Battery's not holding its charge

[stephen Coker]

Over a period of a few days the battery gradually loses its charge. Ive replaced both the alternator and battery and retested. The alternator os charging to 13.5 volts, though if I put on every electrical accessory it struggles to reach 13v. On a long run the batter is charged to 12.5v, but after a few hours it drops to 12.0v and so on.

I can only concllude that something is draining the battery. Could it be the alarm, or maybe the central locking. Has anyone come accross this.

I plan to try and find the problem by isolating electrics one by one, but would appreciate any advise before I try this

 

[Mikesmerc]

Hi Stephen
My dads 230e has the very same problem, new battery, checked altenator but still drains half an amp when idle and alarm isolated, igniton off and all interior lights inc boot light off.
Sorry I cant help but maybe someone out there can.
Regards
Mike

 

[Spike]

What I would do is get a good quality multimeter on the battery + lead in series, with everything switched off and measure the current drain if any.

Assuming there is a drain, I would remove and replace fuses one by one until the source of the drain can be pinpointed to a particular circuit and then work from there.

Good luck in your search, you probably need it.

 

[Andy]

Hi


I would agree with Spike. But the best way to test the alternator is to test the out put from the alternator its self. Many people think that if the battery is reading 14v then the alternator is ok. That is not the case or should I say not the acurate case. The alternator feeds the current consumers first. The battery is the last on the line. So if the alternator is not working correctly or to its maximum.... you can see where I am going with this.


Good luck anyway.


Regards

Andy@ www.mercedesservicing.com

 

[Spike]

You been on Holiday or something Andy?

 

[Andy]

Hi Spike

Its not so easy to spend a day chasing & fixing 10 cars. Chasing the parts for the said cars & then fighting with the said parts men as to why my parts have not arrived when they say they were & why they havn't phone me to say they havn't got said parts. Smile sweatly at my customers as there car is invaribly ready. Then come home to spend another couple of hours having a look at all the questions.

Don't worry I am not going any where. But at times I have a few days off and come and have a good look through whats happening.

Its a bit daunting at times.

For those of you reading this & require quicker reply please e mail me from the web sight below. Please don't phone me with questions as it is always a little manic at work.


Regards

Andy@ www.mercedesservicing.com

 

[99clk02Ebreak]

Long standing battery drain problem

Am interested in this post, having been through several new batteries, I am determined to find the reason my 99 CLK 230k, suffers from battery drain. It definitely is not the battery, it is something draining it.

I am about to test each fuse against a multimeter reading, as per the list and already suspect the alarm being the culprit. Assuming this is the case, what is the next step to mitigate the problem once and for all.

I read also that one owner with the same problem, used his key to lock the door rather than use the "blip". I am wondering why that would make a differecne as the alsarm still sets itself on that basis.

Thank you in advance.

Karl
ps have owned 3 MB over the last 6 years, and I have to say this is the only fault any of them has ever had. Oh I just remembered, the E Break had an ABS sensor replaced under warranty after reporting a fault 77 times in a day.

 

[Hal Fisher]

There is a small amount of drain due to alarms and clocks. Mine has been doing this as well and I'm sure its not that small drain causing it. I heard the previous owner of it was always asking for jumps as well.

I guess I'll have to get a second battery and put it in there to use sometimes (good thing its an old '85 500sec and has an additional place for one up by the headlights).

Hal

 

[99clk02Ebreak]

Battery Drain

I've been suffering battery drain since the CLK (7/99) was a year old, I've had Mobilo out to jump start my car about 20 times. My view is, if they offer the service and the car won't start, "sod-em" they can pay for the problem.

Since a few new batteries, and I have to say a local MB dealer tested a 3 month old battery told me it was duff, and told me to go collect the new one. When I went to the garage, he brought over the so called new battery to fit, I asked him if it was a new one.
"Yes of course it is".
"Then why does it have the date written on it (I always mark them and other parts when installed) with indelible pen ??
"Oh my fault" he said.

He blew it, never using that dealership again.

Anyway, I've had the car in the garage for last couple of days, without the central locking/alarm/immobiliser on (I did not use the blip), and I have a trickle charger ( it's off) but registering the battery output..NO DRAIN..Yeehah, I just have to leave the car unlocked and I'm alright.

