Polaris Sportsman 850 Battery Size - The Definitive Guide To Fitment

You’re all geared up. The cooler is packed, the trail map is loaded, and your Polaris Sportsman 850 is ready to conquer the weekend. You turn the key, anticipating that familiar roar, and instead, you get a gut-wrenching click… click… click. A dead battery. Nothing kills a day of riding faster.

We’ve all been there. But getting your rig running again isn’t as simple as grabbing the first battery you see at the auto parts store. Choosing the wrong one can lead to fitment headaches, electrical gremlins, or leaving you stranded miles from the trailhead.

This guide promises to eliminate that guesswork. We’re going to break down everything you need to know about the correct polaris sportsman 850 battery size. We’ll cover the factory specs, explain what all those codes and numbers mean, compare different battery technologies, and walk you through a safe replacement so you can get back on the trail with confidence.

Why Getting the Right Polaris Sportsman 850 Battery Size is Non-Negotiable

It’s tempting to think “a battery is a battery,” but for a high-demand machine like the Sportsman 850, precision matters. The battery is the heart of your ATV’s electrical system, and getting the size and specs right is critical for both performance and safety.

The Risks of an Incorrectly Sized Battery

Using the wrong battery isn’t just an inconvenience; it can cause real damage. This is one of the most common problems with polaris sportsman 850 battery size that we see.

An oversized battery simply won’t fit in the designated tray, forcing you to make unsafe modifications. A battery that’s too small will slide around, risking short circuits as terminals make contact with the frame or other components. Incorrect terminal polarity can instantly fry your ATV’s sensitive electronics, like the ECU—a costly mistake.

Power Demands of a Modern ATV

Your Sportsman 850 does more than just start the engine. It powers the electronic fuel injection (EFI), the digital display, headlights, and any accessories you’ve added.

Think about it: are you running a winch? A light bar? Heated grips or a GPS unit? Each of these adds to the electrical load. A properly sized battery with the right power specs ensures you have enough juice to run everything without issue, which is one of the key benefits of polaris sportsman 850 battery size accuracy.

Decoding the Polaris Sportsman 850 Battery Size: What You Need to Know

Let’s get down to the nuts and bolts. Understanding the language of batteries will turn you from a confused buyer into a confident DIYer. This is your essential polaris sportsman 850 battery size guide.

The Factory Standard: OEM Battery Group Size

For most model years of the Polaris Sportsman 850, the standard factory-equivalent battery size is a YTX20L-BS.

This alphanumeric code is a powersports industry standard. Let’s break it down:

YTX: This designates it as a high-performance, sealed maintenance-free battery manufactured by Yuasa or to their standard.
20: This is a reference to the battery’s power capacity, or Amp Hour (Ah) rating.
L: This is critically important. It indicates the polarity, meaning the Negative (-) terminal is on the left side when you’re looking at the front of the battery.
BS: This indicates that the battery is shipped dry with acid that you add before sealing (Bottle Supplied), though most modern replacements come pre-filled and sealed.

Understanding the Numbers: CCA, Ah, and Dimensions

Beyond the group size, you’ll see a few other key specs. Knowing how to polaris sportsman 850 battery size your needs involves these numbers.

Cold Cranking Amps (CCA): This is the big one. CCA measures a battery’s ability to start an engine in cold temperatures. A higher CCA means more starting power, which is crucial for those chilly morning rides or if you’re running a high-compression engine. For a Sportsman 850, look for something in the 270-310 CCA range or higher.
Amp Hours (Ah): This measures the battery’s storage capacity. A higher Ah rating means the battery can power your accessories for longer with the engine off. If you frequently use a winch, this number is very important.
Dimensions (L x W x H): A YTX20L-BS battery has standard dimensions of approximately 6.87″ x 3.43″ x 6.12″ (175mm x 87mm x 155mm). Always double-check the measurements of a replacement to guarantee a perfect fit in the battery tray.

Terminal Types and Polarity

As mentioned, the “L” in YTX20L-BS means the negative terminal is on the left. This is non-negotiable. Your ATV’s battery cables are a specific length and are designed to reach specific terminals. Reversing polarity by installing a battery with the positive on the left can cause a catastrophic short circuit, potentially damaging your wiring harness, stator, or Engine Control Unit (ECU).

Choosing Your Power: AGM vs. Lithium Battery Options

You have two primary choices for battery technology today: the tried-and-true AGM and the modern, lightweight Lithium. The best option depends on your budget and how you ride.

The Workhorse: AGM (Absorbed Glass Mat) Batteries

AGM batteries are the most common type of sealed, maintenance-free battery. The electrolyte is absorbed in fiberglass mats, making them spill-proof and vibration-resistant—perfect for off-road abuse.

Pros: Very reliable, excellent CCA performance, widely available, and more affordable.
Cons: Significantly heavier than lithium alternatives.

The High-Performer: Lithium (LiFePO4) Batteries

Lithium Iron Phosphate (LiFePO4) batteries are the new-school option, offering incredible performance benefits. They are a fantastic upgrade if your budget allows.

