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deaston



Member Since: 18 Dec 2020
Location: UK
Posts: 150

United Kingdom 
The MHEV system seems to prevent the Defender from coasting
I was driving a familiar route today with cruise set to 30mph and noticed that the car would gently accelerate and then noticeably brake a little, then accelerate, then brake.

I'm guessing it's because instead of coasting, the car goes into a mild regen mode to recharge the batteries?

I notice it when driving normally, too. Lifting my foot off the accelerator and the car coasts for a second and then feels like it's braking.
Post #898498 15th Apr 2021 6:39pm
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Gareth



Member Since: 12 Dec 2011
Location: Bramhall
Posts: 1038

England 2003 Defender 90 Td5 CSW Oslo Blue
Do you have active cruise control? Could have been the car in front slowing and speeding up! 2021 Defender 110 X-Dynamic HSE D300 MHEV
1966 S2a 109 aka Betsy
1968 S2a 88 aka Bob
2014 Jaaaag F Type 3.0 Supercharged.
Post #898526 15th Apr 2021 8:52pm
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deaston



Member Since: 18 Dec 2020
Location: UK
Posts: 150

United Kingdom 
Standard cruise, no vehicles in front.
Post #898564 16th Apr 2021 7:08am
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Digger2000



Member Since: 19 Sep 2020
Location: Newcastle
Posts: 590

United Kingdom 2006 Defender 90 Other HT Tonga Green
I haven’t noticed this on my D250. I was testing the engine braking the other day and it decelerated. Sounds like cruise control wasn’t properly deactivated?
Post #898566 16th Apr 2021 7:30am
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vlad



Member Since: 11 Oct 2020
Location: RO
Posts: 67

Romania 
I've also noticed this, but it's very subtle. It doesn't bother me. MY2021 Defender 90 P400 SE
Post #898567 16th Apr 2021 7:33am
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Digger2000



Member Since: 19 Sep 2020
Location: Newcastle
Posts: 590

United Kingdom 2006 Defender 90 Other HT Tonga Green
That sounds well dodgy. You don’t want any acceleration when your foot is off the pedal. I’m
Going to check mine again now lol
Post #898569 16th Apr 2021 7:38am
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deaston



Member Since: 18 Dec 2020
Location: UK
Posts: 150

United Kingdom 
vlad wrote:
I've also noticed this, but it's very subtle. It doesn't bother me.


True, it is very subtle. But something I've never experienced before - probably something we'll all have to get used to as fossil fuels are phased out.
Post #898572 16th Apr 2021 7:46am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 16809

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
Re: The MHEV system seems to prevent the Defender from coast
deaston wrote:
I was driving a familiar route today with cruise set to 30mph and noticed that the car would gently accelerate and then noticeably brake a little, then accelerate, then brake.
...


I am sure that the reasons are different, but your description reminds me of my Disco2. There is a road near me which has a long series of undulations or dips with humps in between. With cruise control set on the Disco the "ups" and "downs" are exactly the right length to match the reaction time of the cruise control, with the result that at the first "down" you rocket down it, the car realises it is accelerating just as you hit the bottom and eases the power just as the first "up" begins, slows drastically on the uphill, only to realise that it is slowing just as you reach the crest. It then rockets over the hump, then the cycle repeats on the next dip, then the one safter, and the one after that. It is quite disturbing until you figure out what is happening.

The Disco2 CC is quite immature, and I would expect the L663 CC to be unrecognisably better. Perhaps this is a heritage feature!
Post #898573 16th Apr 2021 7:47am
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deaston



Member Since: 18 Dec 2020
Location: UK
Posts: 150

United Kingdom 
I'm happy to be wrong but I think my surmisation that it's the MHEV system is correct.

It's very obvious when lifting my foot off the accelerator (without cruise activated). You can feel that the acceleration stops and the car cruises for a second or two and then, subtly but noticeably, there is a braking force. I'm guessing that's the MHEV system charging the batteries.

Maybe I'm noticing it because the car is new and the batteries are low of charge. Sadly there's no way to see what level the batteries are at nor as and when it's charging them. And I can't find any Defender-specific technical info on the MHEV system - only the Evoque. Even the iGuide doesn't mention MHEV, only PHEV.

I'd prefer it if it only did it during active braking though.
Post #898582 16th Apr 2021 8:16am
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Tim in Scotland



Member Since: 23 May 2007
Location: The Land that time forgot
Posts: 3748

 
Is there anyway you can see how much charge there is in the MHEV battery to see if what you are telling us stops when the battery is fully recharged like you have in PHEV’s and EV’s? In my short experience of running a PHEV the regen stopped automatically once the motive battery was fully recharged until the battery had been depleted by around 10% when the regen would resume working. Pangea Green D250 90 HSE with Air Suspension, Off-road Pack, Towing Pack, Black Contrast roof , rear recovery eyes, Front bash plate, Classic flaps all round, extended wheel arch kit and a few bits from PowerfulUK Expel Clear Gloss PPF to come
2020 D240 1st Edition in Pangea Green with Acorn interior. Now gone - old faithful, no mechanical issues whatsoever ever but the leaks and rattles all over the place won’t be missed!
Post #898585 16th Apr 2021 8:36am
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deaston



Member Since: 18 Dec 2020
Location: UK
Posts: 150

United Kingdom 
Not that I’ve found in any menu and the iGUIDE doesn’t really mention the MHEV system.

There’s also no indication that the car is using or charging the battery.
Post #898587 16th Apr 2021 8:48am
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DSL



Member Since: 20 Aug 2007
Location: Wandering the wasteland.
Posts: 837

United Kingdom 
Would sticking a 12v readout in the aux/ciggie lighter socket help see what the alternator is doing. If the voltage goes up when the car is trying to coast, might mean the alternator/system is taking energy out of the system to put in the battery? All questioned in a non techie manner as waaaaaaaay above my technical pay grade. Whistle
Post #898589 16th Apr 2021 8:52am
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Simon Audi



Member Since: 19 Nov 2020
Location: Newport
Posts: 544

United Kingdom 
Last weekend - I had something similar with the ACC active

Was like the car was hunting or missing... but only when at something like 70MPH....

Was not shutting down due to traffic...

It was only barely noticeable - but there was something.

Once I got off that road - all was normal and has been all week (less speed)
Post #898590 16th Apr 2021 8:53am
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zilch



Member Since: 11 Sep 2019
Location: Whitsundays & Sydney
Posts: 771

Australia 
7500 K's in 6 months and not experienced anything like this, and someone who is pretty lazy when it
comes to pulling up in traffic/red lights, i usually let the vehicle coast in and brake towards the end when
most of the "speed" has been taken out.. P400 MHEV yet another pommie bar steward down under

MY20 110 P400 SE Defender
MY10 3.0 RR Sport
Post #898611 16th Apr 2021 9:59am
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J77



Member Since: 04 Nov 2019
Location: Fife
Posts: 3223

Scotland 
I’ve yet to use cruise control but in normal driving if I lift off the accelerator there’s a noticeable slowing/breaking effect. 23.5MY 90 D250 X-Dynamic SE, Pangea Green
Gone - 23MY 110 D250 XS Edition, Hakuba Silver
Gone - 21MY 90 D200 S, Tasman Blue, Fuji White roof.
Post #898612 16th Apr 2021 10:00am
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