How can I sort this problem out ?? Oh and the other problem, living in Belgium, the garages don't speak a great deal of "technical" English to explain the problem fully.

How can I stop the immobiliser/alarm/CL system from draining the battery ?? Or am I stuck ?

Incidently, this car I've owned for over 5 years from new and am determined to keep this forever. Having such a car for 20-30 years or more is some thing.

Incidently, I am not a big fan of the new CLK. C'est la vie.

Karl
ps the E220 CDi Break, is probably the best "overall" car I have ever owned. And that includes, BMW 730iSE, Audi A6 2.5l, Renault Safrane 3l. V6 (Like an armchair on wheels) Rover 8 series Sterling (another armchair), most of the 80s hot hatches/GTis (Golf/205 1.9) Escort RS Turbo (2 of them) and RS2000, Renault 5 Gordini.........

No wonder I have no money !!!!

 

[flyingtech55]

Hi Stephen

I was interested by your battery charge (discharge) problems. You said that you (only) get 13.5V when the engine is running. This doesn't sound correct.

The voltages are as follows:

Terminal voltage of fully charged but rested battery 12.2-12.6V (engine stopped, no load).

Terminal voltage of fully charged battery just off charge just under 13V (engine stopped, no load).

Terminal voltage of battery with engine running at about 2000 rpm but no load 14.3-14.6V. This is the important one.

Terminal voltage of battery with engine running at about 2000 rpm with headlights on full beam, the heater blower motor on full and the heated rear window on should not fall below 13.4V.

The alternator should be able to throw out 60 to 90 amps at 2000 engine rpms depending on the model. With the loads I've specified the alternator should be easily able to maintain the battery terminal voltage.

Obviously, you need a reasonably accurate meter to check these voltages. An Avo Model 8 is no good for this job. You need to use a DVM of some sort. I have an elderly Beckman DVM (I'm an electonics type techy) but most modern DVMs are sufficienly accurate provided you don't buy it in the local 'Pound Shop'.

As I mentioned above, the important voltage is the engine running at 2000 rpm but no loads switched on. If you do not get between 14.3V and 14.6V then you definately have a problem. You said that you have changed the alternator. Was this a brand new or reconditioned one or was it a second hand one. A common fault with alternators is a leaky or short circuit rectifier. This will reduce the output voltage (and therefore current) and will leak the battery charge to earth at a rate dependant on the magnitude of the leak. One easy way of checking is to run the car and then feel the temperature of the alternator body. It should be pleasantly warm. If it is actually hot then it is almost certainly faulty. I know that "warm" and "hot" are subjective but basically, if you can't kept your hand on it without discomfort then there is a problem. Incidently, alternators are surprisingly easy to damage. If you jump start the car and accidentally 'short' the jump leads even briefly with engine running, you will almost certainly damage one or more of the rectifiers.

Hope this helps. Let me know the outcome.

Gliderman

 

[desert joe]

Hello Flyingtech55; My 1979 300cd is also giving me fits with draining the battery. Here is what I've done. I hooked my Fluke multimeter between the neg cable and the neg post on the battery and read 11.4 volts. I also used my battery load tester to prove the reading on the Fluke. 11 volts also. I left tester hooked up and started pulling the fuses one at a time while observing both meters. I pulled all the fuses and never dropped the voltage! I figured that the short had to be somewhere between the batt and BEFORE the current got to the fuse box. I disconnected the batt cable end and the big red wire from the starter solenoid and bolted the two together (but not to the solenoid) to see if the short was in the solenoid but still had 11 volts across the neg . I then disconnected the alternator and still have the short. I then removed the ignition switch and disconnected the electrical plug off the back of the switch but still had the short. needless to say,,, I am at a loss here. Do you know if there is wiring diagram available on this site that might shed some light on this problem? I am almost convinced that the short has to be on the big red wire from the solenoid to the ignition switch as switch is what allows current to pass from battery to the various fuses, right? What do you suggest? Many thank yous desert joe

 

[philharve]

Hi All

An interesting thread. If there is some piece of equipment draining the battery then placing an ammeter (not voltmeter) in 'series' with either the +ve or -ve battery lead will reveal the magnitude of the current drain.

