One of the major causes of an emergency generator not to start is starting batteries. Corrosion, sulfation, and loss of electrolyte are the most common reasons. With proper maintenance and testing, these failures can be prevented and extend the life of your battery. Not caring for your starting batteries could cost the life of a patient, or possible financial loss, from extensive downtime.

In this article, we will explain the different types of generator starting batteries and battery conductance testing.

Generator Starting Batteries

There are three types of batteries in use today for emergency and standby power systems, flooded lead-acid, valve-regulated lead-acid (VRLA), and nickel-cadmium (NiCad). Each includes charging plates and are subject to electrolyte loss. During charging, hydrogen and oxygen vents from the battery decreasing levels of electrolyte. Improper maintenance and charging could severely limit the life of your starting batteries.

Flooded Lead-Acid

Flooded lead-acid batteries include a removable cap for each cell, allowing visual inspection of the battery plates and electrolyte level. Venting is standard during charging. To replenish electrolyte levels always use deionized water. If electrolyte levels are not “topped off” during scheduled maintenance, permanent damage may occur.

VRLA (Valve Regulated Lead-Acid)

Valve regulated batteries, also known as “maintenance free” or sealed batteries, do not have a removable cap. Instead, gas escapes through vents designed to release at increased pressure levels. The term “sealed” means there is no way to access the individual battery cells as you can with a flooded lead-acid battery. Therefore, the battery charger must be set correctly to prevent the battery from drying out. Electrolyte levels are not replenishable.

Nickel Cadmium or “NiCad”

While not as common as lead-acid, the nickel-cadmium battery, or NiCad, is best for its ability to operate through a high-temperature range. It has a higher life span and fewer maintenance requirements. Also, NiCad batteries initially cost more than lead-acid and include cadmium, a potentially hazardous material.

Battery Conductance Testing

Lead-acid and NiCad batteries have been around for a long time. However, until the introduction of the battery conductance tester, battery maintenance was a slow and challenging process. Taking specific gravity readings from each battery cell and recording on maintenance checklists is time-consuming. The use of a hydrometer is no longer needed.

Maintenance Requirements

NFPA 110, “Battery conductance testing shall be permitted in lieu of the testing of specific gravity when applicable or warranted.”

With the battery conductance tester, personnel can save time and money with more accurate results, quickly identify battery health, and uncover potential problems before an actual emergency. Batteries fail due to buildup on charging plates. This buildup disrupts the flow of energy increasing the batteries resistance to charge. A battery conductance test will measure impedance and provide a report on the batteries health.

Personal Protective Equipment (PPE)

Before performing any maintenance or testing task, appropriate PPE is mandatory. Personal protective equipment should include gloves, apron, and goggles or a face shield. Visually inspect the battery for any signs of:

  • Cracking, buckled, or leaking cases.
  • Corroded, loose, or damaged cables and connections.
  • Corrosion on the battery terminals.
  • Dirt or acid on the case top.

Testing Procedures

Depending on the brand of battery conductance tester, set up may vary. The tester should guide you through the steps in selecting the correct settings. The most important will be “Cold Cranking Amps” or CCA. This specification is the measure of a battery’s ability to supply a certain amount of power for a short period. Make sure the CCA setting is identical to the rating of your battery.

When connecting the battery conductance tester to the battery ensure the positive (+) clamp attaches to the positive terminal, and the negative (-) clamp connects to the negative terminal. Make sure both clamps grip the terminals. A poor connection will prevent testing. Most testers will indicate if the link is weak or not so you can make adjustments if necessary. Some also come pre-installed with a printer, or the ability to add one, or transfer the data to a computer for further analysis and archiving.


Whichever method you choose, written, printed, or electronic format, ensure you keep good records. Analyzing results over time will allow you to make informed maintenance decisions and avoid costly downtime. Although conductance testing will give you a good indication of the batteries health, cranking voltage is the truest test of readiness. Be on the lookout for an additional article on Voltage Drop Testing in our upcoming newsletters.