Battery Equivalents and Replacements

Best Sump Pump Backup Battery

Battery-powered sump pumps are a type of emergency equipment that must operate reliably when required, and saving money on these pumps or their batteries may be a very expensive thing to do.

The sump pump backup battery must be strong enough to power the sump pump motor, and it must store enough energy to power the whole unit long enough to prevent as much damage as possible until mains power is restored.

Updated: November 10, 2022.

On This Page:

 

wayne esp25 sump pump

Battery Powered Sump Pumps Features and Specifications

The most important feature of the battery-powered sump pump is the nominal strength of the pump motor, and it is usually given in the HPs.

The most common battery-operated sump pumps come with 1/6 HP, 1/4 HP, 1/3 HP, 1/2 HP, 3/4 HP, or even 1 HP motors.

Note: Mains-powered sump pumps, especially those powered by three-phase electric power, may feature several HPs motors, but these are mostly commercial units, rarely used at homes.

The most common type of battery-operated sump pumps are 12V sump pumps, with 24V sump pumps being used where a larger flow (gallons per hour, gallons per minute) or larger lift (given in feet) is required - or both!

  • 12V sump pumps, normal conditions: go for a single, high-quality AGM battery,
  • 12V sump pumps, a long operating time required: go for 2 or more high-quality AGM batteries and connect them in parallel - use the same battery model of the same brand, preferably from the same batch,
  • 24V sump pumps: choose 2 high-quality AGM batteries and connect them in series.

Most popular sump pumps come with their own battery boxes and their own battery chargers, somewhat limiting the users regarding battery selection.

But, in the case of emergencies, one has to know that sump pumps don't operate continuously. For example, some motor controllers, when the alarm is triggered, will run the pump motor for 10-20 seconds continuously (to prevent short cycling) or until the float switch resets itself.

How often will sump pump cycle, depends on the sump pump volume (gallons per minute, for example) and the amount of incoming water.

In the case of a "worst case scenario" emergency, one may assume that the basement will be fully flooded and that the sump pump will work continuously until the battery is fully discharged - and that is really the worst-case scenario!

In that case, it is important to know how many gallons the sump pump may pump out on a single battery charge, depending on the required height.

All these values are good to know BEFORE choosing and installing a battery-powered sump pump.

Sump Pump Battery Types

The most popular sump pump battery types are lead-acid batteries:

  • A Wet/Flooded Lead-Acid Battery is not a maintenance-free battery, nor is it a spill-proof battery. It is up to the user to periodically check the battery electrolyte and, if required, add distilled water. Wet lead-acid batteries may operate only in the upright position.
  • A Gel-Cell Lead-Acid Battery features electrolytes in the form of silica gel, hence the name. Gel-cell batteries are maintenance-free and spill-proof batteries that can operate in almost any position except upside-down. They also cycle well and feature a long standby operating life.
  • An AGM Lead-Acid Battery uses Absorbent Glass Matt and is also a maintenance-free and spill-proof battery that can operate in any position except upside-down. AGM batteries also cycle well and feature a long standby operating life.

Deep-cycle lithium batteries based on the Lithium Iron Phosphate (LiFePO4) chemistry offer many benefits over AGM and Gel-Cell lead-acid batteries, including weight savings, longer standby life, a larger number of supported charging/discharging cycles, can operate in any position (even upside down), etc.

Also, with the advances in electronics and chemistry, lithium batteries don't cost (much) more than lead-acid batteries.

But, to operate safely, lithium batteries come with a Battery Management System (BMS) that monitors the battery charge and discharge parameters and, if required, protects the battery by shutting off the battery when some unwanted event happens.

That also means that if there is a glitch of some kind in the electric system, there is a risk of BMS shutting off the battery - the last thing one needs when the basement starts to flood.

Personally - when looking for a new sump pump backup battery, go for a good AGM or Gel-Cell battery and don't look any further.

Sump Pump Battery Boxes and Chargers

Sump Pump battery chargers operate as both chargers and maintainers, keeping the battery fully charged and in optimal condition over a long period of time.

