Mighty Max ML75-12 SLA AGM Battery
Mighty Max ML75-12 SLA AGM Battery is a very popular, general-purpose BCI Group 24, Sealed Lead-Acid (SLA) Absorbent Glass Mat (AGM) battery, designed for both standby/float and deep cycling use in off-the-grid applications, security, and medical systems, as trolling motor battery, as sump pump backup battery, as wheelchair battery, in electric vehicles, etc.
Mighty Max ML75-12 SLA AGM Battery is a very balanced design, having very good features at an affordable price. As an SLA AGM battery, it is a spill-proof and maintenance-free battery.
Published: August 3, 2020.
Mighty Max ML75-12 Battery Features and Specifications
Mighty Max ML75-12 battery physical dimensions are (L x W x H) 10.2 x 6.65 x 8.19/9.09 inches (260 x 169 x 208/231 mm) and it weighs 48.5 lbs (22.0 kg).
Mighty Max ML75-12 battery is labeled as BCI Group 24 battery, that have maximum dimensions of 10.25 x 6.8125 x 8.875 inches (260 x 173 x 225 mm). As one can see, Mighty Max ML75-12 battery may fit easily in the battery compartment intended for group 24 batteries, except its terminals - with terminals, Mighty Max ML75-12 battery is slightly taller.
Mighty Max ML75-12 battery comes with F17 terminal posts, positive terminal on the left side, ensuring the firm connection between the battery and cables.
Mighty Max ML75-12 battery is labeled as having a nominal voltage of 12V and a nominal capacity of 75 Ah. While actual voltage depends on the state of charge, Mighty Max ML75-12 battery features 20h capacity of 77 Ah (at 77°F, 25°C):
- 20-hour rate (3.85 A, down to 10.8V): 77 Ah,
- 10-hour rate (7.5 A, down to 10.8V): 75 Ah,
- 5-hour rate (13.5 A, down to 10.5V): 67.5 Ah,
- 1-hour rate (48.5 A, down to 9.6V): 48.5 Ah.
Like all lead-acid battery, Mighty Max ML75-12 battery also features actual capacity drop with the increase in discharge current - 48.5 Ah (1h capacity) is ~62% of 77 Ah (20h capacity), which is a good result for a general-purpose battery that comes at a rather affordable price.
Mighty Max ML75-12 battery capacity depends on the temperature - if the temperature goes up, so does its capacity and vice versa, if the temperature goes down, the capacity of the battery is decreased as well:
- 104°F (40°C): 102%
- 77°F (25°C): 100%
- 32°F (10°C): 85%
- 5°F (-15°C): 65%
Note: with the increase in temperature, the self-discharge rate is increased and the operating lifetime of the battery is shortened.
When the fully charged battery is being stored, its remaining charge depends on the storage temperature and storage time:
- at 104°F (40°C): 90% after less than a month, 80% after slightly less than two months, 60% after 4 months,
- at 86°F (30°C): 90% after 1.5 months, 80% after slightly less than 4 months, 60% after 8 months,
- at 68°F (20°C): 90% after 2.5 months, 80% after 6 months and 60% after 12 months.
When storing Mighty Max ML75-12 or any other lead-acid battery, charge it fully and keep in a cool and dry place. If possible, after charging, connect it to a battery maintainer that will keep the battery fully charged.
If the battery charge drops below 80% SoC, it should be recharged to avoid any issue with the battery.
When the battery is in use, its charging end voltage depends on the battery use (at 77°F, 25°C):
- Float/Standby use: 13.6-13.8 V,
- Cycle use: 14.5-14.9 V.
The maximum charging current should be kept below 22.5 Amps (some official sources claim 18.8 volts).
If the Mighty Max ML75-12 battery is discharged down to 80% DoD (20% SoC), 10 Amps battery charger can fully charge it in slightly more than 6 hours and 15 Amps battery charger can fully charge it in slightly more than 4 hours.
Personally, if there is no need for rush, use advanced 10 Amps AGM battery charger with temperature compensation that adjusts charging according to the battery condition and includes desulphation and equalization charging modes.