Onboard security equipment could easily draw a few tens of milliamps from the battery but given its huge capacity it would take literally months to flatten it.

The faster the drain, the larger the current. To flatten a high capacity MB battery overnight would require a load similar to the headlamps being left on. You would easily measure such a current but it would probably require a professional grade shunt-type ammeter or clip-on DC ammeter and a multimeter to measure it. If current is being drawn from the battery then removing fuses, one at a time, would eventually isolate the cause.

Of course, all this assumes the battery is in A1 condition and the altenator is capable of supplying whatever current is necessary to supply the electrical load AND charge the battery.

A battery test by a professional must be considered. New batteries rarely give trouble but best not take a chance.

Another possibility is poor connections. I have encountered a situation in which the altenator 'appeared' to be charging the battery but when a load was applied the battery voltage dropped quickly. The problem was isolated to a poor alternator connection to the battery. There was a high resistant (HR) joint which would allow sufficient current to pass to trickle charge the battery but not supply the car's electrics. The result was the full load was being taken by the battery and it flattened very quickly. Remedy - clean all connections.

Of course, the altenator could be defective. Have it checked professionally.

I did once discover a very unusual problem which manifest while the car (not my MB) was not used for several days. I couldn't start the car but there was sufficient current to illuminate the instrumentation. The altenator was fine as was the battery. There was no current being drawn from the battery when the car was switched off. Very odd! The problem was the exposed location of the battery. A film of oil and other substances had built up on the battery casing and between the terminals. This concoction was electrically conductive and drew about 2 - 3 amperes from the battery thus draining it. The remedy was WD40 and a clean rag to remove the deposit.

REGARDS Phil

 

[desert joe]

Hello Phil; Many thanks for your response. I used a professional Fluke brand multimeter that will indicate either a/c or d/c voltage, a/c or dc mili voltage, a/c or dc amps, mili amps and ohms. I kept this meter hooked up between the neg cable and the neg post while pulling the fuses and the voltage drain remained constant. I have not tried the meter on amps but will do so soon. Do you know where on this site I might find a wiring diagram for my car? If pulling the fuses does not stop the drain,, then it must be between the battery and the ignition switch, right? I have checked the alternator charge rate and it puts out 13.5 volts at ldle and goes to 14.4 volts when reved up. I did a load test on the battery and shows to hold up to the load for the required time. I am stumpted! What should I try now? thanks again for your help. desert joe

 

[jons086]

Flat battery problem

I have a 1999 E280 that developed an intermittent electrical fault which was a real pain!! - the battery would go flat - although tests showed that the battery and alternator were fine.

The problem with battery draining re-appeared 3 years in a row, however the problem only returned when the temp outside dropped below zero deg.

Battery drain was via engine residual heat system!!!

I noticed that the two Coils/solenoids under the bonnet continued to 'cycle' every 20 secs and remained hot to touch for over 5 hrs!! Three pipes are attached - two are connected to the in-car heater, and one pipe connected to the engine block.
I pulled fuse No.4 and the 'cycling' stopped and did not start to re-cycle after the fuse was refitted until I started the engine once again.

Someone gave me the following address for wiring diagrams
http://www.autolib.diakom.ru:8001/CAR/Mercedes-Benz/1997/S320/SYSTEM WIRING DIAGRAMS/

Anyway, it turns out that the residual heating system operates to heat the inside of the car when it gets too cold! It is connected (and fed from) the air con unit. The unit has two feeds - one direct from the battery and one from the ignition switch. I disconnected the permanant feed and replaced it with a 'jump' wire from the feed from the ignition switch. The problem has now gone away!

I went through the trials of connecting an ammeter in series with the battery and unplugging fuses to identify which circuits were dragging the battery down, and whilst this is a good idea you should wait about 20 minutes after connecting up your ammeter - after reconnection, the battery circuits are auto powered up and then power down (which takes about 20 mins). Then if your system is pulling more than 3 m.amps you can proceed with pulling fuses untill you find which circuit is giving you the problem.