If the sump pump doesn't have a reliable battery charger/maintainer, consider buying a dedicated one and connecting it to the battery.

Note: battery-powered sump pumps and similar emergency equipment MUST work reliably in the case of emergencies - if they don't operate reliably, what's the point of having them? Thus, any work on the sump pumps and their electric and electronic systems should be done by certified personnel or at least by someone who actually knows what to do. Seriously!

odyssey 31m pc2150st m battery 2The preferred battery types of sump pump batteries are dual-purpose or deep-cycle AGM (Absorbent Glass Mat) SLA (Sealed Lead Acid) batteries or Gel-Cell SLA batteries.

Note: Car batteries are designed as starting/cranking batteries, being able to provide short bursts of power for shorter periods of time and thus are not the best choice for, what is easily possible, deep cycle applications. However, if your sump pump battery is dead for who knows what reason, hook your charged car battery and let it work - one(!) deep discharge cycle will not harm starting battery, but the cycle use may shorten its operating life significantly.

Thus, when choosing a sump pump battery, go for a reliable deep cycle (or maybe dual purpose) AGM battery from a reputable brand.

Most sump pump battery boxes accept BCI Group 27 batteries or BCI Group 31 batteries.

Their sizes are:

- Group 27 batteries (L x W x H): 12.0625 x 6.8125 x 8.875 (12 1/16 x 6 13/16 x 8 7/8) inches, 30.6 x 17.3 x 22.5 cm,

- Group 31 batteries (L x W x H): 13 x 6.8125 x 9.4375 (13 x 6 13/16 x 9 7/16) inches, 33 x 17.3 x 24 cm.

As one can see, the battery box designed to accept group 31 battery may also accept group 27 battery or any other battery group that is smaller than group 31 battery.

However, the smaller the battery, the smaller the capacity in Ah and, thus, the shorter the operating time of the sump pump when there is no mains power available.

The following two charts list the most popular group 27 and group 31 dual-purpose and deep cycle batteries.

Most Popular Group 27 Batteries

Model

Battery Type

Chemistry

Capacity (Ah)

RC (min)

CCA

MCA

Weight

Review

Banshee 27M

Dual Purpose

Enhanced Flooded

77

140

800

1000

51 lbs; 23.1 kg

-

Banshee LFP-27M

Dual Purpose

LiFePO4

70

~165

900

-

18.8 lbs; 8.52 kg

-

GreenLiFE GL80-80AH

Deep Cycle

LiFePO4

80

~190

-

-

28 lbs; 12.8 kg

-

Mighty Max ML100-12

Deep Cycle

AGM

100

-

-

-

63.9 lbs; 29 kg

Review

NorthStar NSB-AGM27

Dual Purpose

AGM

92

195

930

1080

68 lbs; 31 kg

Review

Optima 8027-127 D27M

Dual Purpose

AGM

66

140

800

1000

54 lbs; 24.5 kg

Review

Renogy RBT100LFP12S-G1

Deep Cycle

LiFePO4

100

~200

100A cont.

26 lbs; 11.8 kg

-

UPG UB121000

Deep Cycle

AGM

100

170

-

-

64 lbs; 29 kg

Review

VMAXTANKS MR127-100

Deep Cycle

AGM

100

200

-

800

68 lbs; 31 kg

Review

VMAXTANKS SLR100

Deep Cycle

AGM

100

220

-

-

68 lbs; 31 kg

-

VMAXTANKS XTR27-110

 Deep Cycle

AGM

110

220

660

880

68 lbs; 31 kg

Review

Note: Amazon links in the table open in the new windows ('Model' column), so feel free to check them for the most up-to-date prices and offers.

On average, Group 27 AGM batteries feature 20h capacity in the 90-100 Ah range, with Reserve Capacity (RC) values of 190-220 minutes.

Note: Optima batteries use spiral wound cells and are somewhat lighter than other batteries of similar size and feature smaller capacity and shorter RC. Other than that, they are popular and rather reliable batteries.

