2004 Polaris Sportsman 400 Battery Size – Your Complete Selection

There’s nothing more frustrating. You’ve got the gear loaded, the trail is calling your name, you turn the key on your trusty 2004 Polaris Sportsman 400, and all you get is that soul-crushing “click… click… click.” We’ve all been there. A dead battery can stop a great day of riding before it even starts.

But don’t let a simple component sideline your machine. We promise this comprehensive guide will demystify everything you need to know about your ATV’s power source. We’ll turn that frustrating click into a confident roar.

In this post, we’ll cover the exact 2004 polaris sportsman 400 battery size you need, help you choose the best battery type for your riding style, walk you through a safe and easy installation, and share some pro tips to maximize your new battery’s lifespan. Let’s get that rig powered up and ready to ride.

Why Getting the Right 2004 Polaris Sportsman 400 Battery Size is Non-Negotiable

You might be tempted to just grab any powersports battery off the shelf that looks “close enough.” Take it from us at FatBoysOffroad—that’s a recipe for trouble. Using the wrong battery size isn’t just an inconvenience; it can lead to serious issues down the trail.

The benefits of 2004 polaris sportsman 400 battery size accuracy are huge. A correctly sized battery fits perfectly in the designated battery tray, ensuring it’s secure and won’t vibrate excessively, which can cause internal damage and premature failure. More importantly, it guarantees the electrical connections are sound and the terminals align without stretching or stressing the wiring harness.

The Risks of an Improper Fit

Physical Damage: A battery that’s too large simply won’t fit. A battery that’s too small will slide around in the tray. This constant vibration can crack the casing, damage the internal plates, and lead to a dead battery when you’re miles from the truck.
Electrical Gremlins: Using a battery with incorrect terminal orientation can force you to stretch cables, leading to poor connections or even shorts. This can cause intermittent starting problems, damage sensitive electronics like the ECU, or even create a fire hazard.
Inadequate Power: A battery with insufficient Cold Cranking Amps (CCA) will struggle to turn over your Sportsman’s 425cc engine, especially in colder weather. This puts a massive strain on your starter and other components.

Getting it right the first time saves you money, prevents headaches, and ensures your ATV is reliable when you need it most. This is one of the most important 2004 polaris sportsman 400 battery size best practices to follow.

The Definitive 2004 Polaris Sportsman 400 Battery Size Guide

Alright, let’s get straight to the point. Your 2004 Polaris Sportsman 400 was designed from the factory to use a specific group size battery to ensure perfect fitment and performance. No more guessing games.

The standard OEM replacement battery size for your ATV is a YTX14AH-BS. This is a universal part number used across many brands, making it easy to find a replacement.

Key Battery Specifications to Know

When shopping, you’ll see more than just the part number. Here’s what those specs mean for you:

Battery Type Number: YTX14AH-BS (or a direct cross-reference like CTX14AH-BS, ETX15, etc.)
Voltage: 12 Volts. This is standard for nearly all ATVs.
Cold Cranking Amps (CCA): Aim for 190 CCA or higher. CCA measures the battery’s ability to start an engine in cold temperatures. More is always better, especially if you ride in chilly climates or run accessories like a winch or light bars.
Amp Hour (Ah) Rating: Look for a rating of 12 Ah. This indicates the battery’s capacity—how long it can provide power.
Dimensions (Approximate): 5.25″ (L) x 3.5″ (W) x 6.5″ (H). Always double-check the manufacturer’s listed dimensions against your battery tray before buying.
Terminal Configuration: The positive (+) terminal should be on the left, and the negative (-) terminal should be on the right when looking at the front of the battery. This is critical for your cables to reach properly.

Sticking to these specifications will guarantee your new battery drops right in and provides the reliable power your Sportsman 400 demands.

Choosing Your Power: AGM vs. Lithium vs. Lead-Acid

The YTX14AH-BS size is available in a few different chemistries. The type you choose affects performance, maintenance, and cost. Let’s break down the options so you can make an informed choice.

