Member Since: 07 Sep 2018
Location: Munich
Posts: 29
Voltage at 12V when engine running
Hi community, I am looking for some advice.
Because my start stop system did not work, LR dealer installed a new main battery and start stop battery two weeks ago on warranty.
Start-stop system now works fine again (although I turn anyway it off all every time).
But since that time, I experience a new problem: the fridge in the centre console always turns on and off during driving in the city. I’ve monitored voltage today with my IID tool during driving and could see and voltage always going up and down. Only when driving faster than 60 KMH, it goes up to 14.0 to 14.7 V. (Always when voltage at 12.7v or higher fridge turn on). When driving slow or standing at the traffic lights (lights off, radio off, no other consumers, engine running), it goes sometimes down to 12.0 V although engine is running.
Here my questions:
what should be the voltage when the engine is running?
And is it normal that it goes down to 12.0 V with running engine?
Could this be something that has to do with the Battery Management System/calibration?
Thank you very much in advance
2nd Aug 2019 9:02 pm
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8044
The D4 charging system is technically very advanced, charging stops when accelerating and charges at maximum when braking or for the first few minutes on first start up.
At 12.7 volts the battery state of charge is low (65%) and the fridge will shut down on the D4 not like the D3 when it will stay on until the battery is flat.
I can’t possibly understand why anyone would want to disable stop start in normal road driving it is fully automatic has an excellent state of battery indicator , when ss stops working you know the battery is in a low state of charge (either volts and/or amps) and needs topping up with a smart charger or replacing It can when others can't,
It will when others won't,
It goes where others don't.
3rd Aug 2019 7:26 am
dgardel
Member Since: 03 Nov 2009
Location: Greater Venice
Posts: 2025
Stop&Start increase the wear of the engine (bearings)Discovery 5 tdv6 HSE Corris Gray Outback Engineering Limited Edition
IID Pro MV License
3rd Aug 2019 9:34 am
Canburne
Member Since: 15 Jan 2013
Location: Devon
Posts: 2027
2016 D4 Landmark Club Waitomo ...or is it Club Tempest????
2015 D4 HSE Aintree Green
3rd Aug 2019 10:10 am
dgardel
Member Since: 03 Nov 2009
Location: Greater Venice
Posts: 2025
My friend, I'm an engine designer and developer and , trust me, Stop&Sart is one of the best way to increase bearings wear. Every start you have 0 bar oil pressure, mind itDiscovery 5 tdv6 HSE Corris Gray Outback Engineering Limited Edition
IID Pro MV License
3rd Aug 2019 10:15 am
adam
Member Since: 20 Sep 2005
Location: Home and Happy
Posts: 6917
Never use mine - having a turbo spinning at up to 17k per minute suddenly being deprived of oil pressure when red hot seems counterintuitive.Now Golf GTI PP, 7 speed DSG.
Ex D3 and D4
3rd Aug 2019 10:58 am
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8044
dgardel: not with the correct oil for how long the engine is stopped.It can when others can't,
It will when others won't,
It goes where others don't.
3rd Aug 2019 11:17 am
M3DPO
Member Since: 22 Sep 2010
Location: Notts.
Posts: 8044
adam: mine doesn't rev that high at tickover when my engine stops. The SS can be controlled to stop when the driver wants it to with very little practice, if any in my case.It can when others can't,
It will when others won't,
It goes where others don't.
3rd Aug 2019 11:22 am
Mcflori
Member Since: 07 Sep 2018
Location: Munich
Posts: 29
@M3DPO: your explanation seems to make very much sense. I monitored it once again today. When I release the accelerator pedal or use the break, voltage goes up to 14.7V. When accelerating again or driving constantly, it immediately goes down to 13V. It really seems to be an intelligent system.
So thanks for your reply.
Only thing I am still wondering why the fridge didn’t turn off so often before I had new batteries (or why I didn’t recognise it).
And regarding the SS, I prefer to turn it off to hopefully protect the engine a little...
3rd Aug 2019 6:37 pm
dgardel
Member Since: 03 Nov 2009
Location: Greater Venice
Posts: 2025
M3DPO wrote:
dgardel: not with the correct oil for how long the engine is stopped.
I done several test with the major oil companies (Castrol, Mobil, Ravenol, ENI) and bearing companies (King, Schaeffler, Miba, Mahle) you can mitigate a bit but the real wear is more than double.
Remember, Stop&Start it's only for reduce the CO2 total emission on city routeDiscovery 5 tdv6 HSE Corris Gray Outback Engineering Limited Edition
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