how much water can be safely added to a battery?

Question

My 2008 Jetta SE 2.5L has the battery as follows: ENERTEC EMC // 1J0 915 105 AD // 12V 61 Ah 330A DIN // 540A EN/SAE.

It would appear that the battery can no longer hold the starting charge after an unfortunate incident of having the battery drained up (with the engine being off), and now it seems like it basically can only hold the surface charge, even though it was running just fine prior to the aforementioned discharge.

The top of my battery (including the six caps) looks exactly the same as the one featured at Should i check quantity of battery liquid?, except that mine also has an eye between the terminals and the caps themselves are beneath a sticker.

How many ml's of distilled water would it be safe to add to the battery, without risking creating any more problems?

I've opened up two of the six caps so far, and I couldn't see any plates, so, I'm not exactly sure if I can or cannot add more water to it. I've owned the car all along, and I'm pretty certain that no water has yet been added in the 6 years the car had the battery.

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UPDATE: I've added 2x 10ml syringe shots into each cell (I got the free oral-use-only syringe from Walmart Pharmacy for free; I got distilled water for small appliances from Target); that's a total of 6x 20ml = 120ml of H2O. It seems small enough to not cause any leaks; not sure if it's large enough to make it hold a charge sufficient for the start motor. And, just to be clear -- the discharge was only enough to stop powering the starter; the battery has not been fully discharged (to not power anything at all) in the last year; it has only been fully discharged (through a lightbulb) once, about two years ago. Right now, prior to adding this water, the battery simply stopped holding a charge to power the motors -- it is still holding a good charge for the electronics and power locks etc. I hope this extra 120ml of distilled water would help revive it without any ill effects. BTW, it does have a min/max marker on the side, however, it's not really visible, due to the battery being wrapped up in some special blanket.

Answer 1

Since your battery is six years old, you just need to replace it. This is a longer life than most would expect from a battery. There are some off the wall ways in which you could salvage the battery, but your best/easiest bet is just replacement. Adding water or acid is not going to salvage it, so put it out to pasture and buy a new one.

Answer 2

I have looked further into the issue, and have discovered that the OEM battery from Volkswagen does actually have the MIN and MAX signs on the side of the case, and the case itself is actually transparent, however, due to it being wrapped into the warming blanket, together with also being in a protective bucket, it would appear that it's very difficult to actually ascertain the condition of the electrolyte from the outside of the case.

However, as per http://www.wikihow.com/Check-Car-Battery-Water-Levels, it would appear that the easiest way to know whether or not the battery requires a top-up is by looking into the filler tubes for the presence of the meniscus.

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In my own case, as per above, my first go was to blindly add 2× 10ml syringe shots into each cell (I figured a 6-year old battery must have lost enough water during all the time it was in use), for a total of 120ml of distilled water; when doing this (I did each cell individually, without knowing what the next one would bring), I did notice that the middle cells did appear to have meniscus, whereas the side cells certainly did not.

Subsequently, after I realised how easy it was to add the water to the battery after all, and after no accidents or explosions for a day or two, but, more importantly, still not having the battery hold much charge overnight around 4°C, I had decided to have a second go to ensure each filler tube reaches meniscus, as per the newly discovered guide as above.

I looked into each filler tube; if all I could see is a sea of water, I added a shot or two; otherwise, I would go to the next filler tube; this approach had me do:

• 7 of 10ml shots into the first frontal cell, which was facing the front of the car, and closest to the empty space that must be quite hot from all the heat and quite windy from all the air;
• 3 shots into the second cell;
• none into the third, fourth or fifth;
• and 2 shots into the final sixth cell, to ensure meniscus in each cell.

This brings the total distilled water addition at 120ml top up + 120ml to reach meniscus on the side cells, for a total of 240ml overall, or some 40ml per year.

So far, it seems like it might have worked -- I was able to successfully start the car after 24 hours of disuse, although my whole experiment is not really a controlled one, due to the varying ambient temperature between 0°C and 30°C during all of these experiments, as well as altitude variation between SoCal, Arizona, New Mexico and Texas, that surely must have been affecting the ability of the electrolyte to collect, hold and supply the charge.

I kinda wish to have had done it earlier -- would have saved me a lot of trouble, and would have had a higher likelihood of fixing the issue for a longer term! With the proper tools (oral-use-only 10ml syringe from a Pharmacy, plus latex gloves to hold the filler-tube caps; and a flat key to pose as a screwdriver; plus the distilled water for small appliances), the job is easier than it looks.

Answer 3

Judging by the photo and your description it looks like a normal serviceable battery. It should have marks somewhere on it to indicate the full level. If not just top it up until all of the plates are covered.

If you take it out of the car you may be able to carefully tip or angle the battery so that you can see the plates and/or the acid level. If it's just been run flat, it would also be a good idea to put it on a charger overnight.

I'd leave a few mm free at the top. But wouldn't be too worried about the level. As the can obviously handle fluctuation.

If it's been low for a long time the battery may be damaged. And if its really low you may want to consider taking it to a workshop and getting them to put acid in it rather than water.

Keep in mind that batteries don't last forever. It may be at the end of its life anyway.

Answer 4

If your battery has the ability to add water to it. Do it only after the battery has been charged overnight. Never add water to a dead battery prior to charging. When a battery charges the plates thicken and as a result the water level rises in the cell. Filling a dead battery results in leaking electrolyte (water and acid mixture) which would have to neutralized. Adding water to batteries is sometimes needed in hot climates due to evaporation.

Be very carefully in doing so, use protective equipment -safety glasses and mask. Sulfuric Acid fumes attack the moist mucous membranes in the eyes, mouth, lungs, and digestive tract causing severe irritation potentially resulting in hospitalization or death.

For your information:

When manufactures initially fill the batteries with electrolyte they start with adding the acid first then very slowly add the water. This is done this due to an thermochemical reaction. The water helps absorb the heat from the reaction. It is also mixed in precise proportions.

If water is put in first then the acid, a very violent and potentially explosive reaction occurs. Translation: Don't do it.

Answer 5

The car tries to charge the battery during deceleration and uses the battery as source the only power source when not decellerating. To keep it charged there is a system with a shunt which monitors the current in and out. In the 80's alternators only produced 13.8 -14 V. A battery will accept a constantly diminishing current as as it becomes fuller. Theorethically a battery would then take 70 hours of constant driving to be fully charged. Car manufacturers have raised the voltage slowly and now it is 14.4 to 14.6V. At 14.4 Volts. It would still take 24 hours to fully charge a battery. Excessive gassing occurs only when the battery is full and charged with more than 14.4V So what the regenerative braking system does is charging at 14.6V in (decelleration bursts) while maintaining a 75% charge.