Battery Keeps Going Dry????
 

I have a 1981 300D and I put a (high) maintenance battery on it about a year ago. It is the proper battery for the car and has given me no trouble until the last two weeks.

About two weeks ago in the course of a day it stopped holding a charge. After two boosts I took off the covers and it was BONE dry.

I got some distilled water and filled it up and it held a charge beautifully for about two weeks. It started the same thing today. I take off the caps and sure enough it is dry again.

My question is what would cause my battery to go dry?

I will say that I beat on the post a bit the day it first stopped holding a charge when I was tightening the clamp and I have put the post under a bit of strain in the past when trying to get a ground wire on it.

Besides a crack in the battery itself, how could the water be gone that fast?

Could my alternator be "boiling" off the water?

I'm stumped.

It looks like the water has come out from the caps based upon the debris around the area that apparently stuck to it when it was wet. Also, there is a hole eaten through the battery tray and into the fender well.

I suspect that this has been there a while but I don't know for sure.

Multimeter on battery posts engine "On"
 

Will tell you if voltage is off.
Advance ,Kragens,Autozone will test it running for you

I've got a meter I can put on it but I don't know how that would cook it off.

You certainly can be boiling off the water (if the case is not cracked. )
Your voltage reg might be shot, cheap fix, but it will kill batteries.

When mine was boiling the battery, I could smell it.

I've got a meter I can put on it but I don't know how that would cook it off.

Over charging can boil off the water. Either the charging voltage is too high (on American cars over 14.50 volts too much). Another possible is that the charging voltage is OK but when your battery is fully charged the regulator is not stopping it from charging.
My understanding of batterys are that each cell is separate from the other cells; so if you had a leak it would be unlikely that all of the cells would be dry. Also If a cell leaked out several times and you replaced it with water soon there would not be enough acid left in the cell and your batter would be no good.
I could not find the Max voltage in the factory manual but in the Mitchelle manual it said the output should be 13.7 to 14.5 volts.

Now that you mention it I can smell mine too.

Almost a sulfur-y smell at times.

I have an extra regulator in my car but I just bought the alternator about a year ago.

It never gets over 14.00.

I revved it up and it always stopped at 14.00 like clockwork.

At first it was 13.44 and then slowly rose to 14.00.

It's time for a new battery. "Boiling" is typical for a battery that won't take or hold a charge.

Well, it's a seven year battery that is a year old.

It will hold a charge if there is water/acid in it.

Take the fully charged battery to a parts place that will put a load test on it for free and you will know for sure. I think we have all had even new parts go bad. This will eliminate the battery as a cause.
If the Alternator is off take that too and have them test it.

http://jgdarden.com/batteryfaq/lifemap.jpg

The probablilty that a battery will last 7 years in a hot climate is close to zero. 2-3 years is typical. Failure after one year is hardly unusual.

I'll see if Autozone will give me a new one.

Thanks for the help everybody.

They smell like cooking tomatoes

What does that smell like?

I also could have confused the smells my farty dog makes for the battery smell.:o