5 Best Battery and Coolant Refractometer Instruments

Last updated on November 3rd, 2019 at 03:08 pm

An alternative device for a battery hydrometer that is safer and more accurate for measuring the specific gravity of battery electrolyte is a battery refractometer. Unlike a hydrometer which uses the principle of buoyancy to determine the specific gravity of fluids, a refractometer works by utilizing the refractive properties of liquids. Generally, refraction is the property of bending light. Liquids that are denser than water or that have higher specific gravity tend to bend light through a prism more than less dense fluids. Thus, a refractometer uses this concept to determine the specific gravity of electrolyte.

In this article, we shall review the 5 best battery refractometer instruments for measuring the specific gravity of charging electrolyte. Furthermore, these precision optical instruments also have a secondary functionality of determining the freezing point of ethylene-glycol and propylene-glycol based radiator antifreeze or coolant fluids. So, any auto mechanic or car owner who understands the importance of measuring the freezing point of engine coolant, especially after mixing with water, should get one of these portable easy-to-use optical instruments.

This is the science of how radiator antifreeze relates to temperatures. A properly mixed radiator coolant remains in liquid form even very cold temperatures. This keeps the engine protected throughout the period of extremely cold weather such as during winter. On the other hand, an improper antifreeze mixture solidifies in freezing temperatures hence exposing the engine to damage, especially during startup. Therefore, a coolant refractometer is a very handy tool that helps you to get the right water-coolant ratio so that the antifreeze can remain effective in all weathers thus keeping the engine protected all year round.

Best Coolant and Battery Refractometer Units Comparison Table

Aichose 3-in-1 Antifreeze Tester in Fahrenheit ScaleRobinair Coolant and Battery RefractometerTRZ 4-in-1 Refractometer for antifreeze liquids and battery electrolyteExtech RF41 Portable Battery Coolant/Glycol RefractometerAde Advanced Optics ATC Glycol Antifreeze/battery Fluid Refractometer
trz-4-in-1-Refractometer-Ethylene-Glycol-Propylene-Glycol -n-antifreezetrz-4-in-1-Refractometer-Ethylene-Glycol-Propylene-Glycol -n-antifreeze
Users' Ratings
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  • Measures the freezing point of ethylene glycol or propylene glycol based automobile antifreeze coolant.
  • Also measures concentration of those coolants.
  • Determines the specific gravity of battery electrolyte.
  • Has three scales: specific gravity scale (1100 - 1400), ethylene glycol scale, and propylene glycol scale.
  • Has 3 scales for measuring battery fluids, ethylene glycol coolants, and propylene glycol coolant blends.
  • Coolant scales are in Fahrenheit
  • Features an automatic temperature compensation mechanism
  • The specific gravity scale ranges from 1150 to 1300 with a resolution of 0.01 sg
  • The temperature scale has a resoultion of 10 degree F
  • Measures specific gravity of battery electrolyte
  • Determines the freezing point of ethylene glycol and propylene glycol based antifreeze coolant.
  • Also measures and checks Windshield Wiper Fluid
  • Has 4 scales for measuring four types of fluids: battery acid, washer fluid, antifreeze liquids, and urea solution.
  • Temperature scale is in fahrenheit.
  • Built with automatic temperature compensation feature
  • Just 2-3 drops of electrolyte or radiator antifreeze needed
  • Measures the specific gravity of battery acid from 1110 to 1300
  • Also measures freezing point of Propylene/Ethylene Glycolin from -50°C to 0°C.
  • Has an easy-to-read scale
  • The automatic temperature compensation from 10°C to 30°C feature is integrated.
  • The prism and lens have a simple focus adjustment.
  • Measures freezing point of Propylene or ethylene glycol
  • Has multiple scales for measuring ethylene, propylene glycol, and brake fluid.
  • Temperature scale is in degrees fahrenheit
  • Also measures the specific gravity of battery acid
  • Has automatic temperature compensation for temperatures between -60 Deg F and 32 Deg F.
  1. The body is made of aluminum alloy for increased durability.
  2. It is resistant to abrasion and corrosion
  3. Requires only 2 to 3 drops of sample
  4. Convenient for use in different temperature because of its automatic temperature compensation feature.
  5. Performs three different functions
  6. Sturdy carrying case
  7. Fairly priced
  8. Covered by full 12 months replacement warranty.
  1. Only needs 2 to 3 drops of solution and a few seconds to get accurate readings.
  2. Its rugged aluminum housing protects the internal components.
  3. Has an easy to read scale
  4. The ATC guarantees temperature compensated refractometer readings
  5. Made in the U.S.A.
  6. Ultra smooth focusing
  7. High quality optics
  1. Has most functions; 4 distinct functions
  2. Resistant to corrosion
  3. Portable, safe, and reliable
  4. Has a 2 year warranty Free Replacement Guarantee
  5. Cheapest
  1. Easy to use and calibrate
  2. Only requires 2 to 3 drops of solution.
  3. The tool has an easy to read scale
  4. It is compact and easy to carry
  5. It stows away nicely in a tool box in its carrying case
  6. The ATC guarantees accurate refractometer readings
  7. Includes a 1 Year Warranty cover
  1. Free replacement guarantee within the warranty period
  2. Requires only 2 to 3 drops of sample
  3. Aircraft aluminum body and premium optical lens make the refractometer durable
  4. Checks brake fluid for water absorption
  5. Fairly priced
  6. Has a 2 years warranty
  1. None
  1. More expensive than some other instruments
  1. Carrying case is not robust enough to protect the instrument from heavy impact.
  1. A bit pricey.
  2. Only measures specific gravity between 1150 to 1300
  1. Cloth carrying case wont protect the instrument from impact
Parts Included Firm plastic case
Cleaning cloth
Suction tube
Screw driver
Operating instructions
Rigid foam-lined plastic case
Cleaning cloth
Screw driver
Vial of distilled water
Plastic case
Cleaning cloth
Suction tube
Screw driver
Operating instructions
Tool with case
Calibration screwdriver
Plastic pipette
User manual
Cloth case
Calibration screwdriver
Plastic pipette
User's Manual
Temperature Scale -84°F - 32°F for ethylene glycol and -60°F-32°F for propylene glycol -60° F to 32° F for antifreeze coolant -60°F-32°F -60° F to 32° F -60° F to 32° F
Specific Gravity Scale 1.100 - 1.400 1.150 - 1.300 1.100 - 1.400 1.150 - 1.300 1.110 - 1.400
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Detailed Review of Battery and Coolant Refractometer Instruments

