LiPo Battery: The Definitive Guide (2024 Update)

When I first started the RC hobby about three years ago, nickel metal hydride (NiMH) battery packs were the go-to. They’re bulky and expensive.

Due to their affordability, lithium polymer battery packs have begun to take over in the RC world.

However, there is always a risk that they could catch fire, especially in an impact if one of the cells is damaged.

Before you start moving to electric RC cars, I’ve prepared a complete guide for you to use the LiPo battery safely and quickly.

In this article, you’ll learn:

What is a LiPo Battery?

LiPo (AKA “Lithium Polymer“) battery is a type of rechargeable battery that uses lithium-ion technology with a polymer electrolyte instead of the more common liquid electrolyte found in other lithium-ion batteries.

One of the good things about using lithium polymer batteries compared to nickel metal hydride batteries is that they offer more power and longer running times.

As long as you follow the correct procedure for charging and maintaining LiPo batteries, they are extremely safe.

LiPo Battery Chemistries

A polymer electrolyte results in several performance enhancements, including high energy density and lightweight batteries.

Depending on the structure of the polymer layers, it can enhance battery safety.

Compared with conventional Li-ion batteries, LiPo batteries can be fabricated with a wider range of specific energy densities (Wh/kg) and specific power densities (W/kg), making LiPo batteries more flexible across a wider range of potential applications.

As a result, LiPo technology is used across all the main lithium battery chemistries:

• Lithium cobalt oxide battery (LCO)
• Lithium-ion ternary battery (NCA, NMC)
• Lithium-ion manganese oxide battery (LMO)
• Lithium iron phosphate battery (LFP)

LiPo Battery Basic Terms

When you think of batteries, is voltage or current the first physical unit that comes to mind? Now let’s quickly review them.

“S”= Voltage / Cell Count

Whether you go to your local RC hobby store to pick up a LiPo battery or Google search it, every LiPo battery package is marked with a number in front of “S” or “Cell”.

It refers to the number of cells in a LiPo battery.

You can think about the “S” as the amount of water that’s in a tank and how much capacity it has to push through.

A LiPo cell has a nominal voltage of 3.7V. The voltage of the 2S battery pack is 7.4 volts, which means that the cells are connected in series.

Similarly:

• 3S = 3 cells = 11.1V
• 4S = 4 cells = 14.8V
• 5S = 5 cells = 18.5V
• 6S = 6 cells = 22.2V
• ……

Higher voltage packs allow more powerful operation of brushless systems. This will decrease to around 3.0V when the battery is discharged.

Capacity (mAh)

It indicates how much charge the battery can hold, measured in milliamp-hours (mAh). Sometimes you’ll see it represented as amps, like 1400mAh; it’s really 1.4Ah.

Higher mAh equates to longer runtimes.

Think of it as liters of fuel in the tank. A larger tank allows longer driving time before needing to refuel.

When selecting a LiPo battery, choose a capacity rating suitable for your desired runtimes. Typically 4000-5500mAh offers a good balance for many RC cars.

Discharge (C) Rating

This often confusing metric indicates how fast a LiPo battery can safely discharge without damaging cells.

C-rating equally applies for both charging and discharging. Since we’re focused on draining power from batteries, we’ll focus on the discharge perspective here.

The higher the C rating, the more fuel it can supply to your thirsty motor. Batteries with higher C-ratings tend to be heavier and larger even at the same capacity.

Here is the simple formula to understand discharge C-rating:

Maximum Current Draw = Capacity (mAh) x C-Rating

Let’s walk through an example situation with two different battery options:

• 5500mAh battery with 50C discharge rating
• 5000mAh battery with 100C discharge rating

Plugging this into our formula:

• 5500 x 50 = 275A maximum safe discharge
• 5000 x 100 = 500A maximum safe discharge

The 100C battery can deliver almost double the current (500A vs 275A) compared to the 50C option of similar capacity.

In real world operation, the electronic speed control (ESC) for your RC model determines the actual amp draw. The battery’s discharge rating limits the maximum current.

When selecting LiPo batteries, choose a C-rating capable of safely delivering your electronic system’s peak power demand.

Overstressing a pack with too high discharge risks cell damage and potential fire.

LiPo vs Li-ion vs LiFe Battery

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LiPo vs NiMH Battery

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First of all, they are much lighter in weight and can be in almost any shape or size. LiPo batteries also offer higher capacities and can store more energy when it comes to discharge rates.

They offer higher discharge rates compared to their nickel-metal hydride counterparts, meaning that LiPo batteries pack more of a punch.

