2020 Isuzu NQR Battery Size, Group & CCA Guide

As an ASE-certified master technician, I’ve serviced countless medium-duty commercial trucks, and the 2020 Isuzu NQR is one of the most reliable workhorses on the road. Powered primarily by the robust 5.2L 4HK1-TC diesel engine, this truck relies heavily on its starting and charging system to handle everything from cold morning starts to running heavy-duty liftgates.

If your 2020 Isuzu NQR is cranking slowly or failing to hold a charge, it’s time to replace the batteries. Here is your comprehensive guide to the correct battery group size, CCA requirements, and replacement procedures for your NQR.

Quick answer

For the 2020 Isuzu NQR (5.2L Diesel), you will need to replace both batteries at the same time to ensure system balance. Here are the precise specifications:

• BCI Group Size: Group 31 (Dual-battery setup)
• Cold Cranking Amps (CCA): 750 CCA minimum per battery (925 to 1000+ CCA highly recommended for cold climates)
• Reserve Capacity (RC): 175 - 200 minutes per battery
• AGM vs Flooded: Heavy-duty commercial flooded batteries are standard, but AGM is highly recommended for high-vibration and deep-cycle demands (like operating liftgates).
• Terminal Layout: Typically 31 stud or standard SAE top post (verify your existing cable ends, as Isuzu commercial trucks commonly use threaded stud terminals, designated as Group 31S).
• Physical Dimensions: Approximately 13.0" L x 6.8" W x 9.4" H per battery.
• Dual-Battery Setup: Yes. The NQR runs a parallel 12-volt system (positive to positive, negative to negative) to double the total amperage while maintaining 12 volts.

Replacement battery options

When replacing commercial batteries, you want proven, heavy-duty construction. Always replace both batteries simultaneously. Here are top-tier replacement options for your 2020 Isuzu NQR:

• Interstate Workaholic 31-MHD: A heavy-duty flooded workhorse offering 950 CCA. Perfect for standard box trucks without excessive aftermarket electrical draws.
• Odyssey Extreme Series ODX-AGM31 (31-PC2150): A premium AGM battery delivering a massive 1,150 CCA. Ideal for extreme cold and heavy accessory usage.
• ACDelco Gold 31 BCI (31900CTS): A reliable, severe-duty flooded battery with 900 CCA and standard commercial stud terminals.
• Optima YellowTop D31T: An AGM dual-purpose deep-cycle and starting battery offering 900 CCA. Excellent vibration resistance for rough delivery routes.

AGM vs flooded — which does this vehicle need?

From the factory, the 2020 Isuzu NQR is usually equipped with heavy-duty flooded lead-acid batteries. If your truck is used for basic delivery routes and driving, standard heavy-duty commercial flooded batteries (like the Interstate 31-MHD) are perfectly adequate and cost-effective.

However, an upgrade to Absorbent Glass Mat (AGM) is strongly recommended if your truck experiences the following:

• High Vibration: If you drive on rough, unpaved job sites, AGM batteries are completely sealed and highly resistant to vibration damage.
• Heavy Accessory Loads: If your NQR is outfitted with a hydraulic liftgate, heavy-duty winches, or a high-draw inverter system, AGM batteries recover from deep discharges much faster and last longer under these conditions.

Post-installation relearn / reset procedure

Unlike modern European passenger cars, the 2020 Isuzu NQR does not require a complex Battery Management System (BMS) scan tool reset. However, after reconnecting the parallel battery bank, follow these steps:

1. Check Engine Light: The ECU may temporarily clear its readiness monitors. Drive the truck normally for 30-50 miles to allow the transmission and engine modules to relearn their adaptive strategies.
2. Radio/Clock: You will need to manually reset the clock and any radio presets.
3. Power Windows: If equipped with auto-up power windows, roll the window all the way down, then all the way up and hold the switch for 2 seconds to reset the limit switches.
4. DPF System: Ensure the truck is not in an active Diesel Particulate Filter (DPF) regeneration cycle before disconnecting the batteries.

Signs of a failing battery

Commercial trucks will usually give you warning signs before leaving you stranded on a route:

• Slow Engine Crank: The 5.2L diesel requires immense torque to turn over. If the starter drags or hesitates, the batteries are likely weak.
• Liftgate Stalling: If the hydraulic liftgate struggles to lift a load unless the engine is revved up, your batteries are losing their reserve capacity.
• Clicking from the Starter: A rapid clicking sound means the batteries have dropped below the necessary voltage to engage the starter solenoid.
• Dimming Headlights: Headlights or interior cab lights that dim significantly when accessories are turned on indicate a voltage drop.

Common battery issues for this generation

For the 2020 Isuzu NQR and its N-Series siblings, the most common battery issues stem from the harsh commercial environment.

Corrosion on parallel cables: The jumper cables connecting the two batteries in parallel are notorious for accumulating green corrosion. This creates immense electrical resistance. Even with two brand-new batteries, a corroded parallel cable will cause a no-start condition. Always clean or replace the connecting cables during a battery swap.

Vibration failure: The stiff suspension of the NQR means the battery box takes a beating. Flooded batteries are prone to internal plate shorting if the battery hold-down brackets are loose. Ensure the hold-downs are tight, but do not overtighten and crack the battery case.

Uneven wear: If one battery fails and you only replace that single unit, the older battery will draw down the new one, ruining both within a few months. Always replace Group 31 commercial batteries in matched pairs.

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