Group 24 vs Group 27 vs GC2: which lithium battery size do I need?
Start with the space you have. Group 24 and Group 27 are standard 12V tray sizes used in trailers, truck campers and boats; Group 27 is about 1.7 inches longer and holds more. GC2 is the taller golf-cart footprint found in fifth wheels and larger rigs. In Expion360 LiFePO4, Group 24 comes in 60Ah and 80Ah, Group 27 in 100Ah and 120Ah, and GC2 in 162Ah at 12V, all with a 12-year warranty.
How big is each Expion360 battery?
Dimensions and weights are from each product's published specification. Voltages are nominal.
| Model | Footprint | Voltage | Capacity | Weight | Dimensions (L × W × H) |
|---|---|---|---|---|---|
| 12V 60Ah | Group 24 | 12.8V | 60Ah | 19.2 lb | 10.2 × 6.8 × 8.6 in |
| 12V 80Ah | Group 24 | 12.8V | 80Ah | 24.0 lb | 10.2 × 6.8 × 8.6 in |
| 12V 100Ah | Group 27 | 12.8V | 100Ah | 29 lb | 11.9 × 6.8 × 8.6 in |
| 12V 100Ah SmartTalk™ + VHC™ | Group 27 | 12.8V | 100Ah | 34 lb | 12.6 × 6.8 × 8.7 in |
| 12V 120Ah | Group 27 | 12.8V | 120Ah | 30 lb | 11.9 × 6.8 × 8.6 in |
| 12V 162Ah SmartTalk™ + VHC™ | GC2 | 12.8V | 162Ah | 39.5 lb | 10.2 × 7.1 × 10.9 in |
| 48V 36Ah SmartTalk™ | GC2 | 51.2V | 36Ah | 38.5 lb | 10.2 × 7.1 × 10.9 in |
What does Group 24, Group 27 or GC2 actually mean?
They are Battery Council International (BCI) case sizes. A group number fixes the battery's length, width and height and the terminal layout, so any Group 27 battery fits a Group 27 tray. The number says nothing about chemistry or capacity — a Group 27 lead-acid battery and a Group 27 LiFePO4 battery share a box, but the lithium one delivers roughly twice the usable energy at about half the weight.
What is the difference between Group 24 and Group 27?
Length and capacity. Both are 6.8 inches wide and about 8.6 inches tall; Group 27 is roughly 11.9 inches long against Group 24's 10.2. That extra length holds more cells: Expion360's Group 24 tops out at 80Ah and Group 27 at 120Ah. If your tray takes a Group 27, use it — you get 50% more capacity for about six more pounds.
Check the length before you buy a heated model. The 12V 100Ah Group 27 SmartTalk™ + VHC™ is 12.6 inches long, about 0.7 inches longer than the standard Group 27, because the heating and monitoring hardware lives inside the case. Most Group 27 trays and hold-downs accept it; tight marine boxes sometimes do not.
What is a GC2 battery, and can one 12V GC2 replace two 6V batteries?
GC2 is the 6V golf-cart footprint — 10.2 × 7.1 inches and about 10.9 inches tall. Many fifth wheels and larger trailers wire two 6V GC2 lead-acid batteries in series to make 12V. Expion360's 12V 162Ah GC2 does that job in one case, so a pair of 6V batteries can become two 12V GC2s in parallel, roughly doubling usable capacity in the same compartment.
When converting, rewire from series to parallel. Two 12V batteries in series make 24V, which will damage a 12V RV system. The 48V 36Ah GC2 shares the same footprint and is built for 48V golf carts, low-speed vehicles and 48V power systems.
Two 6V 225Ah lead-acid GC2s in series: about 112Ah usable at 12V, roughly 125 lb.
Two 12V 162Ah Expion360 GC2s in parallel: 324Ah at 12V, about 79 lb.
Which size gives the most capacity for the space?
GC2. Among Expion360's standard footprints, the 162Ah GC2 holds about 0.21 amp-hours per cubic inch, against roughly 0.17 for the 120Ah Group 27 and 0.13 for the 80Ah Group 24. If height is free, GC2 is the densest drop-in. If you are building from scratch, the 12V 450Ah EX1 goes further still, at about 0.22 Ah per cubic inch in a single battery.
Group 24 vs Group 27 vs GC2 at a glance
The right footprint is the one that fits your tray. Within that, here is how the three compare in Expion360 LiFePO4.
| Group 24 | Group 27 | GC2 | |
|---|---|---|---|
| Expion360 capacity (12V) | 60Ah or 80Ah | 100Ah or 120Ah | 162Ah |
| Length × width | 10.2 × 6.8 in | 11.9 × 6.8 in (12.6 in heated) | 10.2 × 7.1 in |
| Height | 8.6 in | 8.6–8.7 in | 10.9 in |
| Weight | 19.2–24.0 lb | 29–34 lb | 39.5 lb |
| Heated (VHC™) option | No | Yes, 100Ah | Yes |
| SmartTalk™ Bluetooth | No | On the 100Ah SmartTalk™ + VHC™ | Yes |
| CAN Bus | No | On the 100Ah SmartTalk™ + VHC™ | Yes |
| Typical home | Pop-ups, small trailers, small boats | Travel trailers, truck campers, bass boats | Fifth wheels, large trailers, off-grid |
| Warranty | 12 years | 12 years | 12 years |
All models are 12.8V nominal LiFePO4 and UL1973 certified (UL File No. 22D01).
What if none of the standard sizes fit?
Expion360 makes two non-BCI formats. The EX2 Edge is 4.2 inches tall and 21.9 × 17.5 inches in footprint, built to slide under a bed, bench or false floor; it comes as a 12V 240Ah and a 48V 60Ah, both heated with VHC™. The EX1 puts 450Ah at 12V — 5,760 Wh — into one 14.8 × 13.0 × 10.4 inch battery for Class A coaches and large off-grid systems.
Can I move up from a Group 24 to a Group 27?
Usually, if the tray, hold-down and cable reach allow the extra 1.7 inches of length. The terminals and voltage are the same, so nothing else in a 12V system changes. Measure the compartment, not the old battery, and confirm the hold-down strap or bracket will secure the longer case. Expion360 sells Group 27 mounting kits for the heated model.