Mighty Max ML75-12 75Ah 12V SLA AGM Battery
Mighty Max ML75-12 is a general-purpose SLA AGM battery featuring a nominal capacity of 75 Ah and a nominal voltage of 12 volts - hence the label 'ML75-12'.
As a Sealed Lead Acid (SLA) Absorbent Glass Mat (AGM) battery, Mighty Max ML75-12 battery features spill-proof design and can operate in almost any position - don't use it upside-down, although Owner's Manual says 'any position'.
This maintenance-free, deep-discharge battery is one of the most popular Group 24 batteries, thanks to the acceptable price, reliable operation, and sturdy design.
Mighty Max ML75-12 Battery Dimensions and Features
Physical dimensions of Mighty Max ML75-12 battery 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 pounds (22.0 kg).
Although the battery is labeled as ML75-12 and advertised as having a nominal capacity of 75 Ah, its nominal (20 hours) capacity is 77 Ah. Since all lead-acid batteries feature capacity loss with the increase of discharge current, the actual capacity of Mighty Max ML75-12 is also decreased with higher discharge currents and is given in the following list:
- 20 hours discharge rate (3.85 Amps, down to 10.8 volts): 77 Ah capacity,
- 10 hours discharge rate (7.5 Amps, down to 10.8 volts): 75 Ah capacity,
- 5 hours discharge rate (13.5 Amps, down to 10.5 volts): 67.5 Ah capacity,
- 1 hour discharge rate (48.5 Amps, down to 9.6 volts): 48.5 Ah capacity,
- 30 minutes discharge rate (82.3 Amps, down to 9.6 volts): 41.65 Ah capacity.
Also, capacity is affected by the temperature. Actual 10 hours capacity temperature dependency of the Mighty Max ML75-12 battery is given in the following list:
- at 104°F (40°C): 102%,
- at 77°F (25°C): 100%,
- at 32°F (10°C): 85%,
- at 5°F (-15°C): 65%.
As the battery temperature drops, so does its capacity - this behavior is typical for lead-acid batteries, not just for Mighty Max ML75-12 battery.
Mighty Max ML75-12 battery features low-self discharge rate which depends on the storage temperature:
- at 104°F (40°C), battery capacity drops down to 80% in less than two months, down to 70% in slightly less than 3 months and down to 60% in around 4 months,
- at 86°F (30°C), battery capacity drops down to 80% in ~3.5 months, down to 70% in 6 months and down to 60% in ~8 months,
- at 68°F (20°C), battery capacity drops down to 80% in ~6 months, down to 70% in ~9 months and down to 60% in ~12 months.
In order to avoid adverse effects of storage on the battery performances, it is recommended to charge the battery when its capacity drops down to 80% of the nominal capacity of the new battery.
Note: If you are going to store your lead-acid batteries, keep them in a cool and dry place, charge them fully before the storage and if possible, leave them connected to the smart battery charger or to the battery maintainer.
Mighty Max ML75-12 battery features F17 terminal posts - positive to the left and negative to the right side of the battery.
Also, it comes with a pair of carrying handles - since the battery weighs 48.5 pounds (~22.0 kg) it can be easily carried by an adult, just don't carry it too far (better safe than sorry!).
Mighty Max ML75-12 battery is a general-purpose, deep-discharge battery.
Although it features 8 mΩ internal resistance and is able to provide 700 Amps for 5 seconds (at 77°F, 25°C), it should not be used as a starting battery for larger gas and diesel engines.
Note: small internal engines commonly found at small to medium size generators can be cranked with Mighty Max ML75-12 battery. But, just in case, be sure to check required cranking Amps of your device/engine - if it is anything more than 250-300 Amps, consider adding dedicated starting battery.
How to Charge Mighty Max ML75-12 Battery?
Mighty Max ML75-12 may be charged in many ways, depending on the application.
Maximum allowed charging current is ~18.8 Amps, while recommended charging voltage depends on the battery's type of use (values are given at 77°F/25°C):
- Float/Standby Use: 13.6 - 13.8 volts,
- Cycle Use: 14.5 - 14.9 volts.
When the battery is connected to the electrical system (backup device, medical/security system, sump pump backup battery, generator, etc.) let the onboard battery charger do its job as intended.
However, if you are going to charge Mighty Max ML75-12 directly, using a smart AGM battery charger is highly recommended for many reasons, including temperature compensation, battery analysis, desulfation, cell equalization, etc.
For example, 15 Amps AGM battery charger is able to fully recharge Mighty Max ML75-12 battery discharged down to 80% DoD in less than 5 hours.
Note: Using stronger battery chargers is not recommended - some users even go for 10 Amps battery chargers in order to avoid any additional stresses on the battery, but prolonging the recharging time.
Mighty Max ML75-12 Battery Constant Current Discharge Chart
Mighty Max ML75-12 battery's constant current discharge features are given in the following chart - values are given in Amps, at 77°F/25°C:
|End Point Voltage||End Point Voltage
|5 min||10 min||15 min||30 min||1 hour||3 hours||5 hours||10 hours||20 hours|
As one can see, although it is not intended for high-discharge applications, Mighty Max ML75-12 is able to provide 200 Amps for 5 minutes easily, without being discharged too low.
Also, it can easily provide 7.5 Amps for 10 (ten) hours for an effective 10h capacity of 75 Ah.
Mighty Max ML75-12 Battery Constant Power Discharge Chart
Mighty Max ML75-12 battery's constant power discharge features are given in the following chart - values are given in Watts, at 77°F/25°C:
|End Point Voltage||End Point Voltage
|5 min||10 min||15 min||30 min||45 min||1 hour||2 hours||3 hours||5 hours|
Constant power discharge chart is very important for inverter batteries, since such charts allow the user to accurately calculate inverter's runtime depending on the load and the battery specs.
Mighty Max ML75-12 Battery as an Inverter Battery
Since the actual capacity of the deep discharge AGM battery sharply drops when they are discharged for less than 10-20 minutes, Mighty Max ML75-12 battery is ideal for inverters up to 500 watts.
For example, Mighty Max ML75-12 battery may power 500 watts inverter for up to an hour.
Note: power that the battery must provide is inverter's output power (500 watts in this example), plus the energy losses in the inverter itself. Modern inverters commonly found on the market feature energy efficiency in 90+ % range, sometimes even 95-96%, thus requiring Mighty Max ML75-12 to provide some 530-550 watts of power to the inverter, so that inverter may provide 500 watts of power to other devices (inverter's load).
New, fully charged Mighty Max ML75-12 can provide ~586 watts (at 77°F, 25°C) for one hour, down to 9.6 volts.
Stronger inverters may also be used, but for shorter runtime.
Long Story Short: Mighty Max ML75-12 battery is a very popular battery used in deep-discharge and standby applications like off-the-grid applications (wind, sun), medical/security systems, backup systems, as trolling motor battery and similar.
It is well designed, robust, and reliable battery that comes at an acceptable price - there are group 24 batteries that are stronger and more powerful than Mighty Max ML75-12 battery and that feature large capacity.
But, such batteries also cost more.
For more reviews and recommendations, feel free to check Mighty Max ML75-12 AGM Battery Amazon link (link opens in the new window).