My battery won't hold a charge and I want to ensure that low water is not part of the cause.

In the past, I have used distilled water. Is this the best?

Also, do I just barely cover the "things" in the cells or do I put in as much water as the battery will take (e.g., fill it all the way to the top)?

thanx
Kreg

How old is the battery? How are you charging and testing?

As another post indicated, you shouldn't be using water in normal conditions. Look for a leak or overcharging IF it's a good battery
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a few 1985-92 240s & 245s - parts cars & drivers

When the car sits for 3 weeks or longer, it needs a jump start. I am not testing any voltage. After the jump, it starts just fine until I let it sit.

The battery is about 45 months into a 60 month warranty. It is an Interstate.

What I need to do is to ensure the proper water level (I got the answer here) and then see if it still happens.

I do not know if this matters, but the car has about 220k on it. The previous owner kept good records. He replaced the alternator twice during his ownership - from 90K to 210K.

Again, I am going to try the water level.

thanx,
Kreg

The cells' openings should have a collar that extends down to a point above the plates -- these collars have a slot on the side. This slot is to allow a pocket of air to move freely from the collar to the are over acid solution that cover the plates, so you don't have a trapped air pocket in the collar.

Proper fill level is up to the bottom of the collar, leaving the air slot open (rather than submerged).

Trouble is, some stores don't originally fill (with the acid) the battery properly (batteries are shipped dry), so adding (distilled only!) water to a different depth changes the electrolyte concentration. So I guess, in practice, the proper level should be to whatever the battery was originally filled (assuming there hasn't been any spillage and loss of acid -- i.e., that only water has evaporated from the solution).

As noted, fill only to the ring, which is usually about a half-inch above the plates and 3/4 inch below the top. Do not fill it completely full or it will blow out the caps or split the case when it gets warm.

I usually add a few ounces of distilled water to my batteries every couple of years.

If a battery is loosing water faster than that, it is being overcharged (check charging voltage, should not be much more than about 14.5 volts at 2000 RPM) or the battery is shot and is off-gassing too much, and the gas is carrying out water vapor.

A battery that is off-gassing a lot is dangerous, because that gas is hydrogen (explosive) and hydrogen sulfide (toxic).

Your battery really shouldn't go through water. Unless you are in a hot part of the world. Little if any. Yes, the plates must be covered. Is the outer case damp or wet. Does the battery smell like rotten eggs? is it warm to touch?
--
420,000KM and still ticking

Yes use distilled water only and fill each cell to the bottom ring on the plastic cover. The plates need to be covered. Dan