Lithium Polymer Charging/Discharging 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.
• Be absolutely sure that the Lithium Polymer charger settings are correct for the battery pack being charged – both voltage and current settings.
• 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: Be sure that the correct polarity is observed when connecting battery packs to charger or ESC.

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

Charging/Discharging: Your new pack arrives half charged.  Charge your pack fully before first use.  Charge your LiPo battery pack at 5C or less on the LiPo setting only.  You must use a balance charging system similar to the Hyperion chargers offered here at MaxAmps.  Otherwise, you risk your pack becoming severely out of balance over time, which 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.

Please refer to your owner’s manual regarding the recommended ESC cutoff voltage for your particular application prior to first use to avoid accidentally over-discharging your batteries.

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.

It is dangerous to draw more power than what the pack is rated for.  This will void any warranty on the pack and can also cause your battery pack to ignite into flames.  The temperature of the pack should never exceed 140F degrees.  If it does, you may need a pack that is rated to handle more power.

Storage Procedure: When not using your LiPo/Life battery pack, store it at 60-70% 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 the packs to get severely out of balance, puff/swell or even go dead.

Balancing taps on LiPo/LiFe Packs: All MaxAmps LiPo/LiFe packs come standard with a JST-XH style balancing tap (white connector). This tap is compatible with all Hyperion balance chargers. Always balance charge your pack before each use as this “matches” the voltage of each cell to give you the highest performance and longest life.

Handling Cautions:

1. Never leave batteries inside a car on a hot day or any other place where temperature may exceed 140F / 60C.
2. 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.
3. Immediately discharge damaged batteries at 1/2 C rate and dispose.
4. 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.
5. Do not place the loose cells on any conductive surface, such as a metal-topped table.
6. We recommend purchasing pre-assembled packs rather than assembling packs from loose cells.
7. Take care that the cells are not punctured, especially by metallic objects like hobby knives.
8. 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.
9. 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.

Some Tips For LiPo Battery Safety

LiPo batteries are generally safer and more environmentally friendly than NiCd and NiMH. LiPo batteries are becoming the most popular high performance RC battery and are used in RC cars, boats, planes, helis, multirotors and more. However, if charged, discharged, stored, maintained, or handled improperly, they can become extremely dangerous. This is a simple guide for safe LiPo battery ownership and use. This guide applies to all RC LiPo batteries including all DJI Smart Batteries used in the Phantom 2 series and Inspire 1. Here we can recommend you Gens Tattu and Ace lipo batteries for you, Gens provides a whole set of battery system for customers in areas of electric cars, electric tools, RC planes, RC race cars, military equipment, solar and wind energy storage, and National Grid. Gens aiming goal is “serve the society with high quality products”. 

Gens Tattu and ACE Lipo Batteries

 Storing and Transporting your battery

If your LiPo batteries are going to sit on the shelf for a while, they are happiest if the cells are at about 3.7 to 3.8 volts each. If you've just finished flying then chances are your batteries will be close to this but if you've charged your packs and then didn't use them, it's vital to have a method handy that will allow you to discharge your packs to this storage level. Some balance chargers have a discharge function but if you're running high capacity (mah) packs they can be slow to complete a discharge cycle. If you rig an alternate method just be sure that it won't discharge the packs too quickly as that can damage your packs making them very unhappy and a true LiPo Ninja can't have unhappy packs.

It's preferable to store your packs in a cool area where they can enjoy a relaxing chilled period of inactivity. Storing batteries in cars, trailers, sheds, etc can expose them to high heat which can degrade the materials in the battery making them not last as long and not hold as much of a charge.

Before putting batteries away after flying be sure to check them for damage as even minor looking dings and dents can cause internal shorting which can lead to a fire. If after putting your stuff away after a day of flying it would be a surprise to find out one of your packs is burning in the basement, no? LiPo fires are hot and intense as well as being difficult to put out. Avoid fires at all costs by understanding your batteries and by maintaining good habits for use, charging, and storage.

LiPo Battery Handling & Storage 

• Keep LiPo battery packs WELL out of reach of children.
• Do not put battery packs in pockets or bags where they can short circuit.
• Do not store or transport batteries where they can come into contact with sharp or metallic objects.
• Do not store your LiPo pack in extreme temperatures below 0C or above 50C.
• Always store your LiPo pack in a safe and non flammable container away from flammable objects. A LiPo Sack or metal / ceramic storage container is best.
• Always store your LiPo?ˉs partially charged. They will maintain their performance levels over time and there's no need to cycle them unless stored for periods longer than 3-6 months. 
• Do not immerse the battery in water or allow the battery to get wet.
• Do not dispose of in fire or heat.

When mailing or shipping LiPo batteries, always ship them at a 30% charged state for safety reasons.When storing batteries for extended periods, store at a half charged state. To dispose of a LiPo battery, discharge it fully then place it in a bucket of salt water for one week. To dispose of, follow your municipal battery disposal guidelines.

Lipo Charging

Charging Lithium Polymer or LiPo batteries have very specific charging requirements and MUST only be changed by specific chargers designed to charge lithium polymer batteries. We recommend only balance charging your lipo batteries. All good quality Lipo battery packs come with 2 leads. The main charge / discharge lead and connector and a balance lead and connector. Using a computerised balance charger to charge your Lipo batteries will ensure that all the cells in the battery pack have the same voltages. The voltage value is critical to the condition (during use) and safety of each cell, which we will cover more in this article.

• Never charge Battery's unattended
• Always use chargers designed specifically for charging LiPo battery's
• Never charge LiPo batteries with chargers meant for NiMh, or NiCd battery's
• Do not charge battery's on or near any flammable materials, this will help ensure that if there is a malfunction it can be contained with the least amount of damage and injury possible.
• Always charge your battery in a fire proof container or LiPo safe sack. Do not charge your battery in your RC vehicle. 
• Always visually inspect your battery before charging and after charging.
• Always allow your battery to cool to its safe ambient temperature before charging after its previous discharge cycle.
• Monitor the resting voltage of your battery before charging, Do not charge any battery that has lower voltage than 3.0Volts in any cell.
• Always select the correct cell count on your charger, please reference the chargers settings to the battery's label.
• Never charge the battery exceeding 2C, C=the thousand value capacity of the battery (5000Mah = 10amp max charge).
• Monitor the battery's voltage after charging to ensure that your charger has not exceeded 4.2V per cell.
• Always double check to ensure that your charge leads from your charger and to your battery are of the correct polarity.

LiPo Balancing

For your multi-celled (2S and higher) LiPo to run at its best and last its longest, the individual cells need to be charged equally. The term for that is balancing.

A charger can't supply the same charge to all three cells. For example, if you have a 3S where the three cells are discharged to 3.1V, 3.3V and 3.7V and you plugged them into a non-balancing charger, the 3.7V cell would hit the maximum 4.2 volts well before the other two. And then it would exceed the maximum as the other cells continued to charge "C" destroying the cell and possibly resulting in a fire.

That's why every LiPo with one or more cells will have a balance plug (sometimes referred to as a balance tap). The charger uses the balance plug to monitor the individual cells while charging.

Conclusion

It is my hope that all RC hobbyists are responsible lipo users. This includes both using and maintaining lipos, as well as disposing of them properly when the time comes. All it takes is fully discharging a lipo to render it inert and safe, and then can be simply tossed in the trash. Being responsible for your lipos is not hard, it just takes some basic knowledge and a little bit of effort. So keep that in mind next time you have a lipo that needs retired.