At 77°F (25°C), a fully charged Mighty Max ML75-12 battery features internal resistance of 8 mΩ, and maximum discharge current of 700 Amps for 5 seconds - although Mighty Max ML75-12 battery can provide rather large currents, it should not be used as cranking battery, except perhaps for smaller gas and diesel engines that require 200-300 Amps max. for starting.
When the battery is used for deep cycle applications, its operating life is defined as the number of charging/discharging cycles that the battery may withstand:
- at 100% DoD: ~190 cycles down to 80% capacity, ~220 cycles down to 60% capacity,
- at 50% DoD: ~375 cycles down to 80% capacity, ~460 cycles down to 60% capacity,
- at 30% DoD: ~900 cycles down to 80% capacity, ~1200 cycles down to 60% capacity.
In order to prolong its operating life, don't discharge Mighty Max ML75-12 battery too much - when being regularly discharged down to 80%, it can withstand some 260-270 cycles with the capacity drop down to 80%.
Mighty Max ML75-12 SLA AGM Battery Discharge Charts
The following chart lists the Mighty Max ML75-12 battery constant current discharge rates (measured at 77°F, 25°C, given in Amps):
|End Point Voltage||End Point Voltage (per cell)||5 min||10 min||15 min||30 min||1 hour||3 hours||5 hours||10 hours||20 hours|
The following chart lists the Mighty Max ML75-12 battery constant power discharge rates (measured at 77°F, 25°C, given in Watts):
|End Point Voltage||End Point Voltage (per cell)||5 min||10 min||15 min||30 min||45 min||1 hour||2 hours||3 hours||5 hours|
Mighty Max ML75-12 SLA AGM Battery as Inverter Battery
Mighty Max ML75-12 battery is often used for powering devices in the off-the-grid applications.
When being used as an inverter battery, Mighty Max ML75-12 battery may provide approximately 550 watts for 1 hour - it can power 500W power inverter for 1 hour.
Note: inverters are labeled according to their output power. For example, a 500W inverter features 500W output power, but it requires more input power. With 90% efficiency, a 500W power inverter requires an input power of ~550-560 watts.
Mighty Max ML75-12 battery is able to provide even more power (for example, ~1500 watts for 15 minutes), but stronger inverters simply drain the battery too fast.
If you are looking for the battery that can power 500W inverters for at least an hour, Mighty Max ML75-12 battery is a very balanced choice - there are better and perhaps tougher BCI Group 24 batteries, but such batteries usually cost more.
Similarly, if the Mighty Max ML75-12 battery is being used as a sump pump backup battery, its runtime depends on the sump pump power, its inverter efficiency, and the actual time that sump pump runs.
For example, a 1HP sump pump requires ~746 watts (rounded to 750 watts) of power when it runs, with some more power required when the motor starts.
If its inverter features an efficiency of 85%, that means that the battery must provide at least ~880 watts (for safety reasons, rounded to 900W).
If we check the constant power discharge table, that means that Mighty Max ML75-12 battery may power such a sump pump for at least 30 minutes constantly.
As said before, in real life sump pump motor draws more power when it starts and it doesn't operate constantly. Since the initial current is high for a very short moment, practically, it can be ignored in this calculation.
If the sump pump motor operates 30 seconds, ever 5 minutes, that means that Mighty Max ML75-12 battery can support 1 HP sump pump backup power for at least 5 hours.
Note: actual power requirements, efficiencies, and other important data vary, so be sure to check actual values for Your sump pump backup system.
Long Story Short: If You are looking for an affordable group 24 battery for powering trolling motors, wheelchairs, electric vehicles, power inverters, sump pump backup systems, and other off-the-grid applications, consider Mighty Max ML75-12 battery.
It is spill-proof, maintenance-free, AGM SLA battery, resistant to vibrations, and mechanical impacts (just don't abuse it!) that comes with a 1-year warranty.
For the most up-to-date offers and prices, feel free to follow Mighty Max Battery ML75-12 12V 75 Ah AGM SLA Battery Amazon link (link opens in the new window).