How to Choose the Best Battery for Backup Sump Pump System.

(Last Updated On: November 20, 2023)

Choosing the Best Battery for Backup Sump Pump Use

A battery backup sump pump system plays an important role in ensuring that your basement remains free of water. The battery for a sump pump that is used to power such a system is equally important. If the battery you use is of poor quality, even the best backup system available will be utterly useless.

Whether you have had to at some stage clean up a flooded basement or simply prefer to be prepared, you know that prevention is always better than cure.

When there is a power outage, a sump pump won’t work without backup power provided by a sump pump battery.

The problem is that there are many types of batteries available and very few are labeled as a battery for backup sump pump use.

This makes it very difficult to select the best one. The Renogy Deep Cycle AGM Battery is an excellent sump pump battery at an excellent price.

Renogy Deep Cycle AGM 12 Volt 100Ah Battery, 3% Self-Discharge Rate, 1100A Max Discharge Current, Safe Charge Appliances for RV, Camping, Cabin, Marine and Off-Grid System, Maintenance-Free
  • Renogy AGM Batteries: Trusted Worldwide, Exceptional Safety, Extreme Performance!
  • 【Warranty】2-year material and workmanship warranty guarantee.
  • 【Leading AGM Batteries】With over 230,000 units sold worldwide in the past six years, Renogy Deep Cycle AGM batteries have earned widespread trust from customers globally.
  • 【Exceptionally Safe Chemistry & Minimal Troubleshooting】Compared to batteries made of other chemistries, Renogy Deep Cycle AGM batteries offer exceptional safety due to their higher chemical stability. Their integrated internal structure and sealed design spare you from intricate internal troubleshooting, a feature not shared by lithium batteries.
  • 【Better Performance at Extreme Temp】The upgraded electrolyte formula ensures outstanding discharge performance within a temperature range of -4 to 140°F/ -20 to 60°C, surpassing that of other counterparts. You can use the battery at extreme temperatures without concerns about discharging performance in RVs or cabins.
  • 【Power Most Appliances】 Featuring a 1100A (5 seconds) max discharge current and providing consistent, stable discharge, the battery can power most home appliances, including a fridge, microwave, CPAP, coffee maker, laptop, and more.

It is possible to buy a backup sump pump that already has a battery included. However, if you don’t have one or need to replace a battery, this article will help you decide which one is best for your needs.

Terms Used to Describe Batteries

When you want to buy a backup battery for your sump pump, you’ll come across many terms being used such as:

  • wet-cell
  • gel-celled
  • deep-cycle
  • maintenance-free
  • marine
  • solar

As these terms are used interchangeably to describe lead-acid batteries. Finding the right one to buy can be very confusing.

Let’s look at battery terminology to help you distinguish one battery from the next. Then you’ll be able to select the perfect type of backup battery for your sump pump.

The Basement Watchdog battery 30HDC140S must have the acid purchased separately. You can see what is needed below. It is an unsealed lead acid battery that needs some maintenance.

THE BASEMENT WATCHDOG Model 30HDC140S Big Standby Sump Pump Battery
  • Pumps intermittently for days to help protect your basement
  • Provides longer run times than the Basement Watchdog Emergency Standby Battery (model 24EP6)
  • Accommodates the Basement Watchdog fluid sensor to sound an alarm when distilled water is needed
  • Shipped without battery fluid to remain fresh until activated
  • Can be easily and safely filled with a 6 qt. battery fluid pack (sold separately Model # Z-PACK)
  • 1 year limited warranty

Maintenance-Free Batteries

Batteries labeled “maintenance-free” can be a misnomer depending on the type of battery.

For wet-cell batteries, maintenance-free means that the battery is sealed and sometimes valve-regulated (VRLA).

With this type of battery, the oxygen and hydrogen produced by the battery are recombined back into water, and this reduces rapid evaporation and leakage.

Although they are called “maintenance-free”, it is really misleading as they still need maintenance to avoid the cells from drying out and losing their cycle capacity.

The WAYNE WSB1275-75Ah Maintenance-Free sump pump battery is a sealed lead acid (SLA) battery.

