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Adding distilled water to my car battery, I've noticed only the side cells very short of reaching the meniscus.

The most positive cell, facing the front of my '08 Jetta 2.5L (which has empty space, and probably collects a lot of heat from the engine, especially when the two frontal engine cooling fans are on), required almost 90ml of water, the next cell only some 50ml, the following ones seem to already be at around meniscus (added 20ml each for prophylactics after 6 years of service), and final negative one, closer to the cabin, 40ml.

Is it always like this? If so, why aren't they making cells of varying size and level of meniscus, so that more water could be contained within the cells more likely to be kept at a higher temperature and evaporate and/or gas prematurely?

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cnst
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2 Answers2

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In a word, no. Any of the cells might need water. All of them would need water (or electrolyte) if it were tipped over. Usually when one needs it they all need it, but no rhyme or reason to it.

Pᴀᴜʟsᴛᴇʀ2
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Battery manufacturers make batteries to international standards, one of which was selected by VW as the battery for your vehicle. The problem you describe is specific to your vehicle, so a battery manufacturer would not be able to solve the problem as you are suggesting without violating the standard or creating a problem for the owner of some other vehicle that uses the same battery type.

The solution that battery manufacturers have come up with for the problem you describe is a maintenance free battery.

Paul
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