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How to refill & restore sealed lead acid batteries

How to refill sealed, non spillable lead acid batteries with distilled water. The small 7 and 12 Ah lead acid batteries can be refilled and often brought back into service. With time these batteries, left on charge constantly, boil off all their water and lose their ability to hold a charge.


If you fill these batteries back up you can often put them back into service and charge them back up again using a normal battery charger.


Even then, if the batteries will not take a charge with a standard charger because they are badly sulfated, I can often bring them back into service using my homemade battery desulfator. You can find the plans here: How to make a Bedini type battery desulfator


Most of your small sealed lead acid batteries can be filled back up by removing the top cover and the rubber boots underneath. Then filling the cells with distilled water.


I will show you how.


Types of batteries you can refill


You can fill many types of sealed lead acid batteries in this manner and repair many of them to like new condition. This of course depends in their physical condition.


Alarm batteries, UPS batteries, scooters batteries, fisher price kids car betteries and most other small sealed 6 or 12 volt lead acid batteries can be restored in this way.


Some motorcycle and lawn mower batteries are also sealed like this and can be restored by following this article.


Wheel chair and mobility scooter batteries are often sealed and can often be saved using this method.



Types of sealed lead acid batteries you can restore




Warning! Lead acid batteries contain lead and sulfuric acid. Both can be deadly. This article is for information purposes only and I am in no way urging anyone to do this at home. If you do work with lead acid batteries take every precaution to protect yourself and your work area. Acid burns and can cause severe injury or death. Injesting lead can kill you.





First of all get some protective gear. Use old clothes or something to cover you while you work. Battery acid will eat a hole in your clothes very rapidly. One drop will guaranty a hole in your clothes. That is all it takes.


Use protective eye wear and rubber gloves. Protect your work surface from acid spills as well. Battery acid will eat most materials with time.


Have plenty of water on hand in case of emergency so you can flush it away.


Have some baking soda nearby to neutralize any acid that may spill out.


Get some distilled water to refill your batteries. Use ONLY distilled water. Never put tap water, rain water or anything else into lead acid batteries.


Have a sharp pointed object such as a screw on hand. I use a 3 inch screw to pry off the lids.


Get a small flat tip screwdriver for prying.


Find a medicine dropper, eye dropper or syringe for filling the battery cells.


Small flashlight for looking into the battery cells.


Optional: magnifying glass to help you see into the cells better.



How to refill your batteries


I use a sharp screw or other pointed object to get under the lid and start prying it off. There are indentations in the lid which allow you to do this for service. Get something jammed up in there slightly and then use a small flat edge screw driver to slip underneath the lid. Now you can carefully pry the lid off using the screwdriver.


Using an angled motion, keeping the tip of the screwdriver under the lid and working towards the outside, you can carefully break away the glue that keeps the lid in place. The lids are not held in place by much at all. Just a few points of glue hold them secure.


Pry the lid off a sealed lead acid battery


Once you have the lid off you can remove the rubber boots which cover each cell. Set these aside with the lid for later.


Remove the rubber seals from each battery cell


Now use an eye dropper, medicine dropper or syringe to slowly fill the battery cells with distilled water. Again use ONLY distilled water in lead acid batteries.


Use a flashlight to see into the cells. The openings are tiny so work slowly.


Often when putting water into a battery cell it will form a bubble and close up the hole. I use a piece of paper towel to absorb the water out of the opening so I can continue to fill the cell with distilled water.


Refilling lead acid battery cells with distilled water


Take your time. The cells will absorb water slowly as you work. Put some water in one cell and move to the next. Continue on with all six cells and then come back to the first. In this way you give the cells time to absorb the water into the battery plates.


It will take a surprisingly large amount of water to fill the batteries depending on how dry they were. In most cases the batteries will be nearly dry inside due to long neglect and abuse.


After filling all the cells I leave the caps off and come back in a few hours to check again. Often you will find a few cells in need of more water. Then return the next day as well to ensure that the battery is full.


To finish, after you are sure the battery cells are filled up, you can close the battery cells and put the cover back on.


Put the rubber boots back onto the battery cells. Now you can use a few drops of super glue or all purpose glue to seal the lid back in place. Do not use much glue. Glue only a few places to secure the lid down. This will allow you to remove the lid again in the future for service.


Depending on the conditions you will use the battery in, you can also use large, heavy duty rubber bands or zip ties to secure the lid back in place if you want to be able to easily maintain the batteries again in the future.


Now you can charge your battery on a standard battery charger. If the battery voltage is too low for your charger to recognize it, then you can put a good battery in parallel with the bad one for a few hours. This will allow some charge to get into the empty battery and bring it up a bit. Often you can then remove the good battery and charge up the old one as normal.


If the battery is too badly sulfated and will not take a charge you will need a battery desulfator like I mentioned in the link above. You can build one for free using junk parts or you can buy the parts and build a new one. Either way I have had good success with batteries through the years using this device.


You can watch today's video here: How To Refill Sealed Non Spillable Lead Acid Battery With Water


While you are over there please subscribe to my YouTube channel and follow our daily videos as we strive to become self sufficient and off the grid on a budget.

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Troy Reid


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