Battery Water Level Indicator


Instantly know if your battery needs water!

Just imagine seeing the exact water level in your battery without removing the vent cap and without getting acid on your fingers! No more struggling to peer into the vent opening to determine whether you need to add water to the battery or not!

Simply remove the original battery cap and replace it with our level indicator. This product is so unique and innovative that it was recently awarded U.S. Patent No. 10,361,468 by the U.S. Patent and Trade Office.

Battery Water Level Indicator Benefits:

  • Eliminates the need to remove the vent cap to check the water level
  • Saves time and effort
  • 360° sight glass allows viewing the battery water level from any angle
  • Water Miser™ technology reduces water evaporation
  • Dual spark arrestors
  • No electronic sensor to fail
  • No valves to malfunction
  • The acid-proof seal is included
  • Made in the USA in our Ohio factory

Quantity Discounts

101 +Contact Us

This battery water level indicator is available in several different models. To choose the correct one for your battery, please read the instructions.

To buy, select a model number in the drop-down box below. Then enter the quantity and select the Add to cart button. Then select the Checkout button that appears at the top left.

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Testimonial- “They are perfect so far, our guys sure do like them!” – Don (Maintenance Supervisor – Texas USA)
Our battery water level indicators made their job of checking the electrolyte levels in their batteries much easier. They liked them so much, they recently ordered more. They installed the water level indicators on backup battery arrays in their oil refinery to ensure that correct water levels are always maintained.

Battery Water Level Indicator Installation Example

The picture below shows our battery water level indicators that were installed at the Texas oil refinery mentioned above. This particular set of batteries provide backup power to critical pumps that supply oil to their 40 MW generators. In the event that one of these generators experiences a loss of primary power, shaft damage can occur as a result of a lack of oil during the time it takes for the generator to coast to a complete stop. These batteries will give the oil pumps additional time to keep the generators supplied with oil until primary power has been restored.

Prior to installing the battery water level indicators, it was a time-consuming task to verify whether the battery water levels were within the acceptable tolerance or not. After installing them, the water levels of each battery could be instantly seen because the red indicator in the sight glass can be viewed from any angle. Not only did this save their maintenance workers much time and effort, but it also ensured that each battery contained an acceptable level of electrolyte to prevent damage and the possibility of battery failure.

Battery Water Level Indicator installed in battery array

Features & Benefits

  • Easy to use and see.

A mechanical float with a red tip is easy to see in the vertical sight glass. Knowing when to add water to your batteries is essential. If the battery plates do not remain submerged, this will eventually result in a ruined battery.

  • Patented Technology

The added Water Miser™ technology will reduce water loss in the battery cell. This saves you time and effort since watering your batteries will be required less often.

  • Easy Installation

The bayonet 1/4 turn installation will ensure a correct fit into the battery cell opening.

  • Safety

The flame arrestors will prevent any external spark from entering the cell. Since lead-acid batteries produce hydrogen gas, this feature is designed to prevent the ignition of this gas that forms inside the battery.

A major problem with battery maintenance is the uncertainty of knowing when to fill batteries with water. Without a visual indication of the battery water level, operators often need to devise watering schedules or carry out periodic inspections to maintain the batteries. With our Battery Water Level Indicator, the guesswork of knowing when to add water is gone. No schedules are needed and less time is wasted. The red and green indicator ensures that mistakes are not made by operators so that your batteries are always properly watered.

Several models are currently available to match the water level specifications for different batteries. The chart below is for general reference only, and should not be relied on to determine which water level indicator will fit on your battery. Please measure your battery before ordering by following the instructions below.

Battery Water Level Indicator Chart

Fill HeightMount TypeIndicator Model #
Group L161.39"Bayonet4000425
Rolls Surrette
Series 4000
Rolls Surrette
Series 5000
Enersys Varta2.62"Threaded4000600 with
M27X3-SIA adapter

To view the M27X3-SIA threaded adapter dimensions, please refer to the part drawing.

Please measure your battery before ordering by following these steps. Follow all safety precautions recommended by the battery manufacturer.
1) Make certain that the battery is fully charged. Failure to do so will affect the water level in the battery.
2) Make certain that the water level in the battery is full per the battery manufacturers’ instructions. For most lead-acid batteries, the recommended water fill level is 1/4″ below the bottom edge of the battery vent well.
3) Measure the distance between the electrolyte and the top surface of the battery. Then locate the model number in the chart above that corresponds to the water fill level dimension of your battery.

To view the battery water level indicator dimensions, please select a model below.
Battery Water Level Indicator #4000425
Battery Water Level Indicator #4000550
Battery Water Level Indicator #4000600
Battery Water Level Indicator #4000600 (with M27X3-SIA threaded adapter)

Electronic water level monitors are susceptible to failure due to battery acid and the harsh environments that are usually associated with batteries. Our water level indicator has a mechanical float made of polypropylene which is not affected by battery acid.

Valves in single-point watering systems can fail. You simply cannot rely on gadgetry when the life of your batteries is at stake.

Fast, accurate visual inspection of a mechanical water level indicator is the only foolproof way of knowing when you need to add water to your battery.

How it works:

To indicate when the battery water level is full, the float raises the indicator mark to the “MAX” water level line  (see Fig. 1). As the water inside the battery evaporates, the float lowers the indicator mark in the sight glass. If the indicator is within the green area (see Fig. 1), you do not need to add water to the battery.

When the indicator mark is in the yellow area (see Fig. 1), this indicates that you should add water to the battery. If the level indicator mark is in the red area, the battery should be watered immediately because low water levels can damage the battery.

If the level indicator mark falls below the “MIN” line (see Fig. 1), eventually the plates in the battery will dry out and permanent damage to the battery can occur.

When filling a battery, always use distilled water. Never add sulfuric acid to a battery. Normally a battery only loses water because sulfuric acid does not evaporate.

Custom float lengths are available to accommodate the water levels of most batteries. Please contact us for further details.

Made in the USA at our factory in Ohio. Dealer inquiries are welcome. For more information, please view the Battery Water Level Indicator Brochure. Quantity discounts are available for 100 or more. Please contact us for pricing.

The Wikipedia website has a very informative article on lead-acid batteries that we highly recommend. It covers everything from the history of lead-acid batteries to how they are constructed.


Additional information

Weight .05 lbs
Dimensions 5.5 × 1.63 × 1.63 in
Model #

4000425 (1.39" Fill level), 4000550 (2.50" Fill level), 4000600 (3.10 Fill level)

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