Pros: Extremely lightweight (often saving 5-10 lbs), longer service life (2-4x longer than AGM), and can provide stronger, more consistent cranking power.
Cons: Much higher upfront cost, can be sensitive to very cold weather (some have built-in heaters), and require a lithium-specific battery charger/tender.

Step-by-Step Guide: How to Replace Your Sportsman 850 Battery

Alright, you’ve got your new battery. Let’s get it installed. This process is straightforward, but following the correct order is crucial for safety. These are the polaris sportsman 850 battery size best practices for installation.

Tools and Safety Gear You’ll Need

Socket set with an extension (typically 8mm and 10mm sockets)
Safety glasses
Gloves
Terminal cleaning brush or sandpaper
Dielectric grease or terminal protector spray (optional but recommended)

1. Locate and Access the Battery

On most Polaris Sportsman 850 models, the battery is located under the front storage rack. You’ll need to remove the cover to access the battery compartment. Consult your owner’s manual if you’re unsure.

2. The Safe Removal Process (The Most Important Step!)

To prevent accidental short circuits, you must disconnect the terminals in the correct order.

Disconnect the NEGATIVE (Black, -) terminal first. Loosen the bolt and pull the cable away from the battery post. Tuck it aside so it can’t accidentally touch the terminal again.
Disconnect the POSITIVE (Red, +) terminal second. Loosen the bolt and move the cable clear of the battery.
Remove any hold-down brackets or straps securing the battery.
Carefully lift the old battery out of the tray.

3. Installing the New Battery

Installation is the reverse of removal, and again, the order is critical for safety.

Clean the battery tray of any dirt or debris. Clean the cable terminals with a wire brush.
Place the new battery securely in the tray.
Install the hold-down bracket to ensure the battery can’t move.
Connect the POSITIVE (Red, +) terminal first. Tighten the bolt securely, but don’t overtighten.
Connect the NEGATIVE (Black, -) terminal second. Tighten the bolt. Applying a thin layer of terminal protector spray can help prevent future corrosion.
Replace the battery compartment cover and front rack.

4. Final Checks and Startup

With everything reconnected, turn the key to the “on” position. You should see the display light up. Now, fire it up! Your Sportsman 850 should start right up with its new source of power.

Extending Your Battery’s Life: A Polaris Sportsman 850 Battery Size Care Guide

A new battery is a significant investment. With a little care, you can maximize its lifespan and reliability. Following this polaris sportsman 850 battery size care guide can save you money and headaches down the road.

The Importance of a Battery Tender

ATVs often sit for weeks or even months between rides. During this time, the battery will slowly self-discharge. A smart battery tender (or maintainer) is the single best tool for preventing this. It monitors the battery and provides a slow, steady charge only when needed, keeping it topped off without overcharging.

Keeping Terminals Clean

Periodically check your battery terminals for corrosion (a white or greenish powdery substance). If you see any, disconnect the battery (negative first!) and clean the posts and cable ends with a wire brush and a mixture of baking soda and water. This ensures a solid electrical connection.

Sustainable Choices and Eco-Friendly Disposal

A longer-lasting battery is a more sustainable polaris sportsman 850 battery size choice. Investing in a quality AGM or Lithium battery and maintaining it properly means you’re buying fewer batteries over the life of your ATV. When your old battery finally gives up, be sure to practice eco-friendly polaris sportsman 850 battery size disposal. Never throw it in the trash. Nearly all auto parts stores and recycling centers will accept old lead-acid batteries for free.

Frequently Asked Questions About Polaris Sportsman 850 Battery Size

What is the standard battery size for a Polaris Sportsman 850?

The most common OEM-equivalent battery group size for the Polaris Sportsman 850 is the YTX20L-BS. This ensures correct physical dimensions, terminal layout (negative on the left), and adequate power for the machine.

Can I use a bigger battery in my Sportsman 850?

Physically, you are limited by the dimensions of the battery tray. While you can often find batteries within the same group size that offer higher Cold Cranking Amps (CCA) or Amp Hours (Ah), you generally cannot fit a physically larger battery without significant modification, which is not recommended.

How often should I replace my ATV battery?

With proper care and maintenance (especially using a battery tender during storage), a quality AGM battery should last 3 to 5 years. A lithium battery can often last longer, from 5 to 8 years. Signs of a failing battery include slow cranking, dimming lights, and needing to be charged frequently.

Do I need a special charger for a lithium ATV battery?

Yes, absolutely. Standard lead-acid battery chargers can damage a lithium battery. You must use a charger specifically designed for LiFePO4 (Lithium Iron Phosphate) batteries. These chargers have a unique charging algorithm that is safe for lithium chemistry.

Choosing the right battery for your Sportsman 850 is about more than just starting the engine. It’s about reliability on the trail, protecting your machine’s electronics, and getting the most performance out of your investment. By understanding the specs, choosing the right technology for your needs, and following safe installation practices, you’re ensuring your rig is ready to go whenever you are.

Now you’ve got the power and the knowledge. Get that new battery installed, fire up your rig, and hit the trails with confidence. Stay safe out there!

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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.