Sale
Wayne WSB1275-75Ah Maintenance-Free Battery – Recommended ESP25n, WSS30Vn Basement Guardian Back-Up Sump Pump Systems
  • Always Have a Plan – Wayne WSB1275 battery helps keep your basement sump system running, especially when you lose electricity.
  • Back-Up Ready – Compatible with the Wayne ESP25n, Wayne WSS30Vn, Wayne Basement Guardian, and all other Wayne battery back-up systems.
  • Fully Charged – 12V/75Ah sealed battery comes fully charged with carry handles for convenience.
  • Additional Features – Sealed lead acid battery is easy to install or remove. Battery is rechargeable for repeated use. No need to mix acid and add water – this battery is maintenance free!
  • Quality You Deserve – 1-year limited warranty for dependable performance.

Deep-Cycle Batteries

A deep-cycle battery is not a type of battery but describes the battery’s charging cycle. This term is important to be aware of when shopping for a sump pump battery.

This type of battery is made to constantly charge and discharge (cycle). This doesn’t reduce the expected life of the battery. Although they can’t deliver as high a current as wet-cell batteries can, they have thicker plates that can be discharged to a much higher degree.

Marine and RV type batteries are often a compromise between the higher starting capacity and the lower discharging capacity characteristics.

These types of batteries are rated in ampere-hours (AH). The AH rating indicates the number of amps the battery can provide for more than 20 hours. If a battery for example has a rating of 100 AH, it would provide 5 amps an hour (100/20) for 20 hours. The AH rating is normally printed on the battery.

Types of Lead-Acid Batteries

People are generally familiar with lead-acid vehicle batteries used in cars. This type of battery is designed to provide a big current for a short period.

The capacity and output of the battery is rated in CCA (cold cranking amps). The number of CCAs is often printed on the battery. This type of battery is not suitable as a battery for sump pump use except in emergencies. For example: If the backup battery has failed, then a car battery could be used temporarily.

Gel Batteries

A gel battery is filled with a gelled electrolyte that uses silica gel. The small satchels often found in vitamin bottles use the same type of gel as these batteries.

These batteries are “maintenance-free” as the gel won’t evaporate, making them ideal in situations where there are extreme vibrations and temperatures.

They are therefore most often used in off-road and racing vehicles, as well as solar and wind applications. As the gel design prevents fast movement of electrons, maximum current capacity and ion exchange are reduced. Also, the time to recharge the battery is slowed down.

Wet Cell Batteries

Wet-cell or “flooded” type batteries are inexpensive and are mostly found in automotive applications. They provide short bursts of current to start a car but are not suitable as battery for backup sump pump use. Generally, they are not suitable for use over extended periods. However, the deep-cycle versions can be used, but they are not the best choice.

Wet-cell batteries have lead plates that are submerged in an acid electrolyte and come in unsealed and sealed versions. Both versions need a periodic inspection to prevent the lead cells from drying out.

Maintaining these batteries is dangerous as it exposes you to noxious gas, acid, lead, and the risk of explosion.

AGM Battery For Backup Sump Pump Use

Absorbed Glass Mat (AGM), no-maintenance batteries are the best battery for backup sump pump use.

AGM batteries really are maintenance free. That is because homeowners don’t have to check or replace the water (acid electrolyte) levels.

Here we have a very popular low cost AGM battery. Note thatthe Weize deep cycle AGM SLA battery has a 100AH capacity where others are just 75AH.