Most Popular Group 31 Batteries

Model Battery Type Battery Chemistry Capacity (Ah) RC (min)
CCA
MCA
Weight (lbs/kg) Review
Aicipow PDAC-12100 Deep Cycle
LiFePO4
100
~240
100A cont. 26 lbs; 11.8 kg
-
AIMS Power LFP12V100A Deep Cycle
LiFePO4
100
~240
-
-
30.2 lbs; 13.7 kg
-
AIMS Power LFP12V100B Deep Cycle
LiFePO4
100
~240
100A cont.
200A 10s
28.5 lbs; 12.9 kg
-
Ampere Time 12V 100Ah Deep Cycle
LiFePO4
100
~240
280A 5s 24.25 lbs; ~11 kg
Review
Banshee LFP-31M Dual Purpose
LiFePO4
100
~240
1200 CCA 24.2 lbs; 11 kg
-
Battle Born 100Ah 12V LiFePO4 Deep Cycle
LiFePO4
100
~240
-
-
29 lbs; 13.2 kg
Review
Bioenno Power BLF-12100WS Deep Cycle
LiFePO4
100
~240
100A cont.
200A 5s
28.1 lbs; 12.8 kg
-
Chins 12V100Ah Deep Cycle
LiFePO4
100
~240
100A cont.
300A 5s.
23.9 lbs; 10.8 kg
-
Eco-Worthy 12V150Ah Deep Cycle
LiFePO4 
150
~360
150A cont. 36.7 lbs; 16.6 kg
-
Exide XMC-31 Deep Cycle
AGM
100
200
925
1110
68 lbs; 31 kg
Review
ExpertPower EP12100 Deep Cycle
LiFePO4
100
~240
-
-
29.7 lbs; 13.5 kg
Review
ExpertPower EXP100 Deep Cycle
AGM
100
-
-
-
63.94 lbs; 30 kg
-
FLYPOWER 12V 100Ah Deep Cycle
LiFePO4
100
~240
100 cont.
200A surge 3-5s
24.3 lbs; ~11 kg
Review
GreenLiFE Battery GL100 Dual Purpose
LiFePO4
100
240
-
-
28 lbs; 12.7 kg
-
GreenLiFE GL5024V Deep Cycle
LiFePO4
50Ah @24V
~120 @24V
- 32 lbs; 14.5 kg
-
GreenLiFE GL36V40 Deep Cycle
LiFePO4
40Ah @36V
~96 @36V
50A cont. 31.3 lbs; 14.2 kg
-
Interstate DCM0100 Deep Cycle
AGM
110
3h @23.2A
351.5A 5 min 67.5 lbs; ~30.6 kg
Review
JITA 12V100Ah Deep Cycle
LiFePO4
100
~240
100A cont. 24.2 lbs; ~11.0 kg
-
Lifeline GPL-31T Deep Cycle
AGM
105
195
600
750
69 lbs;  31.5 kg
-
Lifeline GPL-31XT Deep Cycle
AGM
125
230
650
800
69 lbs; 31.5 kg
-
Lifeline GPL-3100T Dual Purpose
AGM
100
228
810
950
67 lbs; 30.4 kg
-
Miady LFP100AH Deep Cycle
LiFePO4
100
~240
-
-
28.9 lbs; 13.1 kg
-
Mighty Max ML100-12 DS-IGEL Deep Cycle
Gel
100
180+
-
-
68.2 lbs; 30.9 kg
-
NorthStar ELT-AGM31 Dual Purpose
AGM
100
190
925
1050
