Mighty Max ML4D 12V 200Ah 4D SLA AGM Deep Cycle Battery

Mighty Max ML4D is large and heavy Sealed Lead Acid (SLA) Absorbent Glass Mat (AGM) BCI Group 4D battery, being able to store large amounts of energy for powering various loads, including electric trolling motors, various pumps, winches, UPS devices, etc.

Mighty Max ML4D is designed for deep cycle applications and is not suitable as cranking/starting battery, except for rather smallish gas and diesel engines, commonly found in power generators, smaller boats, and similar.

Published: February 24, 2021.

Mighty Max ML4D Battery Features and Specifications

Mighty Max ML4D battery belongs to the BCI Group 4D batteries and features dimensions of (L x W x H) 20.9 x 8.23 x 8.46 (8.66 with terminals) inches (530 x 209 x 215 (220 with terminals) mm) and it weighs respectable 114.6 pounds (~52 kg).

Despite that it also features carrying handles, carrying it around via handles is not recommended, not even to two adults - it is that big and heavy. After all, it is 4D battery.

Fully charged Mighty Max ML4D battery features internal resistance of ~4.3 mΩ at 77°F (25°C), with the short circuit current of 'only' 3430 Amps and the maximum allowed 5 seconds discharge current of 'only' 1000 Amps.

Note: We say 'only' because much smaller SLA AGM batteries feature similar internal resistance, short circuit current, and 5 seconds current - this is just to emphasize 'deep cycle' features of Mighty Max ML4D battery.

Mighty Max ML4D battery is SLA AGM battery designed for long standby operating life (up to 10 years) and for use in deep cycle applications, typically as solar/wind battery, security/medical battery, UPS battery, trolling motor battery, RV house battery, boat/yacht battery, industrial battery, etc.

Mighty Max ML4D battery features M8 nuts and bolts terminals, ensuring strong and firm connection between the battery and cables.

It is a very popular battery in its class and is used (and sometimes abused) in countless real-life situations.

The maximum recommended charging voltage for cycle use is 14.4 - 14.7 volts, and for standby use 13.2 - 13.8 volts, with the maximum allowed charging current of 52.5 Amps.

Mighty Max ML4D battery may be charged using solar/wind battery chargers/controllers, using vehicle/boat built-in alternator, using battery chargers, etc.

However, it is highly recommended to periodically charge the battery with a smart AGM battery charger that will charge the battery after analyzing its condition, and that will after charging, switch to equalization mode and in the end, switch automatically into the battery maintenance mode.

Since maximum allowed charging current for Mighty Max ML4D battery is 52.5 Amps, good AGM battery charger with 25 Amps maximum current should be just fine.

When the battery is discharged down to 50% DoD, it takes 25 Amps AGM battery charger some 5 hours to fully recharge 200 Ah battery (charging process is not 100% efficient!).

Mighty Max ML4D battery features a good self-discharge rate. Generally, it is recommended to recharge the stored battery when its capacity drops down to 80% - slightly less than 2 months at 104°F (40°C), slightly less than 4 months at 86°F (30°C) and ~6 months when the battery is stored at 68°F (20°C).

Also, if the battery is going to be stored for a longer period of time, keep it in the cool area, recharge it fully and connect a smart AGM battery maintainer to keep it charged during storage.

Mighty Max ML4D Discharge Features

Constant current discharge values or Mighty Max ML4D battery are listed in the following chart - values are given in Amps, at 77° (25°C):

End Cell Voltage	End Battery Voltage	15 min	30 min	45 min	2h	3h	5h	10h
1.60V	9.6V	324	195	141	67.1	51.1	33.5	18.0
1.65V	9.9V	309	187	137	65.3	49.9	32.7	17.9
1.70V	10.2V	298	183	134	64.1	49.4	32.1	17.7
1.75V	10.5V	280	178	130	62.6	48.4	31.5	17.6
1.80V	10.8V	246	169	125	60.3	46.2	31.0	17.5

