General: How to operate the Start-Stop function?

[volvo for ever]

soc state of charge battery above 76% ,,soc state of health 100%

so idaelly both batterys must be fully charged and you must disconect bms on negative terminal for 20 seconds then refit and try it ..if this doesnt another fault with this model there is a unit fitted to gearbox and sometimes linkage comes of as it becomes siezed please illiminate this you dont have to strip car just need torch clearly seen do all this and update

regards

[ymc30]

Originally Posted by volvorocks

shorter stop and start urban journeys did. Think it is also something to do with regeneration energy the fact it works after say 30 miles of urban whereas after 200 miles motorway it may not.

To be honest when I read this Wednesday evening I said "What a loads of rubbish, this cannot work in a million years" so I went and bought a £160 Varta AGM battery*.

Unfortunately I could not fit it in as I had to go yesterday to South London to view an offtopic car and that meant an 80 minutes drive each way in tube-strike-hit London traffic. On the way back I stopped at a traffic light and the engine stopped!! I just looked at the dash and it said: "Auto start function"


SOLUTION:

So this bloody works and volvorocks WAS right! Also it is clear that you do not need a fancy battery and it works with a NON AGM £45 battery from eBay. Mind though that this battery probably dies sooner then a proper AGM one although you can buy 3 for that price and you still spare some cash for a cinema ticket for two

BTW it did NOT work today - but it showed 28C on the gauge and I considered it as over 30C and that's one of the criteria. If anybody interested I have found the manual and trimmed it a bit down and attached to my post.

Now I have a spare battery if I ever need it...


*on eBay for £30 - I'm not mad

[ymc30]

I am double posting so it will hopefully be a bit more clear to see the limitations...

The engine does not auto-stop even if the Start/Stop function is activated if

• the driver has opened the seatbelt's buckle. (tested)
• the car has not stopped - however, the Start/Stop function does accept slow rolling, the equivalent to normal walking pace. (tested)
• the capacity of the battery is below the minimum permissible level.
• the engine does not have normal operating temperature.
• outside temperature is below 0 or above 30 °C. (I think that just happened today)
• the environment in the passenger compartment differs from the preset values - indicated by the ventilation fan running at a high speed. (or maybe this 'cos it was @ full blow)
• the car has been reversed and reverse gear is disengaged.
• battery temperature is below 0 °C or above 55 °C.

[tomweston]

I was wondering what was meant by the stop start only works when battery is better than 60% charged? I found this interesting table on the web:
State of Charge Specific Gravity Voltage
12V 6V
100% 1.265 12.7 6.3
75%. 1.225 12.4 6.2
50%. 1.190 12.2 6.1
25% 1.155 12.0 6.0
Discharged 1.120 11.9 6.0

So if the battery is showing 12.4V then the stop start should work. Mine worked when the voltage was above 12.6v, but not at 12.5v. When new my AGM battery was 12.8v.

[Mike Hatch]

The start stop system on my V50 DriveE has been bugging me for a long time now, it worked for a year or so and then stopped, no messages, no errors just stopped, but it always says its on.

I would’nt go so far as to say it is useless but it does have some strange quirks. I've investigated the Volvo circuit diagrams and basically worked out the bits the system uses even going so far to scope the battery monitor signals, and to scotch some of the statements seen, its the main battery that starts the car, the secondary runs auxiliary systems, its wired that way, the aux battery cannot start the car.

In the end it seems to come down to battery charge and driving style, and what the "computer" thinks is the charge level. If you stall the thing it auto restarts perfectly even when the stop/start is not operating !.

One of the Volvo statements - "the capacity of the battery is below the minimum permissible level."

Nowhere can I find what that "minimum" level actually is, on these forums and elsewhere. I've seen 80% mentioned, 76%, 50% but no hard and fast level quoted by Volvo. Recent posts mention voltage as an indicator of charge and a voltage level below which the stop star does not work (12.55/12.69V).

Currently mine is sitting at 12.5V (below a supposed minimum of 12.55) and the stop/start is working, whoopee, first time in ages.

What I did I do ?, I stuck it on charge for the day, 5 Amps in for 6 hours, the stop/start is currently now working, but I wait to see for how long. As Volvo advise, charge at the +VE terminal and the chassis, that way the battery current sensor is in circuit monitoring the charge going in, you could charge at the +VE and -VE, but it would not know how much has gone in.

From the circuits both the voltage and current flowing in and out of the battery is monitored so the state of the battery charge would appear to be a more sophisticated calculation than just the voltage.

