Can I hook up a battery to my existing sump pump?

Hooking up a battery backup system to an existing sump pump is absolutely possible for most homeowners. Having battery backup power for your sump pump provides crucial protection against basement flooding during power outages. While professional installation is recommended, a DIY battery backup can be a complex but doable project for a handy homeowner.

What is a sump pump and why does it need battery backup?

A sump pump is used to remove water that collects in a home’s sump pit, typically located in the basement. The water enters the pit from the foundation drains that run around the foundation walls. The sump pump pumps the water up and out of the home through a discharge pipe. This keeps the basement from flooding during heavy rains or snowmelts when too much water enters the foundation drains. It also removes groundwater that naturally seeps into the basement over time.

Sump pumps usually run on regular AC power from the home’s electric system. However, if the power goes out during heavy rains or flooding, the sump pump won’t work. Without a backup power source, water can rapidly fill the sump pit and flood the basement. Having a battery backup ensures the sump pump keeps working even during blackouts to prevent expensive water damage.

How does a battery backup system for a sump pump work?

A basic battery backup system consists of a marine battery connected to a power inverter. The inverter converts the DC current from the battery into AC current that the AC-powered sump pump requires. The setup sits alongside the sump pump, connected so that power is automatically transferred to the battery and inverter when the main AC power fails.

More complex systems have a control box that monitors power and battery levels, charging the battery when needed and automatically switching over to battery power during an outage. Advanced systems can send alerts about power status and battery life to your phone or connect to home automation systems.

Can I connect a battery backup to my existing sump pump?

In most cases, yes. Any standard submersible sump pump can be hooked up to a battery backup system. Here are some tips for adding battery backup to an existing sump pump:

• Check that your pump is in good working order before connecting backup power.
• Measure the power draw of your sump pump. This determines how much power your battery backup needs to supply.
• Choose a marine battery or batteries with enough capacity to power the pump for at least 8 hours.
• Select an inverter that can handle the power needs of the pump.
• Install a control box if you want automated power transfer and notifications.
• Connect all components according to the manufacturer’s directions.

With the right batteries, inverter, and cabling, you can successfully hook up a backup power source to any conventional sump pump. Just take precautions to ensure everything is connected properly.

What do I need for a DIY battery backup for my sump pump?

Here are the main components you’ll need to assemble a DIY battery backup system:

Component	Details
Marine battery	12V deep cycle battery, sized according to your pump’s power needs
Inverter	12VDC to 120VAC inverter, again sized to your pump
Cables	12 gauge electrical cables for connections
Fuse/breaker	Fuse or circuit breaker for safety
Battery box	Protective enclosure for the battery
Bus bars	For connecting multiple batteries if needed
Controller (optional)	Controls battery charging and power transfer

You’ll also need basic tools and accessories for wiring and connecting the components securely.

How do I size the battery backup system correctly?

Figuring out the right battery and inverter size is crucial for proper functioning of your DIY sump pump backup power system. Here are the key factors to consider:

• Pump power rating – Check nameplate for wattage or amps. This is the minimum the system must deliver.
• Inrush current – The initial spike of power needed to start the pump. Usually 2-3 times the running watts.
• Duration – How long the system needs to run the pump during an outage. At least 8 hours is recommended.
• Battery capacity – Dependent on amp hour (AH) rating and whether using single or multiple batteries.
• Inverter wattage – Must be 20-30% higher than pump running watts.

Always size your battery backup to exceed the pump’s demands for safest operation. Consult an electrician if unsure about matching system components.

How do I wire up a sump pump battery backup?

Carefully follow these steps to wire up your DIY battery backup system:

1. Mount the marine battery securely on a base near the sump pit.
2. Install the inverter near the battery according to the manufacturer’s directions.
3. Connect the positive and negative battery terminals to the corresponding inverter terminals.
4. Connect the pump’s existing AC power cord to the inverter’s 120V AC output.
5. Connect a fuse/breaker between the battery and inverter if one is not already integrated.
6. Connect any control box and alarm/monitoring systems according to directions.
7. Run test cycles and confirm the pump activates on battery power when main power is disconnected.

Always follow proper polarity, cable gauge, and overcurrent protection when wiring. Consult an electrician if you are unsure of any part of the installation and connections.

