What “R” Means on a Battery

On batteries, the letter “R” most commonly indicates either a round (cylindrical/coin) cell in IEC product codes (as in CR2032, LR6, R6), or reversed/right-hand positive terminal orientation in automotive and powersports battery group sizes (as in 51R or U1R). In older or basic IEC labels, “R” alone before the size digits (such as R6 or R03) typically denotes a zinc–carbon round cell. Understanding where the “R” appears in the code tells you which meaning applies.

Where you’ll see “R” and what it means

Because battery markings follow different standards across consumer cells and vehicle batteries, “R” can signal shape, chemistry context, or terminal orientation. The points below outline the main places you’ll encounter “R” and how to read it accurately.

• IEC consumer cells (AA, AAA, coin/button cells): “R” indicates a round cell. If it appears by itself before the size code (e.g., R6 for AA, R03 for AAA), it usually means a zinc–carbon round cell under IEC 60086. When combined with another letter, the first letter signals chemistry and “R” still marks it as round—for example:
  – LR6 = alkaline-manganese AA (L = alkaline, R = round, 6 = AA)
  – CR2032 = lithium manganese dioxide coin cell (C = lithium MnO2, R = round, 20×3.2 mm)
  – SR626SW = silver-oxide round button cell
• Automotive and powersports batteries: A trailing “R” in the group or model (e.g., 51R, 26R, U1R) means reversed (right-hand) positive terminal orientation compared with the same size without the “R.” In Japanese JIS codes (e.g., 55D23L/R), the last letter L or R tells you whether the positive post is on the left or right.
• Rechargeable cylindrical cells: In codes like HR6 (NiMH AA) or KR6 (NiCd AA), the first letter(s) indicate chemistry (H = NiMH, K = NiCd), and “R” still marks the round form factor. Here, “R” does not mean “rechargeable” by itself; the chemistry letter does that.
• Other IEC chemistries with “R”: You may also see FR6 (lithium iron disulfide AA), PR (zinc–air button cells), and BR/CR (lithium coin cells). In each case, “R” is the round shape indicator while the leading letter(s) define the chemistry.

When in doubt, read the entire designation: the position of “R” (prefix, infix, or suffix) and the surrounding letters or numbers determine whether it refers to shape, chemistry context, or terminal layout.

How to decode common labels with “R”

CR2032

C = lithium manganese dioxide chemistry, R = round coin shape, 20 = 20.0 mm diameter, 32 = 3.2 mm thickness.

LR6 (AA alkaline)

L = alkaline-manganese chemistry, R = round/cylindrical, 6 = AA size. Same size in zinc–carbon would be R6.

R6 (AA zinc–carbon)

R = round cell; with no chemistry letter ahead of it, this typically denotes a zinc–carbon (Leclanché) primary cell in the IEC scheme; 6 = AA size.

51R (automotive battery)

Group 51 size with reversed polarity relative to a standard Group 51. The “R” tells you the positive post is on the right (when oriented per the standard reference), which is crucial for cable reach and fitment.

Practical tips to buy or replace the right battery

Misreading “R” can lead to buying the wrong chemistry, size, or terminal orientation. Use these quick checks to avoid mistakes.

• Look for the full IEC code: Letters before “R” tell you the chemistry (L, C, S, F, H, K, etc.); the digits after it indicate size.
• For vehicles, match the entire group number including any “R” or “L” suffix; terminal orientation affects cable reach and mounting.
• Don’t assume “R” means rechargeable: Rechargeability depends on chemistry (e.g., NiMH/“H”), not the “R.”
• Cross-check equivalents: LR6 (AA alkaline) is the same size as R6 (AA zinc–carbon) but with different performance; pick the chemistry you need.
• Mind coin cell dimensions: In CR-series, “R” is shape; the four digits are critical for fit (diameter × thickness in tenths of mm).

Confirming the full code and context will ensure you get a battery that fits physically, connects correctly, and delivers the performance your device requires.

Summary

“R” on a battery usually designates a round form factor in IEC codes (as in CR2032, LR6, R6), and when used as a suffix in automotive and powersports part numbers (like 51R or U1R) it indicates reversed/right-hand positive terminal orientation. If “R” appears alone before the size digits (R6, R03), it typically denotes a zinc–carbon round cell. Always read the entire code—letters around “R” define chemistry and, in vehicle batteries, terminal layout.

What does 26R mean on a battery?

On a car battery, “26R” indicates the battery’s physical size and post (terminal) orientation. Specifically, “26” refers to the battery’s physical dimensions (BCI Group 26), while the “R” signifies a reverse post orientation, meaning the positive and negative terminals are on opposite sides compared to a standard Group 26 battery. 
Here’s a more detailed explanation:

• Group 26: This is a standard battery size classification (BCI Group 26) established by the Battery Council International (BCI). Batteries in this group share similar dimensions. 
• R (Reverse): This suffix indicates that the positive and negative terminals are in the opposite position compared to a standard Group 26 battery. A standard Group 26 battery has the positive terminal on the left and the negative on the right when facing the terminals. A 26R battery would have the terminals reversed, meaning the positive terminal is on the right and the negative on the left. 
• Importance: The “R” designation is crucial because it ensures the battery will fit correctly in vehicles that require a specific terminal orientation. If a 26R battery is needed, replacing it with a standard 26 would require modifications to the battery cables or hold-down mechanism. 

How to know if battery is L or R?

Last letter represents the battery polarity: R is for negative terminal on the right, L is for negative terminal on the left, although it is an industry standard to ask which side of the battery is the positive terminal when both terminals are closest to you.

Is a 24R and 24F the same battery?

24: The standard Group 24 battery, commonly used in various applications. 24F: Slightly taller, designed for specific Asian vehicles. 24H: Similar to Group 24, but with slight differences in lid design or terminal placement. 24R: Features a “reverse” terminal layout compared to the standard Group 24.

What do letters on a battery mean?

Battery letters have different meanings depending on the context. They can indicate battery chemistry (like lithium iron phosphate or LFP), battery size (like AA, AAA, C, or D), or even specific features or construction (like sealed or AGM). 
Here’s a breakdown of common letter meanings:
Battery Chemistry:

• LFP: Lithium iron phosphate (LiFePO4).
• ICR: Lithium cobalt oxide (LiCoO2).
• LP: Lithium polymer.
• IMR: Lithium manganese oxide (LiMn2O4).
• IFR: Lithium iron phosphate (another notation for LiFePO4).
• AGM: Absorbent Glass Mat, a type of lead-acid battery.
• EFB: Enhanced Flooded Battery, a type of lead-acid battery. 

Battery Size (and sometimes shape):

• AA, AAA, C, D: Standard battery sizes, with the number of “A”s indicating size, and larger letters indicating larger sizes.
• CR2032: Coin cell battery, where C indicates lithium, R indicates round, and 2032 is the size (20mm diameter, 3.2mm height). 

Other Meanings:

• BS: Battery sealed, indicating a maintenance-free, sealed battery. 
• CCA: Cold Cranking Amps, a measure of a battery’s power at low temperatures. 
• CA: Cranking Amps, a measure of a battery’s power for starting a vehicle. 
• RC: Reserve Capacity, the time a battery can run at a specific amperage without alternator assistance. 
• L: Negative terminal on the left (often in automotive batteries). 
• R: Negative terminal on the right (often in automotive batteries). 
• S: Sealed (in some battery types, like those with the “BS” designation). 
• X or Y: In some battery models, may indicate different terminal styles or performance levels. 
• W: May indicate compliance with the IEC 60086-3 standard for watch batteries.