2017 Kenworth W900 Battery Size & Specifications

As an ASE-certified master technician, I’ve worked on countless heavy-duty rigs. The 2017 Kenworth W900 is a legendary Class 8 truck, demanding massive cranking power to turn over its massive 15-liter Cummins or PACCAR diesel engine. Whether you are running long hauls with a full sleeper or doing heavy vocational work, your battery bank is the heart of your electrical system.

Here is the complete guide to the battery specifications, replacement options, and maintenance for your 2017 Kenworth W900.

Quick answer

• BCI Group Size: Group 31 (Industry standard for Class 8 heavy-duty trucks).
• Cold Cranking Amps (CCA): 925 to 1150 CCA per battery.
• Reserve Capacity (RC): 180 to 205 minutes per battery.
• AGM vs Flooded: Standard heavy-duty flooded (lead-acid) is factory, but AGM is highly recommended if you run an APU or have heavy "hotel loads" in the sleeper.
• Terminal Layout: Typically 3/8-inch threaded stud terminals (Group 31C), though some use standard SAE posts (Group 31A) depending on the cable harness.
• Physical Dimensions (per battery): Approximately 13.0" L x 6.8" W x 9.4" H.
• Multi-Battery Setup: Yes. The W900 utilizes a parallel battery bank, almost always consisting of three (3) or four (4) Group 31 batteries to achieve the 2,800+ total CCA required for heavy-duty diesel starting and cold-weather operation.

Replacement battery options

When replacing batteries in a multi-battery bank, you must replace all of them at the same time with the exact same brand, age, and specification. Mixing old and new batteries will cause the new batteries to drain and fail prematurely. Here are some of the most reliable replacement options for the W900:

• Interstate Batteries (Flooded): Interstate 31-MHD (950 CCA) – A staple in the trucking industry known for rugged reliability.
• Odyssey (AGM): Odyssey ODX-AGM31 (Extreme Series) – Offers a massive 1150 CCA and deep-cycle capabilities. Excellent for sleeper cabs with heavy electrical demands.
• Optima (AGM): Optima YellowTop D31T – Features spiral-cell technology that is highly resistant to extreme chassis vibration.
• ACDelco (Flooded/AGM): ACDelco Gold 31 BCI Group Heavy Duty – A solid OEM-grade replacement available in both flooded and AGM variants.

AGM vs flooded — which does this vehicle need?

From the factory, many W900s ship with heavy-duty flooded lead-acid batteries. However, upgrading to Absorbed Glass Mat (AGM) is highly beneficial depending on your application.

If you drive a day cab and your primary concern is simply starting the engine, heavy-duty flooded batteries are perfectly fine and more cost-effective. However, if you are running a sleeper cab with a refrigerator, microwave, TV, inverter, or an Auxiliary Power Unit (APU), AGM batteries are practically a requirement. AGM batteries handle deep cycling (draining and recharging) far better than flooded batteries. They also charge up to five times faster and are completely maintenance-free, meaning you don't have to worry about topping off electrolyte fluids.

Post-installation relearn / reset procedure

Unlike modern luxury passenger cars, the 2017 Kenworth W900 does not have a highly restrictive Battery Management System (BMS) that requires a computer scan tool to register the new batteries. However, there is a strict procedure you should follow:

1. Safety First: Always disconnect the main negative (-) cables first, followed by the positive (+). When reinstalling, connect the positive cables first, then the negative.
2. Clean the Harness: Wire brush all copper ring terminals and the battery box grounds. High resistance in a parallel circuit is a truck killer.
3. ECM Reset: Disconnecting the battery bank will reset the Engine Control Module (ECM) and clear volatile memory. Your truck may take a few key cycles to relearn optimal idle strategies.
4. Check Engine Light: If the Low Voltage Disconnect (LVD) system was triggered by the dead batteries, you might have a residual low-voltage code in the ECM. This usually clears itself after a few miles of driving, but you can clear it with a heavy-duty code reader if necessary.

Signs of a failing battery

• Slow Engine Crank: A 15L diesel engine should turn over aggressively. If you hear a sluggish "rrr-rrr-rrr," your battery bank is losing its CCA capacity.
• Low Voltage on the Dash Gauge: When running, your gauge should read around 13.8V to 14.2V. If it dips below 12V when the engine is off (with key on), the batteries are weak.
• LVD Activation: If your radio, sleeper lights, or HVAC controls are shutting off prematurely when the engine is off, the truck’s Low Voltage Disconnect is stepping in to save enough juice to start the engine.
• Clicking Starter: Rapid clicking from the starter solenoid means the bank lacks the amperage to engage the starter gear.

Common battery issues for this generation

The most common issue on the 2017 Kenworth W900 regarding batteries isn't always the batteries themselves—it's the parallel wiring harness. Because four batteries are wired together, corrosion on even one terminal can create unequal charging. This forces the alternator to overcharge one battery while undercharging another, ultimately destroying the whole bank. Always ensure the cross-over cables between the batteries are free of green corrosion and the nuts are torqued properly. Additionally, vibration in the battery box can wear through cable insulation, so check for chafing during your pre-trip inspections.

If you are dealing with persistent charging issues, don't throw parts at it. Find a trusted shop on Repairius to properly load-test your battery bank and diagnose your electrical system.