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The battery tray is empty, the old battery is done, and the question is what size to put back in. That sizing question is what group 27 vs group 31 deep cycle battery comes down to. The short verdict: pick the group 31 side if you need an actual battery, like the Mighty Max MM-G31 with 12V 100Ah, 140RC and 900 CCA in AGM. Pick the group 27 side only if you need the holder: the A.A listing is a polypropylene tray with a strap for group 27 batteries, not a battery at all. We compared the two listings on what each states: capacity, size, build and warranty terms.
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group 27 vs group 31 deep cycle battery: side by side
| Group 27 vs Group 31 | Mighty Max MM-G31 Group 31 | A.A Group 27 battery tray |
|---|---|---|
| Side | Group 31 deep cycle battery | Group 27 |
| What it is | 12V 100Ah AGM battery | Battery tray with strap |
| Capacity | 100Ah, 140RC, 900 CCA | Not stated, tray only |
| Weight | 57.6 pounds | 16 ounces |
| Size | 12.88 x 6.75 x 9.5 in | Fits up to 7 x 12.5 in |
| Warranty | 3 Year (bullets), 1 Year (table) | 30 day |
Specifications are manufacturer rated as listed, collected 22 October 2026.
What each listing actually is
The Mighty Max listing is a battery: a BCI Group 31 12V 100Ah AGM car battery with 140RC and 900 CCA, sealed and spill-proof, with deep discharge recovery, rugged construction against shock and vibration, and mounting in multiple positions except upside down. It measures 12.88 by 6.75 by 9.5 inches at 57.6 pounds, with the positive terminal on the left and the negative on the right, and includes mounting screws. The A.A listing is a tray: an extreme-duty battery tray in high impact heavy polypropylene plastic for automotive, marine, boat and RV use, holding 27 series batteries up to 7 by 12.5 inches, with a safety strap and buckle included, 4 mounting points with 2 per long length, and tray, strap and screws in the box at 16 ounces.
Capacity and build
Only the battery side states capacity. The Mighty Max states 12V 100Ah with 140-minute reserve capacity, 900 CCA for starts in any season, 6 cells, 12 ohm resistance and a bolt terminal, built in an ISO-certified facility meeting CE standards. The tray side states no capacity: it keeps a group 27 battery securely mounted and limits movement with its strap. Build differs too: the Mighty Max lists rugged AGM construction for wide temperature ranges and tough environments, while the A.A lists heavy polypropylene plastic. The Mighty Max bullets state a 3 Year Warranty while its spec table states a 1 Year Manufacturers Warranty; trust the bullets over the table. The A.A states a 30 day manufacturers warranty.
What the listings leave unclear
The group 27 side tag suggests a battery comparison, but the A.A listing is a holder, so only one side offers a battery. The Mighty Max 3 Year versus 1 Year warranty figures do not match. The A.A spec table carries odd fields like screw terminals and X-10 protocol that read like a different product’s data. The Mighty Max lists wire harness and mounting accessories as not included.
Two examples
Mighty Max MM-G31 Group 31
A group 31 12V 100Ah AGM battery with 140RC and 900 CCA, sealed and spill-proof.
Pros
- 12V 100Ah with 140-minute reserve capacity
- 900 CCA for strong starts in any season
- Sealed spill-proof AGM with deep discharge recovery
- Resists shock, vibration and harsh conditions
Cons
- Bullets state 3 Year, table states 1 Year warranty
- 57.6 pounds, heavy for a small boat
- Wire harness and mounting accessories not included
- No specific depth of discharge figure is stated
Detailed Review
The listing states a BCI Group 31 12V 100Ah AGM battery with 140RC and 900 CCA, sealed and spill-proof, with deep discharge recovery and rugged construction against shock and vibration. It measures 12.88 by 6.75 by 9.5 inches at 57.6 pounds, with a bolt terminal, 6 cells and 12 ohm resistance, mounting in multiple positions except upside down, with the positive terminal on the left and the negative on the right. It states CE standards from an ISO-certified facility. The bullets state a 3 Year Warranty while the table states 1 Year Manufacturers Warranty.
Who it's for: car, boat and RV owners who need a group 31 battery with stated certifications. Who should skip it: anyone who only needs a tray to mount a group 27 battery.
Its Solar Score of 9.6/10 comes from performance 30/35, build 21/25, value 20/25, safety 5/10 and warranty 3/5: 79 of 100 points, placed on our 9.2 to 9.8 scale.
Key Specifications
| Voltage | 12 volts |
|---|---|
| Capacity | 100Ah, 140RC, 900 CCA |
| Type | AGM, sealed spill-proof |
| Size | 12.88 x 6.75 x 9.5 in |
Figures as published on the retailer listing, collected 22 October 2026. Performance figures are manufacturer rated.
Safety and Warranty
What this listing states. CE standards, ISO-certified facility stated, so safety scores 5 of 10. 3 Year Warranty stated (bullets); 1 Year in table. It does not say everything a buyer needs, such as who pays return shipping, so warranty scores 3 of 5. See How We Pick.
Battery safety. Charge with a charger and settings that match the stated chemistry, fuse the positive lead as the manual directs, cover terminals, keep within the stated temperature range, and never charge a damaged battery.
