What Is a Group 34 Battery? Size, Specs, and What It Fits

A Group 34 battery is a BCI-defined case size — roughly 10¼ × 6¹³⁄₁₆ × 7⅞ inches, 12 volts, positive terminal on the left — not a capacity or performance rating.

Two batteries can both be Group 34 and still start your truck very differently: one may be 800 CCA flooded lead-acid, another 63 Ah AGM with a taller case. The group number promises the battery will physically land in the tray with the terminals where your cables expect. Everything about power, chemistry, and warranty comes from the model, not the group.

The sections below cover exact dimensions, what that number does and doesn’t guarantee, and the fitment checks that decide whether a Group 34 actually works in your vehicle or boat.

Group 34 Battery Size and Specs

Nominal Group 34 dimensions are about 10¼ inches long, 6¹³⁄₁₆ inches wide, and 7⅞ inches high, with 12 volts nominal and the positive terminal on the left. Height is the spec that varies most between models, so measure your existing case before ordering.

AutoZone lists the standard approximate case size and identifies the left-positive terminal arrangement. Interstate’s MTP-34 shows a slightly shorter case at 10¼ × 6¹³⁄₁₆ × 7¼ inches — proof that a group number sets a size class, not a millimetre-exact box.

Power figures differ just as widely. Interstate’s MTP-34 is a flooded lead-acid battery rated 800 CCA, 1,000 cranking amps, 110 minutes reserve capacity at 25 A, backed by a 30-month warranty. The AGM MTZ-34 in the same group is rated 12 V, 63 Ah, 800 CCA, 1,000 CA, and 125 minutes reserve capacity, at 10.82 × 6.76 × 7.84 inches.

Representative specs across current listings:

Prices shift by location and core charges; the listings behind these numbers were dated 2025–2026, so confirm at checkout. If you want the shortlist without comparing specs yourself, our tested Group 34 battery roundup ranks these by real-world cranking and warranty.

What a Group 34 Battery Fits — And What the Number Won’t Tell You

Group 34 batteries fit cars, light trucks, SUVs, marine equipment, and RVs that call for that case size — but the group number alone never confirms fitment. Your vehicle’s owner’s manual or battery tray decides.

Retailers stock Group 34 in several forms: standard flooded starting batteries, dual-terminal versions, AGM, and marine/RV dual-purpose products. That range is the point. The case is shared; the job is not. A deep-cycle trolling-motor bank needs a product rated for that duty, not a starting battery with the same footprint.

Check these before you buy:

• Height. A taller case can foul the hood or hold-down hardware even when length and width look right.
• Terminal polarity. A left-positive battery won’t work in a tray routed for the opposite layout.
• Hold-down style. The replacement must clamp with the vehicle’s original retention system — never leave a battery unsecured.
• Cable reach and venting. Confirm both, especially on tight engine bays and in-cabin RV installs.
• Chemistry requirements. Don’t swap an AGM original for flooded without checking the charging system and battery-management needs.

One tempting shortcut deserves a warning: a Group 34/78 is not automatically a Group 34. Terminal placement and case geometry differ between the two, and the 78 half adds a second terminal pair. Interstate notes its MTZ-34 may fit some Group 24 applications, but only with a height adapter and only after application-specific confirmation.

Interstate’s product pages are the clearest reference for current Group 34 ratings and case dimensions. The Interstate MTP-34 specification page lists the full flooded specs and warranty term directly.

Safety and Disposal Basics

Lead-acid batteries release explosive hydrogen gas while charging, so install with eye protection, no flames nearby, and no tools bridging the terminals. Reversed polarity or a shorted wrench can cause sparks, burns, and battery damage.

Most retailers charge a refundable core deposit — $22 on several Duralast Group 34 listings — to encourage return of the old battery. Hand the used one back to the retailer or an approved recycling program rather than putting it in household waste.