New Battery

[LordGozer]

They are definitely aware of an issue as there is great long process of checks they have to go through to change it under warranty. Next time call out VW assist and don’t opt for an AA patrol.

This is a copy of some of the paperwork given to me, doesn’t mean anything to me but it may to someone else.

 

[Murdoch]

Well it wouldn’t start / turn over again today .... so VW have it for diagnosis .....

 

[Robuk]

Try disconnecting the battery sensor on the negative rail, charge the battery with a Ctek charger, then run the car without sensor, this will then keep the battery fully charged, with the sensor in place you only get 80% charge, you might loose stop/start, in my case that`s exactly what was intended.

Radio didn't play when vehicle turned off "battery saver" - Ford F150 Forum - Community of Ford Truck Fans neg rail sensor
DISABLE Auto Start/Stop - Ford F150 Forum - Community of Ford Truck Fans neg rail sensor

I am testing this on my Mercedes CGI coupe, no issues at 3 weeks and a fully charged battery of 12.7/8 volts at 6 years old.

ECO Start/Stop SLK55 switching off! - Page 5 - Mercedes Benz SLK Forum

 

[travelvolts]

Not a good idea as the ECU will not know the true state of charge of the battery. This could result in the battery being damaged by overcharge on the braking regen phase.

 

[Robuk]

Quote : Not a good idea as the ECU will not know the true state of charge of the battery. This could result in the battery being damaged by overcharge on the braking regen phase.

Read the links, unless the brake regen charges above 14.4 volts it cannot possibly over charge the battery. You can check the voltage when driving with this, first check the volt meter is accurate with a digital multimeter across the battery terminals. Do you actually believe that if the senor failed it would over charge your expensive AGM batterys causing them to fail, it did not do that to the Honda cars the sensor just caught fire.

12V-24V Dual 2 USB Port Car Boat Charger Socket Voltage Digital Panel Volt Meter | eBay

 

[travelvolts]

T6 reaches 15.5 volts on regen. I wouldn't trust those cheapo meters either. If you truly feel that you know better than VW or Merc, carry on.

 

[Robuk]

Quote, T6 reaches 15.5 volts on regen. I wouldn't trust those cheapo meters either. If you truly feel that you know better than VW or Merc, carry on.

T6, I am testing the system, up to the present 14.3 volts is all I see, I will try tomorrow and connect my digital multimeter to car battery, strap it to a windscreen wiper and brake down a hill where I live, that should tell me if you are correct.

Regards.

 

[travelvolts]

Knock yourself out. You can't argue with the manufacturers specs.

 

[Robuk]

To replenish this ‘free space’, during deceleration or braking events, the voltage on the alternator shoots up to approximately 15V+. This higher voltage fast charges the stater battery to replenish its capacity. As you are using the inertia of the vehicle to charge the battery, rather than fuel, it is seen as ‘free energy’
To replenish this ‘free space’, during deceleration or braking events, the voltage on the alternator shoots up to approximately 15V+. This higher voltage fast charges the stater battery to replenish its capacity. As you are using the inertia of the vehicle to charge the battery, rather than fuel, it is seen as ‘free energy’. Then the voltage drops to about 12.4V to allow the free energy to be consumed by the vehicle allowing the battery to deplete itself by about 20% ready for the next speed reduction and so on and so forth.

If the negative rail sensor has failed or is disconnected the system will not know the SOC , in this case it will either default to 14.3 volts which appears to be the case on my car at present or it will pile 15volts or more into the battery and distroy it.

http://www.ysebaert.be/assets/pdf/nieuws/regenbraking_e_rev.pdf

 

[Robuk]

Sorry, start again.

However, in order for this system to be affective the starter battery must have ‘free space’ to boost the energy into the battery, this requires the battery to be about 20% depleted ( low enough to allow more power to be boosted into it but not too low as to prevent the engine from restarting when switched off). To replenish this ‘free space’, during deceleration or braking events, the voltage on the alternator shoots up to approximately 15V+. This higher voltage fast charges the stater battery to replenish its capacity. As you are using the inertia of the vehicle to charge the battery, rather than fuel, it is seen as ‘free energy’. Then the voltage drops to about 12.4V to allow the free energy to be consumed by the vehicle allowing the battery to deplete itself by about 20% ready for the next speed reduction and so on and so forth.’

If the negative rail sensor has failed or is disconnected the system will not know the SOC , in this case it will either default to 14.3 volts which appears to be the case on my car at present or it will pile 15volts or more into the battery and distroy it.

 

[travelvolts]

Or you could just deal with the initial problem (faulty battery)and leave things as they were meant to be.

 

[Robuk]

What is regenerative braking and why don't we use it?

In answer to the question "What is regenerative braking and why don't we use it?", we do. With normal braking, forward momentum of the car is scrubbed off by the brakes by turning them into heat in the brake disc with subsequently dissipates and is lost. With regenerative braking, instead of the movement of the car being lost to the atmosphere as heat, it is converted to electrical energy and stored in the vehicles battery.

The Volkswagen Bluemotion range of cars (and I'm fairly confident other manufacturers do this but I'm sure Volkswagen do) have a very sophisticated alternator. When the car detects is it being slowed by pressure being applied to the brakes and the car is still in gear and that clutch is up, the alternator steps up into a mode where it draws significantly more power from the drive. This drive would normally come from the engine but in a braking situation, it is provided solely through the transmission and is effectively running against the drivetrain.