However, LiPo batteries tend to have a shorter lifespan, lasting for around 100 to 300 cycles. Give or take, sensitive chemistry can lead to a fire if the battery gets punctured.

Are LiPo Battery Safe?

In fact, LiPo fires are extremely rare. When you look after a LiPo pack properly, it will look after you.

Now let’s examine best practices for charging and handling LiPo batteries to maximize performance and safety.

What LiPo Charging Safety Gear Do You Need?

Before connecting batteries to chargers, invest in basic LiPo safety equipment:

1. Lipo Charging Bag

Flame resistant bag houses battery during charge session. Contains damaging fires in a failure event. Generally made of fiberglass.

2. Lipo Storage Container

Non-flammable sealed container for unused LiPo storage. Prevents accidental short circuits when batteries are not in models. Some have integrated locking mechanisms.

3. Battery Mat

Heat resistant pad for underneath charging batteries. Catches ejected materials if battery swells and ruptures during charging. Important layer between batteries and flammable workbench surfaces!

Safety gear minimizes fire risks inherent to LiPo charging. Always exercise caution when charging and discharging RC battery packs!

How to Charge Your LiPo Packs? (Step-by-Step)

Once outfitted with adequate safety equipment, let’s walk through actually charging your shiny new LiPo…

Step 1: Connect Battery to Charger

First up is physically linking your LiPo to the charger via discharge leads and balance connector. This enables active cell balancing while charging.

Connect battery’s discharge connector to corresponding port on LiPo charger. This carries main charging current to the LiPo. Use charging cables included with your charger.

The balance lead is a multi-pin connector with one wire running to each cell in the LiPo. This taps voltage readings from each individual cell.

Connecting the balance lead enables the charger to actively balance while charging. Meaning it monitors per-cell voltages, adjusting charge rates as needed to bring all cells to precisely 4.20V full charge.

Balancing is CRITICAL to maximize LiPo lifespan and prevent individual cell failure as packs age after repeated charge cycles.

❗️Always connect balance lead to enable per-cell voltage monitoring!

Step 2: Configure Charger Settings

Next, dial in proper charge settings on your LiPo charger for the pack you’re charging. Key item to set correctly:

Chemistry

Set charger mode to “LiPo”. This programs appropriate nominal voltage (3.7V) and max voltage (4.20V) for lithium cells.

Cell Count

Indicate number of battery cells to the charger. Ie: 2S, 3S etc. This sets total pack voltage so charger knows proper cutoffs.

Charge Rate (1C, 2C etc)

How fast should we charge? Charging at 1C is best for battery longevity. That means charging at 1x the battery’s mAh rating.

So for a 5000 mAh LiPo, 1C = 5000 mA (5A) charge rate. 2C would be 10A, and so on – doubling charge speed.

Faster charge rates are OK if you’re in a rush, but understand this slightly diminishes total lifetime charge cycles of your pack. Another reason to buy multiple LiPos – rotate packs instead of abusing single sets!

❗️Tip: Most modern LiPo chargers default to 1C out of the gate for battery longevity.

Optional settings like storage charge, delta peak detection etc can wait til you’re more experienced. Ignore for now.

Step 3: Charge Battery

With connectors secured and settings dialed in, let the actual charging commence per the charger’s prompts.

Carefully monitor the ENTIRE charge process. Never set it and forget it! Disconnect immediately if you notice:

• Battery swelling
• Smoke
• Extreme heat
• Strange odors
• Leaking substances

Any of those phenomena indicate trouble. Don’t risk your safety or equipment! You also cover charging LiPo with an appropriate fireproof bag or charging container.

Healthy LiPos charge up just fine with no excitement. Let the charger do its thing until indicating a full charge.

Step 4: Disconnect When Done

Once your charger shows fully charged status (solid green lights etc), immediately disconnect the LiPo. This prevents overcharging.

First disconnect balance/cell taps. Then disconnect the main discharge connector.

Step 5: Unplug From RC Model When Not Using

LiPo packs continue slowly discharging even when sitting unused in your RC models, car, boat etc due to minor electrical draws that are always present.

Prevent this “passive discharge” by disconnecting LiPos from electronics when not actively bashing or racing your RC.

Those are basics of smart LiPo charging. Let charger actively balance, monitor for issues, disconnect promptly when fully charged. Simple right?

Final Words

I hope this guide covered everything needed to safely operate LiPo batteries for new RC enthusiasts. While this chemistry certainly carries risks if mishandled, plenty of hobbyists enjoy LiPos for many years without issues.

Let me know if you have any other LiPo questions – or want to see more RC technical tutorials in the future!

LiPo Battery FAQs

Here are answers to a few common questions you may have about LiPo battery: