What is a Group 51 Battery: Technical Information and Comparison with Alternatives

Group 51 Battery Dimensions

Battery Design

Dimensions and Sizes (Length x Width x Height)
9.375'' x 5.0625'' x 8.75'' Inches 238 x 129 x 223 Millimeters

Group 51 Battery Post Terminals

Post Terminal Types and Locations	Posts Used
	Type "A", "A2" or manufacturer's custom post design

Group 51 Battery Voltage and Current Characteristics

Volts	Cells	CCA Range
12	6	270-500

Best Group 51 Batteries

List of recommended batteries

Good Choice	ACDelco Gold B24R Hybrid Vehicle AGM BCI Group 51 Battery Cold Cranking Amps (CCA): 325, Reserve Capacity (RC): 70, Amp-Hours (AH): 45 Battery Group: 51 Type: AGM Warranty: 24 months Check Price	Check Price
Good Choice	Optima Batteries 8071-167 D51 YellowTop Dual Purpose Battery Cold Cranking Amps (CCA): 450, Reserve Capacity (RC): 66, Amp-Hours (AH): 38 Battery Group: 51 Type: AGM Warranty: 36 months Check Price	Check Price

Equivalents with the Reverse Polarity

Batteries in this section have identical sizes and a positive post terminal on the opposite RIGHT side.

Good Choice	SLI51R Duracell Ultra BCI Group 51R Car and Truck Battery Cold Cranking Amps (CCA): 450, Battery Group: 51R Type: Lead-Acid Warranty: 24 months Check Price	Check Price
Good Choice	Optima Batteries 8073-167 D51R YellowTop Dual Purpose Battery Cold Cranking Amps (CCA): 450, Reserve Capacity (RC): 66, Amp-Hours (AH): 38 Battery Group: 51R Type: AGM Warranty: 36 months Check Price	Check Price
Good Choice	EverStart Maxx Lead Acid Automotive Battery, Group Size 51R (12 Volt / 500 CCA) Cold Cranking Amps (CCA): 500, Battery Group: 51R Type: Lead-Acid Warranty: 36 months Check Price	Check Price
Good Choice	Exide S51R Sprinter Classic 51R Battery 450 CCA Cold Cranking Amps (CCA): 450, Battery Group: 51R Type: Lead-Acid Warranty: 24 months Check Price	Check Price
Good Choice	Megavolt Lead Acid Flooded Car Battery BCI 51R, 12V 55AH CCA500 CA525 (51R-60-500) Cold Cranking Amps (CCA): 425, Reserve Capacity (RC): 70, Amp-Hours (AH): 45 Battery Group: 51R Type: Lead-Acid Warranty: 24 months Check Price	Check Price
Good Choice	Duralast Gold Battery 51R-DLG Group Size 51R 500 CCA Cold Cranking Amps (CCA): 500, Reserve Capacity (RC): 85, Battery Group: 51R Type: Lead-Acid Warranty: 36 months Check Price	Check Price

Group 51 Alternatives and Closest Battery Groups by Dimensions

Interchangeable Battery Groups for 51 Battery

These groups have the same dimensions and performance but can have different terminal post types, post locations, and polarity.

Battery Group Number	Dimensions	Shape	Volts	Cells	Post Terminal Type
Group 51 Battery	9.375'' x 5.0625'' x 8.75'' in. 238 x 129 x 223 mm		12	6	"A", "A2"
Group 51R Battery	9.375'' x 5.0625'' x 8.75'' in. 238 x 129 x 223 mm Positive post on the Right		12	6	"A", "A2"

Closest but not Identical Size Battery Groups

Battery groups in this section below are not identical to the group 51 battery, they can be a little bigger or smaller. Please pay attention to the post terminal types and their location

Closest Groups that Have Slightly Smaller Dimensions

Smaller batteries can have less capacity, performance, and power in comparison with 51 group.

Battery Group Number	Dimensions	Shape	Volts	Cells	Post Terminal Type
Group 51 Battery	9.375'' x 5.0625'' x 8.75'' in. 238 x 129 x 223 mm		12	6	"A", "A2"
Group 151R Battery	7.4375'' x 4.9375'' x 8.875'' in. 188 x 125 x 225 mm Positive post on the Right		12	6	"A"
Group 400 Battery	5.875'' x 3.4375'' x 5.625'' in. 150 x 88 x 143 mm		12	6	"AuxTerminal"
Group 401 Battery	5.875'' x 3.4375'' x 5.125'' in. 150 x 88 x 130 mm		12	6	"AuxTerminal"

Closest Large Dimensions

Bigger batteries can have more capacity and power compared to 51 batteries.

Battery Group Number	Dimensions	Shape	Volts	Cells	Post Terminal Type
Group 51 Battery	9.375'' x 5.0625'' x 8.75'' in. 238 x 129 x 223 mm		12	6	"A", "A2"
Group 22NF Battery	9.4375'' x 5.5'' x 8.9375'' in. 240 x 140 x 227 mm		12	6	"A", "A2"
Group 45 Battery	9.4375'' x 5.5'' x 8.9375'' in. 240 x 140 x 227 mm		12	6	"A", "A2"
Group 2H Battery	10.25'' x 5.3125'' x 8.9375'' in. 260 x 135 x 227 mm		12	6	"A"

How to Get 24 Volts from 12V of a 51 Battery Group

If you need 24 Volts, you can connect two group 51 batteries in series to double the voltage. The voltage of a series connection is equal to the sum of the voltages of all its batteries. If one 12V lead-acid battery is connected to another 12V lead-acid battery, you have 24V total power output. Each battery must be fully charged and completely isolated from the other before connecting them in series, or there will be damage to at least one of them.

Increasing a Capacity of 51 Batteries with a Parallel Connection

If you need to increase current capacity and reduce charging time, connect batteries in parallel. When group 51 batteries are in parallel, their voltage is equal to the voltage of one battery, while current capacity equals to the sum of all its battery capacities. If you have two 12V lead-acid batteries with 60 Ah capacity and you connect them in parallel, you'll get 12 Volts with 120 Ah.