W220 dead battery

Page may contain affiliate links. Please see terms for details.

design guru

Active Member
Joined
Feb 28, 2004
Messages
486
Location
Hampshire
Car
2001 W220 Mercedes S320cdi & 2001 W208 CLK230K (SORN since 2008)
I have a 2001 W220 S320cdi and had an issue with a dead battery, in the past I had left it for a few days and found the battery would lose some charge especially during cold winter months but today was a bit more. I used the car on Sunday and it was fine starting and driving.

Today I drove to the supermarket and went inside for less than 20 minutes and when I came out it was totally dead. Used the blade on the key fob to get in the car and no alarm came on, not dash lights nothing, even connecting the icarsoft would not register.

Mechanic showed up and checked the battery and said there is on 0.5v showing. Nothing was left on car was simply parked and locked. When he charged the battery the alarm went off and car started and was showing 13.65 whilst running did not change when revved, stayed the same.

Anyway got it home and checked it 2 hours later and again its stone dead, keyfob will not unlock. I have owned the car since 2012 and never had the battery drain to the point where it totally dead. Any thoughts on what could cause this, I will buy a new battery as the current one is probably 5 years old now but don't want the new one draining.

In the past few weeks my clock has been going forward and back one hour randomly as if the British summer/winter times and also I do have an issue with the steering wheel sensor showing a fault linked to the ABS light being illuminated, would this cause the battery to drain?
 
Sounds like your battery is not holding a charge reliably given it is over 5 years old. I would suggest investing in a battery from MB, or failing that get a Varta battery instead of other brands. If your budget allows, get the highest quality Varta battery with the longest warranty and get this from a reputable Varta dealer as you want to avoid buying one that has been sitting on the shelf a long time. If you have ECO Start/Stop make sure you get an AGM battery as the smart charging will reduce the life of a non-AGM battery.

A good battery costs more, and the OEM fitted battery from MB has lasted over 11 years in my older A-Class - but I do put a Lidi battery charger on the A-Class overnight twice a year (on the onset of Winter and on the onset of Spring). Eventually sold the A-Class after 11 years still with the factory fitted battery going strong.

If you suspect that your car has a high drain issue, suggest you get the 'next size' up battery for your car. In my experience, the battery space for most MB is big enough to go one size up. For example on my old W202, I was able to replace the original battery with one from the E-Class (albeit i needed to order a new battery clamp from MB to fit the second mounting hole). On my R172 I was able to fit a larger 80Ah battery from Varta instead of the OEM 70Ah despite the space being tight. This gives me a larger capacity with a bigger cranking power. The cost difference was small (like 10 quid) but gives peace of mind that it can hold a bigger charge between charge.

Your MB dealer will try to sell you the same battery (as they will go on what EPC says), but a Varta dealer will be more willing to discuss and upset you the next size up battery. Your an also try to find it via the Varta battery locator - if nothing else you can see what size battery fits your model

Car battery finder from VARTA® - Find the best and most reliable battery for your car
 
Last edited:
Well I suppose a new battery is the way to go,but I would get a mobile car electrician to spend a hour finding out if you have a battery drain somewhere on your car,as for getting a higher power battery thats a good idea,but make certain it will fit in the space you have,the W220 battery is in the boot and it is years since I looked at one but seem to remember there is a small amount of room to increase the actual size of battery.
 
I have ordered a new battery which is a 100Ah as in the past the Mercedes dealer recommended due to the amount of electrics the car has, hopefully the old battery has just died and its not something my car id doing to kill the battery, my main concern is what would kill a battery from being 14V to nothing within 20 mins as I have found if the battery is not charged anything above 12V minimum it will not even start the car in the past.

So it was definitely charged at anything between 12-14v when I drove it but for it to die within 20 minutes to 0.5v seems a bit extreme for an electrical component to do this.

I have a new Highest rated Silver Brand Varta battery on its way so hopefully it will be fine but if it does die within the hour has anyone got a though on what could possibly drain a battery within an hour to 0v. I am guessing if the belt is snapped the car running on pure battery could do this. When it was boosted by recovery it started and held charge but as soon as it was parked up it drained to 0 again.

I did put the old battery on charge and when I connected the cables without switching the charger on it did show the red warning light to say it needs charging, but soon as I switched it on it went to green to say fully charged. So it does look like the battery is knackered, but I always thought it would slowly die over time and rather than just go instantly like it did.

I will be back if it kills the new battery to find out how best to find the problem if it does get to that stage.
 
I have a new Highest rated Silver Brand Varta battery on its way so hopefully it will be fine but if it does die within the hour has anyone got a though on what could possibly drain a battery within an hour to 0v. I am guessing if the belt is snapped the car running on pure battery could do this. When it was boosted by recovery it started and held charge but as soon as it was parked up it drained to 0 again.

If you are getting a brand new 100Ah battery, when fully charged, theoretically the battery will be capable of providing 100A for one hour. I highly doubt that the electrics in your car will be capable of draining a quiescent current 100A without displaying some noticeable signs (such all wires being melted or something catching fire).
 
All batteries capacities these days are quoted at the 20 hour rate - so 100 amp hour will supply 5 amps for 20 hours. :thumb:
 
5 years old? Crikey I can get through one a year!
Careful you get the right Ah for the car, one that is too high rated can cause problems for the alternator.
100Ah should be ok for a Diesel, but check first.
 