Aichose 3-in-1 Battery Acid and Coolant Refractometer Review

The Aichose 3-in-1 refractometer is a high precision optical instrument used to test antifreeze coolants and battery electrolyte. It comes in a nice hard plastic case with tools to clean and adjust if necessary. Among the three parameters it measures are 2 properties of ethylene glycol or propylene glycol based automobile antifreeze coolants and the specific gravity of battery acid hence the term 3-in-1.

The instrument features high quality optics with ultra smooth focusing including an optical lens that has a high refractive index for high precision. All these are protected under a durable aluminum alloy body. You see three scales when viewing through the viewfinder; the specific gravity scale, temperature scales for ethylene glycol fluids and propylene glycol fluids, and concentration scale. The temperature scales are in Fahrenheits, concentration scale in percentage, and the specific gravity scale is unitless and ranges from 1100 to 1400.

Battery acid is very corrosive. However, the materials used to build the aichose refractometer are resistant and therefore do not corrode with acidic or alkaline solutions. This makes the instrument a perfect choice for using to check the strength of battery electrolyte and for measuring glycol levels even in hydronics heating systems. Storage of this instrument is nothing to worry about because it has a compact sturdy plastic casing that protects it from impact.

In a nutshell, Aichose 3-in-1 refractometer is a very useful, easy-to-use optical instrument that performs three important functions that help keep your car engine and flooded battery in good condition. You can use it to measure the specific gravity of battery acid, the freezing point of antifreeze ethylene glycol and propylene glycol coolants, and the concentration of those coolants.

Robinair Coolant and Battery Refractometer Review

This is another optical refractometer for glycol, antifreeze, coolant, and battery acid. It has a solid construction and comes packed together with other accessories in a hard plastic carrying case. The instrument is equally easy to use and has easily readable scales for making accurate readings. In addition, the tool has a smooth focus adjustment to enhance viewing and a vial of distilled water for tool calibration.

The robinair refractometer measures three different types of liquids. It measures the freezing point of ethylene glycol blends of antifreeze as well as propylene glycol blends. It also measures the specific gravity of battery electrolyte in flooded batteries. Each of these fluids has its own scale that is temperature compensated

Unlike the Aichose refractometer, robinair displays temperature in ° F. The temperature ranges from -60° F to 32° F. The specific gravity scale, on the other hand, ranges from 1.15 to 1.3. Together with its high quality optic, the tool has an ultra smooth focusing that makes reading the scales very easy. This makes it a great multipurpose tool for determining the freezing point of radiator antifreeze and for checking the strength of charging fluid in flooded batteries.

Generally, the Robinair refractometer, though pricier, is a great, well built optical instrument for measuring automotive coolants and battery acid. Furthermore, it comes packaged with other accessories in a nice rigid plastic carrying case that is durable enough to withstand life in a toolbox.

