Group 75 Batteries - Dimensions, Features, and Recommendations

BCI Group 75 batteries are automotive and light industry batteries, designed mostly as either starting or dual-purpose batteries with very good starting features.

As such, BCI Group 75 batteries are commonly used in cars, light trucks, and other vehicles where they are used for starting internal combustion engines, but also for powering various other loads like pumps, winches, lights, etc.

odyssey 75 pc1230

Group 75 Battery Specifications and Features

Modern BCI Group 75 Batteries are mostly AGM (Absorbent Glass Mat) SLA (Sealed Lead Acid) batteries, designed with increased vibration resistance in mind and thanks to the modern technologies, with vary vague difference between starting/cranking and dual-purpose batteries - most 'starting' batteries are made with Start/Stop applications in mind, combined with powering various other devices while the main engine is off.

Similarly, dual-purpose batteries are designed for powering all kinds of loads while the main engine is turned off, but they are also designed to provide large amounts of current required to crank the gas/diesel engines.

The most popular group 75 batteries are given in the following comparison chart:

Model Battery Type Cell Type Ah CCA MCA RC Weight (lbs/kg) Review
Delphi BU9075DT MaxStart Starting AGM 60 680 - 100 41.0 lbs; 18.6 kg -
Odyssey 75-PC1230 Dual Purpose AGM 55 760 815 110 45.5 lbs; 20.6 kg -
Odyssey 75/86-PC1230DT Dual Purpose AGM 55 760 815 110 45.5 lbs; 20.6 kg -
Optima 8022-091 75/25 RedTop Starting AGM 44 720 910 100 33.1 lbs; 15.0 kg -
Optima 8042-218 D75/25 YellowTop Dual Purpose AGM 48 620 770 98 37.8 lbs; 17.2 kg -

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As one can see, group 75 batteries feature a nominal (20h) capacity in the 44-60 Ah range, they feature CCA in 620-760 Amps range, 770-910 Amps MCA and RC value of ~100-110 minutes.

Also, they weigh between 33.1 and 45.5 pounds (15.0 - 20.6 kg).

optima 75 25 red top

By default, group 75 batteries feature side battery terminals (positive to the left), some models feature both top and side terminals, often being additionally labeled with 'DT' (Dual Terminals) letters.

Some dual terminal group 75 batteries are labeled as 'group 75', some are labeled as 'grout 75/25' and some models as 'group 75/86' batteries - this is due to the similar dimensions between BCI battery groups 25, 75, and 86:

- BCI Group 25 Battery: 9 1/16 x 6 7/8 x 8 7/8 inches (230 x 175 x 225 mm),

- BCI Group 75 Battery: 9 1/16 x 7 1/16 x 7 11/16 inches (230 x 179 x 196 mm),

- BCI Group 86 Battery: 9 1/16 x 6 13/16 x 8 inches (230 x 173 x 203 mm).

As one can see, physical dimensions differ, but not by much. Because of that, some manufacturers offer '75' and/or '75/25' and/or '75/86' size batteries.

delphi bu9075dt

Of course, when ordering a new group 75 battery, it is very important to check the size of the battery compartment and the actual size of the new battery.


How to Charge Group 75 Battery?

If the battery is installed in the car or any other vehicle that features an onboard battery charging system, let it charge the battery.

It is a good practice to periodically check the voltage on the battery and terminal connections - AGM batteries are practically maintenance-free batteries, but they must be properly connected to the car/truck in order to work as intended.

Those batteries that are not charged by an alternator connected to the internal combustion engine should be charged using smart AGM battery chargers that analyze the battery prior to charging and adjust the charging process according to the battery's condition.

Since their capacity varies between 44-48 Ah (spiral-wound batteries) and 55-60 Ah (flat plates) they can be charged with the battery chargers featuring an output current of 5 - 10 Amps.

Such a battery charger can recharge 50Ah battery discharged down to 50% DoD in around 3 hours, depending on the battery condition, temperature, and similar.


Group 75 Battery as Inverter Battery?

When being used in the car, group 75 batteries are often used for powering various devices via car power inverters.

When the cigarette lighter adapter is used, current is limited to mostly 10 Amps, leading to the maximum inverter output power of ~100 watts.

However, if the inverter is connected directly to the battery, stronger 300-500W power inverters may be used.

On average, 300W power inverters feature an efficiency of ~85%, requiring ~350 watts from the battery (30 Amps @12V).

Since RC values for group 75 batteries vary between 100 and 110 minutes, group 75 batteries may provide ~250 watts (output power) up to 50-55 minutes without being drained below 50% DoD.

But, for something like that, one needs a good 300W pure sine wave power inverter.


Long Story Short: Group 75 batteries are able to easily crank gas and diesel engines and still be able to power other devices when the main engine is offline. They are AGM maintenance-free batteries, that often feature dual terminals and are built to fit either group 75, group 75/25, or group 75/86 battery compartments.

As always with the batteries, be sure to check the terminal orientation and actual size of both the new battery and the battery compartment.

Model Battery Type Cell Type Ah CCA MCA RC Weight (lbs/kg) Review
Delphi BU9075DT MaxStart Starting AGM 60 680 - 100 41.0 lbs; 18.6 kg -
Odyssey 75-PC1230 Dual Purpose AGM 55 760 815 110 45.5 lbs; 20.6 kg -
Odyssey 75/86-PC1230DT Dual Purpose AGM 55 760 815 110 45.5 lbs; 20.6 kg -
Optima 8022-091 75/25 RedTop Starting AGM 44 720 910 100 33.1 lbs; 15.0 kg -
Optima 8042-218 D75/25 YellowTop Dual Purpose AGM 48 620 770 98 37.8 lbs; 17.2 kg -

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