What size marine battery is needed?

Choosing the proper marine battery size depends on several factors:

• Your sump pump’s wattage rating
• The expected runtime needed during an outage
• Whether you’ll use a single battery or multiple batteries
• The battery’s ampere-hour (AH) capacity

As an example, a 1/2 HP sump pump that draws around 500 watts would need at least a 100AH 12V marine battery for an 8 hour runtime. Using two batteries doubles the available power. Go even bigger if you can, allowing longer runtimes during extended outages.

Can I use a car battery instead?

It’s not recommended to use a regular automotive starting battery for a sump pump backup. Here’s why:

• They’re not designed for deep discharge needed for long runtimes.
• Don’t have the sustained power delivery that a deep cycle marine battery provides.
• Often have less capacity than an equivalent marine battery.
• Not created for constant charging and discharging.
• Could fail quickly when depended on for primary backup power.

Get a true deep cycle marine battery formulated to withstand repeated deep discharges for the most reliable performance.

How long will a marine battery run my sump pump?

Approximate marine battery runtime depends on these factors:

• Sump pump power rating
• Marine battery capacity (AH)
• Age and condition of the battery
• Whether pump runs continuously or sporadically
• Single or multiple batteries

For example, an average 500W sump pump paired with a 100AH marine battery could provide 6-8 hours of continuous runtime. Batteries in good condition powering an occasional pump cycle would extend runtimes further.

Can I connect two batteries together for longer backup time?

Yes, you can double your runtime by wiring two marine batteries together. The batteries are connected in parallel, meaning the positive terminals are connected to each other, and the negative terminals are connected. This keeps the voltage the same at 12V but doubles the capacity and available power.

When wiring two batteries:

• Use similar size and capacity batteries.
• Utilize short, thick jumper cables between the batteries.
• Ensure terminals are clean and corrosion free.
• Follow proper polarity – positive to positive, negative to negative.

Take care that connections are tight and secure. Adding bus bars can create reliable parallel connections between batteries.

What size inverter is needed for a sump pump battery backup?

Selecting the correct inverter involves:

• Checking the power rating of your sump pump – wattage or amps.
• Accounting for startup surge, which can be 2-3 times the running load.
• Getting an inverter rated at least 25% higher than the pump’s demands.
• Ensuring the inverter can accept the proper battery input voltage, typically 12V.
• Choosing a true sine wave output for compatibility.

As an example, a 500W sump pump would need at least a 750W 12VDC input, 120VAC output inverter, preferably 1000W or larger.

What gauge wire should be used?

12 AWG wire is recommended in most sump pump battery backup installations. Key points about proper wiring:

• 12 AWG can safely handle up to 20 amps on a 12V DC system.
• Ensure wires are sized for expected system current, with margin.
• Use stranded wire for flexibility and corrosion resistance.
• Separate AC and DC wires.
• Use proper terminal connections and insulating covers.
• Don’t undersize wires or overheat and fire risks occur.

Refer to wiring diagrams and consult an electrician to ensure proper wire sizing for your system’s power needs.

What precautions should be taken when installing a sump pump battery backup?

Key safety precautions include:

• Isolate AC power supply before starting work.
• Wear protective equipment like gloves and eyewear.
• Double check all wiring before restoring power.
• Ensure terminals and connections are tight and secure.
• Use proper fuse/breaker overcurrent protection.
• Prevent short circuits by insulating exposed wiring.
• Allow ventilation around batteries to prevent gas buildup.
• Handle batteries carefully – they contain corrosive acid.
• Have an electrician review the installation if unsure.

Rushing the process or ignoring safety procedures can put you, your home, and equipment at risk. Take things slow and get help when needed.

Conclusion

Installing battery backup power for your existing sump pump is an achievable DIY project that provides tremendous protection against basement flooding. While professional installation is the safest route, a technically inclined homeowner can successfully assemble their own system with the right components and preparation.

The most critical steps are properly sizing the marine battery and inverter to adequately power the pump, wiring all connections securely, and practicing essential safety precautions. Patience and caution reduce the risk of errors and equipment damage. Get assistance from an electrician if any part of the process is unclear before proceeding.

With a reliable sump pump battery backup in place, you can rest easy knowing your basement is safe from water damage, even when the power goes out.