65.7 lbs; 29.8 kg
-
NorthStar NSB-AGM31 Dual Purpose
AGM
103
220
1150
1370
75 lbs; 34.0 kg
-
NorthStar NSB-AGM31M Dual Purpose
AGM
103
220
1150
1370
75 lbs; 34.0 kg
-
Odyssey 31-PC2150S Dual Purpose
AGM
100
205
1150
1370
77.8 lbs; 35.3 kg
Review
Optima 8052-161 D31M Dual Purpose
AGM
75
155
900
1125
59.8 lbs; 27.1 kg
Review
PacPow 12V 100Ah Deep Cycle
LiFePO4
100
~240
100A cont.
300A 10s
27.56 lbs; 12.5 kg
Review
Power Queen 12V100Ah Deep Cycle
LiFePO4
100
~240
100A cont. 25.25 lbs; 11.0 kg
-
Renogy RNG-BATT-AGM12-100 Deep Cycle
AGM
104
180+
-
-
66 lbs; 29.9 kg
Review
Renogy RNG-BATT-GEL12-100 Deep Cycle
Gel-Cell
100
180+
-
-
60 lbs; 27.2 kg
Review
Renogy RBT100GEL12-G1 Deep Cycle
Gel-Cell
100
~175
-
-
63.9 lbs; 29 kg
Review
Renogy RBT100LFP12S-G1 Deep Cycle
LiFePO4
100
~240
-
-
26 lbs; 11.8 kg
Review
Scream Power 12V100Ah Deep Cycle
LiFePO4
100
~240
? 24.3 lbs; 11 kg
-
Trojan T31-AGM Deep Cycle
AGM
102
200
-
-
69 lbs; 31.3 kg
-
Trojan T31-GEL Deep Cycle
Gell-Cell
102
200
-
-
70 lbs; 31.7 kg
-
UPG UB121100 Deep Cycle
AGM
110
-
-
-
70 lbs; 29.8 kg
-
Vatrer 12V 100Ah Deep Cycle
LiFePO4
100
240
100A cont. 33 lbs; 15 kg
Review
VMAXTANKS SLR125 Deep Cycle
AGM
125
260
-
-
75 lbs; 34 kg
Review
VMAXTANKS MR137-120 Deep Cycle
AGM
120
230
-
900
75 lbs; 34 kg
Review
VMAXTANKS VPG12C-100LFP Deep Cycle
LiFePO4
100
~240
-
-
26.4 lbs; ~12.0 kg
-
VMAXTANKS XTR31-135 Deep Cycle
AGM
135
265
730
920
77 lbs; 34.9 kg
-
XS Power XP3000 Deep Cycle
AGM
120
240
-
-
73 lbs;  33.1 kg
-
Weize 12V 100Ah AGM Deep Cycle
AGM
100
-
-
-
60 lbs; 27.2 kg
Review
Weize 12V 100Ah Gel Deep Cycle
Gel-Cell
100
<180
-
-
67 lbs; 30.4 kg
Review
Weize FPLI-12100AH Deep Cycle
LiFePO4
100
~240
100A cont.
200-250A surge
26.4 lbs; 12.0 kg
Review
WindyNation BAT-NSAP12-100 Deep Cycle
AGM
106
180+
-
-
67 lbs; 30.4 kg
Review
Wingda W100-12V100AH Deep Cycle
LiFePO4
100
~240
50A cont. 23.8 lbs; 10.8 kg
-
Zooms 12V 100Ah Deep Cycle
LiFePO4
100
~240
100A cont. 25.35 lbs; ~11.5 kg
Review

