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Battery Care

This page is a chapter in 'Advice on successfully and safely flying your AeroQuad'

General description

Advantages of LiPo packs

  • Have nearly double the capacity with half the weight of NiCad or NiMH battery packs
  • Retain charge significantly longer than NiCad or NiMH batteries when not being used
  • Do not develop a "memory" as NiCad batteries do
  • With LiPo cells in combination of series and parallel, LiPo packs can be built to power most all RC aircraft

Disadvantages of LiPo packs

  • Have very short shelf life of two to three years
  • Very sensitive to high temperatures
  • Very sensitive to high and low voltages. Exceeding either will damage the battery
  • Prone to explode if exposed to heat, or charged/discharged improperly

Charging, discharging and storage tips

Lithium ion polymer batteries harness an enormous amount of energy in a very small space. These batteries will explode if used improperly. When proper LiPo battery safety precautions are followed, these batteries are completely safe. Lithium polymer battery care can be broke down into three categories, which are:
  1. Discharging
  2. Charging
  3. Storage

Discharging Lithium ion polymer batteries

It is important to have a properly sized LiPo battery pack for the motor being used. An RC LiPo battery pack is designed to delivery a set amount of current to the motor. This value is determined by the C rating of the battery. To determine how much current a battery is rated for, simply multiply the C rating by the capacity of the battery pack.

For example, a 5000mah LiPo battery pack with a 20C rating can safely provide 20 x 5000mah = 100,000 mA or 100 amps. Discharging a LiPo battery pack at higher current than it is rated for is very dangerous.

Charging Lithium ion polymer batteries

It is absolutely critical that every precaution is taken when charging LiPo battery pack. Lithium polymer chargers use a different algorithm than any other type of battery charger. For this reason, a lithium polymer charger must be used when charging LiPo battery pack. Using a charger that is not specifically designed for LiPo batteries will damage the battery and could result in an explosion.

Lithium polymer battery packs do not develop a "memory" as NiCad batteries do. We don't have to worry about fully discharging LiPo battery packs before charging them. Any RC LiPo battery will be especially hot immediately after a flight. Always wait until the battery has reached ambient temperature before charging.

Current and voltage are the two variables that must be determined when charging LiPo batteries. The voltage should be set to the nominal voltage of the LiPo battery pack. A 5000mAh 11.1V LiPo battery pack would be charged at 11.1V.

The current should never exceed a 1C charge rate. For example, a 5000mAh 11.1V pack should be charged at 5 Amps or less. Charging at lower rates down to .77C could increase the life of the battery, although there is not conclusive evidence that I am aware of to support this. For example, a .77C charge rate of a 5000mAh pack would be 3.85 Amps.

Most LiPo chargers automatically detect the voltage (or cell count) of the LiPo battery pack. It is always a good idea to double check, or confirm that the charger detects correct the voltage pack.

LiPo balancers

As stated above, lithium polymer cells must stay between 3.0V and 4.2V for optimal performance. A standard LiPo charger looks at voltage of the entire LiPo battery pack when charging. Sometimes the individual LiPo cells become unbalanced over time. For example, one cell may have a voltage of 3.8V while the rest are at 4.2V.

A LiPo balancer monitors and controls how much each cell in the LiPo pack is charged or discharged. Balancing the pack will allow for the fullest possible safe voltage which results in more power while in flight. A balanced pack also tends to last longer as no individual LiPo cells become over charged.



This schematic illustrates the normal connections between the charger and a 3S LiPo pack. The thick wires are the main (dis)charge leads and are used for the main charging current. Small wires are on balance connector and are used to monitor the voltage levels on each cell and also provide small current to equalize the cell voltages during charging.

Storing Lithium ion polymer batteries

LiPo batteries should always be stored in a cool environment. In other words, don't leave them in your car with the windows up on a hot summer's day. Keep them in a cool location out of the direct sunlight. It is highly recommended that Lipo batteries be kept in a charging bag (e.g. those on eBay) while being charged and while not in use.

Safety Tips

Lithium Polymer cells are a tremendous advance in battery technology for RC use. However, due to the chemistry of lithium cells, there is a possibility of fire if charging is not properly done. It is unavoidable due to the nature of lithium itself. This is no different from many things we use in daily life – knives, kitchen cleaners, automobiles, for a few examples – which are inherently dangerous, but which can be used safely by adhering to simple rules and precautions.
  • Batteries should NEVER be left unattended while charging.
  • Always let LiPo batteries cool to ambient temperature before charging.
  • Make sure the charger is designed specifically for LiPo battery packs.
  • Be absolutely sure that the Lithium Polymer charger settings are correct for the battery pack being charged – both voltage and current settings.
  • 1C charge rate!
  • Lithium Polymer must be CHARGED and STORED in a fire-safe container like a Lipo Sack.
  • Do not charge batteries near flammable items or liquids.
  • Keep a dry fire extinguisher nearby or a large bucket of dry sand, which is a cheap and effective extinguisher.
  • Never charge inside an automobile even when parked.
  • KEEP BATTERIES AWAY from children and pets at ALL times.

Connection: You must be sure that the correct polarity is observed when connecting battery packs to charger or ESC.

RED = POSITIVE (+)
BLACK = NEGATIVE (-)

Charging/Discharging: Charge your LiPo battery pack at 5C or less on a LiPo approved charger only. If you choose to charge at any rate higher than 1C, you must use a balance charging system similar to the Hyperion chargers offered here at MaxAmps.com. Otherwise you risk your pack becoming severely out of balance over time, which in turn will significantly decrease the lifespan.

