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Why Do Generators Need Batteries? Full Explanation

Why Do Generators Need Batteries? Full Explanation

Generators can be a lifesaver during a power outage. They provide backup power to keep your lights on, your fridge running, and charge your devices. But why do generators need batteries if they’re already powered by gasoline?

The battery in your generator has two primary purposes. The first one is to provide power to the starter motor. This is the engine component that starts the generator when you turn it on. The second one is to power the electronics, including the controls and lights.

This article covers everything you need to know about generator batteries. Below, I’ll discuss their purpose, how to pick the right size battery for your generator, and how to properly care for them.

The Reason Why Generators Need Batteries

To understand this, you need to first learn how generators work:

A generator is an electrical machine that converts mechanical energy into alternating current (AC) electricity. The engine drives a rotating shaft, which spins the generator’s rotor. The rotor has coils of wire wrapped around it, and as it turns, these coils cut through the magnetic field produced by the generator’s stator. This interaction between the stator’s magnetic field and the rotor’s coils produces electricity (source).

The battery is connected to the generator’s starter motor. When you turn on the generator, the starter motor uses battery power to spin the rotor. That means the battery provides an initial power source for the starter motor when the engine is not running. It also provides power for the generator’s electrical accessories, such as lights and USB charging ports.

Still, not all generators need a battery. Some have a self-contained starting system that doesn’t require an external power source. These are called direct current (DC) generators. However, most generators on the market are alternating current (AC) generators that require a battery.

How To Pick the Right Size Battery for Your Generator

The size of the battery you need depends on the wattage of your generator. As a general rule of thumb, you need a battery that can provide at least 75 percent of your generator’s wattage. For example, if you have a 4,000-watt generator, you’ll need a 3,000-amp battery.

It’s also important to choose a battery with a high reserve capacity. This is the time measured in minutes that the battery can provide power at a given discharge rate. For example, a battery with a reserve capacity of 60 minutes can provide power for one hour at a discharge rate of 25 amps.

A higher reserve capacity means that the battery will last longer before it needs to be recharged. This is important because you never know how long a power outage will last.

Do Diesel Generators Need a Battery?

Diesel generators usually don’t need batteries because they have a self-contained starting system. However, if your diesel generator features a key start, it will require a battery to power the starter.

The good thing about diesel generators is that they’re very efficient. They have a high power-to-weight ratio, so they can generate a lot of power without being too big or heavy.

Overall, if you want the convenience of an electric starter, you’ll need to make peace with having a battery in your generator. If you don’t mind using a recoil starter, you will never have to worry about a gen-battery.

How To Care for Your Generator Battery

Generator batteries are maintenance-free, meaning you won’t have to add water or perform any other type of upkeep.

The best way to care for your generator battery is to keep it clean and dry. If you live in an area with high humidity, you can store your battery in a plastic bag to keep it from rusting.

You should also check the terminals and cables on your battery every few months to ensure they’re clean and tight. Loose terminals can cause your battery to lose power, resulting in startup issues.

I have also found it helpful to keep a spare battery on hand. If your generator battery does die, you can quickly swap it out for a spare and get the equipment back up and running in no time.

Alternatively, you can get a battery charger for your generator. This will keep your battery ready to go, even if you don’t use your generator for a while.

How Long Does a Generator Battery Last?

The average generator battery will last for about 3-5 years with proper care. However, if you live in a hot climate or use the generator frequently, your battery may not last as long.

To extend the life of your generator battery, try to avoid running it all the way down. This will degrade the battery by up to 70% of its original capacity in just a few hundred cycles. This means you should manually start your generator once in a while. That’s how you’ll maintain its voltage even when the generator is mostly idle.

Is It Okay To Trickle Charge Your Generator Battery?

It’s okay to trickle charge your generator battery. In fact, it can help extend the life of your battery. However, if you’re using a standard charger, be sure to disconnect the battery from the generator.

A trickle charger is a battery charger that slowly charges a battery over time. It’s designed to be left connected to the battery for long periods, perfect for generator batteries.

Trickle chargers are beneficial if you live in an area with long winters. By keeping your generator battery trickle-charged, you can prevent it from losing power due to cold weather.

I have seen people trickle charging batteries while still connected to the generator, but this is not a good idea. It is better to disconnect the battery and trickle-charge it separately.

Do Generators Have Built-In Battery Chargers?

Most generators don’t have built-in battery chargers. However, there are a few models that do have this feature. Honda, for example, has included this feature on some of its generators.