This is general buying information, not professional advice. Follow each product manual and local rules, and see our Safety Disclaimer.
A.A Group 27 battery tray
An extreme-duty polypropylene tray with strap for group 27 series batteries up to 7 by 12.5 inches.
Pros
- Fits 27 series batteries up to 7 by 12.5 inches
- Heavy polypropylene plastic construction
- Safety strap and buckle included
- 4 mounting points with 2 per long length
Cons
- A holder only; not a battery
- No battery capacity is stated
- No certification is stated
- 30 day warranty only
Detailed Review
The listing states an extreme-duty battery tray in high impact heavy polypropylene plastic for automotive, marine, boat and RV use, holding 27 series batteries up to 7 by 12.5 inches. It includes a safety strap and buckle, 4 mounting points with 2 per long length, and tray, strap and screws in the box, at 16 ounces, part BT24/27. The spec table carries odd fields like screw terminals and X-10 protocol that read like another product's data. The listing states a 30 day manufacturers warranty and no certification.
Who it's for: owners who need to mount a group 27 battery in a car, boat or RV. Who should skip it: anyone shopping for the battery itself.
Its Solar Score of 9.4/10 comes from performance 27/35, build 20/25, value 19/25, safety 0/10 and warranty 2/5: 68 of 100 points, placed on our 9.2 to 9.8 scale.
Key Specifications
| Fit | 27 series up to 7 x 12.5 in |
|---|---|
| Material | Polypropylene plastic |
| Mounting | Strap, 4 mounting points |
| Weight | 16 ounces |
Figures as published on the retailer listing, collected 22 October 2026. Performance figures are manufacturer rated.
Safety and Warranty
What this listing states. No battery management system, protection or listing is stated, so safety scores zero. 30 day manufacturers stated. It does not say everything a buyer needs, such as who pays return shipping, so warranty scores 2 of 5. See How We Pick.
Battery safety. Charge with a charger and settings that match the stated chemistry, fuse the positive lead as the manual directs, cover terminals, keep within the stated temperature range, and never charge a damaged battery.
This is general buying information, not professional advice. Follow each product manual and local rules, and see our Safety Disclaimer.
As an Amazon Associate I earn from qualifying purchases.
Where the points went
The Solar Score weighs performance, build, value, safety and warranty. For batteries, safety means stated protections or certifications the listing names: the Mighty Max states CE standards from an ISO-certified facility, and the tray states none. The Mighty Max states a 3 Year term in its bullets and the tray states 30 days. How we pick explains the weights.
| Product | Solar Score | Perf. /35 | Build /25 | Value /25 | Safety /10 | Warranty /5 |
|---|---|---|---|---|---|---|
| Mighty Max MM-G31 Group 31 | 9.6 | 30 | 21 | 20 | 5 | 3 |
| A.A Group 27 battery tray | 9.4 | 27 | 20 | 19 | 0 | 2 |
Scores run from 9.2 to 9.8: each product’s point total is placed on that range, so more points always means a higher score.
group 27 vs group 31 deep cycle battery: which should you choose?
Choose group 31 when you need the battery itself. The Mighty Max suits cars, boats and RVs with 12V 100Ah, 900 CCA and AGM spill-proof build. Choose group 27 hardware when you need to mount a battery you already own: the A.A tray suits automotive, marine, boat and RV installs with its strap and 4 mounting points. For more battery options, see the best 12 volt deep cycle battery for rv and the best lithium battery for RV boondocking.
| If you need | Look at |
|---|---|
| An actual group 31 battery | Mighty Max MM-G31 Group 31, 12V 100Ah |
| Mounting a group 27 battery | A.A Group 27 battery tray, strap included |
| Stated safety certification | Mighty Max MM-G31 Group 31, CE standards |
Sizing Notes
- Match the battery to the space: group 31 batteries need group 31 room; the A.A tray fits group 27 up to 7 by 12.5 inches.
- The Mighty Max states 12V 100Ah with 140RC and 900 CCA in sealed AGM.
- The A.A tray is a holder only and states no battery capacity.
- Warranty: 3 Year in the Mighty Max bullets against 1 Year in its table; 30 days on the tray.
- Secure the battery with the tray’s strap and 4 mounting points.
FAQ: power away from the grid
Is the A.A listing a battery?
No. It is a polypropylene tray and strap that holds group 27 series batteries; it states no battery capacity.
What does the Mighty Max warranty say?
The bullets state a 3 Year Warranty while the spec table states 1 Year Manufacturers Warranty; trust the bullets over the table.
What size battery fits the A.A tray?
Group 27 series batteries up to 7 by 12.5 inches, secured with the included strap and buckle.
Is the Mighty Max a deep cycle battery?
The listing describes AGM with deep discharge recovery, 12V 100Ah, 140RC and 900 CCA.
Which listing is heavier?
The Mighty Max battery at 57.6 pounds; the A.A tray at 16 ounces.
Related solar guides
See every Deep Cycle and RV Batteries guide and all Batteries and Charging guides.
More picks: best 12 volt deep cycle battery for rv, best lithium battery for RV boondocking.
