Distilled water is not necessarily pure. If the water had a funny smell before you distilled it, it will have a funny smell after you distill it. Water contaminated by gasoline will still be contaminated by gasoline after distillation. But, gasoline molecules are too large to go through the molecule sized pores in a RO membrane.
Just boil some RO water until there’s nothing left. Does a film of minerals stay behind? If not, it’s pure enough.
Perhaps one way to make super pure water for lab use is to break it down into hydrogen and oxygen by electrolysis and then burning the hydrogen back into water. Just don’t let it come in contact with air or it will no longer be super pure.
I would be afraid to use reverse osmosis water in a battery because it might reverse the polarity of the battery and the negative terminal would become the positive and the positive terminal become the negative. It would be best to use distilled water to maintain the present polarity of the battery or use forward osmosis water to insure the polarity remain correct. (sorry, friends. I just couldn’t resist this post).
Well, someone should mention water purity standards and classification. RO technology has improved quite a bit in the recent past and some systems are on par with deionization systems in many regards. Type II water is still typically DI water and Type III is RO but not necessarily so. Water that conforms to Type II standards is a better conductor and leaves less residue than Type III. Type III is still a considerable improvement over tap or distilled since the contaminants in the latter two can disturb the acid-base equilibrium in your battery resulting in inoperability or performance reduction. How the water was treated is increasingly less important so examining water’s conformity to established standards as well as knowing the entities that regulate the industry may be the better guide currently.
My personal opinion is that the battery generally should be restored to its original electrolyte state as closely as possible. This is usually best accomplished by adding the correct amount of Type II or even Type I water and analyzing the results analytically with simple tests like pH, conductivity, specific gravity, etc.
I can’t see how the small amount of minerals is any potable water (especially deionized, distilled, or RO) would have a significant impact on battery operation. The electrolyte has orders of magnitude greater amount of effect. What’s the basis for your comments?
Could you please be more specific about what you mean by the effect of the electrolyte?
Contaminants present at levels which may seem to be practically insignificant alone are often not when considered in tandem with other contaminants. Evaluating their significance is possible when the contaminant levels are known along with the battery specifics (volume, water concentration, acid concentration). Using the initial masses of the reactants with their stoichiometry will provide an expectation for amounts of undesirable products to be expected and their production will be evidenced by changes that can be confirmed experimentally like change in pH and conductivity. Experimentally you would add known amounts of contaminant to the electrolyte solution and observe the effect. So that’s very basically (trying not to bore everyone to death) how to theoretically and empirically show the effects and their magnitude. A decent understanding of electrochemistry does help bridge the reasoning gap between theory, experiment, and making sound and reliable generalizations about battery behavior. Of course, they may not be true for absolutely every situation but most of the time they will be. I would wager there are some places where tap water would not produce a noticeable practical difference. More importantly, these generalizations are effective predictive tools based on reasonable inference from existing scientific knowledge and data. I had to leave out quite a bit but I hope that makes sense. I would certainly encourage anyone with the resources and opportunity to experiment for themselves to do so.
Nice to see the question was still in the same century and all the folks that used to be here. The question is 11 years old though but I think @ok4450 got it right. You don’t change the fluid and really makes little difference what kind of water. But who has a battery anymore that you can add water to except a lawn mower?
on the maintenance free batteries you can peel the label up on the top and there are plugs under it. if you pop them out with a pick you can add water and replace plugs. but that will probably void any warranty.
As far as I’m concerned it’s all mind over matter. If you don’t mind, it doesn’t matter.
The discussion about water has no practical application here. We’re talking about a $150 car battery. It’s a use item. Buy one, use it for 5-7 years, and buy a new one. Preferably buy a sealed maintenance free battery with no caps.
I’ve never heard of anyone shortening the life of or ruining their battery by using distilled or RO water.
Also, these days I’d bet very few batteries get topped off more than once in their lifetime.
Perhaps more likely in tropical climates.
Put me on the list of people that really don’t see the need of making the adding of water to a battery a major operation . This comes under the heading of looking for a problem that is not worth the time and effort.
I think the point was that once a battery is put into service, it is continually deteriorating until the day it is no longer usable. Not much you can do. The plates continue to be consumed by time. Lack of use or discharging can shorten the life though, but like old age no way to stop it. Just be lucky it is a %150 battery and not $2000 yet.
But yeah, this was ten years ago so anyone that had a good battery back then, has had to replace it maybe several times by now.
Is this a multiple choice question? No one has touched any of my batteries for at least 20 years including adding anything to a sealed battery. I have added a little distilled water to the lawn mower battery about once every couple years but the water was pretty clean, so I dunno guess it was a hypothetical question but have a nice day.
I’m not a battery expert, but it’s been my experience, if you have to add water to a battery it’s either on it’s last leg and will need replaced soon anyway, or you have a charging problem and overcharging the battery.
I have only ever used tap water on the rare occasion it’s been needed with plans to replace the battery and/or get the charging system corrected asap.
The main cause of battery failure is not being used. This means when there is no charge being applied by a charger or the car’s alternator. Acid sticks to the lead plates and whenever a charge is applied the acid is driven off of the plates.
Each time this happens more of the acid remains on the lead plates until the point is reached where the battery has failed due to sulfation.
Clean water should be used of course but RO is not necessary.
People still add water to batteries and they will for another ten years.
The owner of an $85,000 car added water to this battery, over filling it. He then brought the car in with a dead battery, acid leaking and getting onto the paint.
