What Battery Does A Generac Generator Use? (Size, Type)

generac generator battery size

Has your Generac generator refused to start? Maybe you need a new battery.

What Battery Does A Generac Generator Use?

It is common practice to select a battery capable of providing 75 percent of the generator’s wattage. For instance, a 4000W generator (4kW) needs a battery with a wattage of at least 3,000W.

The figures in the table below take that minimum requirement into account.

What size battery do I need for my Geneac generator?

15kW11,250 amps
16kW12,000 amps
17kW12,750 amps
18kW13,500 amps
20kW15,000 amps
22kW16,500 amps
24kW18,000 amps

The battery you select will determine whether or not your Generac generator even starts. Try to keep the following in mind:

1). What The Battery Does?

Have you ever stopped to wonder why a generator needs a battery? After all, you use these devices to generate electricity in an emergency. Why do they need batteries? Generators have a rotating shaft that works with the engine to turn the rotor. The interaction between the rotor (coils) and starter (magnetic field) allows the generator to make electricity.

But the generator cannot perform any of these tasks in the beginning because the engine is off. The machine needs a power source to operate the starter motor during those initial moments, allowing the component to spin the rotor.

The battery fulfills this role. Some generators don’t need batteries. Manufacturers call them direct current generators. But you’ve probably never heard of them because most generators on the market are alternating current models. They use batteries. Batteries will run the digital control panel and operate small motors.

2). Categories of Batteries

When you go battery shopping, your retailer will ask you to specify the category you prefer. Your options include:

  • Maintenance-free batteries are resistant to shock and high temperatures. They last a long time. One type requires the retailer to add electrolytes at the time of purchase. The second type already has electrolytes. It is also sealed at the factory. In both cases, maintenance is not necessary.
  • Ordinary batteries are cheaper and more stable. But they don’t last as long as their maintenance-free counterparts. Additionally, they require maintenance.
  • Dry-charged batteries have a negative plate with a high storage capacity.
  • Wet-charged batteries require small amounts of electrolytes.

3). Types of Batteries

  • Flooded Lead Acid – These are extremely popular. You find them in many backup energy systems in the US. But from what EC&M has seen, you can’t store them for more than six months (at 65 – 85 degrees F). Additionally, you must add water to them routinely.
  • Valve-regulated Lead Acid – These are superior to the flooded lead acid type. However, they are not as maintenance-free as people assume.
  • Lithium-ion – You find this type in smaller backup systems. Companies use them because of their compact, lightweight design.

According to Generator Source, most generators use lead-acid batteries. Therefore, this is the type with which you should concern yourself.

4). How Generac Generators Charge Batteries?

You can buy external chargers that charge a generator’s battery. However, Generac generators have an internal charging system that includes an alternator. The alternator and regulator work together to send electricity to the battery when you start the generator.

In other words, the battery only charges when the generator is running. The regulator matters because it makes sure the battery gets the correct amount of power, preventing overcharging. You can add a trickle charger.

Trickle chargers use small amounts of current to increase and maintain a battery’s charge over a long duration. People use trickle chargers when they want to keep a generator in storage for extended periods. The trickle charger keeps the battery alive and healthy.

5). Battery Size and Capacity

Selecting a battery means taking several variables into account. For instance:

  • CCA – The cold cranking amps reveal the battery’s ability to start an engine when the weather is cold. To be more precise, it shows you the number of amps the battery can support for thirty seconds at 0 degrees F. This unit tells you volumes about the battery’s performance.
  • C20 – The capacity index shows you the time it takes for a specific current to discharge continuously. It tells you the battery’s storage capacity.
  • AH – The ampere-hours reveal the battery’s capacity by showing you how long a battery takes to provide an amp per hour.

Many people emphasize the AH when they select a battery, but the CCA is more important in generators because the battery is concerned with a generator’s ability to start. This makes the CCA the most valuable component. A larger CCA points to a more reliable battery.

Regarding the size, you need a battery capable of providing 75 percent of a generator’s wattage. This is the minimum size requirement.

What Battery Do You Recommend For A Generac Generator?

You need a 12V lead-acid battery. The generator type (Diesel or Petrol) is unlikely to make a difference. However, you should check the manual to clarify because the model could influence your selection.

Consumers need a large-capacity battery for industrial generators. In other words, don’t assume that a conventional 12V lead acid battery will suffice in every situation.

Industrial generators are massive. This shows you the importance of identifying the type of generator you want before finding a suitable battery.

This isn’t necessary if you already have a Generac generator with a battery because you can use the old battery to find a replacement. But if you don’t have an old battery to guide you, the manufacturer will tell you everything you need to know.

They know their generator better than you. Therefore, the manufacturer is best placed to recommend a battery. This is why manuals are so important. They will tell you the specs you must look for when shopping for a battery.

How Long Does A Generac Generator Battery Last?

These batteries last three to five years. But you cannot guarantee that your battery will last that long. Use the following tips to extend the battery’s lifespan:

  • Make sure the battery matches the application. That means taking factors such as temperature into account during the selection process. The wrong battery won’t last long because it can’t tolerate the conditions.
  • Keep an eye on the electrolytes. Maintain the correct water levels, topping up where necessary.
  • Use a trickle charger to maintain the battery’s health.
  • Perform regular load tests.
  • Keep the battery clean and dry.
  • Keep the battery charged. Use a high-quality charger.

Replace the battery every two to three years. Fight the urge to continue using the battery until the generator can no longer start. This practice is dangerous because the generator may refuse to start during an emergency.

This is why many consumers take note of the purchase date. It allows them to replace the battery at the appropriate time. If you’re hesitant to replace a seemingly functional battery, test it for defects.

You can use a digital volt meter. Test the voltage at the battery terminals. Check both the battery and its charger, especially if the battery has refused to charge. Some batteries refuse to charge because the charger is defective. If the battery is well and truly dead, use the following steps to replace it:

  • Disconnect the charger.
  • Remove the outer panel.
  • Disconnect the old battery using a ½-inch wrench.
  • Install the new battery. Inspect the terminals before proceeding and clean them if they are dirty. If the terminals are clean, connect the positive terminal without bringing the wrench into contact with the battery’s metal parts. Do the same for the negative terminal.

Once you’re done, wash your hands thoroughly just in case battery acid touched your skin.

How Much Does A Generac Generator Battery Cost?

You can probably get a conventional Generac generator battery for $40 or less. But it depends on the type of battery and the system you want to buy. For instance, according to Forbes, the batteries in a 9kWh Generac PWRcell system cost $2,000 each.

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