What Is a Hydrometer, and How Does It Work?

We use scales to measure the weight of solid objects, but what about liquids? How do we measure their mass and density? We use a hydrometer. What is a hydrometer? Put simply, it’s a device used to measure the weight of liquids.

It has several applications—from measuring the purity of a cow’s milk, the potential alcohol content of a liquid or the amount of sugar in a liquid to measuring the specific gravity of the acidic solution in a battery.

This article will cover what a hydrometer is and how it works with some FAQs.

What is a hydrometer, and how can it be used with a battery?

A hydrometer is a scale to weigh liquids. This can tell you information about a battery. For instance, the liquid inside the battery changes weight as the battery charges and discharges. As a result, using a hydrometer, you can tell if the battery needs to be charged more or is completely charged.

Are there any specific steps I need to take to get a precise reading from the hydrometer?

Yes. When testing a battery, you should ensure the battery is fully charged to get the most accurate reading. A hydrometer can tell you if your battery needs to be charged more and can tell you how much more you need to charge it and how long it will take to bring the battery to a fully-charged state.

What type of scale does a hydrometer use?

Depending on what you’re measuring, a hydrometer can use a variety of different scales. For a battery, you’ll be measuring the density of the battery acid used as an electrolyte. Hydrometers measure liquid density relative to water, so distilled water has a 1.000 reading on a hydrometer.

If you test a battery and receive a 1.300 reading, that’s considered high. A completely depleted battery will provide the same reading as water, or 1.000. As a baseline, most car, truck and vehicle batteries are fully charged when the weight of the liquid is 1.265.

Does the size of the battery matter?

Yes. To help determine how much to charge a battery, you must have an idea of the size of the battery in terms of amp hours or size.

Not all batteries provide a specification in amp hours in their manual, but knowing the group size can help. The group size of a battery is related to the physical size of a battery established by a group of battery manufacturers called the BCI (Battery Council International).

What’s an example of battery group size and specs?

Here’s an example of battery specs: A battery has a group size of 24, with dimensions of 10” x 7” x 9.8” (length x width x height). The amp hours for this battery are roughly 80 amp hours, so if the hydrometer shows 1.225 (or 50 percent), then the number of amps that return to the battery is 40. In our example, the charge should be 8 amps (or 10 percent) of the battery amp hours (80/10) 40/8 = 6 hours.

Call for battery service today

This article covered how to use a hydrometer for battery testing. If you find that your battery doesn’t hold a charge like it used to, call us at Texford Battery Co, where we’ve been offering quality battery services for over 70 years.

Categorised in: Battery Service

This post was written by Writer