is configured to charge up to 13.2V (cant recall other setting, as the car is at dealer) so when Car starts and alternator starts charging at 14.2V (for me it seems bit high, but what do I know) the Victron detects higher voltages and stops chargin while engine is running.

Sometime in July I looked at power trends on Victron app on my phone, and I noticed that every night main battery voltage stops then sunlight come and Victron start charging battery again.

I contacted dealer, if that is normal. Then asked to come by to investigate. I did and they did some test according to procedure and found that all is good. But I have connected my Victron wrongly, negative cable should not be on battery rather connected to chassi as car has some intelligent sensing sensors. Ok, browsed forum again and seemed like valid point.

I drove home, disconnected negative Victron cable from main battery and also in Victron app, I disabled battery charging - just to monitor myself what is going on.

At Friday (11th of July) afternoon when I did that, I measured main battery just before locking car and leaving it. Main battery was: 12.89V.
Few hours later I realised that I need to measure aux battery as well. I measured both:
main: 12.49V (-0.4V in few hours?)
aux: 13.05V

On Monday (14th of July) morning before going back to dealer I measured again:
main: 12.3V (that is -0.19V)
aux: 12.9V (that is -0.15V)

So I left the car at dealers (25km drive), on Friday (18th of July), they called and told me that when Victron positive cable was connected they detected small battery drainage, when they disconnected positive cable from main battery they told that no more battery draining occurred. I told that this cannot be, as Victron cannot do anything with only positive cable connected and also Victron is turned off a week aga. Car was left there to be monitored through weekend.

On Monday (today 21st of July) they called and said, that still everything is in the limits and car does not consume battery, and it should be like this as batteries must not be full all the time. Well… I am out of ideas, is the Victron malfunctioning and draining battery via it’s body ground connection to car body?

Their last measurements on Monday (21st of July) were:
main: 12.5V
aux: 12.84V

Now I have to wait until Friday 25th, the they will measure again.

Or is it that I’m just too stupid?

I have a tractor battery in ma garage, about same size in Ah, in a month it went from 12.8 - > 12.7V. I think that is normal, but what is going on with my Grenadier is a mystery to me. So far the result is, that I have been weeks without the car and there is a diagnostics bill waiting for me…