Mighty Max ML4D battery nominal voltage is 12V and its nominal (20h) capacity is 200Ah. As the battery is discharged faster, its capacity is decreased - typical behavior of lead-acid batteries:

- 20h rate, 10 Amps, down to 10.5 volts: 200 Ah capacity,

- 10h rate, 17.6 Amps, down to 10.5 volts: 176 Ah capacity,

- 5h rate, 31.5 Amps, down to 10.5 volts: 157.5 Ah capacity,

- 1h rate, 115 Amps, down to 9.6(!) volts: 115 Ah capacity,

- 30 min rate, 195 Amps, down to 9.6(!) volts: 97.5 Ah capacity,

- 15 min rate, 324 Amps, down to 9.6(!) volts: 81 Ah capacity.

As one can see, the effective capacity drops significantly, down to ~40% of nominal capacity when the battery is being discharged in 15 minutes.

Constant power discharge values for Mighty Max ML4D battery are listed in the following chart - values are given in watts, at 77° (25°C):

End Cell Voltage	End Battery Voltage	15 min	30 min	45 min	2h	3h	5h	10h
1.60V	9.6V	3504	2208	1614	750	580.8	385.2	212.4
1.65V	9.9V	3324	2082	1566	738	573	378.6	205.8
1.70V	10.2V	3168	2046	1524	726	565.2	373.2	202.2
1.75V	10.5V	3066	1998	1494	711	549.6	367.2	198.6
1.80V	10.8V	2940	1962	1476	696	361.2	361.2	193.8

When the Mighty May ML4D battery is discharged for a longer period of time, it can power 200 watts load for ~10h, which is a good result, considering the battery's price, reliability, and other important features.

Note: if the battery is used in cycle applications, the number of charging/discharging cycles depends on the Depth of Discharge (DoD):

- 100% DoD: ~190 charging/discharging cycles with the capacity loss down to 80%, ~210 cycles charging/discharging cycles with the capacity loss down to 60%,

- 50% DoD: ~380 charging/discharging cycles with the capacity loss down to 80%, ~450 cycles charging/discharging cycles with the capacity loss down to 60%,

- 30% DoD: ~900 charging/discharging cycles with the capacity loss down to 80%, ~1210 cycles charging/discharging cycles with the capacity loss down to 60%.

So, in order to prolong the operating life of the battery, don't discharge it too deep - nonetheless, you can expect some 190 charging/discharging cycles down to 100% DoD. After that, be sure to fully charge the battery using smart AGM battery charger and let it, at least from time to time, to equalize the cells.

Mighty Max ML4D As Trolling Motor Battery

Mighty Max ML4D battery is an excellent trolling motor battery. As SLA AGM battery, it is almost maintenance-free battery and it can power electric trolling motor for a long time:

- 50 Amps continuously: almost 3 hours,

- 30 Amps continuously: slightly more than 5 hours,

- 15 Amps continuously: more than 10 hours.

If you have an electric trolling motor with a maximum current of 50-60 Amps and you push the motor to the max only periodically, Mighty Max ML4D battery can power such electric trolling motor for a long time.

Note: for safety reasons, don't let your trolling motor battery voltage drop below 10.8 volts, even below 11.2 volts. AGM battery discharged to 11.2 volts (or 10.8 volts) still has some energy left and when trolling, it is good to have some energy extra for safety reasons.

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Long Story Short: Mighty Max ML4D battery is well balanced, deep cycle battery, being able to store large amounts of energy and to release it when required.

Mighty Max ML4D battery is designed as a deep cycle/standby battery and it should be used as such - it can be used for starting smaller internal combustion engines (both gas and diesel) if their cranking currents are few hundred Amps, but not more.

As a trolling motor battery, it can be used as a single battery or connected in series/parallel in order to create battery packs of much larger voltage and capacity.

For more reviews and recommendations, feel free to check Mighty Max ML4D Battery Amazon link (link opens in the new window).