However, even if your generator has a built-in battery charger, keeping a separate charger is still a good idea. That way, you won’t have to waste fuel to maintain voltage in your battery. As mentioned, it’s better to trickle-charge your generator battery separately.

What To Do When Generator Battery Isn’t Charging

There are a few things you can do if your generator battery isn’t charging.

First, check the terminals and cables on your battery. Loose terminals can break the connection between the battery and the electrical outlet. If the terminals and cables are tight, you may need to replace the battery.

Another possibility is that the charging system on your generator isn’t working properly. This is a serious problem that will require the attention of a qualified technician.

However, this is a general overview of what to do if your generator battery isn’t charging. For more specific advice, consult your generator’s owner’s manual. You can also ask a question in your favorite generator forum to get opinions from other users. Model-specific forums are particularly helpful.

How Many Volts Is a Generator Battery?

Most small generators are 12 volts, but some units may need 24V or 48V to run. A higher voltage means that the battery can store more energy and power a bigger generator than you could with a smaller option.

During run time, the battery powers the electrical components of the generator. This includes the control panel, the lights, and any other accessories plugged into the generator’s USB ports.

These electricals don’t need much power, so a 12-volt battery is usually enough to keep them running for a long time. This is especially true for generators that have an automatic shut-off feature.

If you want to increase the voltage of your generator battery, you can do so by adding more batteries in parallel. This means connecting the positive terminal of one battery to the positive terminal of another battery and doing the same for the negative terminals.

How To Tell the Difference Between a Dead and Low Charge Battery

If your generator battery is dead, it will not hold a charge. A low-charge battery can still be up and running, but it won’t be able to power the generator.

You’ll need to use a voltmeter to tell the difference between a dead battery and a low-charge one. A voltmeter is a tool that measures the voltage of a battery.

If the voltmeter reads a little lower than 12 volts, the battery is low-charge but not dead. If the voltmeter reads closer to zero volts, the battery is dead and needs to be replaced.

Can a Battery Pack Replace a Generator?

A battery pack alone cannot replace a good generator. It just can’t provide the reliability you need from a backup system. However, it can work if it’s hooked to a solar and wind power system.

A generator is a mechanical device that converts mechanical energy into electrical energy, while a battery pack is just that – a collection of batteries that stores electrical energy. They cannot be used interchangeably.

Essentially, a battery pack can be used to supplement a generator. For example, if you have a generator that can provide 1000 watts, but you need 1200 watts to supply enough power to your devices, you could use a 200-watt battery pack to supplement the generator.

Alternatively, if you have a generator that can provide 1000 watts, but you only need 800 watts, you could use the battery pack to store the extra 200 watts.

A battery pack can also be used as a backup for a generator. If your generator fails or runs out of fuel, you could use the stored energy in the battery pack to power your home.

In short, a battery pack alone cannot replace a generator, but it can be used to supplement or back up a generator.

Can You Jump Start a Generator Battery?

You can jump-start a generator battery. This is called “battery boosting.” And you’ll need two batteries: the generator’s battery and another battery of the same voltage. You’ll also need jumper cables.

Here’s how to do this safely:

  1. Connect the generator’s battery’s positive terminal to the other battery’s positive terminal.
  2. Connect the generator’s battery’s negative terminal to the other battery’s negative terminal.
  3. Start the generator.
  4. Let the generator run for 30 minutes to charge the battery.
  5. Disconnect the jumper cables in reverse order: start with the negative terminal, then disconnect the positive one.

Note: If you don’t have another battery, you can jump-start the generator’s battery with a car battery. However, you should only do this if you know what you’re doing. You’ll also need at least 30 minutes for the car battery to charge the generator’s battery.

How Much Does a Generator Battery Cost?

A good generator battery can cost anywhere from $100 to $400. However, it’s important to note that price is not always indicative of quality, so it’s best to base your purchasing decision on other criteria.

To get the most bang for your buck, research the different batteries available and read reviews from other consumers. It’s also a good idea to talk to someone who knows more than you do about generators and batteries before purchasing.

You want to get a generator battery that is big enough to meet your needs. If you’re not sure what size battery you need, err on the side of caution and ask a professional first. They should be able to give you sound advice based on their experience with gen-batteries.


A battery is an integral part of any electric start generator. It powers the ignition system, which is what starts the engine. If your battery is dead, your generator won’t start.

While you can jump-start a generator battery using another battery, it’s good to have a backup plan. This could be a backup generator or a battery pack.

When shopping for a generator battery, don’t just go for the cheapest option. Do some research and find a battery that’s the right size for your needs and has good reviews. That’s how you’ll get the most bang for your buck.

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