From past journey experience the journey type makes a difference EG -
2000 miles plus to Italy, all motorways, no start/stop.
400 miles to France, uphill, overrun downhill, no motorways, stop/start working again.
150 mile to Bristol, up and down some steep hills, stop/start working again and continued so for weeks, only stopping when the car went in for service and Volvo left it ignition on in the shop, witnessed by the hour or more on the dashcam looking at a brick wall !!.

I've found that if you use a "regenerative" style of driving the stop/start works much better, essentially use your gears.


It would be nice if Volvo would actually make a statement about this and the level at which the stop/start will or not work at. Better still put a message up on the dashboard, "Stop/start not working battery at xx%, xx% required" at last we would know why.


I've spoken to all our local Volvo dealers, no one knows how it works, "Oh we will stick it on the computer and see", “sorry sir, nothing wrong”, then, "Ah, we'll charge the battery", so how come I can charge the battery and it works, they charge it and it doesn’t !!


Come on Volvo help out your customers.

[tomweston]

[QUOTE=

I've found that if you use a "regenerative" style of driving the stop/start works much better, essentially use your gears.

.[/QUOTE]

The driver handbook suggests that the battery only charges when car is slowing down i.e. braking or slowing down without the brakes. I saw this in action on a hire (Merc) car which had a charge meter attached. During normal running there was no charge going to the battery but when I took my foot off the accelerator the charge level increased dramatically.
The Stop/Start will not work if the DPF is trying to regen which can be seen by considerable increase in fuel consumption, leave the display on instantaneous and you will see it happen.

[Mike Hatch]

Well my charging the battery lasted just about a month, with it being intermittent for the last week.

I've now "charged" the battery sensor. I usually use a lab power supply for charging as it has better controls, I set it to 0.1V and 10A constant current and connected to the sensor, stop/start is again working.

I'm sure there is a software problem with this system, it allways starts well and the stop-start kicks in if stalled, it just does not seem to work out the regenerative energy recovered that well.

[westbayaab]

Originally Posted by Mike Hatch

Well my charging the battery lasted just about a month, with it being intermittent for the last week.

I've now "charged" the battery sensor. I usually use a lab power supply for charging as it has better controls, I set it to 0.1V and 10A constant current and connected to the sensor, stop/start is again working.

Can you give more details/how to please ...

[Mike Hatch]

Originally Posted by westbayaab

Can you give more details/how to please ...

I have a PSM2/5A power supply that has two 30V 5A outputs (channels) with switching that can be set to series or parallel outputs, controls allow constant voltage (for float charging) or constant current operation from 0-30V or 0-5A per channel. Its a laboratory PSU not really meant to charge batteries but works well with suitable cables.

After looking at the V50 circuits I came to the conclusion that the car probably does not directly measure voltage but measures the current in the battery circuit, this is why the Volvo battery charging instructions pointedly mention to use the chassis for the -VE not the battery terminal.

Having previously confirmed that charging the battery as recommended (+VE and chassis) reinstated the stop-start function, but under what I considered not good conditions for the battery (>17V) I then thought to "charge" the battery sensor only, without the battery.

The sensor is located on the battery –VE terminal, its a large normal looking battery clamp but with a further metalwork part to the cable and a plastic box marked 30659084 and the Volvo logo, off the side is the thick cable to the chassis connection. A smaller 2 pin connector connects to the cars electronics with CAN signals (I believe) for the monitored value. Electrically in the scheme of things the battery cable to chassis is 0V, the battery -VE connection is at about +0.1V (Voltage drop across the sensor) above chassis and the battery +VE is around 12V (typically 12.5-13.2V)

I set the PSU voltage control to about 1V and current control to about 1A, in constant current mode and parallel operation (shares the current between both channels) and turned on. I then carefully connected my PSU -VE to chassis, and the PSU +VE to the actual battery -VE. No connections at all to the battery +VE. Monitoring the PSU meters, the voltage did not need changing (it actually drops to 0.1V), the current control was slowly increased. In the end I got it up to 10A (5A per channel), the voltage displayed stayed at just under 0.1V.

I left it there "charging" for as long as I had (about 5 hours). In this method NO actual charge goes into the battery, but 10A goes through the battery current sensor, so it "thinks" the battery is being charged but without the high voltage on the battery that would be required to charge at that sort of current.

Warning - batteries on the V50 are VERY, very high power with peak currents in the order of 300A plus, be very careful !, if in doubt use leads with a fuse, approx 20A max. If in further doubt DON'T attempt it.

I’ll get photos when I get home tonight, didn’t think to get some at the time.

[Mike Hatch]

Photos attached.