TRZ 4-in-1 Hand Held Refractometer Review

This instrument as well has a solid sturdy construction with an aluminum alloy body for imcreased durability. Its optical components including the prism are made of materials that are resistant to abrasion and corrossion to allow them work with acid and alkaline solutions. This measurement tool features a focus adjustment and a rubber grip just like the rest of the refractometers reviewed thus far. In order to ensure that the readings are not affected by temperature variations, this optical instrument features an automatic temperature compensation for temperatures between 32 degree F to -60 degree F

The Hamh Optics&Tools 4-in-1 portable refractometer combines functions: 1) checks the health of battery electrolyte, 2) determines the freezing point of ethylene and propylene glycol automotive coolants, 3) measures the freezing point of windshield washer fluids, and 4)determines the concentration of urea in AdBlue (a solution of water and urea used to lower emissions in diesel powered engines). The scales for measuring the freezing point of engine coolants are in Fahrenheits and range from -60° F to 20° F with a resolution of 5° F while that of screenwash fluid ranges from -40° F to 15° F. The scale for AdBlue, on the other hand, is in percentage and ranges from 30% to 35% with a resolution of 0.19%.

If you are looking for a portable optical tool that will not only measure the freezing point of antifreeze liquids and sniff out bad batteries, the Hamh Optics & Tools 4-in-1 battery refractometer is a great choice. It will also measure the concentration of AdBlue to ensure that you get the right concentration which will break down harmful exhaust gases from your diesel-powered engine. In addition, this tool will also measure the freezing point of screenwash fluid. The only downside is its less robust plastic carrying case that may not effective protect the instrument from impact. Other than that, the tool is affordable and great to have in place of a hydrometer.

Extech RF41 Portable coolant and Battery Refractometer Review

The Extech RF41 portable battery acid and coolant refractometer is a high precision optical instrument from Extech company. It measures the freezing point of automotive coolants and the specific gravity battery electrolyte. It is easy to operate and has an quick to read scale for specific gravity readings and the freezing point temperature in degrees celcius. It also comes packed nicely in a solid plastic carrying case that stows away nicely in a tool box.

Like the Agricultural Solutions refractometer, this optical instrument is also built with high quality and non-corrosive optics and requires only 2-3 drops of sample for fast and accurate readings. It also features an automatic temperature compensation from 10° C to 30° C to ensure that the readings are as accurate as possible. However, it only has 2 scales; the specific gravity scale ranging from 1150 to 1300, and the temperature scale for ethylene glycol/propylene glycol ranging from -50°C to 0°C.

Extech RF41 refractometer is a high performance optical instrument from Extech company. It works well for measuring the freezing point of automotive coolants, glycol in chiller systems, hydronic and free cooling systems among others. The exceptions, however, are that the instrument does not measure concentration percentage of glycol, its automatic temperature correction does not cover lower temperature, and that the instrument is quite expensive.

Ade Advanced Battery and Antifreeze Refractometer Review

Ade advanced optics refractometer is a portable precision instrument for measuring the freezing point of ethylene or propylene glycol based coolants. It is very similar to the other competitors as far as the compact aluminum alloy body construction is concerned. It is also made of high quality optics with smooth focusing for accurate measurements. In addition, the components are resistant to corrossion allowing it to perfectly work with acidic and alkaline solutions.

The hand refractometer is capable of measuring three different properties of fluids. In other words, it can be used to check the strength of battery elctrolyte, determine the freezing point of automotive coolants as well the concentration of ethylene or propylene glycol antifreeze in water by percentage. Like the other units, this refractometer has an automatic temperature compensation for temperatures between 32 degree F to -60 degree F therefore allowing you to make accurate measurements.

Ade Advanced Refractometer is a great tool for in-depth analysis of lead acid batteries. It is good for testing golf cart batteries and flooded batteries of your offgrid system because it provides more accurate specific gravity readings than a hydrometer and is quick to read. It also measures the freezing point of engine coolants and displays the temperature in Fahrenheits. In addition, this tool can be very handy in determining the concentration in percentage of ethylene/propylene glycol based solutions. The downside, however, is the cloth carrying case that does not protect the fairly delicate tool from impact.

How to Use Battery Refractometer

    Requirements: You need a pipette, soft cleaning cloth, and RODI water for rinsing the equipment.

