Battery dying. - PeachParts Mercedes-Benz Forum

Base1375 · #1 11-06-2014, 09:47 AM

I have an 86 300sdl. 200k. Put a brand new battery in it last year and it seems that when I leave the car off for about 4-5 days or longer it will not start due to the battery being completely drained. Brought it to stay tire and they said the battery seems fine. Any idea what might be draining it?

Junkman · #2 11-06-2014, 10:13 AM

Look up "parasitic drain". There are many straight forward trouble shooting instructions. Begin by first confirming charging level with glows off and enging warm at idle.

97 SL320 · #3 11-06-2014, 04:01 PM

With the key off / engine not running, place a steel object against the face of alternator pulley or back of alternator. If it sticks like a magnet ( maybe weak ) the diode bridge has a shorted diode or the trigger wire leading to the alternator is remaining powered up keeping the field alive.

jbach36 · #4 11-09-2014, 12:27 AM

I tell people NOT to buy stuff at Walmart if they can feasibly do so, since most of what they sell is GARBAGE made in CHINA, who are STEALING OUR SECRETS via computer hacking, making COUNTERFEIT ITEMS, and PUTTING USA COMPANIES OUT OF BUSINESS.

That all means when you BUY SOMETHING FROM CHINA, you now get to pay FOOD STAMPS and HOUSING by way of your TAX INCREASE since the guy in the USA has lost his job since you BOUGHT SOMETHING FROM CHINA.

So....try to AVOID products from China where possible!

That all said, I needed a battery a few years ago, called around, and I think they were about $125. Much to my surprise, I called Walmart, and I think it was $79, and I think it was made in the USA. (I wasn't on my anti-China kick at the time).

Good luck.

Check the trunk light, see if that's off when the trunk is closed.

leathermang · #5 11-09-2014, 12:38 AM

Quote:

Originally Posted by jbach36

.....Check the trunk light, see if that's off when the trunk is closed.

Be sure to have a friend there to let you out......

BillGrissom · #6 11-09-2014, 01:27 AM

Did "Stay Tire" load test your battery or just look at it? Most auto parts near me will do a free load test in the parking lot. It seems batteries today don't last over 3 years, and I have been replacing many in my vehicles and trailers lately. A month ago, I went back to Auto Zone with one, tested bad, and I recalled it being fairly new. Turned out I bought it just last April. The guy said it might have been sitting on the shelf too long (I'd guess the currently high prices do that). Anyway, still under full warranty.

My tip-off is first that the Battery Brain (on all my cars) trips off (its purpose is to save enough juice to start the car). I then put it on a charger, and if it says fully charged in too short a time (say 15 min), I suspect it isn't "holding a charge". I then take it in, and invariably it fails the load test.

People argue widely on the best brand to buy. I understand there are only 3 manufacturers in the U.S., for ~50 brands. In my limited research, people seemed to diss Walmart's Everstart brand at a higher rate. Could just be perception, but some claim their's are made to poorer spec's, perhaps how they can sell them cheaper than others.

Knuckleballerr · #7 11-09-2014, 03:35 PM

Here's what you should do.

Go buy a multimeter from a store of your choice, don't buy a super expensive unit.. just one that can read voltage and current.

First, start and let your car idle. Put the leads on their respective polarities on the battery (Black should be in COM port & Red should be in VΩ set to DC V.. some read differently).

Whats the voltage of the reading? It should be north of 12 volts. If not, go rev the engine and see if you notice any change. If at no point you see +12 volts you got a problem with the alternator.

~

Now turn the car off, take the negative cable off the battery and open that fusebox. (Remember to move your red connection on the meter from VΩ to 20A as well as move the dial to 20A). Put the leads to both the cable and the battery and see your reading. This should be a small number.. never higher than 50ma (0.05 on the meter). If this number is high.. then start pulling fuses.. whenever that number drops like a rock.. you got your electrical problem. Be careful that your not pulling so much current that the wires of the multimeter don't get hot and melt.

Hope this helps out!

leathermang · #8 11-09-2014, 04:31 PM

Quote:

Originally Posted by Knuckleballerr

...... just one that can read voltage and current. .......

LOL, How is he going to read OHMs if it only reads voltage and current ?