Sump Pump Battery Buying Guide

A reliable backup sump pump system is crucial for preventing costly water damage, but selecting the right battery can be a complex process. That's why we're here to be your partner, providing the expertise you need to navigate your options with confidence.

Here's the essential guide to choosing the perfect battery and backup system for your home, updated with specialized details on battery types.

What is a Deep Cycle Battery?

Before you select a battery, it's important to understand that you cannot simply connect any battery (like the one used to start your car) directly to your existing AC-powered sump pump.

Your main pump has a high ampere draw and requires too much power for a simple battery hookup to sustain it. A direct connection will, at best, run your pump for only 5 to 15 minutes. To achieve reliable, long-lasting backup power, you'll want to use a dedicated system that is connected to a deep-cycle battery.

When shopping, you'll see the term deep-cycle. This is a critical designation, as it refers not to the type of battery, but to its charging cycle.

• Deep-cycle batteries are specifically designed for constant charging and discharging (cycling) without rapid degradation. They feature thicker plates and can be discharged to a much greater degree than "starting batteries" (like a standard car battery).
• Starting batteries are designed only for short bursts of high current, which is why they are insufficient for long power outages.

Selecting Your Backup System

Your choice of system will determine the pump and power requirements, but both require a deep-cycle battery.

Auxiliary Power System (The Inverter)

This is a premium, often more expensive, system that offers maximum convenience by leveraging your existing primary pump.

This system operates the AC-powered pump you already have installed, eliminating the need for an additional pump in the pit. It acts as an inverter, converting the DC power from the battery to the AC power required by your main pump.

You'll need to find your pump's running amp draw to select the right-sized inverter system and you must connect a minimum of one deep-cycle battery, though multiple batteries can be connected for extended runtime.

The Dedicated Backup Pump (12-Volt System)

This is typically the less expensive route, relying on a completely separate, low-voltage pump.

This system requires you to install a separate, DC-powered pump right alongside your main pump in the pit. The entire system runs directly off of a 12-volt deep-cycle battery.

How to select the right sump pump battery

Now that you understand the importance of a deep-cycle battery, you can select the type that best suits your preferences in terms of maintenance, performance, and budget.

Wet Cell (Flooded) Batteries

These are the most common and often the most inexpensive option, made up of lead plates submerged in a liquid electrolyte (battery acid).

Wet cell batteries require the most hands-on maintenance. After initial filling with acid, you must periodically inspect the cells and add distilled or demineralized water to prevent the lead plates from drying out. The term "maintenance-free" can be misleading for some sealed wet cell types, as they still require checking to prevent the cells from losing capacity.

Maintaining these batteries exposes you to lead, acid, and noxious gas, and carries a risk of explosion, making diligent safety practices essential.

AGM (Absorbed Glass Mat) Batteries

AGM batteries are a technologically superior choice, perfect for homeowners seeking a true set-it-and-forget-it solution.

AGM batteries are truly maintenance-free. Their unique design encapsulates the lead-acid cells in a glass fiber material that absorbs the electrolyte, meaning you never have to add water.

Because they won't leak if punctured, they are considered safer to use. The design allows for increased cell density, resulting in higher energy capacity and faster charging times. While they tend to be more expensive, their many safety and performance features often make the cost worthwhile.

Gel Batteries

Gel batteries are ideal for specialized or extreme conditions, though they have certain performance trade-offs.

Similar to AGM, these batteries are maintenance-free. They are filled with a gelled electrolyte using silica gel, which will not evaporate. Their design makes them extremely durable and ideal for situations with extreme temperatures and vibrations, which is why they are often found in racing, off-road, or wind and solar applications.

The gel design prevents the rapid movement of the electrolyte. This reduces the ion exchange and peak current capacity, leading to slower charging times and less peak current output compared to AGM or wet cell types.

Pro Tip: Never place a battery directly on the ground, as this can drain the battery and reduce its lifespan. Use a battery case or keep it elevated a few feet off the ground, and clean your battery terminals regularly per the manufacturer's recommendations.