2020 Kenworth T680 Battery Specs, Group Size & Replacement Guide

The 2020 Kenworth T680 is a premium Class 8 heavy-duty truck designed for long-haul efficiency and driver comfort. With advanced aerodynamics, heavy-duty diesel engines (like the PACCAR MX-13 or Cummins X15), and demanding sleeper cab hotel loads, keeping your electrical system in top shape is non-negotiable.

As an ASE-certified master technician, I regularly field questions about heavy-duty battery setups. For a commercial truck like the T680, battery failure doesn't just mean an inconvenience—it means lost revenue and expensive road calls. Here is the definitive guide to the battery requirements for the 2020 Kenworth T680.

Quick answer: 2020 Kenworth T680 Battery Specs

• BCI Group Size: Group 31
• Multi-Battery Setup: 3 or 4 batteries wired in parallel (4 is standard for sleeper cabs)
• Cold Cranking Amps (CCA): 925 to 1150 CCA per battery (yielding 3,700+ total CCA in a 4-battery bank)
• Reserve Capacity (RC): 190 to 205 minutes per battery
• AGM vs Flooded: Heavy-duty flooded or AGM (AGM is highly recommended for sleeper cabs with inverters and high hotel loads)
• Terminal Layout: 3/8-inch threaded stainless steel stud terminals (center layout)
• Physical Dimensions: Approximately 13.0" L x 6.8" W x 9.4" H (per battery)

Replacement battery options

When outfitting a Class 8 truck, always replace all batteries in the bank at the same time. Mixing old and new batteries will quickly degrade the new units. Here are some of the most reliable Group 31 replacements:

• Odyssey Extreme ODX-AGM31: (AGM) 1150 CCA. An absolute powerhouse with incredible vibration resistance and deep-cycle capabilities for heavy hotel loads.
• Interstate 31-MHD: (Flooded) 950 CCA. A commercial-grade workhorse that offers excellent starting power for a lower upfront cost.
• Optima YellowTop D31T: (AGM) 900 CCA. Features a threaded stud and spiral-cell technology, making it extremely resistant to road vibration.
• ACDelco Gold 31 BCI: (Flooded) 900 CCA. A reliable, standard replacement option for day cabs or trucks with minimal hotel loads.

AGM vs flooded — which does this vehicle need?

While the 2020 Kenworth T680 comes from the factory with options for both, the right choice depends heavily on your application.

Flooded lead-acid batteries (like the standard PACCAR OEM batteries) are adequate for day cabs or line-haul trucks that don't have excessive accessory usage. They provide massive starting power and are cost-effective.

AGM (Absorbent Glass Mat) batteries are practically a requirement if you run a 76-inch sleeper cab equipped with a large inverter, microwave, refrigerator, or CPAP machine. AGM batteries excel in deep-cycling (discharging and recharging) and charge much faster than flooded batteries. Furthermore, their sealed design handles the severe chassis vibrations of a Class 8 truck much better than flooded plates.

Post-installation relearn / reset procedure

Unlike modern passenger cars with complex Battery Management Systems (BMS), a Class 8 truck like the T680 does not require a scanner-based "battery registration." However, there are important steps to follow:

1. Low Voltage Disconnect (LVD): The Kenworth T680 is equipped with an LVD system to protect starting power. After reconnecting the batteries, verify that the LVD module is functioning and hasn't locked out accessory power.
2. ECM Codes: If the old batteries voltage dropped low enough, the Cummins or PACCAR engine ECM may have thrown low-voltage fault codes. You may need a heavy-duty diagnostic tool to clear these inactive codes.
3. Clock and Radio: Basic interior electronics will need to be reset.

Signs of a failing battery

In a multi-battery bank, one failing battery will mask itself by drawing power from the good ones. Look out for:

• Slow engine cranking: Especially during cold mornings.
• Early LVD tripping: If your accessories cut off shortly after shutting off the engine, the battery bank's reserve capacity is depleted.
• Constant APU cycling: If your Auxiliary Power Unit has to run continuously to keep the batteries charged while parked.
• Swelling or leaking: Visible acid on the battery box tray or swollen battery cases.

Common battery issues for this generation

The most common issue on the 2020 T680 isn't the batteries themselves, but the parallel interconnect cables. Due to their location along the frame rail, the battery box is subjected to road spray, winter salt, and debris. Corrosion builds up quietly on the threaded studs and jumper cables. This leads to unequal resistance between the four batteries, causing the alternator to overcharge the closest batteries while undercharging the furthest ones. Always clean all cable ends and use terminal protection spray when replacing the batteries.

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