A Beginner's Guide to LiPo Battery Connectors

The Difference Between Red JST-RCY and White/Black JST-XH

You've just received your first LiPo battery for your new RC car or drone. You open it up, and you notice two different plugs dangling off of it—a large red one and a smaller white or black one with a number of small wires. It's natural to feel somewhat puzzled. What are they? Do you plug both of them in? What if you do it incorrectly?

Do not worry; it is much easier than it appears. Those two plugs have extremely different, yet extremely vital, functions. This tutorial will describe in simple language what each one does, why you require them, and how to properly use them.

The Main Plug: The One That Delivers the Fun

First, you'll notice the big main power plug. This is the workhorse. This may be a red JST-RCY plug, a yellow/black XT60, or a number of others, depending on your battery, but whatever type it is, its purpose is the same.

What Does It Do?

Consider this plug as your car's fuel line. It has one purpose only: to deliver all that power from the battery to the motor of your RC car. When you are ready to drive your car or fly your drone, this is the plug that allows you to do so. It is designed to carry plenty of electricity.

What to Look For

You can readily identify the main plug. It will have just two wires: a red for positive and a black for negative. You'll also see that these wires are a lot thicker than those on the other plug. The thickness is significant, as it allows plenty of power to pass through safely without the wires becoming hot.

When to Use It

This is a simple one: you plug this in when you are ready to run. It connects your battery to your car's Electronic Speed Controller (ESC). This is your "go time" plug.

The Small White or black Plug: The One That Keeps Your Battery Healthy

The second smaller plug is the balance plug. It is typically a white or black JST-XH connector. It may seem less significant, but this small fellow is the key to enabling your battery to have a long life.

Note: While JST-XH balance plugs are most commonly white, many modern packs also use black housings. Functionally they are the same.

What Does It Do?

To understand what this plug does, you have to know that a LiPo battery (such as a 2S or 3S) is really composed of several individual battery "cells" bundled together. In order for the battery to function properly, all of these cells must be storing the same amount of power, or voltage. The balance plug is like a doctor examining your battery. When you insert it into a suitable charger, the charger can examine each cell individually and ensure they're all balanced. This prevents one cell from becoming overcharged, which is a major concern for battery health and safety.

What to Look For

The balance plug is easy to identify. It has a bunch of small, thin wires. The number of wires is always one more than the number of cells in the battery. So:

• A 2S battery (2 cells) will have 3 wires.
• A 3S battery (3 cells) will have 4 wires.
• A 6S battery (6 cells) will have 7 wires.

Because these wires are so thin, they can only handle a tiny bit of power.

When to Use It

You'll use this plug when you're charging your battery. You plug it into a special "balance port" on your charger. This lets the charger do its important job of keeping all the cells healthy and balanced.

Now, there is one tiny exception. On some super-small FPV drones, where every gram matters, the builders sometimes use this plug for both charging and powering the drone.

This is a very specific situation for low-power models. For 99% of RC cars, boats, and bigger drones, you should only ever use this plug for charging.

All the Differences in One Simple Chart

To make it even clearer, here’s a simple side-by-side comparison.

How to Actually Use Them (The Right Way)

Let's put it all together with a super simple guide for what to do.

When You Are Charging

This is when you use both plugs. To charge your battery safely with a balance charger, you need to plug both of them in.

1. Plug the big main power plug into the main output on your charger.

2. Plug the white or black balance plug into the matching balance port on your charger. The little slots are designed so it will only fit one way.

3. Set your charger to "Balance Charge" mode and start. Now the charger is filling the battery with power through the main plug while using the balance plug to keep everything safe and healthy.

When You Are Using the Battery

This part is even easier. When you’re ready to hit the track or the field, you only need the big main plug.

1. Connect the main power plug from the battery to your vehicle.

2. The small white or black balance plug just hangs out. Most people will tuck it under the battery strap to keep it from flopping around and getting caught in anything.

3. Quick Warning: Never, ever try to power your car or drone with the balance plug. The tiny wires can't handle the power, and you'll likely fry the plug, the battery, or your vehicle.

The big plug powers it, the small one protects you

And that's it! Those two plugs aren't so confusing after all. Just remember the simple rule: the big plug is for power, and the small plug is for safety. Use both when you charge, and only the big one when you play. Understanding this one basic thing is a huge step toward enjoying the RC hobby safely and getting the most out of your batteries.