Sale
WEIZE 12V 100Ah Deep Cycle Battery, Group Size 31 Battery for RV, Solar, Camping, Cabin, Marine and Off-Grid System, 1150A Max Discharge Current, 3% Self-Discharge Rate
  • Deep Cycle Battery 12V 100 Amp Hour Sealed Lead Acid Rechargeable ; Parcel: 1 x Battery (screws included, but no wire harness or mounting). Terminal: Left : Positive (+)-Red, Right: Negative (-)-Black.
  • Dimensions: 12.99x 6.73x 8.43 inches (Replace UB121000, Renogy 100 AMP Hour). This sealed lead acid battery has a maintenance-free and spill proof design.
  • This 100AH SLA battery fits applications like wheelchair, scrubber, generator, lawn & garden, trolling motors. Also great for commercial customers in for schools, healthcare, and property management.
  • Also For Electric Vehicles, Golf Carts, Hunting, Lawn and Garden Tools, Portable Tools, Toys and Hobby, UPS System, Industrial and Medical Equipment,Emergency Lighting, Leisure, Alarm Security and more.
  • We aim for quality followed up with quality customer service, Amazon doesn’t deal with the return of battery-related products, so please contact the seller directly. Weize support team is on standby for YOU.

Although they are generally more expensive, their better performance and safety features are well worth the price.

The unique design of AGM batteries surrounds the lead plates in a glass fiber material which absorbs the acid electrolytes. So, the plates are not completely submerged in liquid acid, but only kept wet. Which also means that the batteries won’t leak when punctured, meaning they are relatively safe to use.

This design also allows the cells to be stacked together closer, enabling faster charging times and increased energy capacity.

As previously mentioned, gelled batteries silica gel and acid. AGM batteries provide all of gelled batteries’ advantages but without exhibiting their disadvantages.

An AGM battery’s acid is contained by the fiberglass mat but is still available for the battery plates, resulting in faster acid migration. This means the battery has a higher rate of absorption and delivery of current.

Most gelled batteries need to be charged at slower rates to prevent excess gas from damaging cells. However, an AGM battery is charged at standard voltages. Without needing to buy special chargers.

There is also no discharge or charge current limits. With its low internal resistance, the buildup of heat is virtually non-existent during heavy and normal charge and discharge currents.

Other gel type batteries could potentially lose capacity due to gaps developing in the gel if they are overcharged.

If you can afford the best long lasting 125AH Zoeller 508 Aquanot battery – get it. Few batteries have a 125AH rating which will keep you sump pump going longer than the lower amp hour (AH) batteries.

12V 125AH SLA Battery for Zoeller 508 Aquanot Backup Sump
16 Reviews
12V 125AH SLA Battery for Zoeller 508 Aquanot Backup Sump
  • ML125-12 SLA is a 12V 125AH Sealed Lead Acid (SLA) rechargeable maintenance free battery – UL Certified
  • Dimensions: 13.11 inches x 6.81 inches x 8.74 inches. Listing is for the Battery and Screws only. No wire harness or mounting accessories included.
  • SLA / AGM spill proof battery has a characteristic of high discharge rate, wide operating temperatures, long service life and deep discharge recover.
  • Rechargeable battery that can be mounted in any position, resists shocks and vibration. Long lasting high performance in high and low temperatures.
  • Backed by a 30 day refund policy and full 1 year warranty.

An AGM battery’s self-discharge is typically between a low 1% and 3% on average per month, allowing them to be stored for longer periods without charging. AGM batteries can be recharged to almost full capacity even after being discharged for a month or more.

An AGM battery for backup sump pump use preserves water through electrolysis as it charges. This is done by oxygen and hydrogen recombining to convert to water while inside the battery. Water loss in other types of gelled batteries is common, especially in hotter climates. Which often times results in the premature death of a battery after only a few years. As water loss is not a problem with an AGM battery, it is truly maintenance-free.

Acid won’t spill or leak from an AGM battery due to the glass fiber material between the lead plates. As the plates are tightly packed, they can withstand vibration and shock.

AGM batteries are also non-hazardous, making them a cheaper and more viable option for shipping.

As you can see, the PumpSpy Deep Cycle Maintenance-free AGM Battery with 75AH capacity is not that much less than the Zoeller battery shown above. Whereas the 100AH PumpSpy battery is even more expensive than the Zoeller 125AH battery.

