Mighty Max ML75-12 SLA AGM Battery

Mighty Max ML75-12 is Sealed Lead Acid (SLA) Absorbent Glass Mat (AGM) general-purpose battery, often used in various standby and deep-cycle applications like trolling motor battery, UPS battery, sump pump backup battery, solar/wind battery, in medical and security applications and similar.

Mighty Max ML75-12 is a spill-proof, maintenance-free battery, that comes at a rather acceptable price. Also, it features good deep-discharge characteristics, low self-discharge rate, tolerates a relatively large number of charging/discharging cycles, etc. Mighty Max ML75-12 is for many reasons one of the most popular batteries in its class.

Published: July 6, 2020.

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Mighty Max ML75-12 Battery Features and Specifications

Physical dimensions of the Mighty Max ML75-12 are (L x W x H) 10.2 x 6.65 x 8.19 inches (26 x 16.9 x 23.1 cm) and it weighs 48.5 pounds (~22.0 kg).

Due to its dimensions, Mighty Max ML75-12 battery belongs to the BCI Group 24.

Mighty Max ML75-12 features a relatively low self-discharge rate. New, fully charged Mighty Max ML75-12 battery when stored at 68°F (20°C) retain:

- 90% of its nominal 20h capacity after being stored for 3 months,

- 80% of its nominal 20h capacity after being stored for 6 months,

- 60% of its nominal 20h capacity after being stored for 12 months.

When the battery is stored for a longer period of time, it should be kept in a cool and dry place, preferably connected to the smart AGM battery charger/maintainer.

Mighty Max ML75-12 battery comes with F17 terminal posts (positive to the left, negative to the right side), ensuring solid contact between the battery and cables.

terminal post

Mighty Max ML75-12 AGM Battery Discharging Charts

Constant current discharge features for the Mighty Max ML75-12 battery are given in the following chart - values are given in Amps, at 77°F/25°C:

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
9.6V 1.60V 237 178 137 82.3 48.5 19.7 14.0 7.88 4.10
9.9V 1.65V 223 168 132 79.8 47.9 19.5 13.9 7.82 4.05
10.2V 1.70V 210 158 126 77.2 46.2 19.2 13.7 7.75 4.00
10.5V 1.75V 196 149 121 74.5 46.5 18.9 13.5 7.65 3.95
10.8V 1.80V 181 140 114 72.0 45.7 18.5 13.2 7.50 3.85

Nominal 20h capacity of the Mighty Max ML75-12 is 77 Ah (down to 10.8 volts), but as the discharge current is increased, the actual capacity is decreased - this is typical behavior of lead-acid batteries.

For example, the actual capacity of Mighty Max ML75-12 battery is given in the following list:

- 20h, 3.85 Amps (down to 10.8 volts): 77 Ah,

- 10h, 7.50 Amps (down to 10.8 volts): 75 Ah,

- 5h, 13.5 Amps (down to 10.5 volts): 67.5 Ah,

- 1h, 48.5 Amps (down to 9.6 volts): 48.5 Ah.

Note: as the battery is being discharged faster, lower end-voltage is acceptable.

Constant power discharge features for the Mighty Max ML75-12 battery are given in the following chart - values are given in watts, at 77°F/25°C:

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
9.6V 1.60V 2490 1950 1530 918 720 586.2 329.4 240.0 164.4
9.9V 1.65V 2430 1812 1500 906 702 575.4 323.4 223.2 161.4
10.2V 1.70V 2262 1752 1476 888 690 564.4 317.4 219.0 158.4
10.5V 1.75V 2148 1656 1392 876 672 553.8 311.4 214.8 154.8
10.8V 1.80V 2058 1578 1320 858 654 543.0 306.0 210.6 151.8

As one can see, although it is not designed for strong currents, Mighty Max ML75-12 is able to provide almost 2kW for 10 minutes, or ~180 Amps for 10 minutes.

Mighty Max ML75-12 as Deep Cycle Battery

When the Mighty Max ML75-12 battery is used in deep cycle operations, its actual capacity decreases after a certain number of cycles:

- 100% DoD: 80% capacity after ~180 cycles, 60% capacity after ~220 cycles,

- 50% DoD: 80% capacity after ~370 cycles, 60% capacity after ~460 cycles,

- 30% DoD: 80% capacity after ~880 cycles, 60% capacity after ~1200 cycles.

