Batteries are an integral part of a generator set. Many generator service providers report the most common reason for generator failure is a failed battery. This article will provide information on styles of batteries available, battery connection (multiple batteries), selection and maintenance of batteries.
Role of Batteries
The main role of an emergency generator batteries is to provide power to the generator engine starter with power when a facility power outage occurs. Depending on the configuration of the generator system setup, batteries can also provide:
• Power to the digital control panel.
• During generator operation, battery power can provide power to ancillary panes, small motors that operate on DC current and any DC supplied device within the enclosure.
• If a secondary or redundant battery set is used in an enclosure, the primary battery source can provide backup power to the secondary or redundant set.
• Automatic louvers and vents are powered by an AC source. When the system automatic transfer switch allows power to the grid, power is routed to vents and louvers.
Types of Batteries Used in Industrial Power Generation Systems
Most generator sets use a standard lead acid battery. There are two types of batteries available:
• Maintenance Free – Often referred to as a sealed battery. Cannot add electrolyte or check specific gravity of battery.
• Conventional – Cells have individual caps for filling and testing electrolyte.
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 options.
Common Sizes of Commercial Generator Batteries
The size of the battery is dictated by generator size and configuration the battery is connected in.
Example: A 350 kW generator has only one 4D battery while a 1500 kW and 2MW units have two 8Ds or four 4Ds depending on the enclosure. Below are examples:
• 4D and 8D batteries are mostly used for larger generator applications (500 kW and above).
o Batteries can cost up to $500 each.
o Batteries are heavy.
• 3100 Series batteries are used for smaller units (30 to 150 kW).
• 535 Series batteries are often used in mid-sized gensets (150 to 500 kW).
Two or more 12 VDC (depending on current requirements) are connected in a series. Smaller configurations require 12 VDC and can use one or more batteries. If a second set of batteries are require they are connected in parallel. For common battery connection configurations, refer to Figure 1.
Figure 1, Battery Connections
How to Maximize Lifespan
Many things contribute to maximizing the life span of a battery. Below is a list to consider when purchasing and maintaining the battery:
• Purchase the correct size battery for the application.
• When determining battery, consider application the battery is used for.
• Maintain the battery, steps to include:
o Maintain a log of purchase date, determines when battery lifespan is approaching end.
o Check specific gravity of electrolyte for each cell (must be to manufacturer specification).
o Add appropriate mixture of electrolyte and distilled water to reach manufacturer specification.
• Monitor battery according to manufacturer guidelines, including:
o Insure a trickle charge is available at all times.
o Test battery voltage with a multimeter at appropriate intervals.
o Perform load test on battery at appropriate intervals.
When maintained properly the common lifespan of a quality battery can be up to three years or 32-5 depending on usage, charging setup and application.
To make sure the generator set will start on demand the batteries must be maintained and fully charged at all times. Most systems today have an installed charger. For older generator sets that do not have battery charger options, a portable charger must be used when voltage drops below minimum. Some charging options include:
• Battery charger installed but must be activated manually, generally has automatic shutoff when battery is charged. This charger must be shutoff manually after charge complete.
• Battery charger connected to electronic control system. On demand trickle charge with automatic shutoff.
• Multiple generator systems can have banks of batteries. Depending on application, these systems can have:
o Alarm and monitoring systems in local and remote spaces.
o Uses a converter to change AC to DC for battery charging functions.
o Uses inverter to change DC to AC for alarms and indications.
Determine Battery Size
Many factors add into battery size. It is important to check all specifications of the battery prior to purchase. Following below steps will aid in purchase:
• Make sure battery type is approved for application (high temp, low temp, hazardous atmosphere etc.).
• Check generator set manufacturer specifications for battery recommendations.
• If, battery is available compare installed battery with manufacturer specifications. If installed battery exceeds manufacturer’s specifications, choose installed battery.
• Review data from research to insure accuracy and purchase.
How and Where to Buy
Many vendors of batteries are available. It is important to consider cost vs performance when selecting a vendor for battery purchase. Some things to consider are:
• Lifespan of battery.
• Meets or exceeds generator set manufacturer specifications.
• Warranty of battery.
• Vendor ability to deliver battery when needed.
At Generator Source we take pride in shipping batteries that are new or in good condition. For a battery to be qualified as good condition it must meet manufacturer’s specifications and have a low hour count.
Batteries are used in daily operations in the shop. The shop also has battery carts available for their use on large applications. Our battery stock fills multiple rooms.