Mikexe

Hi all, Mike here from Manchester in the uk, I drive a 2009 C200 W204 and came out to it this morning and had a flat battery, so got my charger out and yes I have a large battery in the boot, but opened the engine compartment hood and have positive connection under red plastic slide and black neutral connection bolted to bodt but under black cover there's no battery, it looks like an investor of something, will take a pic and put on site...so can I ask do I have 2 batterys for my car or not ?

Mikexe

So guys after taking guard of in the engine compartment were I thought a 2nd batterys was, it seems its a battery charge investor is this correct, and so that means I have one battery ? Which is in the boot

chassis

Welcome! Try posting the questions in the W204 section of the site where helpful owners can offer suggestions.

Mikexe

Guard cover removed , showing some form of power invertor for charging

Positve and neg connections to charge battery

Removed cover which i thought covered a battery

MJ50

moved to W204 forum...

alynch

I'm not sure this is a power inverter. From the two connectors on the top and the tape-wrapped cables, it looks like this is perhaps the ECM or some similar control module. I would either recharge the battery in the boot directly or through the + post in the engine compartment.

Elemento Tuning

Yes, you only have 1 battery in the rear.

Mikexe

Update on drained battery ....car was flat on tuesday so charged fully and didn't take that long to charge on a fast charge setting....tried it today Thursday and flat again...so going to charge on a tricle charge...does this make any difference ?

gamma300C

Howdy,

If battery is 5-7 years old, it may have died a natural death. If you have a Auto Parts store nearby, they should be able to "load test" your battery to confirm if it is kaput. Agree that the aluminum module with the heat sink fins and 2 major pin connectors is your ECM. May I suggest you obtain an inexpensive multimeter if you don't have one to check alternator input, battery drain via main battery ground cable, continuity, other areas. Good luck with your troubleshooting.

Mikexe

Battey drama goes on...so went to it this morning and again flat battery...put on fast charge ad started after 15 mins...so checked with muti metre when car was turned off...read 12.2 volts then started car up ad went up to 14.07 volts...am I correct that this shows battery is good and alternator is charging....advice pls 🙏

alynch

The 12.2V at rest is too low; that's only around 50% of the battery's capacity. The 14.07V while running is healthy and means the alternator appears to working correctly. I suspect the battery is at fault and is unable to retain a charge. Take it to one of the auto stores and have them perform a load test on the battery as gamma300C recommended.

gamma300C

Alternator charging voltage within spec. After quick charge voltage is low.....should see12.6 or higher in a "happy" battery. Age of battery...? Battery may have a dead plate, internal short. Again a load check would spot a problem.

gamma300C

Alynch beat me to the punch 😁

gamma300C

This is what I have....

Mikexe

Battery still dead yet again...so going to replace with new tomorrow....1 question is it as simple as disconnect old and replace...or do I lose any electric settings etc

alynch

It's a simple swap. As far as I remember, all of the electrical settings are maintained if there is not too long a delay. If you disconnect the old battery and wait a few days before connecting the new one then you might lose some settings.

meazz1

I had the battery disconnected for over a wk when I was working to replace the oil filter housing and only thing I lost was the clock settings. So, you should be good.

Mikexe

Cheers for everyone's input...let you know how it goes today