How to Use a Battery Hydrometer

There are many ways to test flooded lead acid batteries; Voltage readings, discharge tests, and using a hydrometer to name a few. According to Trojan Battery Company, the most accurate view into the strength of your battery comes from taking the specific gravity readings of each battery cell using a battery hydrometer (amazon).

This short article will take you through the process of using a battery hydrometer to test your golf car’s flooded lead-acid batteries.

Equipment needed


Before beginning the process of testing your golf cart batteries with a hydrometer, you’ll want to go through some preparation first.

Flooded Lead-Acid batteries contain an electrolyte solution (aka battery acid). This acid is strong, so you’ll want to wear appropriate protective equipment, especially eye protection.

I’ve seen battery acid splash up pretty high and just barely miss landing on my face. This can happen when adding distilled water to the battery or when the battery is going through an equalization charge and bubbling.

Also, wear old clothes or put on a polyester apron. Battery acid will burn holes in cotton clothing. You should see some of the jeans my technicians have destroyed with battery acid. (We now provide them work uniforms that are resistant to battery acid.

Additionally, before you conduct the hydrometer test, you’ll want to make sure that all cells in the battery have the appropriate amount of fluid and that the batteries are fully charged.

Step 1. – Turn off the golf cart

Step 2. – Open or remove the battery cell caps

Step 3. – Draw the battery fluid (electrolyte) into the hydrometer several times.

Drawing the electrolyte solution into the hydrometer several times allows for the hydrometer built-in thermometer to adjust to the electrolyte temperature. Be careful to avoid losing any electrolyte solution due to splashing or spilling. Once lost, it cannot be replaced and will negatively impact your battery performance.

Using a high-quality hydrometer with a built-in thermometer is important in measuring the electrolyte temperature. The hydrometer readings must be corrected to 80 degrees Fahrenheit (27 degrees C) in order to get an accurate specific gravity reading.

Step 4. – Bring the tip of the hydrometer out of the battery cell and gently place it in the small beaker while holding the hydrometer.

To avoid losing any electrolyte solution while observing the hydrometer reading at eye level, place the tip of the hydrometer into the small glass or beaker.

You can then raise the hydrometer (and beaker) to eye-level to better observe the specific gravity reading and temperature.

At this point, you’ll also want to observe the electrolyte color. A brown or gray color will indicate a problem with the battery and is a sign of the end of its life.

Step 5. – Write down specific gravity reading and electrolyte temperature.

Diagram of a Hydrometer with Float and Thermometer conversion gauge

Write down the battery number (1, 2, 3, 4, 5, 6) based upon its placement, cell number (1-6), specific gravity reading and temperature correction.

The thermometer will likely have a conversion gauge that corrects +/- 0.004 for every 10 deg F above or below 80 deg. F.

For example:

If the battery has a specific gravity reading of 1.250 and the electrolyte temperature is 90 deg. F, add four points (0.004) to the spg reading (1.250 + 0.004 = 1.254).

If the battery temperature was 70 deg. F, subtract four points from the spg (1.250 – 0.004 = 1.246).

Step 6. – Return electrolyte to the battery cell.

After writing down the temperature corrected specific gravity reading, return the electrolyte to the battery cell using either the hydrometer or the beaker with spout.

Step 7. – Repeat steps 2 – 6 for all cells in the battery and all batteries in the pack.

When you’re finished writing down all the specific gravity readings for each battery cell in your battery pack, you’re finished using the hydrometer. Clean according to the hydrometer manufacturer’s guidelines and store in a safe location.

You can use the charge below to compare your specific gravity readings to the battery state-of-charge. You may also want to determine if the specific gravity readings are outside the 0.030 from each other. If so, you may want to consider performing an equalization charge as discussed in the article How To Equalize the Charge on Golf Cart Batteries?

Percentage of ChargeCorrected Specific Gravity
Source: Battery Maintenance | Trojan Battery Company

Recent Posts