Batteries by Group Size
Are you looking for the right replacement battery that fits your vehicle, boat, or equipment tray perfectly? Battery group sizes standardise physical dimensions, terminal positions, and hold-down types so you get a hassle-free drop-in replacement every time. Whether you need a standard car battery, a heavy-duty truck power source, or a deep-cycle marine battery, we carry a full selection of BCI group sizes. Explore our categories below to find your specific size in flooded lead-acid, AGM, or lithium chemistries and get back on the road or water with confidence.
Why Battery Group Sizes Matter
Are you experiencing slow engine cranks, dimming lights, or struggling to fit a new battery into your vehicle's mounting tray? Finding the exact battery group size eliminates these headaches. Established by Battery Council International (BCI), battery group numbers designate the precise physical length, width, height, and terminal configuration for your battery compartment.
Choosing the correct group size ensures your replacement battery fits securely and performs reliably. Here is why proper fitment makes all the difference for your equipment:
- Safe, Secure Mounting: A battery that matches your tray size stays firmly locked down, preventing vibration damage and loose cable connections while driving.
- Correct Terminal Placement: Group sizes specify top-post, side-post, or recessed terminal positions. Proper placement ensures your vehicle cables reach comfortably without stretching or shorting.
- Reliable Starting Power: Matching your recommended group size guarantees your battery delivers the required cold cranking amps (CCA) and reserve capacity your engine needs.
- Versatile Applications: From daily commuters and heavy trucks to marine trolling motors, golf carts, and lawn tractors, matching group sizes keeps every engine running smoothly.
How to Choose the Right Battery Group Size
Selecting your replacement battery is straightforward once you know what to look for. Follow these steps to pick the ideal match for your setup:
- Check Your Current Battery Label: Look at the sticker on your existing battery or check your vehicle owner manual to identify the BCI group number (such as Group 24, 35, 51R, or 65).
- Verify Physical Dimensions: Measure the length, width, and height of your battery tray if you are upgrading or replacing a missing battery.
- Note Terminal Orientation: Pay attention to whether the positive terminal is on the right or left side. A letter like "R" in Group 51R indicates reversed terminal placement.
- Select the Right Battery Chemistry: Choose standard flooded lead-acid for reliable budget power, Absorbed Glass Mat (AGM) for spill-proof vibration resistance, or lightweight lithium for maximum lifespan and rapid charging.
At Battery Mart, we carry an extensive inventory of BCI group size batteries from leading brands like Deka, Odyssey, and Antigravity. If you have questions about fitment, our customer support team is happy to assist you through our contact page. Plus, every purchase is backed by our risk-free 60-day return policy.
Frequently Asked Questions
What does a battery group size mean?
A: A battery group size is a standard code set by Battery Council International (BCI). It defines the physical dimensions (length, width, and height), terminal locations, and mounting style of a battery to ensure it fits properly in a specific vehicle or equipment tray.
Can I use a different group size if it fits in my battery tray?
A: In some cases, a different group size can work if the physical dimensions fit your tray, the terminal orientation aligns with your vehicle cables, and the battery meets or exceeds the required cold cranking amps (CCA). However, using the original recommended BCI group size is always the safest choice to ensure proper fitment and hold-down security.
What is the difference between Group 24, Group 27, and Group 31 batteries?
A: These group sizes share similar 12-volt setups but differ in physical length and energy capacity. Group 24 is the smallest, Group 27 is mid-sized, and Group 31 is the largest. Larger group sizes hold more lead plates, providing higher reserve capacity and amp-hours for demanding marine, RV, and trolling motor applications.
What does the "R" stand for in group sizes like 51R or 24R?
A: The "R" stands for reversed terminal polarity. A Group 51R battery has the same physical dimensions as a standard Group 51, but the positive and negative terminals are on opposite sides. Always verify terminal positions before purchasing so your battery cables reach correctly.
How do I know if I need an AGM or standard flooded battery in my group size?
A: If your vehicle came with an AGM battery from the factory, or if you need superior resistance to vibration and deep discharge (such as in off-road, marine, or start-stop vehicles), choose an AGM battery. Standard flooded batteries are great for typical automotive starting needs where budget is a top priority.
