Charging the battery

Faults and Technical chat for the Volkswagen T-Roc
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brid
Posts: 366
Joined: Fri May 04, 2018 6:47 pm
Location: Alicante Spain

Re: Charging the battery

Post by brid » Sun Apr 26, 2020 11:22 am

I have two SUV's both of which have the stop/start system.
In my wildest dreams and ignorance I never realized that there was such complications when it comes to charging car batteries. I am very old school.
Some have mentioned leaving some "lack of charge" to facilitate the stop/start system.
I relate back to my Mercedes.
I drove the car in the garage and forgot to remove the code key.
Two days later I went to the car and found the battery completely dead, not enough to even light the dash warning lights. Seemingly with the key in all systems continue to be active - lesson learnt.
I put the battery on charge but after 2 days it would not start the car. I tried jump leads but nothing would get that oiler started.
I had to use 2 of the the portable battery packs from a breakdown truck to get it started.
From that day I have considered the battery much weaker so I occasionally give it a boost with the charger until the charger states "FULL", if the car is not used.
This battery is now six years old and has been abused in this fashion through my ignorance but it still continues to function fine.
So my question is - if there has to be some "space" left in the battery for this stop/start system to function then is not that "space" created by the actual starting of a car as surely that is taking a lot more out than a couple of amps "left out" at charging.
Sport 2.0 TDI 150 CV DSG7 Gris Urano, Panoramic Roof.
Collected 12-06 2019

Deleted User 925

Re: Charging the battery

Post by Deleted User 925 » Sun Apr 26, 2020 12:26 pm

brid wrote:
Sun Apr 26, 2020 11:22 am
I have two SUV's both of which have the stop/start system.
In my wildest dreams and ignorance I never realized that there was such complications when it comes to charging car batteries. I am very old school.
Some have mentioned leaving some "lack of charge" to facilitate the stop/start system.
I relate back to my Mercedes.
I drove the car in the garage and forgot to remove the code key.
Two days later I went to the car and found the battery completely dead, not enough to even light the dash warning lights. Seemingly with the key in all systems continue to be active - lesson learnt.
I put the battery on charge but after 2 days it would not start the car. I tried jump leads but nothing would get that oiler started.
I had to use 2 of the the portable battery packs from a breakdown truck to get it started.
From that day I have considered the battery much weaker so I occasionally give it a boost with the charger until the charger states "FULL", if the car is not used.
This battery is now six years old and has been abused in this fashion through my ignorance but it still continues to function fine.
So my question is - if there has to be some "space" left in the battery for this stop/start system to function then is not that "space" created by the actual starting of a car as surely that is taking a lot more out than a couple of amps "left out" at charging.
Not even sure what the craic is about our EFB batteries?
On the varta website it says EFB batteries are used on simple start/stop systems and AMG batteries on more complex regenerative start/stop systems.

Possibly volkswagen saying our cars are start/stop with battery regeneration just means by alternator?
Therefore EFB batteries will charge to 100% and AMG would leave room for possibly a car with brake regeneration?
I don't know it's confusing. :lol:

Charge them 100% I'd say ;)

Rocadoodledo
Posts: 106
Joined: Wed Aug 14, 2019 4:18 pm
Location: Cambridgeshire

Re: Charging the battery

Post by Rocadoodledo » Mon Apr 27, 2020 12:41 am

I think you are right Vernabongo2. As I understand it our T-Rocs have a very simple form of battery regeneration.
Proper "Regenerative Braking" systems as used in electric and hybrid vehicles use their main electric propulsion motor to generate electricity under deceleration and braking by harvesting the car's kinetic energy, and this results in a braking effect which assists the friction brakes.
During deceleration and braking the T-Roc battery management system directs the alternator to accept a greater load, thus producing more electricity which is directed to the battery by the management system. No perceivable braking effect is produced in the process.
T-Roc 1.0L Design, Turmeric Yellow/Black
Act Displ, Nav, Dr Modes, R-Camera, Fogs, Pk Ass.
Winter Pk, Silver Rails, Voice Activ, Lumb Sup.
Ordered 21/3/19
St2 : 26/3/19
St3 : 18/10/19
St5a&5b : 13/11/19
St6 : 03/12/19
St7 : 13/12/19
Collected 20/12/19

Deleted User 925

Re: Charging the battery

Post by Deleted User 925 » Mon Apr 27, 2020 1:00 am

Rocadoodledo wrote:
Mon Apr 27, 2020 12:41 am
I think you are right Vernabongo2. As I understand it our T-Rocs have a very simple form of battery regeneration.
Proper "Regenerative Braking" systems as used in electric and hybrid vehicles use their main electric propulsion motor to generate electricity under deceleration and braking by harvesting the car's kinetic energy, and this results in a braking effect which assists the friction brakes.
During deceleration and braking the T-Roc battery management system directs the alternator to accept a greater load, thus producing more electricity which is directed to the battery by the management system. No perceivable braking effect is produced in the process.
"Stop/start with battery regeneration" its a bit of a joke making this sound fancy if its just the alternator recharging the battery. :lol: :lol: :roll:

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brid
Posts: 366
Joined: Fri May 04, 2018 6:47 pm
Location: Alicante Spain

Re: Charging the battery

Post by brid » Mon Apr 27, 2020 7:20 am

I always was of the opinion that within the alternator there was a regulator which prevented overcharging.
If a car battery was at 100% and then the car started that would drop the amperage quite a bit so there would be plenty of space to charge.
Thus allowing the car to take over management of supply.
Same on long motorway runs, the regulator would only maintain the battery to its requirement.
Is this a bit of a simplistic viewpoint. :roll:
Sport 2.0 TDI 150 CV DSG7 Gris Urano, Panoramic Roof.
Collected 12-06 2019

Tricky2
Posts: 140
Joined: Sun Mar 22, 2020 2:37 pm

Re: Charging the battery

Post by Tricky2 » Mon Apr 27, 2020 8:07 am

Rocadoodledo is absolutely correct, the alternator on all VW's for many years has been variable charge: Increasing the charge and thus the load on the engine during braking to provide a degree of regeneration. I found it most noticeable in a Passat I previously had where you could really feel the engine pulling you back. It conversely reduces the charging to reduce the engine load when starting again.

Brid is also right, the whole purpose of the battery monitoring module strapped to the live post is to monitor and control the charge. My Tiguan mk1 with the same system is now 5 years old, I've never even thought about the battery charge. It starts First time every time, even when left in airport car parks when we're away on holiday. It's still on its original battery, and stop start continues to work.

I think this topic is being "over thought" I've never had an issue leaving the Passat, Tiguan, up!, polo or the T-Cross unused for any length of time, over the last decade. In fact when we moved a few years back we had to leave the polo at my daughters for several weeks as we took the tig down to the new house with the caravan. It was parked up for around 3 weeks and fired up first turn when we eventually collected it.

Deleted User 925

Re: Charging the battery

Post by Deleted User 925 » Mon Apr 27, 2020 8:40 am

Tricky2 wrote:
Mon Apr 27, 2020 8:07 am


I think this topic is being "over thought"
I think you're right, we should go back to the covid19/lock down topic :lol: :lol: ;)

Deleted User 1717

Re: Charging the battery

Post by Deleted User 1717 » Mon Apr 27, 2020 11:05 am

Tricky2 wrote:
Mon Apr 27, 2020 8:07 am

I think this topic is being "over thought*
It has been over thought and dragged off topic too, I agree with what you say the car can be left locked and not touched for quite a few weeks without the need for charging, the issue comes when your in and out of the car over this period, this can drop the battery below the required level fairly quickly if your not careful.

User avatar
T Roo
Posts: 997
Joined: Tue Jan 22, 2019 2:20 am

Re: Charging the battery

Post by T Roo » Mon Apr 27, 2020 4:32 pm

Honest John has some information. Unfortunately, not specifically for VW's as yet but have a read, there's nothing else to do! :mrgreen:

https://www.honestjohn.co.uk/coronaviru ... -warranty/

Impala
Posts: 1910
Joined: Sat May 12, 2018 3:03 pm

Re: Charging the battery

Post by Impala » Mon Apr 27, 2020 4:43 pm

Tricky2 wrote:
Mon Apr 27, 2020 8:07 am
Rocadoodledo is absolutely correct, the alternator on all VW's for many years has been variable charge: Increasing the charge and thus the load on the engine during braking to provide a degree of regeneration. I found it most noticeable in a Passat I previously had where you could really feel the engine pulling you back. It conversely reduces the charging to reduce the engine load when starting again.

Brid is also right, the whole purpose of the battery monitoring module strapped to the live post is to monitor and control the charge. My Tiguan mk1 with the same system is now 5 years old, I've never even thought about the battery charge. It starts First time every time, even when left in airport car parks when we're away on holiday. It's still on its original battery, and stop start continues to work.

I think this topic is being "over thought" I've never had an issue leaving the Passat, Tiguan, up!, polo or the T-Cross unused for any length of time, over the last decade. In fact when we moved a few years back we had to leave the polo at my daughters for several weeks as we took the tig down to the new house with the caravan. It was parked up for around 3 weeks and fired up first turn when we eventually collected it.
I think it will very much depend on the charge state of the battery when you park up for 3 weeks. If your car has been used infrequently and only for short journeys, the drain from cold starts will probably not be replenished, so the battery could be well below full charge but still ample for daily use but maybe not if left for 3 weeks. That is why you may have noticed the stop/start system is unavailable sometimes, as it is an indication the battery is a bit lower than optimum.

Like most things, common sense prevails. I haven't even owned a battery charger for 40 years and only ever had 1 problem with a flat battery probably due to its age. I have breakdown cover with home assist, so I have no intention of forking out extra for a charger which would probably never be used.
1.5 TSI DSG R-Line MY19 Indium Grey, rear view camera, park assist.
Ordered 22/06/18
Built w/c 25/03/19 :(
With dealer 13/05/19 :P
Collected 20/05/19 :D

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