  1. Battery acid and other machine fluids are dangerous. So, safety comes first!. At a minimum, put on safety goggles, rubber gloves, and closed work shoes.
  2. Ensure the Refractometer is clean before using it. Otherwise, rinse it using RODI water and wipe it.
  3. Confirm that the instrument is properly calibrated. If not, jump to the next section first.
  4. Suck the sample (battery electrolyte, engine coolant, AdBlue, or windshield fluid).
  5. Place a few drops of sample on the prism lens or view area.
  6. Allow it to cool briefly.
  7. Put the cover plate back in place carefully.
  8. Look through the view finder. You will see a line marking the split between a white and blue area.
  9. If you are having a hard time seeing the markings clearly, turn the focusing ring on the eye piece until it clears up.
  10. Read the respective scale depending on the type of sample. For battery acid, use the specific gravity scale, and for automotive coolant, use the antifreeze scale. Do the same for AdBlue and Screenwash fluid.
  11. Be sure to check each cell and record readings if you are testing a flooded battery.
  12. Again, for battery electrolyte, use the battery manufacturer’s chart that makes the correlation between specific gravity and percentage of charge to determine the percentage of charge of battery.
  13. Rinse the refractometer using distilled water and wipe using the soft cleaning cloth.
  14. Store the instrument back nicely in its carrying case together with the accessories

How to Calibrate a Refractometer for Machine Coolants and Battery Acid

    In order to properly calibrate a portable handheld refractometer, you need at a minimum the following five items:
    1) RODI water
    2) 35 part calibration solution
    3) Flat head screwdriver
    4) Soft cleaning cloth
    5) User manual
    Once you have all those in place, use the following procedure to successfully calibrate a refractometer.

  1. Open the cover plate and check the prism for any finger prints, dust, dirt, or debris
  2. Wipe the view area clean.
  3. Rinse the refractometer with RODI water.
  4. Remove the rubber cover of the calibration adjustment screw.
  5. Add refractometer calibration fluid on the prism evenly and place the cover.
  6. Let the refractometer sit for about a minute to allow the calibration solution to adjust to the temperature of the refractometer.
  7. Hold the refractometer to a bright source of light and read the scale. The bright light lets you see the measurement lines more clearly.

Maintenance Tips for a Battery/Antifreeze Refractometer

A portable handheld refractometer is a fairly delicate optical instrument that requires care and regular maintenance to keep working optimally and effectively. The following are some of the care and maintenance tips for a battery and antifreeze refractometer.

  • Protect the glass prism from scratches

    Scratches and chips can greatly affect how light enters the refractometer and ultimately affect the accuracy of measurements. It is therefore important to protect the optical instrument from damage to ensure that you are always getting the most accurate readings possible.

  • Proper storage

    Always make sure you store the tool back into its protective case after use because slight drops and bumps can dislodge or move the refractive mirrors inside.

  • Rinse and clean

    It is good practice to always rinse and clean your refractometer after use to ensure that your readings are always correct. This also makes the tool always ready for use every time you want to use it thus saving time.

  • DO NOT Touch the optical surface of a refractometer

    If you have to touch the optical surface, use very clean non-abrasive gloves. Otherwise, mishandling will affect the accuracy of this high precision optical instrument.

Frequently Asked Questions (FAQ)

  1. What is a refractometer?
  2. A refractometer is an optical instrument that uses the concept of bending of light by fluids to determine various properties such as freezing point, concentration, or specific gravity of a sample fluid.

  3. What does a refractometer measure?
  4. A refractometer in the automotive industry can measure the freezing point, concentration, and specific gravity of different types of industrial fluids. For example, you can use it in place of a battery hydrometer to measure the strength of battery acid. You can also use it to measure the freezing point or concentration of ethylene or propylene glycol-based antifreeze coolants such as Dexcool. Some even measure the concentration of AdBlue fluids and the freezing point of windshield fluids. Keeping the vehicle fluids from freezing protects your car during arctic climate such as in the winters. For instance, frozen coolant in the cooling system of your car can severely damage the engine.

  5. How to read a refractometer
  6. To read a refractometer, you place your eye on the eyepiece and through the viewfinder, you will see a line marking a split between a white and blue area. You then read the desired measurement from the respective scale. However, if the scale is not clear enough, you can increase the illumination on the prism and turn the adjustment ring to achieve a fine focus.

  7. What is the difference between a battery hydrometer and a battery refractometer?
  8. The main difference lies in the principle upon which both units operate. While battery hydrometers rely on the principle of buoyancy, a refractometer uses the property of refraction or rather the bending of light when it passes through fluids. Another difference is the amount of sample needed for each tool. A refractometer only needs 2 to 3 drops of sample whereas a hydrometer needs enough sample to carry the float.


An electrical engineer by profession who used to work at a solar microgrid firm as an O&M supervisor. There, he realized that having the right tools for the trade is equal to getting the job half done. That's what inspired him to start this website!

One thought on “5 Best Battery and Coolant Refractometer Instruments

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