UPDATE: I fitted a new VARTA SILVER battery and everything seemed fine I ran it for a good 20 minutes and the output was 13.85 which in the past I have had 14.2 but I googled it and this seemed to be fine. Moved the car, it drove fine but once I parked it up after 30 minutes, went to unlock it and the battery was stone dead, not even enough power to light up the cluster. Something is seriously draining the battery at a high rate and seems to powerful to be component. I had a battery and alternator tester which showed everything as being fine but I'm not relying on that 100% being a cheap gadget off the net.

When I took the battery out it was very warm and you could hear the acid sloshing around in there which I guess is normal for the battery acid to do that. But never had a battery get hot like that.

Any suggestions, my MOT has expired so I need to find a mobile Mercedes Service to come to me.
 
Last edited:
On the 203 it would be a shorted block heater that kills batteries. Does the 220 also have one?
 
On the 203 it would be a shorted block heater that kills batteries. Does the 220 also have one?
Any thoughts on where it would be located, I could pull the wire or fuse and see it it make a difference disconnected.
 
When I did connect the new battery it did not set the alarm off. Would a faulty alarm cause the car to completely drain after 30 mins.
 
I’d call that king sized load. Something else along with battery must be very hot too.
Your 13.85 charging voltage seems to be a clue since it was 14.2 with a fully charged battery.
At that kind of drain you may be able to gently feel the relays for heat. While they will be mildly warm with typical loads like lights and fans and such your suspect circuit will be too hot to touch for long.


Sent from my iPad using Tapatalk
 
I agree with it being the block heater, I have isolated many of these for this exact reason. It tees off the starter feed so there is no fuse you can pull to check. It is similar to a kettle element hence the fact it can drain a big battery so fast.
These do tend to fail at this time of year, my advice is disconnect it, it’s just above the starter motor on the passenger side. Bit of a pain to get to.
 
I agree with it being the block heater, I have isolated many of these for this exact reason. It tees off the starter feed so there is no fuse you can pull to check. It is similar to a kettle element hence the fact it can drain a big battery so fast.
These do tend to fail at this time of year, my advice is disconnect it, it’s just above the starter motor on the passenger side. Bit of a pain to get to.

After reading the W220 encyclopaedia (Alternator - W220 S-Class Encyclopedia) this could be the culprit as they symptoms match the 13.85v when running rather than 14v I would have expected to see the battery icon in the dash if the alternator was the problem and it has never appeared, only once when the belt came off after a pulley wheel came off whilst driving.

The alternator would be the last option given the cost, really at this point just looking to pinpoint the possibilities. Its obviously keeping the car running when switched on and checking the voltage during the engine running for 20 minutes it was staying at 13.85v, the driain really happens after the engine is switched off so with the car switched off can the battery be drained by a fault alternator?

Going back to the block heater which if faulty sounds like its stuck on the on position which would point to the battery drain after the car is off, but is it connected to the battery/live wire directly? and if on constantly would this cause the car to only show 13.85v when the engine is running?
 
After reading the W220 encyclopaedia (Alternator - W220 S-Class Encyclopedia) this could be the culprit as they symptoms match the 13.85v when running rather than 14v I would have expected to see the battery icon in the dash if the alternator was the problem and it has never appeared, only once when the belt came off after a pulley wheel came off whilst driving.

The alternator would be the last option given the cost, really at this point just looking to pinpoint the possibilities. Its obviously keeping the car running when switched on and checking the voltage during the engine running for 20 minutes it was staying at 13.85v, the driain really happens after the engine is switched off so with the car switched off can the battery be drained by a fault alternator?

Going back to the block heater which if faulty sounds like its stuck on the on position which would point to the battery drain after the car is off, but is it connected to the battery/live wire directly? and if on constantly would this cause the car to only show 13.85v when the engine is running?

I see two possibilities:
A) A failed diode in the alternator could relate to the lowered output voltage.
B) A depleted battery coupled with a block heater stuck on could also cause the voltage drop.

I recommend disconnecting the block heater and see if that resolves the voltage and dead battery problems.


Sent from my iPad using Tapatalk
 
Could be any of the above mentioned,but I am guessing alternator voltage regulator
 
UPDATE: I disconnected the block heater completely and started the car, still only showing 13.85v when running. switched the lights on and revved the car, no flickering car ticks over fine, although the ABS light remains on which I have known about. As soon as I turned the car off i checked the scanner and saw the voltage dropping, got to 10v and I quickly disconnected the battery. I am probably looking at the voltage regulator or possibly a bad diode in the alternator after reading about them.

Going to give Green Flag a call and see if they can send a technician to have a quick look and see what they find.

Thanks for the advice so far especially the block heater as reading a few forums people have had similar problems and it all pointed to that so at least thats been ruled out. Alarm did not go off when the battery was connected.
 
Last edited:
I am going to check he alternator with a multimeter to see if the diode is producing a reverse current, if not then it could just possibly be the voltage regulator. Unfortunately my cars MOT and TAX had expired so Green flag would not attend to help diagnose the problem so I am tasked with fixing this myself. The battery drain is so bad I would probably only get through 1 of the 3 main fuse boxes before it drained flat.

Is the block heater and alternator the only 2 main components that have a live feed direct to the battery? I know some of the seat modules have a direct link but they are unlikely to drain a battery at that rate. It drops at a rate of 1 volt every 10 seconds.
 

Users who are viewing this thread

Back
Top Bottom