About 3 weeks ago i let my gurlfriend use the car at night she brought it home and thought she shut the lights off, but left the parking lights on all night for about 9 hours or soo. The next morning I woke up and the lights were just barely on, I got in shut them off and tried to start, it clicked. Turned off key and removed it , put the key in and waited for all the lights to shut off and it started drove it to work and for about 4 days it was fine. Then that weekend it sat from friday night till monday morning it was dead. jumped it and drove it it was fine . As long as i drive it every day its fine but when i leave it in the garage ove rthe weekend its dead on monday morning. So i ha dit jumped by Roadside this weekend. We checked the alternator and it charging fine. After i drove it for about an hour i took a volt meter and checked volts at battery it was 12.59 and 14.2 when running. seems fine. Left for one day went to start next day completely dead again. Brought home a expensive battery charger frm work last night and charged the battery for an hour and 20 minutes. after being charged it had 12.92 volts, checked it this morning it has 12.59 volts, keep in mind it was not connected the battery was out of the car all night, i put a voltage draw to it and it says 11 volts when it has draw on it, which just says weak, but everyones telling me that normal. Is this what it should be or do you think the battery is no good. Cause if the batery is good it means i have a voltage draw somewhere, and thats gonna suck caus eit could be anything. also, how do i find out what the voltage draw should be from the battery if i disconect the negative and stick the volt meter to it an dthen touch the neg battery popst to see what the car is drwaing cause i know it is supposed to draw some volts to keep the clock on right? any help would be great thanks guys

 

How old is the battery?
The symptoms suggest that it has an internal short. Running it down appears to have been the last straw.
It is possible that there is a drain however but why did this only start after loaning the car to your girl friend?

If indeed the battery is about 3 to 4 years old then I believe the solution is a new battery.

To determine drain on the battery you need an ammeter, not a voltmeter. Of course a multimeter is fine so long as current is selected and it is wired in Series not Parallel as you would do for a voltmeter.
You have to be very careful since you are looking for a drain current (when the computers have gone to sleep) the current drain is only a fraction of an amp. If indeed you accidentally then try to start the car, bye bye multimeter.

Suggest you go to a replacement battery garage and see for yourself what the battery test load meter states. If it states OK then this increases the chance of a battery drain being the problem and maybe you don't need a new battery. On the other hand if it says DEAD then you have your answer.
Hope you get sorted,
Stuart

 

thanks for the reply yeah my volt meter reads everything ohm amps volts, its an expensive SNap On one, but I dont have a service manual book, so I dont know what the amps should be being drawn when the car is not running. Also i physically charged the battery and used a battery tester from my work that tells if the battery is good or not and it said good when just on the battery and the volts were about 12.4 or soo, then when you hit the load button to put a load on it, it went to about 11 volts and just said weak. I have heard from numerous people that sometimes if you leave lights on for a long period that it can ruin the battery and it will never hold a charge good again. Has anybody else heard this? I think before i go nuts trying to find out if soemthing is drawing current, I am going to buy a new battery i have onlye owned the car for 8 months so I am not sure when battery was changed although it looks new. Also, its not the oem battery it an Interstate battery.

 

Hi,
I can tell you categorically that once a battery has been flattened it has been irrepairable damaged.

A chemical reaction takes place if the voltage goes below circa 12.4v.

You cannot tell the state of a battery without a load on it. The tester is therefore indicating WEAK.

I'm sure you will find that the battery has had it. Don't blame your girlfirend. Her action was just the final straw. It may well have let you down at an even more inconvenient time.

Stuart

 

just to give anyone the verdict, I bought a brand new MB battery for $130 and its been fine now seems my other battery was no good.

 

You sound surprised!

Anyway glad all is now well.

Stuart.

 

Hey, I have a 95 C280 and I have been having the same problem. As long as I drive the car everyday, it will start fine, but once I rest it for a couple of days (now just one day) the battery dies. It has to be a short somewhere because I have changed the battery like 3 times (thank God for Advantage Auto Parts Warranties) and it still happens. Can anyone tell me the process of trying to figure out where this battery draw is coming from? Bringing it in to my mecanic is my last option since he charges so much. Thanks guys...

 

Hey, I have a 95 C280 and I have been having the same problem. As long as I drive the car everyday, it will start fine, but once I rest it for a couple of days (now just one day) the battery dies. It has to be a short somewhere because I have changed the battery like 3 times (thank God for Advantage Auto Parts Warranties) and it still happens. Can anyone tell me the process of trying to figure out where this battery draw is coming from? Bringing it in to my mecanic is my last option since he charges so much. Thanks guys...

 

Hi,
Your problem may be different to the previous case as you state.

Since your NEW battery (I'll accept your word on that for the moment) goes down if left for longer than a day, it is unlikely to be the battery. Since you have changed it multiple times this reduces the chance of it being the battery still further UNLESS your dealer just charged the battery up and told you it was new! Can you be sure it is NEW? Maybe it is one somebody else returned?
So why didn't your battery dealer check alternator output? This is one of the first things to do when you have flat battery problems...and especially repeated flat battery problems...Hmmm.

So if not the battery your problem is likely:
1. Failure to charge correctly or
2. Some consumer is left on when parked.
If nothing obvious is on then I suggest you get the charging circuit checked out first.

Alternators on NEW cars are very reliable. Your 208 should fit into this class. To DIY you need a multimeter and some expertise so I suggest you get it done by any garage and in particular one specialising in battery replacement/auto electrics unless you are familiar with the process and particularly the risks involved.
Alternators are often rated at 100/150 amps dependent upon vehicle spec/engine type etc so an alternator that is producing lets say 30amps will not deliver sufficient power to meets the demands of the driving duty cycle. i.e. at the end of a journey the battery will have less reserve than when the journey started.

Similar equipment is required to determine the extent of any consumer drain left on when the vehicle is parked up. The current drain from the battery needs to be measured using a procedure that has safeguards in it to protect against a number of risk hazards. Once again I think this may be better left to the garage but if you feel confident all that you need to know is what is the battery drain after say 20mins from parking up. It should be measured in milliamps.

Please forgive me. Voltage and current are very different and also in the way they are measured.

Excessive drain once parked up has been a long standing problem with modern cars due to the quiescent drain taken by the onboard computers. These are intended to go into different states of sleep to protect against a flat battery specifically if the car is parked up for a long period (e.g. 2 to 4 weeks airport parkup.)

Most modern MB's are fitted with a device that ensures all power is cut except to essential services (computers) if lets say a door is left open by mistake. The computer knows that for instance the interior light should not be on for longer tha say 10mins when stationary so cuts it off and if you are reading a newspaper at night or something whilst waiting for someone to arrive it might be necessary to turn the light on again when it trips off. This power management process has been known to fail (IF FITTED ON YOUR MODEL) and if so it could need a new main body computer BUT VERY unlikely.

Bottom line. Its the battery...unless you are absolutely sure you have changed it for a new one multiple times (due to an internal battery short)...or next likely is the alternator working below rated output especially if you use the vehicle around town alot.

So what is the quiescent drain in milliamps at 0, 2, 5, 10, 20 mins? Lets see what is going on.

Of course you could just pull different fuses each night to see if you can hit on the correct combination to cut power to whatever might be staying on......Rough and ready approach but this COULD determine the cause if something is remaining on.
Also check the glovebox, cubby and boot lights to see if they are warm immediately after opening them in the morning. If so they have possibly been on all night since it takes time for the heat from the bulb to percolate through the body of the lamp asembly.

Sorry for such a long reply. I got carried away. Hope this helps.

Stuart