This system is fitted on both petrol and diesel powered Bluemotion equipped Volkswagens. More information is available here and here

What is regenerative braking and why don't we use it?

 

[travelvolts]

OK, I'm sucking eggs.

 

[Robuk]

Quote, or you could just deal with the initial problem (faulty battery)and leave things as they were meant to be.

The smart system charges to default 80% to allow for any regeneration, (I believe you can`t put 15 volts into a fully charged battery without damaging it), that means if you only use the car for short journeys your battery is rarely fully charged which is bad for any battery, the forums are full of owners complaing of bad batteries less than 3 years old, if your car won`t start it may not have a bad battery, just recharge battery remove sensor and see what happens, by disconnecting the neg rail sensor the ecu will not know the SOC of battery and will instruct the smart alternator to default to 14.2/3 volts, you will then end up with a fully charged battery at all times. I finally tested the charge volts into battery down a steep hill this morning on my 2012 blue motion Mercedes coupe CGI, if my car has regeneration then removing the sensor made it default to 14.2/3 volts, there was no sign of the voltage deviating over that rate of charge this morning, it was checked with a digital multimeter connected across the battery terminals.

In my case I just wanted to get rid of stop/start and this was the only way I could finfd

 

[Pete C]

Have you done this on a T6 ?

Pete

 

[Phil_G]

Rob, you're preaching to the converted... BMT has been discussed in depth in many previous threads
Its been properly datalogged by several members and its accepted that on the T6, BMT can approach 15.5v under regenerative braking

...by disconnecting the neg rail sensor the ecu will not know the SOC of battery ...

The neg strap is only a current monitor used for Ah calculations, the BCU still knows the static battery terminal voltage and hence SOC.
This is a necessary function as the neg sensor doesnt take any account of self-discharge
Cheers
Phil

 

[Pete C]

I would strongly recommend no-one with a T6 tries this “hack” because:

The examples given are a Nissan and a Mercedes - there is no indication it works on a T6 within this thread.
It might invalidate the warrantee which most of us still have.
It might cause damage to the electrical components and the battery.

The original thread was started due to a faulty battery, which regular forum members will know is an issue with Moll batteries fitted in a certain date range. This idea does not fix that.

Pete

 

[Pauly]

This can be disabled correctly with VCDS or VCP and negate any risk to equipment or warranty

 

[Robuk]

Quote, The BCU still knows the static battery terminal voltage and hence SOC.

How, where are the sensors, I am not saying the T6 system is same as Mercs, but the tests on my Merc indicate the alternator is working as a standard alternatot with the neg rail sensor disconnected.

It appears F150 is similar to merc, so is BMW, ford, Honda, VW and many other makes, disconnect neg rail sensor and I believe the smart alternator is no longer smart in those makes, perhaps T6 is different.

VW GOLF

All of what I'm about to say relates to those mk7's that have either the Stop/Start system (it's called "bluemotion" down here - not sure if the same badging happens elsewhere), or an energy recovery mechanism. These cars have a "battery sensor" that is fitted in-line into the negative battery cable just next-to the battery clamp. The battery sensor (called J367 by VW) also has a connection to a control module called the "Data bus diagnostic interface".

The role of the battery sensor is to determine the condition of the battery (i.e.voltage, current and temperature) and this information is sent to the diagnostic interface in the car. Through this sensor and the previous history of data that it has sent, the diagnostic interface builds-up a picture of the current capacity in the battery. The SOC reading that kenny_c has mentioned is a measure of the past history of the battery since it was first installed in your car and all the direct battery data came from the "battery sensor".

VW make a distinction between the voltage at the battery and what it calls the "System Voltage", which is the calculated voltage that is available to the car's actual electrical system. All the decisions that are made by the car that reference voltage are taken from the "System Voltage" (not the battery voltage). So, it's real important to maintain the veracity of the System Voltage and incorrectly charging the battery is one way to f&*^k-up this value.

With ANY VW vehicle with bluemotion or an energy recovery mechanism, you should NOT connect the battery charger negative clamp to the negative battery terminal. Doing this by-passes the battery sensor. This means that the battery data is not recorded by the sensor during the charging procedure. The values for the battery state stored in the data bus diagnostic interface then no longer coincide with the real values of the charged battery.

In cars with SS ALWAYS connect the positive charger clamp to the battery positive terminal first. then connect the clamp on the battery charger negative to an earthing point in the car (like a metal component that is screwed to the engine block). This also applies if you are jump-starting the car.

GolfGTIforum.co.uk - An independent forum for Volkswagen Golf GTI enthusiasts.

 

[Phil_G]

Its a current sensor, its not possible to sense the battery voltage from the shunt between the negative and chassis, voltage measurements are done from the positive terminal. The main purpose of the shunt is to compare Ah in from the alternator, and Ah out to the various electrical loads, as a means of monitoring battery capacity.
But it can only do this in a relative sense. Say for example a battery is at 90% SOC, if you take 15Ah by discharging into a load, then add 15Ah by charging, the SOC level is restored relatively, but we're still at 90% SOC. So current monitoring alone is not enough to fully manage the battery - it also needs a voltage sense, which is taken from battery positive, not from the negative shunt

Cheers
Phil