So, if the battery is being discharged every time down to 100% DoD (Depth of Discharge), the battery's capacity will (on average) decrease down to 80% of the nominal capacity of the new Mighty Max ML75-12 battery after 180 charging/discharging cycles.

In order to prolong its operating life, try not to discharge it too deeply.

Mighty Max ML75-12 as Starting Battery

New, fully charged Mighty Max ML75-12 battery features internal resistance of 8 mΩ, and it is not the best option as cranking/starting battery for larger gas and especially diesel engines.

Nonetheless, Mighty Max ML75-12 is able to provide 700 Amps for 5 seconds (at 77°F, 25°C).

Personally, if You need a general-purpose battery for the single battery system that requires the battery to be able to crank 150-250 Amps, Mighty Max ML75-12 is good to go.

Just be sure that that system is able to properly charge Mighty Max ML75-12 battery.

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How to Charge Mighty Max ML75-12 Battery

When the battery is being used as a part of some larger electric system that features its own battery charger, let that charger do its job.

Just note that the maximum charging current of the Mighty Max ML75-12 is ~18.8 Amps and that its end charging voltage depends on the battery use (at 77°F/25°C):

- Float/Standby Use: 13.6 - 13.8 volts,

- Cycle Use: 14.5 - 14.9 volts.

When the battery is being charged 'manually', an intelligent AGM battery charger in the 8-12 Amps range is recommended.

For example, when the ML75-12 is being discharged down to 50% DoD, 10 Amps charger requires around 4 hours to fully charge the battery, without causing any unnecessary stress to the battery.

Such advanced chargers not only that charge the battery in most efficient way, they are also able to analyze the battery and adjust the charging process to the battery condition and temperature and after charging, they automatically switch to cell-equalization and maintenance modes.

Mighty Max ML75-12 Battery as Trolling Motor Battery

newport vessels kayak 55lbs 24inch mWith its 77 Ah nominal capacity, Mighty Max ML75-12 feature a somewhat smaller capacity than larger Group 31 batteries, but it is also lighter than them.

When being used for powering full-size trolling motors that require 50-60 Amps at full throttle, Mighty Max ML75-12 may power such motors for 40-50 minutes, depending on the exact current draw.

But, since such motors are rarely used at full throttle all the time, their runtime on the single battery charge may often be much longer.

For example, when being used for powering some smallish kayak trolling motor that draws ~20 Amps, Mighty Max ML75-12 is able to power such unit for more than 2h 30 minutes, with some energy left for safety purposes.

Mighty Max ML75-12 vs. Other BCI Group 24 Batteries

BCI Group 24 batteries are very popular medium-size batteries, used primarily as dual-purpose and more often as deep-discharge batteries.

Most popular Group 24 batteries are given in the following comparison chart:

Model Battery Type Chemistry Ah CCA MCA RC Weight (lbs/kg) Review
ACDelco M24AGM Deep Cycle AGM 80 500 625 140 43.0 lbs; ~19.5 kg -
Exide Edge FP-AGM24DP Dual Purpose AGM 75 775 930 145 50.0 lbs; 22.7 kg -
Mighty Max ML75-12 Deep Cycle AGM 77 - - - 48.5 lbs; 22.0 kg Mighty Max ML75-12
NorthStar NSB-AGM24F Dual Purpose AGM 76 840 1000 160 57 lbs; ~25.8 kg -
Trojan T24-AGM Deep Cycle AGM 76 - - <120 min 54 lbs; ~24.5 kg -
UPG UB12750 Deep Cycle AGM 75 - - - 49.1 lbs; ~22.3 kg UPG UB12750
VMAXTANKS MB107-85 Deep Cycle AGM 85 - - 170 55 lbs; ~24.9 kg -
VMAXTANKS MR107-85 Deep Cycle AGM 85 - 700 160 55 lbs; ~24.9 kg -
VMAXTANKS SLR-85 Deep Cycle AGM 85 - - 180 55 lbs; ~24.9 kg -

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

mighty max ml75 12 mMighty Max ML75-12 battery comes with a very nice price tag, making it one of the most popular batteries in its group. Other deep discharge batteries feature, for example, larger capacity and generally better discharge characteristics, but they are also more expansive batteries.

So, when choosing your next BCI Group 24 battery (or batteries), consider Mighty Max ML75-12, but choose according to your own needs and requirements.

For more reviews and recommendations, feel free to check Mighty Max 12V 75 Ah AGM SLA Battery Amazon link (link opens in the new window).