Lithium Polymer Battery Overview and Safety First Weedwacker Aero - PowerPoint PPT Presentation

Lithium Polymer Battery Overview and Safety First Weedwacker Aero Squadron Charter 1651

Weedwacker Battery Charging Policy Any individual wishing to charge a lithium polymer battery at Cactus O Park must be a Weedwacker Club member and be a certified electric airplane pilot, or be a guest of a certified electric airplane pilot and under their supervision. All lithium polymer based batteries must be charged at the designated O table in a fireproof container provided by the member or guest. A commercially available container is preferred, although one of the club’s electric airplane safety technicians or EAST, can choose to certify a container upon request. Each person must provide their own charger designed for charging O lithium polymer based batteries. Each person must provide their own power source. Connections shall O be secure and all connections properly insulated. There is no direct charging to be done from a battery installed in a vehicle. Each person who is charging a lithium polymer based battery shall O periodically monitor their battery while it is charging.

Transporting and Storage O Batteries should be transported and stored in a fireproof container such as a commercially available LIPOSACK.

Examples of Containers

For BIG batteries!

Using Lithium Polymer Batteries O Care should be taken with the installation of LiPo’s in the airframe so as to avoid and possibility of cell puncture. O Cooling is also of concern when using high current demand packs.

Fire Safety O In the event of a crash O Pay attention! Use landmarks to identify where the plane went down. O Without delay go to the scene of the crash and evaluate the potential for battery failure and possible fire hazard. O Care is to be taken with any battery involved in a crash. Inspect it visually for damage and let it set away from anything flammable for 30 minut nutes es before transporting or attempting to charge or use it again. O Never use a compromised battery. Dispose of it according to local rules and regulations. O Should any fire event occur call ll 911 O Providing is safe to do so, attempt to knock down the fire with extinguishers and shovels of sand until fire professionals arrive

Matching batteries, speed controls, motors and props O Current draw O All components are rated for optimum and maximum current draw. O Do not exceed this rating or you risk catastrophic failure of one or more components. It is critical to be sure all major components of your aircrafts electric propulsion package are matched for safe and efficient operation. O To ensure the safe operation of your electric plane it is highly recommended you test your electric propulsion system with an amp meter . This is the best way to ensure you are not stressing the battery, esc or motor. Heat is the enemy. Overheating any one component just once, can ruin it beyond repair.

Matching batteries, speed controls, motors and props O Battery O All batteries have a “C” rating. This is the rating related to the discharge current draw. O 1C is always equal to the capacity of the pack. O Example: O A 1000 mAh, or 1 amp pack with a 20C rating can be discharged safely at up to 20 amps. Exceed the safe C rating and the battery will get hot and can fail.

Matching batteries, speed controls, motors and props O Battery Example O In the first example on the left, the battery can handle 800 x 20=16,000 mA or 16 amps O On the right, we can run up to 200,000 mA or 200 amps . O Operating a battery at its peak will reduce the lifetime of the battery. The greater the margin, the more cycles that can be expected.

Matching batteries, speed controls, motors and props O Prop O Prop choice is key in any electric airplane propulsion system. Follow the motor provider’s guidelines to match the proper prop to the motor and cell count (battery voltage) you intend to use. O Prop Load Factor is affected primarily by diameter and, to a lesser degree, pitch, style, tip shape and more.

MotoCalc

MotoCalc

MotoCalc

MotoCalc

Matching batteries, speed controls, motors and props O Wires and Connectors O Use a wire size and connector type that is big enough to get the current safely to the ESC and motor. O Using wires too small is a common mistake and can result in a wire meltdown and even cause solder to melt.

Connector Examples Brand Ratin ing Image age 50 A Deans Ultra EC3 Bullet style 60 A EC5 120 A Anderson Power 15, 30 and 45 A Pole (based on insert) JST 8 A O The wiring used must be rated as well

Matching batteries, speed controls, motors and props O 2.4 Considerations O Power leads, battery and ESC should not be installed near 2.4 receivers and antennas.

Disposal of LiPo Batteries O Unlike NiCd batteries, lithi hium um-pol olymer mer batt tteries eries are envir ironm nmen enta tally y fri riend ndly . For safety reasons, it’s best that LiPo cells be fully discharged before disposal (however, if physically damaged it is NOT recommended to discharge LiPo cells before disposal - see below for details). The batteries must also be cool before proceeding with disposal instructions. To dispose of LiPo cells and packs: O 1. If any LiPo cell in the pack k has been n physical cally damaged ged, resulting in a swollen cell or a split or tear in a cell’s foil covering, do NOT disch charg arge e the batt ttery. Jump to step 5. O 2. Place the LiPo battery in a fireproof container or bucket of sand.

Disposal of LiPo Batteries 3. Connect the battery to a LiPo discharger. Set the discharge cutoff voltage to the O lowest possible value. Set the discharge current to a C/10 value, with “C” being the capacity rating of the pack. For example, the “1C” rating for a 1200mAh battery is 1.2A, and that battery’s C/10 current value is (1.2A / 10) 0.12A or 120mA. Or, a simple resistive type of discharge load can be used, such as a power resistor or set O of light bulbs as long as the discharge current doesn’t exceed the C/10 value and cause an overheating condition. For LiPo packs rated at 7.4V and 11.1V, connect a 150 ohm resistor with a power rating of 2 watts (commonly found at Radio Shack) to the pack’s positive and negative terminals to safely discharge the battery. It’s also possible to discharge the battery by connecting it to an ESC/motor system and allowing the motor to run indefinitely until no power remains to further cause the system to function.

Disposal of LiPo Batteries O 4. Discharge the battery until its voltage reaches 1. 1.0V per cell or lo r lower er. For resistive load type discharges, discharge the battery for up to 24 hours. O 5. Submerse the battery into bucket or tub of salt t water. This container should have a lid, but it does not need to be airtight. Prepare a bucket or tub containing 3 to 5 gallons of cold water, and mix in 1/2 cup of salt per gallon of water. Drop the battery into the salt water. Allow the battery to remain in the tub of salt water for at least st 2 weeks ks. O 6. Remove the LiPo battery from the salt water and place it in the normal trash.

Disposal of LiPo Batteries – one last step O A final precaution to prevent any bounce- back in voltage is to solder the two connectors together. This shorts the cells completely so that they’ll never be a hazard in a waste container or landfill.

FIN