Group 21R Battery Dimensions
Battery of this group has the positive post terminal located on the right. It is marked with the letter "R" because this post terminal position is called Reverse Polarity of Battery. Most batteries have it on the left side. If you want the positive post terminal to be on the left, you can turn around the 21R battery and use it as a group 21 battery, because they have identical dimensions. This will allow you to use the positive post on the left. Make sure you have enough cable length to reach the terminals, because in the turned position the terminals can be located a little further.
Battery Design |
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Dimensions and Sizes (Length x Width x Height) |
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8.1875'' x 6.8125'' x 8.75'' Inches 208 x 173 x 222 Millimeters |
Group 21R Battery Post Terminals
Post Terminal Types and Locations | Posts Used |
---|---|
Type "A", "A2" or manufacturer's custom post design |
Group 21R Battery Voltage and Current Characteristics
Volts | Cells | CCA Range |
---|---|---|
12 | 6 | 310-490 |
Group 21R Alternatives and Closest Battery Groups by Dimensions
Interchangeable Battery Groups for 21R 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 21R Battery | 8.1875'' x 6.8125'' x 8.75'' in. 208 x 173 x 222 mm Positive post on the Right |
12 | 6 | "A", "A2" | |
Group 21 Battery | 8.1875'' x 6.8125'' x 8.75'' in. 208 x 173 x 222 mm |
12 | 6 | "A", "A2" |
Similar Battery Groups With the Same Length, Width and Voltage
These dimensions will fit you in 99% of cases when you want to use a different battery group instead of a 21R battery since most battery compartments have a height margin and strict limitations on height and width only, which match batteries in the table below. Please check the battery compartment before you buy a battery from this group.
Battery Group Number | Dimensions | Shape | Volts | Cells | Post Terminal Type |
---|---|---|---|---|---|
Group 21R Battery | 8.1875'' x 6.8125'' x 8.75'' in. 208 x 173 x 222 mm Positive post on the Right |
12 | 6 | "A", "A2" | |
Group 26 Battery | 8.1875'' x 6.8125'' x 7.75'' in. 208 x 173 x 197 mm |
12 | 6 | "A", "A2" | |
Group 26R Battery | 8.1875'' x 6.8125'' x 7.75'' in. 208 x 173 x 197 mm Positive post on the Right |
12 | 6 | "A" |
Closest but not Identical Size Battery Groups
Battery groups in this section below are not identical to the group 21R 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 21R group.
Battery Group Number | Dimensions | Shape | Volts | Cells | Post Terminal Type |
---|---|---|---|---|---|
Group 21R Battery | 8.1875'' x 6.8125'' x 8.75'' in. 208 x 173 x 222 mm Positive post on the Right |
12 | 6 | "A", "A2" | |
Group 61 Battery | 7.5625'' x 6.375'' x 8.875'' in. 192 x 162 x 225 mm |
12 | 6 | "A" | |
Group 54 Battery | 7.3125'' x 6.0625'' x 8.375'' in. 186 x 154 x 212 mm |
12 | 6 | "A" | |
Group U1R Battery | 7.75'' x 5.1875'' x 7.3125'' in. 197 x 132 x 186 mm Positive post on the Right |
12 | 6 | "X" | |
Group U1 Battery | 7.75'' x 5.1875'' x 7.3125'' in. 197 x 132 x 186 mm |
12 | 6 | "X" | |
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 52 Battery | 7.3125'' x 5.8125'' x 8.25'' in. 186 x 147 x 210 mm |
12 | 6 | "A" |
Closest Large Dimensions
Bigger batteries can have more capacity and power compared to 21R batteries.
Battery Group Number | Dimensions | Shape | Volts | Cells | Post Terminal Type |
---|---|---|---|---|---|
Group 21R Battery | 8.1875'' x 6.8125'' x 8.75'' in. 208 x 173 x 222 mm Positive post on the Right |
12 | 6 | "A", "A2" | |
Group 70 Battery | 8.1875'' x 7.0625'' x 7.3125'' in. 208 x 180 x 186 mm |
12 | 6 | "S" | |
Group 71 Battery | 8.1875'' x 7.0625'' x 8.5'' in. 208 x 179 x 216 mm |
12 | 6 | "S" | |
Group 121R Battery | 8.25'' x 7'' x 8.5'' in. 208 x 177 x 215 mm Positive post on the Right |
12 | 6 | "A" | |
Group 85 Battery | 9.0625'' x 6.8125'' x 8'' in. 230 x 173 x 203 mm |
12 | 6 | "A" | |
Group 86 Battery | 9.0625'' x 6.8125'' x 8'' in. 230 x 173 x 203 mm |
12 | 6 | "A" | |
Group 25 Battery | 9.0625'' x 6.9375'' x 8.875'' in. 230 x 175 x 225 mm |
12 | 6 | "A", "A2" | |
Group 35 Battery | 9.0625'' x 6.9375'' x 8.875'' in. 230 x 175 x 225 mm |
12 | 6 | "A", "A2" | |
Group 75 Battery | 9.0625'' x 7.0625'' x 7.3125'' in. 230 x 180 x 186 mm |
12 | 6 | "S" | |
Group 72 Battery | 9.0625'' x 7.0625'' x 8.25'' in. 230 x 179 x 210 mm |
12 | 6 | "S" | |
Group 73 Battery | 9.0625'' x 7.0625'' x 8.5'' in. 230 x 179 x 216 mm |
12 | 6 | "S" |
How to Get 24 Volts from 12V of a 21R Battery Group
If you need 24 Volts, you can connect two group 21R 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 21R Batteries with a Parallel Connection
If you need to increase current capacity and reduce charging time, connect batteries in parallel. When group 21R 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.
ArrayEric Strong works in the automotive repair industry more than 12 years. His work included repairing electrical systems in various vehicle systems. A hybrid electric car battery replacement experience expanded his understanding of automotive battery technology.
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