Hi all, I picked up my new ‘approved used’ 2020 L405 P400 on Monday. Car had sat around at the dealers for a month or so and the battery was low as the tailgate struggled to open etc. I drove it home from London (about 300 miles) and all seems fine.

I thought the 300 mile drive would have charged the battery, but I decided to plug it in to my Ctek MXS 5.0 charger over night to top it up. Strangely though when I left it at 9pm it was charged up to position 3 on the Ctek, and at 8am this morning (11 hours later) it’s still on charging stage 3…! Surely that can’t be right? 11 hours on charge and it doesn’t seemed to have charged at all?

Everything is hooked up correctly under the bonnet, the bonnet is closed and the car is locked, so it shouldn’t be using more power than it’s receiving.

Any ideas? Or does it really take that long to charge an L405 battery?

I'm very happy to be corrected but as I undertsand it AGM batteries do not like being discharged below 50%, particularly for a long time or to a low voltage, so you will need a new one. Although it must have had quite a bit of charge for the tailgate to move. It may not be able to hold charge anymore.

What is 'position 3'? Is that the 'bulk charge'? Your manual says 'maximim 20 hours' for that step. Chris

2014 FFRR 4.4 SDV8 Autobiography Barolo Black
2012 RRS SDV6 HSE Baltic Blue
and before I saw the light:
2011 Suzuki Grand Vitara SZ5
1998 Ford Mondeo V6 Ghia X
1990 Citroen BX GTi
1973 Triumph GT6

Sorry I wasn’t very clear, by position 3 I mean stage 3 on the Ctek as shown in the image above. When I used the Ctek previously on my Audi S3 it would charge up to the Green stage 7 (fully charged) in about 8 hours or so from stage 3.

I’ve read conflicting info online as to whether charging the main battery simultaneously also charges the MHEV battery, but it stands to reason that if it is charging both it would take longer… I’ll leave it plugged in today and see if it moves any further…

See
https://www.ctek.com/uk/battery-chargers-12v-24v/mxs-5-0-uk
and follow link for manual

Postition 3 is the bulk charge step, it says up to 20 hours. Sorry can' t tell you any more. Chris

2014 FFRR 4.4 SDV8 Autobiography Barolo Black
2012 RRS SDV6 HSE Baltic Blue
and before I saw the light:
2011 Suzuki Grand Vitara SZ5
1998 Ford Mondeo V6 Ghia X
1990 Citroen BX GTi
1973 Triumph GT6

Ok thanks, it’s been on for about 13 hours now so I’ll leave it plugged in and see what happens over the next few hours.

Do you know if charging via the main charging points under the bonnet also charges the MHEV battery too?

Had to unplug the car so my wife could go out and at 17 hours it hadn’t moved off charging stage 3. I’m going to plug it in again overnight tonight and assess it again tomorrow.