Note: Amazon links in the table open in the new windows ('Model' column), so feel free to check them for the most up-to-date prices and offers.

On average, Group 31 AGM batteries feature 20h capacity in the 100-125 Ah range, with Reserve Capacity (RC) values of 200-260 minutes.

For smaller sump pump motors (1/2 HP or less), it is recommended to go for deep cycle/solar batteries, while for stronger sump pump motors (3/4 HP or more), it is recommended to choose dual-purpose batteries.

The reason is simple - at 1/2 HP (US HP -> 746W), a 12V motor draws at least 31.1 Amps, and that is not a problem for 100Ah deep cycle AGM batteries. However, at 3/4 HP, a 12V motor draws at least 46.7 Amps, and dual-purpose batteries may perform better.

At 1 HP, 12 motor draws at least 62 Amps, and the actual capacity of deep cycle batteries optimized for low discharge applications may deteriorate too much.

Rule of thumb: don't overthink - go for a reputable brand, just check the size of the battery and its Reserve Capacity value.

Sump Pump Motors Operating Time Charts

When trying to determine if the battery is good for certain applications, it is recommended to check the battery's constant current and constant power discharge charts.

One of the most popular and affordable 100 Ah batteries is the Mighty Max ML100-12 100 Ah AGM deep cycle battery.

The following charts list Mighty Max ML100-12 discharging features - constant current discharge characteristics (in Amps, at 77°F/25°C) and constant power discharge characteristics (in watts, also at 77°F/25°C):

Constant Current:

End Voltage Per Cell Battery End Voltage 10 min 15 min 30 min 45 min 1 hour 3 hours 5 hours 10 hours
1.60 V 9.6 V 207 162 92.0 66.5 53.5 24.0 16.2 9.20
1.65 V 9.9 V 195 154 89.3 65.1 52.5 23.5 16.0 9.15
1.70 V 10.2 V 183 145 86.4 63.6 51.3 23.0 15.7 9.10
1.75 V 10.5 V 170 136 83.2 62.0 50.0 22.5 15.4 9.05
1.80 V 10.8 V 155 126 80.0 60.0 48.5 21.8 15.0 9.00

Constant Power:

End Voltage Per Cell Battery End Voltage 10 min 15 min 30 min 45 min 1 hour 2 hours 3 hours 5 hours
1.60 V 9.6 V 2250 1830 1032 750 618 372.0 280.8 189.0
1.65 V 9.9 V 2178 1734 1008 738 606 366.0 276.0 187.2
1.70 V 10.2 V 2100 1686 978 726 594 358.2 270.6 185.4
1.75 V 10.5 V 2010 1626 948 708 582 349.2 265.2 183.0
1.80 V 10.8 V 1890 1548 912 690 570 339.6 259.6 180.0

Note: listed values are average values, and they vary slightly from the battery to the battery.

mighty max ml100 12Sump pump motors come in different sizes:

- 1/6 HP: ~125 W, ~10.5 Amps, 5+ hours.

- 1/4 HP: ~187 W, ~15.6 Amps, ~5 hours, but end-voltage is rather low.

- 1/3 HP: ~250 W, ~21 Amps, 3+ hours,

- 1/2 HP: ~375 W, ~31.5 Amps, almost 2 hours,

- 3/4 HP: ~560 W, ~46.7 Amps, 1+ hour,

- 1 HP: ~746 W, 62.2 Amps. around 45 minutes, but the end-voltage is rather low.

These values are given for the brand-new, fully charged battery. Also note that sump pump motors are not working constantly, and these values are for constant operation.

For example, the sump pump features a 12V 1/2 HP motor, and it operates 15 seconds every 30 minutes. In that case, one may expect this battery to power such a sump pump for ~10 days!

If there are issues with the underground water levels and such a motor operates 15 seconds every 1 minute, one may expect this battery to power such a sump pump for ~8 hours.

Mighty Max ML100-12 offers good performances at an acceptable price, however, if the money is not an issue, there are better performers, for example, Renogy AGM and Gel-Cell batteries, Odyssey 31M-PC2150, NorthStar NSB-AGM31, and similar.

For example, Odyssey 31M-PC2150 is an expensive but otherwise excellent dual-purpose group 31 battery suitable for almost any situation, especially during cold weather.

The following chart lists the discharge features of the new, fully charged Odyssey 31M-PC2150 battery.

Time Watts (W) Amps (A) Capacity (Ah) Energy (Wh)
2 min 7025 678.5 22.4 231.8
5 min 4740 438.5 36.4 393.4
10 min 3176 285.9 47.7 530.4
15 min 2428 215.5 53.9 607.0
20 min 1980 174.1 58.0 659.2
30 min 1460 127.0 63.5 730.0
45 min 1059 91.2 68.4 793.9
1 hr 835 71.5 71.5 835.2
2 hr 461 39.0 78.0 922.2
3 hr 322 27.1 81.4 966.8
4 hr 249 20.9 83.8 996.8
5 hr 204 17.1 85.6 1020.0
8 hr 134 11.2 89.7 1070.4
10 hr 110 9.2 91.9 1095.9
20 hr 60 5.0 100.3 1191.9

As one can see, it is a much better performer than the  Mighty Max ML100-12 battery, but again, it costs more.

