S211 Avantgarde Est battery issue

[Gav]

Hadn't used car for 4 weeks & had to jump start it last Sunday. It started first time (on jump leads from Clio) so then gave it a 55 mile run with everything switched off (A/c, Comand Nav, radio, surround lighting etc)

Didn't check voltage on that Sunday as assumed doing so straight after running would read incorrectly anyway. On Tues night multimeter (across jump start terminals under bonnet) said 12.1v and this (Saturday) morning 11.98. (I always thought <12.1 meant >75% discharged).

However, turned ign key, waited for heater plug light to go out and to my surprise it started on the very first turnover !

Now just run it for 20 miles. Got back and checked volatge on same terminals under bonnet & got 14.2v - which suggests alt charging OK ? Next checked at battery in boot also 14.2v (with engine running).

With engine off both readings are 12.1v.

Does this mean battery is most likely faulty ?

 

[Satch]

It does not sound really bad but you have the W/S211 battery drain issue and your battery may be starting to get past it, especially if there has been a deep discharge. (The voltage protection function is also a bit pessemistic.)

Remember you do have a voltmeter display available!

With key in position where things work but warning lights etc do not light up scroll through until you get to speed display. Then press trip rest buttion rapidly three times and it will go bleep. Move key to next position, up & down arrows till you find a Voltage display.

Watch that voltage drop like a stone until you start the engine!

 

[Gav]

Followed your advice and got 11.8V.

Do you happen to know what voltage it should be and at what rate it drops if not run at all?

Or what might be draining it - or is it just old age ?

Looking like it needs a new battery


Gav

 

[Satch]

Mine shows 11.8/11.9V with a battery less than a year old. With the old battery if I left the car unused for two days would get battery protection functions kicking in

With the W211 you get a lot of start up drain especially with the larger diesels and even more so if SBC brakes are fitted: six glow plugs, SBC pump, fans, electric cabin heater etc etc etc.

I think the "welcome light" feature is a most unwelcome current drain on top of that lot and disabled it.

The specified main battery is not really big enough IMO and the secondary is not that impressive either.