I've had my 2015.5 V60 for several months. I routinely turn off the "stop-start" function immediately on starting. The other day I forgot and noticed that it remained "unavailable" on the display. Thinking that I had perhaps exercised some program option to disable it, I delved into the set-up program which yieled a message to the effect that the electrical system was preventing the use of the function - possible causes a battery too cold or charging.

At near 90 degrees, I think that "too cold" is unlikely. Since, like all modern cars, there is no ammeter, I can't tell if it is charging - possible since recently I have driven little - or, it could be a warning of impending battery failure.

Any suggestions?

 

It is very likely that the system has a heuristic to determine if the battery can handle restarting the vehicle, and that heuristic is not just checking the battery's charge. Other likely factors include the current draw of the vehicle (e.g., radiator fan running) and whether the A/C compressor is running. So even if the battery is fully charged, there will be conditions in which the engine will not shut off. At least, a well-designed system would behave that way, IMO.

So I don't think this is any obvious sign of imminent battery failure.

That said, if the car is 2-3 years old, it's not unusual for the battery to fail at that age (in my experience in other vehicle brands).

 

It wouldn't be easy for the car to measure anything but voltage and its own charge rate. Power consumption like paul says above. I can see making decisions based on that, but I don't suppose we could guess whether it had been designed to detect a partly discharged battery or a battery that won't hold a charge. Maybe either one.

 

Thanks - the battery is about 3 years old and may be reaching the end of its life although my recent experience with OEM batteries (Volvo and Mercedes) is that at least 4 years is typical.

I really do wish that cars still had useful gauges instead of all this "big brother" crap that they are laden with these days - If I am not alert enough to read speed limit signs and am dependent on the car doing it for me, I should not be driving! If I had an ammeter, I would know, from the degree and duration of the charge function, how healthy the battery was. An oil pressure gauge and a dipstick would be nice as well.

 

The problem with having an ammeter is there are times when the car might switch the alternator off or turn it down very low. This would obviously worry someone used to a car with a relatively constant charge of about 14 volts but would not indicate a problem. If there is a charging system problem, the car will let you know.

As for Start Stop, there are many factors that determine whether it is enabled or not. The only way to truly tell is by having the dealer check with VIDA. The car logs previous reasons for it to be disabled (as well as reasons the car may restart before the brake pedal is released).

 

While searching my 2015 for the cabin filter, I found a Motorcycle-style battery under the windshield wiper tray. Is this part of the stop/start system?

 

Yes, that's the "support battery" which assists the start/stop. Its a 12V with roughly 180CCA capacity.

 

The charging voltage will be a relatively constant 14 volts. It is the amperage that varies. Just after starting, the ammeter will show a relatively high charge current as the battery is replenished. This should decrease to a low level after a few minutes of driving. (The time will depend on temperature and how quickly the car started) If the current remains high, this is a sign that the battery is dying. The voltage reading is less informative.