Filling batteries

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Mar 21, 2004
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Near the beach in Delaware
In the past I have filled the cells until the level just touched the bottom of the vent tube. Now I read to just cover the plates. And also read to the full indicator.

So is filling to bottom of the vent tubes bad? What is the "full indicator".

I would like the level as far above that plates as can be done to provide the biggest cushion to avoid exposing a plate.

Yes distilled water.

It seems the level in newer batteries does not change much.
 
I always questioned the exact 'full' amount / because I have the habit of over-filling things.

When I bought my last Battery, the fluid level was one inch from the Top.
I maintain that distance.

watering_infographic_v3.jpg
 
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Never added water to a battery in 30 years. Is this common with modern automotive starting batteries? I know with deep cycle it still is.
 
^ It is common with any flooded lead acid battery used on a vehicle (or anywhere else) to whatever extent it is overcharged, which causes electrolysis that converts water to H and O gas. With a bad charger hooked up to a fully charged battery you can hear it bubbling away.

Vehicle charging systems are better than they used to be decades ago (people used to turn their headlights on in the daytime when driving long distances to decrease the amount of battery overcharge), but a bad alternator can still cause this.

Vent caps that don't seal well can also cause it. You stated you never added water, but did you check to see if they were low? When I check and find one low, it's usually at least 4 years old and the goal is catch it before it got low enough to cause a problem. Some batteries may seem fine for their expected lifespan but still be low by the end of it, or have a shorter lifespan as a result.
 
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Sulfuric acid "creeps". AKA capillary action. Those fill tubes are designed to maximize the path to the outside.
So no, the level should not touch those tubes. The level is highest when fully charged.
 
We have a few golf carts that I maintain where I work. I fill them about a quarter inch below the vent tube and they take less water in the long run. I used to fill until the water touched the bottom of the tube and the batteries seems to need water more often.
 
Fill each cell until it winks at you. The vehicle batteries that I have had that had removable caps had an "eye" shaped cutout above the plates. When the water reached the eye it winked at you.
 
Most batteries are the maintenance free style these days. Do you guys still peel off the sticker and pop the caps to regularly check and fill?
 
Fill each cell until it winks at you. The vehicle batteries that I have had that had removable caps had an "eye" shaped cutout above the plates. When the water reached the eye it winked at you.

I use to do that. But you do not want it touching the vent tube. Just below. The sulfuric acid will wick up the vent tube if it touches.
 
MasterSolenoid's drawing is excellent.

The mistake I made during my youth was to fill to it touches the base of the tube....maybe go up 1/8".
There was ALWAYS a gap in the tube -such that just touching the base resulted in a C shaped contact rather than a complete circle.
My bad method got me approximately 1/5 the way up the tube.
Also, when the acid would touch the bottom of the tubes it'd make a meniscus.
I assumed that was where to stop; and a great idea on the part of the battery makers!
 
Most batteries are the maintenance free style these days. Do you guys still peel off the sticker and pop the caps to regularly check and fill?
I'm wondering the same thing. I only learned that the "maintenance free" batteries I've had still have removable caps under the stickers. I cut the sticker around one of the caps on my EverStart battery to verify. My plan was to pop the caps after about a year to see if any of the cells actually needed to be topped off. I got an extra year out of a Duracell branded battery (also made by East Penn) by using a charger/desulfator, but I wondered if it would have lasted longer if I had checked the fluid levels. I only started using the desulfator when the battery was three years old and about ready for replacement. I'm now connecting the thing once a month as PM.
 
I'm wondering the same thing. I only learned that the "maintenance free" batteries I've had still have removable caps under the stickers. I cut the sticker around one of the caps on my EverStart battery to verify. My plan was to pop the caps after about a year to see if any of the cells actually needed to be topped off. I got an extra year out of a Duracell branded battery (also made by East Penn) by using a charger/desulfator, but I wondered if it would have lasted longer if I had checked the fluid levels. I only started using the desulfator when the battery was three years old and about ready for replacement. I'm now connecting the thing once a month as PM.

To add to the point, I've been noticing many (OEM) batteries which are maintenance free have a welded plastic cap on the vents. Kind of a pain to remove and involves significant prying. Other maintenance free batteries hide the caps under the sticker which is alot easier to access.

I seem to be getting ~10 years from my OE batteries and that's with no maintenance and no checks other than following general best practices (eg. never discharging them) so I wonder if it's even necessary to go above and beyond with these.
 
Fill each cell until it winks at you. The vehicle batteries that I have had that had removable caps had an "eye" shaped cutout above the plates. When the water reached the eye it winked at you.
Yes, when you have the liquid level correct, the surface tension of the liquid causes the the fluid surface to bend. The reflection will be upside down and does look like an eye (sort of).
 
Most batteries are the maintenance free style these days. Do you guys still peel off the sticker and pop the caps to regularly check and fill?
There are maintenance free and others requiring maintenance. It’s important you know which you have. Maybe this is why guys are replacing batteries every 3 years. A lot of batteries still have two rectangular tops. You pry those up with a screw driver and check.
 
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