Power outages and water backflow can threaten basement protection. This article spotlights five dependable batteries designed for sump pump backup systems, spanning AGM sealed lead-acid and modern lithium options. Each product is reviewed for maintenance needs, compatibility, and runtime under typical duty cycles. Use the buying guide below to compare capacity, form factor, and compatibility with popular back-up pump brands.
| Product | Brand | Battery Type | Approximate Capacity | Notes |
|---|---|---|---|---|
| The Basement Watchdog BW-27AGM | THE BASEMENT WATCHDOG | AGM Sealed Lead Acid | 27Ah (approx.) | Maintenance free; 40–48 hour protection depending on system |
| Westinghouse Sump Pump Battery Back Up | Westinghouse | Sealed Lead Acid AGM | 75Ah | Fully charged; compatible with multiple back-up systems |
| Mighty Max Battery 12V 100Ah (Wayne, Zoeller, etc.) | Mighty Max Battery | Sealed Lead Acid AGM | 100Ah | UL Certified; out-of-the-box maintenance free |
| Mighty Max Battery 12V 75Ah (Wayne ESP25) | Mighty Max Battery | Sealed Lead Acid AGM | 75Ah | Factory activated; maintenance free |
| Mighty Max Battery 12V 100Ah (Zoeller compatible) | Mighty Max Battery | Sealed Lead Acid AGM | 100Ah | Long service life; wide temperature tolerance |
THE BASEMENT WATCHDOG BW-27AGM Maintenance Free Battery
THE BASEMENT WATCHDOG BW-27AGM is an AGM sealed lead-acid backup battery designed for sump pump systems. It is maintenance free, requiring no fluid additions or water top-offs. It provides substantial run-time support for Basement Watchdog systems, with protection windows up to 40 hours for BWD12-120C+ configurations and up to 48 hours for compatible BWSP+ and BW4000/CITS-50 systems, depending on a 10% duty cycle. This model targets installations where minimal upkeep is preferred and rapid readiness after a power outage is essential.
Westinghouse Sump Pump Battery Back Up AGM 12V 75Ah
The Westinghouse backup battery is a maintenance-free AGM sealed lead-acid unit rated at 12V 75Ah. It ships fully charged and includes carry handles for easy transport. It’s designed for compatibility with multiple back-up sump pump systems beyond Westinghouse, including Wayne, Basement Watchdog, and Zoeller, offering a flexible option for homes with varied back-up configurations. Its ready-to-use status reduces the setup complexity during emergencies.
Mighty Max Battery 12V 100Ah for Wayne Sump Pump
The Mighty Max ML100-12 is a 12V 100Ah sealed lead-acid battery built for high-demand back-up pumps. It is UL certified and ships as a maintenance-free unit, meaning no water top-ups are required. Its large capacity supports extended runtimes and compatibility with Wayne and other back-up pump models. Typical features include a durable case design and suitability for use in varied temperatures, contributing to dependable performance when mains power is interrupted.
Mighty Max Battery 12V 75Ah for Wayne ESP25 Back-Up
This Mighty Max ML75-12 SLA is a 12V 75Ah sealed lead-acid battery designed for back-up pumps like the Wayne ESP25. It arrives factory activated and maintenance free, with no need for water additions. Its compact dimensions and reliable discharge characteristics make it a common replacement option for ESP25 and similar models, delivering predictable performance under power outages.
Mighty Max Battery 12V 100Ah For Zoeller Sump Pump
The Mighty Max ML100-12 is suitable for Zoeller sump pump backup applications as a 12V 100Ah sealed lead-acid battery. It is UL certified and ships maintenance-free, requiring no fluid top-offs. The large capacity supports longer backup durations, while the sealed design minimizes spill risk and simplifies storage and installation in tight basements or crawlspaces. Compatible with a variety of back-up pump brands, it is a practical, long-life option for many sump configurations.
Buying Guide
Key considerations when choosing a sump pump backup battery include compatibility, capacity, maintenance requirements, and lifespan. AGM (absorbed glass mat) sealed lead-acid batteries are common for back-up pumps due to their reliability and maintenance-free nature, though newer lithium options offer higher energy density and lighter weight. Capacity should align with the sump pump’s continuous load and your expected outage duration; larger homes or higher head heights benefit from higher Ah ratings. Consider physical dimensions and mounting orientation, as some units are designed for vertical or horizontal placement. Temperature tolerance and vibration resistance also affect performance in unheated basements. Finally, verify compatibility with your specific sump pump model or brand to ensure seamless operation during outages, and assess whether a maintenance-free design fits your lifestyle or property requirements.
In selecting a backup battery, weigh the trade-offs between traditional AGM batteries, which are robust and cost-effective, and LiFePO4 options, which typically offer longer life and lighter weight but at a higher upfront price. For typical residential use, AGM batteries from reputable brands like Mighty Max, Westinghouse, and Basement Watchdog provide solid reliability and broad compatibility with popular sump pump systems. Always follow manufacturer guidelines for installation, ventilation, and disposal at end of life.