Ex: If charging a 4000mAh LiPo pack at 1C, you would be charging it at 4 Amps.
Ex: If balance charging a 4000mAh LiPo pack at 5C, you would be charging it at 20 Amps.
Set your speed control to hard cut-off at 3V/cell or higher - 3.2V per cell is best. If your ESC does not have this feature, you will need an external cutoff or alarm. (Ex. Novak Smart-Stop or LVA)

Do NOT charge your LiPo packs on a NIMH/NICD charger. Your charger must be designed for lipo cells. Do not charge above 4.2V per cell, over discharge under 3V per cell. Never leave lipo packs unattended during charging or after a crash in your vehicle. Don’t leave the battery pack plugged into a vehicle while not in use. The pack can still discharge to an unsafe level and damage the pack even if all components are turned off.

LiPo Batteries will have a C rating for discharge, for example 25C maximum continuous discharge. Multiply the discharge rating by the capacity of the pack in amp hours to find the maximum discharge current for the pack. For example :
25C 2100mah battery pack
25 * 2.1 = 52.5A
The most you should draw continuously from this pack is 52.5A, so make sure that combined amp draw is less than this. Many packs will also give a surge rating, which is not to be confused with the continuous rating.
It is dangerous to draw more power than what the pack is rated for. This can cause your battery pack to ignite into flames. The temperature of the pack should never exceed 140 degrees. If it does, you may need a pack that can handle higher discharge rates.

Storage: If you don't plan on using your LiPo pack for longer than a week, store it at 60% of the pack's rated capacity. Make sure to cycle your packs at least once per month since leaving them on the shelf for a prolonged period of time can cause performance issues due to increased internal resistance in the cells.

Taps on LiPo Packs: All MaxAmps.com LiPo packs come standard with Hyperion style balancing taps (white connector). This tap can be used with all Hyperion balance chargers. This also “matches” the voltage of each cell to give you the highest performance and longest life.

Handling Cautions

  • Never leave batteries inside a car on a hot day or any other place where temperature may exceed 140F / 60C.
  • Although environmentally friendly, lithium polymer cells must be FULLY discharged before disposal. Use a resistor setup (light bulbs, for example) to accomplish this, to avoid the possibility of a short-induced fire after disposal.
  • Immediately discharge damaged batteries at 1/2 C rate and dispose.
  • Do not put the loose cells in a pocket, bag, or drawer where they could short-circuit against other items, or the battery tabs could be pressed against each other.
  • Do not place the loose cells on any conductive surface, such as a metal-topped table.
  • We recommend purchasing pre-assembled packs rather than assembling packs from loose cells.
  • Take care that the cells are not punctured, especially by metallic objects like hobby knives.
  • If the electrolyte in the cells should get on your skin, thoroughly wash with soap and water. If in the eyes, rinse thoroughly with cool water. Immediately seek medical attention for this, or for burns.
  • Although our batteries are now water sealed, we do not recommend submerging our batteries for extended periods of time. The battery packs will be protected during normal RC conditions.

All Lithium Polymer Batteries we carry are only approved for RC use, and may not be used in any other application. Battery discharging, charging, electric motors, spinning propellers, and flying models all have the potential for serious injury to persons and damage to property. In purchasing these products, the user agrees to accept responsibility for all such risks, and not to hold the battery manufacturer, distributors, or retailers - (all including owners and employees) -responsible for any accident, injury to persons, or damage to property.

The use of Lithium Polymer batteries in radio-controlled models is to be considered experimental, and there is no warranty, expressed or implied, by the manufacturer, distributors, or retailers with respect to the capacity, life in cycles, storage, or discharge characteristics of lithium cells in RC use, nor any other use nor aspect unless otherwise stated.

LiPo Battery Warming Devices/”Bumping” Lipo Packs

Do not, under any circumstances, attempt to “heat up” your batteries or increase the voltage of a pack above 4.2V per cell using these devices or techniques. Some insidious lithium polymer retailers/distributors have suggested using these devices and techniques to increase the performance of your lithium polymer packs. THIS IS NOT SAFE AND IS LITERALLY PLAYING WITH FIRE!

Devices on the market that heat up lithium polymer batteries can increase the risk of a fire. Lithium polymer cell manufacturers suggest that exceeding 140 degrees is NOT a safe temperature for a lithium polymer cell. At 140 degrees, the pack can become unstable and very dangerous. The small increase in performance is not worth the risk of a fire. PLEASE STAY SMART AND SAFE BY NOT USING THESE PRODUCTS!

Some retailers/distributors of other brands of lithium polymer batteries have suggested that their customers and racers “bump” the voltage of their packs using settings other than the lithium polymer setting on their charger. The manufacturers of lithium polymer cells suggest a voltage range of 3V-4.2V. Increasing voltage above 4.2V per cell is not safe. You should never attempt to charge your packs beyond the voltage set for lithium polymer packs on your lithium polymer charger. Using other battery settings to “bump” the voltage beyond 4.2V per cell can cause fire and injury. The small increase in performance is not worth the risk of fire. PLEASE DO NOT USE THESE METHODS!

"My battery is dead - HELP" info

About once a week (or oftener) someone posts a question on how, or whether to, revive an over discharged LiPo battery.
Here are some of the recent threads on that subject: (Always remember, over discharged LiPos are damaged goods and the safety precautions recommended for LiPo packs should be followed!)

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