1994 E320 History:
I had intermittent starting problem and took my car in for a check up before going on my Canada fishing trip in July of 2001.
The mechanic said that the engine harness was bad so I replace it. I had one starting problem on the 500-mi. trip. When I unloaded my gear at the dock, I could not get the car to start.
I left it there and went back in the morning. It started so I moved it and figured I must have a dead cell so I replaced my original 62Ah battery with a 74Ah battery. In Sept of 2002 I went in for a Transmission Oil change. Since then I have drive about 2,500 miles. I'm a creature of habit so my driving habits and distances have not varied when comparing year to year.
Problem:
Last Saturday the car would not start. I had no warnings via the warning lights. First thing I did was rotate all the fuses, this had worked in the past, no luck this time. Then I checked the battery level, and I was surprised to see it below all the plates in all cells.
I topped up the fluid and charged up the battery to 12.4 Volts.
At Idle I get 13.8 V. [no one around to help with that] so, don't know what I'll get at the higher rpms. Battery seems ok.
In the eight years for that original battery life, I never had to top up more than once a year. I always check and top up all fluid levels and give the car a once over before I take it in and I know the battery level was at the correct level.
Question:
What happened to the fluid?
Since I had no warnings of a voltage regulation or alternator problem, what else would cause the loss of fluid? This is a sealed battery and there is no indication of leakage. All the battery plugs were tight.

You have already done what I would have done. That is check the battery charge voltage. Usually when you start losing water, the voltage is much too high.

Check the water and the voltage frequently until you get confidence.

Good luck,

looks like your battery is overcharging to cause the loss of battery fluid

-this causes the release of hydrogen and oxygen -these gases are released during the charging process


why it is overcharging-i do not know