AGM (Absorbed Glass Mat) Batteries

This is the most common and highly recommended type for modern ATVs. The electrolyte is absorbed in fiberglass mats, making the battery spill-proof and highly vibration-resistant—perfect for off-road abuse.

Pros: Maintenance-free, excellent vibration resistance, great value, reliable power.
Cons: Heavier than lithium, can be damaged by overcharging.
Best For: The vast majority of riders looking for a dependable, set-it-and-forget-it solution.

Lithium (LiFePO4) Batteries

Lithium is the high-performance option. They are incredibly lightweight (often saving 5-7 pounds) and offer excellent cranking power. They also have a very low self-discharge rate, meaning they hold a charge for months in storage.

Pros: Extremely lightweight, superior cranking power, long service life, low self-discharge.
Cons: Significantly more expensive, can be sensitive to cold temperatures (some have built-in heaters), require a lithium-specific charger.
Best For: Performance-focused riders, racers, or anyone looking to shed weight from their machine. This can also be considered a more sustainable 2004 polaris sportsman 400 battery size option due to its longer lifespan.

Conventional (Flooded Lead-Acid) Batteries

This is the old-school technology. While they are the cheapest option, they require regular maintenance, including checking and topping off electrolyte levels with distilled water. They are also prone to spilling acid if the ATV tips over.

Pros: Lowest initial cost.
Cons: Requires regular maintenance, can leak acid, less vibration resistant, shorter lifespan.
Best For: Riders on a very tight budget who don’t mind performing regular checks. We generally recommend avoiding these for off-road use.

Step-by-Step Guide: How to Replace Your Sportsman 400 Battery

Now for the hands-on part. This is a simple job that any DIYer can handle with basic tools. Following this process for how to 2004 polaris sportsman 400 battery size installation will ensure it’s done safely and correctly.

H3: Safety First & Tools Needed

Before you start, park your ATV on a level surface, turn off the ignition, and remove the key. Safety glasses are a must! Battery acid is no joke.

Tools You’ll Need:

Safety Glasses & Gloves
Socket Wrench with 10mm socket (or an adjustable wrench)
Screwdriver (usually Phillips head for battery strap/cover)
Terminal Cleaning Brush or a stiff wire brush
Battery Terminal Protector Spray (optional but recommended)

H3: Removing the Old Battery

Locate the Battery: On the 2004 Sportsman 400, the battery is typically located under the seat. Lift the seat to expose the battery compartment. You may need to remove a plastic cover or a rubber hold-down strap.
Disconnect the Negative Terminal FIRST: This is the most important safety step. Use your 10mm wrench to loosen the nut on the black, negative (-) terminal. Once loose, wiggle the cable off the terminal post and tuck it away from the battery. This prevents accidental shorts if your tool touches the frame while working on the positive side.
Disconnect the Positive Terminal: Now, you can safely loosen the nut on the red, positive (+) terminal. Remove the cable and move it aside.
Remove the Battery: Unhook the hold-down strap or remove the bracket. Carefully lift the old battery straight up and out of the tray. Be mindful that it can be heavy and awkward.

H3: Installing the New Battery

Clean the Area: With the old battery out, take a moment to clean the battery tray and the cable terminals. Use your terminal brush to remove any corrosion (white or greenish powder). A clean connection is a good connection.
Prepare the New Battery: If you bought an AGM battery, it may need to have the acid pack added and be initially charged. Follow the manufacturer’s instructions to the letter. Most batteries today come pre-filled and ready to go.
Place the New Battery: Carefully lower the new battery into the tray, making sure the terminals are oriented correctly (Positive on the left, Negative on the right). Secure it with the hold-down strap or bracket. It should be snug and not move.
Connect the Positive Terminal FIRST: When installing, you reverse the order. Attach the red, positive (+) cable to the positive terminal and tighten the nut securely. Don’t overtighten, but make sure it’s snug.
Connect the Negative Terminal: Attach the black, negative (-) cable to the negative terminal and tighten it down. Give both cables a gentle wiggle to ensure they are secure.
Apply Protector (Optional): A light spray of battery terminal protector on the connections can help prevent future corrosion.
Final Check: Replace any covers, lower the seat, and turn the key. Your Sportsman should fire right up with a new surge of power!

