Refilling a lead-acid battery with distilled water is a simple process, but there are some important steps to follow. In the opening paragraphs below, we’ll go over the basics of how and why to refill a battery, along with quick answers to common questions.
Page Contents
- 1 Why Does a Battery Need Distilled Water?
- 2 Step-by-Step Instructions
- 3 Safety Tips
- 4 What if the Battery is Very Low?
- 5 Tools and Supplies Needed
- 6 Types of Batteries to Refill
- 7 Alternatives to Distilled Water
- 8 Signs of Overfilling
- 9 How to Dispose of Old Electrolyte
- 10 How to Troubleshoot an Issue After Refilling
- 11 Conclusion
Why Does a Battery Need Distilled Water?
Inside a lead-acid battery, there are cells made up of alternating lead plates and porous separators. The separators are saturated with an electrolyte solution of sulfuric acid and distilled water. When the battery discharges, the sulfuric acid interacts with the lead plates, converting them to lead sulfate. This produces electricity for the battery’s function. During charging, the process reverses, converting the lead sulfate back to lead and sulfuric acid.
However, over time some of the water in the electrolyte solution is lost due to evaporation. This causes the concentration of sulfuric acid to increase, which can damage the battery. Adding distilled water periodically helps maintain the ideal acid-to-water ratio.
How Often Should I Check/Refill the Water?
For automotive batteries, checking every 1-6 months is a good rule of thumb. Check more frequently in hot climates. For deep cycle batteries, check every 5-10 charges. The battery may need water if the level is below the top of the battery plates.
Why Specifically Distilled Water?
Tap water contains minerals that can contaminate and shorten the life of a lead-acid battery. Distilled water, on the other hand, is pure H2O with no minerals, so it won’t affect the electrolyte solution.
What Are the Signs That Water is Needed?
Here are some signs your battery may need distilled water:
- Water level below top of plates
- “High” or “Low” indicator on clear battery cases
- Failed specific gravity test on cell(s)
- Excessive loss of water in hot weather
Step-by-Step Instructions
Follow these steps to safely refill a lead-acid battery with distilled water:
- Turn off the device and disconnect the battery. This avoids sparks or short circuits during the process.
- Remove the vent caps. Place them upside down so dirt doesn’t get inside.
- Check the water level in each cell. It should be just above the plates or at the indicator on clear cases.
- Use distilled water to fill any low cells. Fill slowly and carefully to avoid overfilling. Leave about 1/4″ of space at the top.
- Replace the vent caps. Make sure they are on securely.
- Clean the battery top with a damp cloth to remove any spilled electrolyte.
- Reconnect the battery and turn on the device to test it.
Safety Tips
When refilling batteries, keep these safety guidelines in mind:
- Wear eye protection and rubber gloves – battery electrolyte is corrosive.
- No smoking, sparks, or flames – batteries may emit explosive gases.
- Have baking soda on hand to neutralize spills.
- Never overfill – electrolyte could leak out.
- Avoid touching your eyes while working near batteries.
- Refill in a well-ventilated area.
What if the Battery is Very Low?
If the water level in any cell is very low or dry, filling it up with distilled water may no longer be enough. The battery has likely lost a significant amount of capacity. In this case, you’ll want to check the battery’s voltage and specific gravity readings. If they are low, consider having the battery recharged and load tested or replaced if it fails testing.
Tools and Supplies Needed
Here are the basic tools and supplies you’ll need:
| Tool/Supply | Purpose |
|---|---|
| Distilled water | For refilling battery cells |
| Eye protection | Protect eyes from splashes |
| Rubber gloves | Protect skin from acid |
| Baking soda | Neutralize any spilled electrolyte |
| Battery terminal brush | Cleaning corrosion from terminals |
| Digital multimeter | Check voltage, if needed |
| Hydrometer | Check specific gravity, if needed |
| Battery carrier | Safe transport of battery |
Types of Batteries to Refill
While all lead-acid batteries can be refilled with distilled water, the most common types include:
Automotive Starting Batteries
The batteries under your car’s hood that start the engine when you turn the key. They are designed to deliver quick bursts of high power.
Deep Cycle Batteries
Found in RVs, boats, golf carts, and more. They are optimized for repeated deep discharge cycles.
Motive Power Batteries
Used in forklifts, floor cleaners, and other motorized industrial equipment. Withstand frequent charging.
Stationary Batteries
Provide backup power for systems like emergency lighting or generators. Float charged at low rates.
Alternatives to Distilled Water
In an emergency or if distilled water is unavailable, there are a couple possible alternatives:
- Deionized water – Water that has had almost all mineral ions removed. Not quite as pure as distilled.
- Bottled drinking water – Much better than tap water if distilled is not available. Avoid mineral water.
However, for continued use, distilled water is highly recommended over any substitutes for optimum battery health and performance.
Signs of Overfilling
It’s important not to overfill the battery cells. Here are some key signs you may have overfilled:
- Electrolyte leaking from the vent caps
- Low electrolyte viscosity – excessive “watery” appearance
- Excessive bubbling when charging
- Lower than normal specific gravity readings
If you notice these, use an eye dropper to carefully remove some electrolyte until it is just above the plates or at the proper fill line.
How to Dispose of Old Electrolyte
When refilling a battery, you may need to remove some old electrolyte to make room for the new distilled water. Here is how to dispose of it safely:
- Wear gloves and eye protection.
- Place old electrolyte in an acid-resistant container.
- Dilute with several volumes of water.
- Neutralize with baking soda until fizzing stops.
- Check pH – should be neutral.
- Pour neutralized solution down the drain with plenty of water.
- Rinse container thoroughly before disposal.
Never pour unneutralized electrolyte down drains or on soil. Check local hazardous waste regulations for proper disposal methods.
How to Troubleshoot an Issue After Refilling
If you refill a battery with distilled water and then have issues starting or running the vehicle or equipment, here are some troubleshooting tips:
Battery Won’t Start Vehicle
- Test voltage with a multimeter. Should be >12.4V.
- Load test battery. May need recharge if failed test.
- Check connections are clean and tight.
- Try jump starting the battery as a test.
Dimming Headlights When Idling
- Test alternator belt tension and output.
- Check cables and connections are in good condition.
- Load test battery for capacity and ability to hold charge.
Battery Discharges Quickly
- Ensure no accessories left on when vehicle off.
- Check for shorts or current drains with multimeter.
- Test charging system voltage and regulator function.
- May need larger capacity or new battery.
If water refilling doesn’t solve discharge issues, further electrical and battery system diagnosis may be needed.
Conclusion
Refilling a lead-acid battery with distilled water is an essential maintenance task to ensure optimum battery life and performance. Just be sure to take the proper safety precautions, follow the step-by-step process, and avoid overfilling. Test the battery afterwards and troubleshoot any issues that arise. With proper care and watering, your batteries will provide many years of reliable service.