PumpSpy Deep Cycle Battery - Maintenance-free AGM Battery w/ 12V 75Ah Mounting Flexibility, 12V AGM 75Ah Ideal for Start-stop Applications, Insusceptible to Vibration, Handles High Electrical Loads
173 Reviews
PumpSpy Deep Cycle Battery – Maintenance-free AGM Battery w/ 12V 75Ah Mounting Flexibility, 12V AGM 75Ah Ideal for Start-stop Applications, Insusceptible to Vibration, Handles High Electrical Loads
  • MAINTENANCE FREE – No more frequent maintenance through regular addition of water or acid just to have a proper operation. Our AGM deep cycle battery 12v pack will rescue you from the danger of acid leakage and frequent water refill.
  • SEALED LEAD ACID BATTERY – You can now eliminate spilled acid from a tipped battery and hydrogen gas venting because our AGM 12v deep cycle battery is completely sealed, averting any form of leakage.
  • BETTER CYCLING PERFORMANCE – Our Absorbent Glass Mat (AGM) Technology enables low internal resistance and high discharge currents. This valve regulated rechargeable battery 12v allows dependable operation in any position.
  • FAST CHARGING TIME – Quickly recharge your AGM deep cycle battery 12v up to 5x faster than a standard flooded battery. The improved electrolyte formula ensures stable battery capacity with increased cycle life and vibration resistance.
  • CONVENIENT AND FUNCTIONAL – Efficient to use, our AGM battery 12v has an internal compression that limits the shedding of plate material caused by cycling, which also allows a significantly longer life. It is designed for demanding conditions and can handle high electrical loads.
PumpSpy 12V 100 Ah Maintenance Free AGM Deep Cycle Battery
  • Maintenance free design does not require regular addition of water or acid for proper operation
  • Sealed enclosure eliminates spilled acid from tipped battery and hydrogen gas venting
  • Absorbent glass mat technology for superior performance; valve regulated, spill proof construction allows safe operation in any position
  • Sealed design is easy to transport and install without worrying about spills
  • 12V, 100 Amp/Hr.

When wanting to buy a battery backup sump pump system, purchasing one with an AGM battery is by far the best battery for backup sump pump use. An AGM battery provides maximize sump pump effectiveness and value for the money spent.

Checking A Backup Battery

The backup pump must start running to protect the basement from water ingress when the primary pump can’t work due to a malfunction or an interruption of power. As emergencies don’t occur often, ensuring the backup battery for sump pump use is in good condition and fully charged is important.

Which is why having the best battery backup sump pump system with Wi-Fi and text alerts is highly recommended. These systems will alert homeowners if a pump or battery is about to fail or needs replacement.

Many sump pump backup systems only have locally audible alarms.  So, it is good advice to check your system before the alarms go off.

Even a maintenance-free battery must be checked occasionally to ensure it will perform as it should. The easiest way to check a sealed battery is if it has a sight glass that will show when electrolyte levels are low.

Another way is to check a battery’s performance with a multimeter. If the battery is not holding a full charge, it may need some distilled water, or acid electrolyte added. Otherwise, the battery might need to be replaced.

Conclusions For: Battery For Backup Sump Pump Use

So, now you have the knowledge to choose the best battery for backup sump pump use.  Let me remind you that the AGM batteries are the best choice.

Consider the ACDelco Gold 94RAGM 36 Month Warranty AGM battery shown below.

ACDelco Gold 94RAGM (88864542) 36 Month Warranty AGM BCI Group 94R Battery
  • High density negative paste, improves performance and increases battery life
  • Enhanced life alloy or Silver Calcium stamped alloy increases cycle life and improves performance, High density plate oxide provides for maximum power-per-pound and dependable high cycling service
  • Calcium Lead positive grid, maximizes conductivity and allows for low resistance
  • Robust Envelope Separator with puncture-resistant back, allows for increased acid circulation and prevents shorts. Improved acid circulation, helps the battery to remain cool, and extend battery life
  • Vent cap design that resists acid leakage
  • Precision manufactured ribbed case that is 100% pressure tested, helps avoid future leaks and adds strength and rigidity

Related article: Why Is My Sump Pump’s Alarm Going Off? What Must I Do?

Last update on 2024-02-23 / Affiliate links / Images from Amazon Product Advertising API

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