Common Problems and Troubleshooting Your ATV’s Electrical System

Sometimes, a new battery doesn’t solve the problem. If your new battery dies quickly or you still have starting issues, you may have one of these common problems with 2004 polaris sportsman 400 battery size and its related systems.

A healthy electrical system should charge the battery while the engine is running. To test this, you’ll need a simple multimeter. Set it to DC Volts. With the engine off, a fully charged battery should read around 12.6V – 12.8V. Now, start the engine and let it idle. The voltage at the battery terminals should jump to roughly 13.5V – 14.5V.

If the voltage doesn’t increase: Your ATV’s charging system isn’t working. This is usually due to a faulty stator or voltage regulator/rectifier. This is a more advanced repair, and it may be time to consult your service manual or a professional mechanic.
If the voltage is too high (over 15V): This indicates a failed voltage regulator, which is “cooking” your battery by overcharging it. Replace the regulator immediately to avoid damaging your new battery and other electronics.
If the battery dies when sitting: You may have a “parasitic draw”—something is draining power even when the key is off. This can be a faulty switch or a short in the wiring. Tracking this down requires patience and a multimeter set to measure amps.

Pro Tips for a Longer Battery Life: Your Care Guide

Want to get the most out of your investment? Follow this simple 2004 polaris sportsman 400 battery size care guide to extend its life for many seasons.

Use a Battery Tender: This is the single best thing you can do. A smart trickle charger (or “battery tender”) keeps your battery at an optimal charge level during storage without overcharging it. This is crucial during the off-season.
Keep Terminals Clean: Every few months, check the terminals for corrosion. A quick cleaning with a wire brush ensures a solid flow of electricity.
Check Connections: Vibration can loosen terminal bolts over time. Before a big ride, give them a quick check to make sure they are snug.
Proper Disposal: When your battery finally gives up, be responsible. Lead-acid batteries are highly toxic. Any auto parts store or battery retailer will accept your old battery for recycling, often giving you a small credit (core charge) for it. This is the cornerstone of an eco-friendly 2004 polaris sportsman 400 battery size lifecycle.

Frequently Asked Questions About the 2004 Polaris Sportsman 400 Battery

What are Cold Cranking Amps (CCA) and why do they matter?

CCA is a rating that measures a battery’s ability to start an engine in cold conditions (0°F or -18°C). A higher CCA number means the battery can deliver more starting power, which is essential for turning over a cold engine with thick oil. For your Sportsman 400, anything over 190 CCA is excellent.

Can I use a bigger or smaller battery in my Sportsman 400?

We strongly advise against it. A smaller battery will likely have insufficient CCA and capacity, leading to poor starting performance. A larger battery will not fit in the designated tray, creating a safety hazard from vibration and potential shorts. Stick with the recommended YTX14AH-BS size.

How often should I replace my ATV battery?

With proper care and the use of a battery tender, a quality AGM battery can last 3-5 years, or even longer. If you notice your ATV is slow to crank or the battery no longer holds a full charge, it’s time for a replacement.

My new AGM battery came with an acid pack. What do I do?

This is common for “dry-shipped” batteries. You must carefully follow the manufacturer’s instructions to fill the battery with the supplied acid pack, seal it, and then perform an initial “formation” charge with a suitable charger before installing it. Rushing this process can dramatically shorten the battery’s life.

Choosing and installing the right battery for your 2004 Polaris Sportsman 400 is a foundational piece of ATV maintenance. It’s a simple job that builds confidence and ensures your machine is ready whenever the trail calls. By selecting the correct YTX14AH-BS size, keeping it charged, and performing basic checks, you’re guaranteeing reliable starts and seasons of fun.

Now you have the knowledge to tackle this job like a pro. Get the right parts, follow the safety steps, and get back out there.

Ride safe, and have fun!

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Thomas Corle

Founder & Automobile expert at FatBoysOffroad

Automobile expert and off-road enthusiast, sharing in-depth knowledge of vehicles, gear, and adventures. Helping readers make smart decisions and enjoy the thrill of off-roading safely and confidently.