2015 Kenworth T680 Battery Size, Specs, and Replacement Guide

As an ASE-certified master technician, I’ve serviced countless heavy-duty trucks, and the electrical demands of a modern Class 8 truck like the 2015 Kenworth T680 are staggering. Whether you are running a day cab or a fully loaded 76-inch sleeper with an inverter and hotel loads, having the right battery bank is critical to keeping your rig on the road and avoiding costly jump-starts.

Here is the comprehensive battery spec reference for the 2015 Kenworth T680.

Quick answer

• BCI group size: Group 31 (Heavy Duty Diesel)
• Multi-battery setup: Yes. The T680 utilizes a parallel battery bank, typically consisting of 3 to 4 Group 31 batteries. Trucks equipped with Auxiliary Power Units (APUs) or extreme hotel loads may feature up to 8 batteries (cranking and deep-cycle banks).
• CCA rating: 925 to 1,000+ Cold Cranking Amps (CCA) per battery. A four-battery bank provides around 4,000 total CCA.
• Reserve capacity: 190 to 200+ minutes per battery.
• AGM vs flooded requirement: Flooded batteries are standard from the factory for day cabs, but AGM (Absorbent Glass Mat) batteries are highly recommended for sleepers due to deep cycling demands.
• Terminal layout: 3/8-inch threaded stainless steel stud terminals (typical for heavy-duty commercial trucks).
• Physical dimensions: Approximately 13.0" L x 6.8" W x 9.4" H (per battery).

Replacement battery options

When replacing the batteries in a Kenworth T680, it is crucial to replace the entire bank at the same time. Mixing old and new batteries will cause the older units to draw down the new ones, leading to premature failure. Here are top choices for the T680:

• Interstate Batteries: 31-MHD (Flooded, 950 CCA) – A reliable, cost-effective standard for over-the-road trucking.
• Odyssey Extreme Series: ODP-AGM31 (AGM, 1150 CCA) – Massive cranking power and excellent deep-cycle capabilities for running sleeper cab electronics.
• Optima YellowTop: D31T (AGM, 900 CCA) – Known for incredible vibration resistance, which is perfect for frame-mounted battery boxes.
• ACDelco Gold: 31-901CT (Flooded, 900 CCA) – A solid OEM-style replacement choice.

AGM vs flooded — which does this vehicle need?

While traditional flooded lead-acid batteries are sufficient for starting the massive PACCAR MX-13 or Cummins ISX15 engine, they fall short if you spend nights in the sleeper.

Flooded batteries are best suited for day cabs or local route trucks that don't rely heavily on inverters for microwaves, TVs, or CPAP machines. AGM batteries are highly recommended, if not required, for sleeper configurations. AGM batteries can handle deeper discharges without suffering internal damage. Furthermore, because the T680’s battery box is mounted directly to the frame rail, AGM batteries provide superior resistance to the intense road vibrations that can literally shake the active material off the lead plates of a flooded battery.

Post-installation relearn / reset procedure

Unlike modern European passenger cars, Class 8 trucks like the 2015 Kenworth T680 do not require a complex Battery Management System (BMS) reset via a scan tool. However, there are a few important steps to follow:

1. Low Voltage Disconnect (LVD): The T680 features an LVD system designed to cut power to the sleeper if voltage drops too low, preserving cranking power. After a battery swap, ensure the LVD system resets properly (usually automatic once stable 12.6V+ is detected).
2. ECM Memory: Let the truck idle for 5–10 minutes after a complete disconnect. The engine control module (ECM) and transmission control module (TCM) will need to relearn adaptive idle and shift parameters.
3. Clock and Radio: You will need to manually reset the clock and any saved radio presets.

Signs of a failing battery

• Low Voltage Disconnect tripping early: If your sleeper accessories are shutting off much sooner than they used to, the battery bank’s reserve capacity is severely depleted.
• Slow cranking: A sluggish turnover on a cold morning, especially when pre-heating the air intake heater, is a major warning sign.
• Dimming headlights at idle: Headlights or interior cab lights that flicker or dim when the RPMs drop.
• Sulfur smell: A rotten egg smell coming from the battery box indicates a flooded battery is boiling over or overcharging.

Common battery issues for this generation

The most common issue with the 2015 Kenworth T680 battery system isn't the batteries themselves—it's the daisy-chain cables connecting the parallel bank. Heavy corrosion on the 3/8-inch studs creates immense electrical resistance, which prevents the batteries from charging fully and evenly. Always clean the terminals and apply a high-quality dielectric grease or anti-corrosion spray during installation. Additionally, vibration damage is a notorious killer for these frame-mounted boxes, so ensuring the battery hold-downs are properly torqued (but not crushed) is vital to battery longevity.

Find a trusted shop on Repairius.