Tony Dyson
Senior Member
- Joined
- Aug 26, 2018
- Messages
- 4,038
- Reaction score
- 2,585
- Location
- God's Country
- Your Mercedes
- 2014 C 220 CDI W204 OM 651
My main battery has been deteriorating for some time now but only evidenced by proactive self-monitoring, after being parked up for a couple of days I now have a resting voltage of 11.2v but the car still starts immediately on the turn of the key and the Stop/Start function turns green within a couple of miles driving, although it soon runs out of juice and needs to recover more often than it used to. Below is a waveform of this morning’s start indicating the 11.2v resting voltage, the first dip at 5s are the glow plugs with the start initiated about 2s later, this created a battery voltage drop down to 5.6v but soon recovered back to 10.5v after less than a second it took to start the car where around 5s later the Battery Control Module ramped up the charging voltage to a steady 14.5v.
Truth is I’ve been expecting the battery to fail completely for a while, but it just keeps on going so I’ve decided to replace it while on a high, rather than run it to destruction as with the weather turning colder the chances are it’s sadly not going to last for much longer, I’ve ordered a couple of batteries from Tayna, a Varta as a direct replacement for the MB branded Varta main battery and an Exide to replace the MB branded FIAMM Aux (Stop/Start) battery, I did try MB Grangemouth for replacements and they were most helpful but unfortunately they couldn’t get anywhere near the Tayna prices.
Truth is I’ve been expecting the battery to fail completely for a while, but it just keeps on going so I’ve decided to replace it while on a high, rather than run it to destruction as with the weather turning colder the chances are it’s sadly not going to last for much longer, I’ve ordered a couple of batteries from Tayna, a Varta as a direct replacement for the MB branded Varta main battery and an Exide to replace the MB branded FIAMM Aux (Stop/Start) battery, I did try MB Grangemouth for replacements and they were most helpful but unfortunately they couldn’t get anywhere near the Tayna prices.