My 'new' 98 e300 has me puzzled on this one. After trying for a couple of weeks to islolate the fault, it still displays 'battery charge' every day. Usually on the first start with glow, but not always. Using the CCU voltage display, it read 10.7 volts right after starting this morning. That explains the message, but heres the list of what has been done trying to correct it;

Valeo 90amp alternator benched, produced 14.5 volts dc with neglible ac. Brushes looked a little short, so I replaced the voltage regulator and had it benched again. Still read the same, 14.5 volts.

Battery tested several times by different methods and people. Its a mercedes battery, but I dont know its age. The local mercedes dealer tells me its not possible to determine its age from any codes but will gladly sell me another. Nice, but the battery tests under load just fine and holds a charge. I can check it any morning and show 12.6v at the battery posts before starting the car.

Checked all the grounds and terminal blocks in the circuit. X12/3 in the engine compartment, X4/C2 in the left footwell, and the braided ground cable on the engine. All clean, bright and tight like they should be. Yes, the short negative cable from the negative battery post to the frame is perfect too. I guess it would have been way too easy to find a corroded connection somewhere..

Serpentine belt and tensioner bracket as well as tensioner shock replaced. I figured at 100k, it was time anyway. Even though the old belt wasnt glazed or slipping, I thought perhaps it was slipping on startup. Another nice try, but still getting the battery charge message.

Current draw at the negative post with everything asleep is about .02 amp. Thats not mamp, and I know its supposed to be somewhere under 50 mamp. The car is completely stock, no added security, lights or stereo. I cant believe this is the problem and so continued looking elsewhere.

So, here I am wondering what have I missed? The alternator puts out 13.2v or so when checked at the battery at 3000 rpm loaded up as per the manual. Idle shows about 12.5volts. Today the CCU voltage remained at 13.0 volts while taking a short drive, so the alternator is working fine. I'll replace the battery with another one from mercedes if I have to. But I'm used to working on the SDL, and have a feeling I'm overlooking something peculiar to the w210.

I'd like to express my thanks to all in the forum for thier help over the years. Up until now, I've been able to search out the answers to all of my questions on the SDL. Especially the heavy hitters, Sixto, GSXR, Hattie and Brian Carlton. How you guys found time to help so many is beyond me. One of these days I'll have to make to a GTG and meet everyone.

Outside of the warning and the low voltage on the first start, everything else seems to check out. I live in Jersey, and have a scangauge attached at all times. Depending on outside temperatures, when I first start my car, the voltage will read 11.4 until the glow plugs cut out, then the voltage will vary between 13.1-13.7. In reading some other posts, it is possible that glow plug system is responsible for the current drain on the first start. Once the engine is started, if you try to start it again, the glow plugs will require less current because they are already partially heated. The other area that could be responsible for some current draw is the pneumatic system located under the rear seat. If you have the cd changer in the trunk, I would make sure that it is not engaged even with the ignition in the "Off" position. I had an episode where the cd changer had a problem with one cd where it would continue to try and load it over and over even with the key out of the car. Good luck...

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96 E300d

Good ideas, but no cd changer in this car. The pnuematic system checked out good, too. I never measured the amperage during a glow cycle, I figure the battery should handle the load with ease until it gets real weak. Maybe the battery really is on its way out? The scangauge is an excellent idea, I'll have to get one and watch the voltage. Thanks for the help, I'll post the results.

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1987 300SDL 174k
1998 e300 102k

Sometimes water can get onto the alternator via some engine drip source, bad plug...... antenna motor?

probably the battery.
you know that Kirkland (costco) batteries are made by Interstate?

Less expensive, same battery.

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

Yeah, I'm thinking battery too. Its been checked three times now and I keep getting told its ok. Before I spring for a new one, I'm going to check voltage drop across the ground cables one more time. I cant believe three different shops with their 'professional' testers can be wrong.

Thanks for the suggestions on the alternator and antenna. The load on the battery when everything is asleep for a couple of hours is still about .02 amp. I check this by hooking up the multimeter between the neg battery post and cable, then leave the meter in the drivers seat. Easy to check it without opening doors and re-starting the clock on everything. This morning it was still .02 amp after sitting all night. Since I blew the 2 amp fuse on my multimeter's mamp circuit, I haven't been able to read the current draw any closer. Incidentally, the initial draw on exiting the car and shutting the door is about 3.7 amps. It decreases quickly as the dome lights shut off and other circuits like the instrument digital display shut down. Worthless information, unless of course, your multimeter is set to read mamps and that circuit is protected by a 2 amp fuse! I've just picked up more fuses and will try again soon.

I heard about the same battery at costco, I'll have to check that out too. Thanks for your help, I haven't given up yet.

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1987 300SDL 174k
1998 e300 102k

Heres the latest;

I charged the battery overnight and started testing in the morning with 12.8 volts at the battery. Voltage dropped to 11.7 after the glow cycle. Engaging the starter dropped the voltage to 9.9 at the battery, and the 'battery charge' warning. Remember, this battery passed load testing 3 times.

Thinking the charging system was at fault, I repeated the voltage drop tests. No change on either positive or negative sides, about .4 volt drop on each. Checked out the starter circuit as well, since I hadn't even looked at it yet. Nope, not the problem either. All the terminals at the starter were clean and tight, voltage drop just under .4 volts.

So, alternator checks out, as well as wiring and battery. I kept watching the voltage at the CCU and was confident the alternator really is charging as it should. I knew the battery code showed a build date of 2005, so was probably ready to replace anyway. Off to the dealer and $153.00 later, I have the following to report;

Voltage at battery before start, 12.8 volts. Glow cycle drops it to 12.1 and engaging the starter shows 11.6 at the battery. No 'battery charge' light! Looks like the problem is solved for now, only time will tell if it really was just a worn out battery. Makes me wonder what the battery testers are good for?

I went with the mercedes battery because I wanted to check the local dealer out. Lets just say the next time I'll head to costco as suggested above.


Thanks to all for helping. I'll post again if the battery really wasn't the problem.

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1987 300SDL 174k
1998 e300 102k