Best Sump Pump Backup Systems

There are many models of sump pump backup systems on the market, with each model offering somewhat different performances in terms of volume (gallons per minute, for example), lift height, and similar.

Here are some of the most popular models that have already been tried and tested by numerous real-life users.

WAYNE BGSP50 Guardian Premium Wi-Fi Connected Total Basement Protection System

wayne bgsp50 w400px

AS its name suggests, the WAYNE BGSP50 Guardian Premium Wi-Fi Connected Total Basement Protection System is an all-in-1 basement protection system.

WAYNE BGSP50 features two sump pumps:

  • AC sump pump, which can pump up to ~3800 GPH up to 10 feet,
  • 12V 1/2HP DC sump pump which can pump up to ~2000 GPH up to 10 feet.

The unit doesn't come with a battery by default, but the manufacturer recommends their WAYNE 12V 75Ah battery.

One of the very interesting features is the support for the smartphone App, allowing the user to receive alerts.

WAYNE BGSP50 is a very sturdy sump pump system built from cast iron and aluminum.

WAYNE BGSP50 comes with a 5-year limited warranty.

Note: this is not a cheap unit, but what You pay is what You get...

For the most up-to-date offers and prices, feel free to check the Basement Watchdog BWE Basement Emergency Back-Up Sump Pump Amazon link (the link opens in the new window).

Basement Watchdog BWE Basement Emergency Back-Up Sump Pump

basement watchdog bwe w400px

Basement Watchdog BWE Basement Emergency Back-Up Sump Pump is able to pump 2000 GPH at 0 feet height and 1000 GPH at 10 feet height.

Basement Watchdog BWE sump pump features a control unit with a dual float switch, a battery fluid level sensor (very helpful when having wet/flooded lead-acid batteries), a pump, a battery box, and a charger.

Note: Basement Watchdog BWE supports both wet and AGM lead-acid batteries. By default, the unit doesn't come with a battery.

Basement Watchdog BWE sump pump battery comes with a 2-year limited warranty.

For the most up-to-date offers and prices, feel free to check the Basement Watchdog BWE Basement Emergency Back-Up Sump Pump Amazon link (the link opens in the new window).

Zoeller 508-0006 Aquanot 508 Sump Pump Backup System

zoeller 508 0006 aquanot w400px

Zoeller 508-0006 Aquanot 508 Sump Pump Backup System features a 12V 1/3HP sump pump rated at ~1800 GHP with a 10 feet lift (~2000 GPH at 10 feet lift, AC powered).

The unit comes almost fully assembled, helping the user with installation - as always, it is highly recommended to have a professional install it and test it.

Note: the package does NOT feature a backup battery, but the battery box accepts both group 27 and group 31 batteries.

Zoeller 508-0006 Aquanot is a durable unit built from cast iron and thermoplastics.

The unit comes with a 3-year limited warranty.

For the most up-to-date offers and prices, feel free to check the Zoeller 508-0006 Aquanot 508 Sump Pump Backup System Amazon link (the link opens in the new window). 


Few Final Words

Best sump pump battery must be reliable and must tolerate float/standby use well - for at least 5-7 years, preferably 8+ years.

AGM SLA batteries are practically maintenance-free batteries, offering great reliability at affordable prices.

When looking for a new sump pump battery, check the dimensions of the available battery box/battery compartment and go for a reliable deep cycle/dual-purpose battery from reputable brands - don't go cheap since your home may depend one day on this battery.

The most common sump pump batteries are group 27 and group 31 batteries, so choose according to your own needs and preferences.

Note: when setting up a sump pump battery backup system, it is highly recommended to check the features of the battery charger and to replace it with a new one optimized for the battery that You have - it is an additional cost, but can prolong the battery lifetime...