By Steve Shupert

We rely on wet cell batteries to provide ignition power for so many machines, from generators to staff cars, medics, and standby generators. This often-neglected piece of equipment can save us or let us down.

This can be problematic in emergency services because equipment may sit for long periods of time, and the batteries can lose power. On many systems, there is no pull cord backup, which puts all the starting responsibility on the battery’s ability to do its job and your ability to make sure it is ready to perform. Research and keep handy the specifications and maintenance recommendations for your batteries.

There are several crucial parameters used to test the health of a flooded/AGM battery. The most common are: voltage testing, load testing, and an internal resistance test. The most accurate way to determine if a battery has gone bad and overall battery health would be to use all three tests: voltage, load, and resistance.

Battery Charging

To correct a low-voltage condition, you should charge the battery. Battery charging reverses the chemical process that occurs when a battery discharges, hopefully restoring the battery back to its original condition. During charging, electrical energy is converted into chemical energy and stored in the battery. Connect the positive and negative clamps to the battery (clean the terminals) in a well-ventilated area. How long to charge depends on how much charge is left in the battery. There are long, slow trickle charges and quick/boost charging—it depends on time and your battery. They all work if your battery is in good condition. You can use a smart automatic charger to prevent overcharging. The battery can be installed while charging.

Bulk charging is what you may do when you try to start your machine and the battery is dead. A 12-VDC battery bulk charge voltage should be about 14 VDC. This is the fastest method to bring the battery back to life. Some limitations include battery age, temperature, and battery condition. Refer to the specific battery specifications for how long to apply this high-voltage charge. You could damage the battery—literally boil out the electrolyte solution, causing excessive internal pressure inside the battery and causing it to overheat and swell.

Trickle/float charging is also known as maintenance charging. Voltage is 13+ VDC to maintain the battery’svoltage, without overcharging. It allows for minor energy draw of small loads. Thirteen to 14 VDC is about what an alternator/voltage regulator applies to the battery in normal operations.

To apply a charger, refer to the following:

• Battery voltage should be a minimum of 12 VDC. If not, apply a battery charger. It may take four to 24 hours to bring it up to this voltage.
• Clean battery terminals.
• Check fuses.
• If still low on voltage after charging, consider desulfating (reconditioning the battery). See below.
• If voltage is okay, start the engine and recheck the voltage. If it is below 13 VDC, consider the regulator/rectifier/ alternator.
• The battery can read 12 VDC and still not be strong enough to crank the engine. Checking the battery voltage while trying to start the engine (battery under load conditions) may help with your troubleshooting.

Simple Load Test for A 12-VDC Battery

Sometimes the battery powering the ignition will seem weak or just crank over slowly. So, is the problem with the battery, the charging system, the engine, or something else? To determine if the battery is on its last leg, it is easy to perform a load test.

Battery load testers work by applying a load and monitoring the voltage response of the battery. This enables the device to identify how much power is left in the battery.

Using your multimeter set to read DC voltage, place the black negative lead on the minus or negative lead of the battery and the red lead on the plus or positive battery terminal. The voltage should be at least 12.5 VDC. If it is below this reading, place the battery on a battery charger to see if the chemical action can be restored, then reinstall the battery and try again. If the voltage fails to rise after charging, replace the battery.

If the meter reads 12.5 VDC (or so), crank the engine over while monitoring battery voltage; if it fails to start or the reading drops lower (10 VDC), replace the battery (this is the “simple” load test). If the meter reads higher, with the engine running, likely around 13+ VDC, the charging system is working too. If itisn’t, test the charger circuit further. It is likely a poor electrical connection, or the voltage regulator, or the alternator if equipped. Always mark the date you put the battery in service. Of course, make sure your electrical connections are bright and tight.

Battery Load Tester

Battery testers work by applying a load and monitoring the voltage and current of the battery. The load is a resistor in the tester simulating a momentary heavy draw of current from the battery. Attach the cables to battery terminals, push the test button, and read the meter.

Digital Battery Tester And Internal Resistance/Cold Cranking Amps

Traditionally, to test these two parameters required some expensive tools and the firefighter doing some electrical calculations. However, by using a digital battery tester, they are easily accomplished.

Internal resistance is a measure of the battery’s ability to deliver current. When the internal resistance is low, the battery can provide the amount of current it was designed to do. However, a battery with high internal resistance will perform poorly.

Use a digital battery tester to complete this test. Simple to operate, it will measure several parameters of the battery’s condition. You need to know the battery’s rated voltage and cold cranking amps (CCA) to set the tester up. This tester will calculate and display the battery’s internal resistance. Look up the battery specifications online or record the internal resistance on the day of purchase to compare. Avoid extremes in temperature when testing.

Associated with internal resistance is the battery’s CCA. The CCA is a rating that measures a battery’s ability to sustain voltage and current under heavy load, such as cranking an engine to start in cold weather. CCA measures the number of amps a fully charged battery can provide at 0°F for 30 seconds before dropping below 7.2 volts. A higher CCA rating indicates that the battery can deliver more power to crank the engine, even in freezing conditions.

Wet Cell Battery Filling

If the battery is labeled “Maintenance Free,” it is sealed, and you cannot check the electrolyte level. If the battery is hot or swollen, replace it. Clean the top of the battery off. Check the electrolyte level by removing the caps and placing them upside down to ensure the underside of the caps is not contaminated. Wear eye and hand protection at a minimum to protect yourself from the battery acid. If the water (electrolyte) level is below the vent well, top it off with distilled/deionized water.

Check the electrolyte level every three months. Do not use tap water—it contains minerals that can degrade battery performance. Do not overfill. You do not have to add the sulfuric acid; only water is consumed by the battery. Do not charge a battery unless the water level is full. During charging, hydrogen and oxygen gas is given off. Charge in a well-vented area.

Absorbed Glass Matte Or “AGM Battery”

An AGM battery uses a separator consisting of fiberglass between the plate and wrappers to hold the electrolyte in its place with capillary action. Combining the lead plates, electrolyte, and fiber glass separation fibers in a confined space, AGM batteries create a “physical bond” by way of capillary action. Similar to how water creeps up a towel when it is put in a bathtub, this capillary action holds the liquid inside the glass matting, making the AGM Battery “spillproof” if it is ever exposed.

Because of the tight packing of an AGM battery, it is also the most impact- resistant and boasts the least internal resistance. The lower internal resistance increases the output voltage, decreases charging time, and reduces losses to heat as power flows through the system.

AGM batteries are maintenance- free. AGM batteries recombine the gases produced internally, back into liquid. This recombination makes the AGM battery maintenance-free—no acid leaks, no mess while charging, no corrosion on surrounding parts. You plug in these batteries and walk away. AGM batteries can do anything that flooded (wet) and GEL batteries do.

Hydrometer

A hydrometer is a bulb or teardrop syringe tool that will suck a sample of the electrolyte from the cell. It is used to determine each cell’s state of health by measuring the specific gravity of the electrolyte (its weight compared with water). Remember that water will sit on top of the acid, so if you are using a hydrometer to test the electrolyte, do so after charging. The bubbles emitted during charging mix the solution.

The specific gravity value indicates how well the cell is working. For example, a reading between 1.274 and 1.239 indicates a 100-75% charge, while a reading under 1.200 indicates a discharged cell. However, the recommended full-charge reading can vary by battery, so check the manufacturer’s data for the specific gravity it recommends.

Battery Terminal Corrosion

Neutralize any buildup on battery terminals, and keep them clean to extend the life of your battery. Apply a coating of anticorrosion protection. A white, fluffy substance or buildup of sulfate or sulfide on the positive terminal can indicate pending battery failure. Keep the top of the battery cleaned off.

Desulfating A Battery

Sulfation can reduce the battery’s ability to hold a charge and is a leading cause of early battery failure. Sulfation occurs when lead from the battery’s plates combines with the battery’s electrolyte to create lead sulfate crystals. Signs of a sulfated battery include the following:

• The battery doesn’t hold a charge.
• The battery dies sooner than expected.
• Poor performance, slow to crank engine, dim headlights, etc.

Batteries develop sulfation each time they are used (discharged/recharged). If they are overcharged, undercharged, or left discharged—even for a day or two—cells can sulfate. Even when a battery is stored fully charged, sulfate will form unless a desulfating battery charger is used.

A desulfator, also known as a reconditioning charger, can reverse sulfation by using a 24-hour cycle of high-voltage, high-frequency pulses to break down the sulfate deposits and return them to solution. This can restore the battery’s performance to almost new condition. However, it’s important to act quickly before the sulfate hardens and becomes difficult or impossible to recover. It can take days to restore a heavily sulfated battery.

Store batteries in a cool, dry place that’s protected from the elements. Avoid storing discharged/dead batteries; recycle them.

Resources

1. https://www.interstatebatteries.com/blog/what-is-an-agm-battery-and-whats-the-big-deal.
2. https://www.powerstridebattery.com/blog/what-is-a-hydrometer-and-how-do-i-read-one.
3. https://www.caranddriver.com/features/a26862050/charging-car-battery/.
4. https://www.chargingchargers.com/tutorials/battery-desulfation.php#:&sim:text=The%20lead%20sulfate%20crystals%20are,desulfation%20(desulphation)is%20about.
5. https://www.homemade-circuits.com/understanding-motorcycle-voltage/.
6. https://www.batteryboys.us/battery-education/stratification-trickle-charging/.
7. https://landtinst.com/what-is-internal-resistance-ir-and-how-to-test- ir/#:∼:text=Direct%20Current%20Internal%20 Resistance%2C%20DCIR,%2C%20 DCIR%3D%CE%94V%2F0/OCE%94I.

STEVE SHUPERT is a lieutenant (ret.) from Miami Valley Fire District, Montgomery County, Ohio. He is rescue team manager and training officer for Ohio Task Force #1 US&R. He is a veteran of 11 federal deployments including WTC and Hurricane Katrina, a member of DHS/FEMA Rescue Sub Group, a certified rescue specialist, a structural collapse specialist instructor, and a heavy equipment rigging specialist instructor. Shupert is director of training for Crash Course Village, a 501C3 nonprofit organization.