The Lipo Battery Guide

LiPo vs. NiMH Batteries

LiPo Batteries

Lithium-polymer batteries, also known as LiPo batteries, are now used in many consumer electronic devices. They have become very popular in model making thanks to their small size, light weight, and high performance. However, they do have some drawbacks, such as their fragility and relatively short lifespan (between 150 and 250 charge cycles).

NiMH Batteries

Lighter and more powerful than NiCd batteries, NiMH batteries are commonly used in model making. They are safer, with virtually no risk of fire, and are therefore more suitable for children. On the other hand, they are also heavier, have size limitations, and offer lower performance than LiPo batteries.

What do the numbers on a LiPo battery mean?

The numbers on LiPo batteries help you understand their properties. There are three specifications you absolutely must understand to determine whether the battery is suitable for your radio-controlled vehicle.

The voltage

A LiPo cell has a voltage of 3.7 V (or 3.8 V in the case of HV batteries). You’ll often find higher values, such as on the battery shown above: 14.8 V means there are four cells connected in series car, and the voltages add up. In the world of model building, you’ll often see 2S batteries to indicate two cells, 3S batteries for three cells, 4S batteries for four cells, and so on.

The battery voltage affects the rotational speed of the electric motor, so it determines the speed of your radio-controlled vehicle. For brushless motors, power is rated in kV (RPM per volt). For example, a motor with a power rating of 3,500 kV will rotate at 3,500 rpm per volt; therefore, with a 2S LiPo battery, it will rotate at 25,900 rpm, with a 3S battery at 38,850 rpm, and so on.

To help you out, here’s a quick summary table:

Capacity

A battery’s capacity determines how long you can use it before it runs out of power. It is measured in milliampere-hours (mAh). The higher the value, the longer the electric vehicle’s range. In model building, the average is 5,000 mAh, but some batteries can reach up to 12,000 mAh. However, a high-capacity battery is heavier and bulkier than its counterparts (be sure to check the battery’s dimensions to ensure it fits in your vehicle).

Discharge Rate

The C-rate is the maximum safe continuous discharge rate of your battery. For example, on the battery shown above, 50C means you can discharge the battery at a rate up to 50 times its capacity continuously—that is, 6,000 mAh × 50C = 6A × 50 = 300A maximum continuous discharge. Exceeding the maximum continuous discharge rate can, at best, cause the battery to degrade more quickly and, at worst, cause the battery to catch fire. Always choose a discharge rate well above your maximum continuous discharge car—this can vary depending on the type of terrain, tire size, or vehicle weight.

How do I take care of my LiPo battery?

Precautions to Take

LiPo batteries offer power and runtime to model enthusiasts, but these benefits come at a cost. If a LiPo battery is damaged—since lithium is highly reactive when it comes into contact with water or moisture—toxic gases may be released and a fire may occur. However, this type of battery poses no danger as long as you follow certain safety guidelines.

• Immediately dispose of any LiPo battery that has started to swell, is damaged, or has a puncture by taking it to a facility authorized to handle hazardous materials.
• Do not attempt to charger a damaged battery.
• After a crash, remove the battery, place it in a safe area (away from any flammable materials), and monitor it for 30 minutes while maintaining a safe distance. After this time, if the battery appears stable, has not leaked, and shows no signs of damage, you may use it again while remaining vigilant.
• Do not leave the battery in a vehicle or directly exposed to sunlight.
• If your LiPo battery catches fire, do not extinguish the fire with water; instead, use sand or a fire extinguisher designed for electrical fires.

Charger a LiPo battery

New LiPo batteries are always charged to 40% of their total capacity car; manufacturers consider this the best way to store them long-term. An initial charge is therefore necessary before use. Do not use the Fast Charge function during the first few charging cycles, and do not use a battery that is less than 50% charged. This is to preserve their lifespan and performance. In general, LiPo batteries should never be discharged below 3 volts per cell, as this may damage them.

Before charger a LiPo battery, remove it from the radio-controlled vehicle and inspect it to ensure it is not deformed or has any cuts. You must use a charger specifically designed for LiPo batteries and never place it on a flammable surface (carpet, wood, etc.) or inside a vehicle with the engine running. You must also monitor the battery throughout the entire charging process.

Storing a LiPo Battery

The ideal place to store your LiPo batteries is a well-ventilated, cool, and dry location, with a temperature between 5°C and 27°C. Batteries should be stored at half charge (approximately 3.8 volts per cell): modern chargers have a “storage” function to set the voltage for storage. During transport, the ambient temperature must be between 5°C and 50°C, and the batteries must be kept out of direct sunlight. You can also use a fire-retardant bag for storing or charging your LiPo batteries to prevent any accidents.

The Lipo Battery Guide on Video