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Established 1981



Battery Testing & Replacement

Batteries are an integral part of the generator set. The main role of emergency generator batteries is to provide power to the generator engine starter with power when a facility power outage occurs. Many generator service providers report the most common reason for generator failure is a failed battery. Our experienced staff can provide consulting and technical services in the following areas:
  • Battery Selection – Including types, sizes and suppliers
  • Maintenance – Monitoring, maintenance

 Battery Selection

Conventional Lead-Acid Battery
Our consulting staff can provide assistance in selecting the type and size.

Battery Types

Most generator sets use a standard lead acid battery. There are two types of these batteries available (Figure 1):
  • Conventional – Cells have individual caps for filling and testing electrolyte
  • Maintenance Free – Often referred to as sealed battery. Cannot add electrolyte or check specific gravity of battery

There are many battery manufacturer options available. When selecting a battery supplier, keep in mind you get what you pay for. Better quality batteries use higher grade materials in construction. This raises the price to the consumer. It is good practice to use generator set manufacturer recommend batteries. Suppliers listed below:
  • CAT – Most expensive, but noted as best performing
  • Interstate – Offers a field service
  • NAPA, Decca – Other battery option

Battery Sizes

The size of battery is dictated by generator size and configuration the battery is connected in. A 350 kW generator can have only one 4D battery, where as a 1500 kW and 2MW units have two 8Ds or four 4Ds depending on the enclosure. Below are examples:
  • 4D and 8D batteries are used for larger generator applications (750 kW and above)
    • Batteries can cost up to 500.00 each
    • Batteries are heavy
  • 3100 Series batteries are used for smaller units (50 to 150 kW)
  • 535 Series batteries are used for approximate (200 to 750 kW)


Our technical staff can make sure generator batteries are maintained to manufacturer’s specifications. All maintenance checks performed are to battery manufacturer specifications. Performing scheduled maintenance maximizes the life span of the battery(s).
  • Purchase the correct size battery for the application.
  • When determining battery, consider application the battery is used for.
  • Maintain the battery, steps to include:
    • Maintain a log of purchase date, determines when battery lifespan is approaching end.
    • Check specific gravity of electrolyte for each cell (must be to manufacturer specification).
    • Add appropriate mixture of electrolyte and distilled water to reach manufacturer specification.
  • Monitor battery according to manufacturer guidelines, including:
    • Insure a trickle charge is available at all times.
    • Test battery voltage with a multimeter at appropriate intervals.
    • Perform load test on battery at appropriate intervals.

When maintained properly the common lifespan of a quality battery can be up to three to five years depending on usage, charging setup and application.


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