Beginner Series - Batteries and Safety

The Flite Test Beginner Series is brought to you by Horizon Hobby. 

Episode 7: Batteries and Safety 

Lithium Polymer also known as LiPo is by far the most common today as they have a high watt/weight rating and can deliver a lot of current so we’re going to just discuss these.

Important parameters:

1. Number of Cells

2. Capacity

3. C Rating

4. Discharging

5. Charging

6. Saftey

• Number of cells

• Determines how many volts the battery will have. 3.7V (nominal) per cell. 1, 2 or 3 cell (or 11.1V) is the most common in beginner planes.

• Capacity

• How much energy that is stored in the battery. Usually written in milliampere hours or mAh for short.

• Milli means a 1000th of. So a 2000mAh battery is the same as a 2Ah battery

• If you draw 2 Ampere through that battery it is going to last for 1 hour.

• If you draw 1 Ampere it’s going to last 2 hours

• If you draw 4 Ampere it’s going to last ½ hour or 30 minutes or 1800 seconds

• C Rating

• Is how much power the battery delivers without dropping too much in voltage

• How many Ampere it can deliver is dependent on the capacity of the battery

• To calculate how much it can deliver you take the C rating and multiply it by the capacity rating

• If you have a 1000mAh battery and a 20C rating that is 20 times 1 which is 20 ampere.

• There are normally 2 different C ratings. One for continuous discharge and one for burst, which means how much it can deliver for a very short time (10 seconds)

• Discharging Your Battery - Do not discharge to much!

• LiPo batteries do not like to be fully discharged. They are destroyed!!!

• Fully discharged cell is 3.0V - Never go below this!!

• If you discharge more than the battery rating it can catch fire!!!

• The 80% rule applies to batteries as well! Never discharge a battery more than 80% of it’s rated capacity. If you have a 1000mAh battery your should never discharge it more than 800mAh.

• Charging Your Battery

• Get a charger that is capable of displaying how many mAh that is put back into the pack.

• Time your flights. If you fly for 5 minutes and then charge the battery and put 500mAh back into the battery your plane draws 100mAh per minute. Which means you can fly for 8 minutes max.

• Charge at 1C

BATTERY SAFETY

• If you have a deformed battery from a crash

• Store, and charge, in a fireproof container; never in your model.

• Charge in a protected area devoid of combustibles.

• Never leave the charging process unattended.

• In the event of damage from crashes, etc, carefully remove to a safe place for at least a half hour to observe. Physically damaged cells could erupt into flame and after sufficient time to ensure safety, should be discarded in accordance with the instructions which came with the batteries. Never attempt to charge a cell with physical damage, regardless of how slight.

• Always use chargers designed for the specific purpose, preferably having a fixed setting for your particular pack. Many fires occur in using selectable/adjustable chargers improperly set. Never attempt to charge Lithium cells with a charger which is not specifically designed for charging Lithium cells. Never use chargers designed for Nickel Cadmium batteries.

• Use charging systems that monitor and control the charge state of each cell in the pack. Unbalanced cells can lead to disaster if it permits overcharge of a single cell in the pack. If the batteries show any sign of swelling, discontinue charging and remove them to a safe place outside as they could erupt into flames.

• Most important: NEVER PLUG IN A BATTERY AND LEAVE IT TO CHARGE UNATTENDED OVERNIGHT.
  Serious fires have resulted from this practice.

• Do not attempt to make your own battery packs from individual cells.

Choosing the right battery:

• Manufacturer recommendation

• Internet / Forums / google

• Connectors - Make sure they are the same or you need to know how to solder

• A bigger battery will let you fly for longer but will also impact the performance of your airplane

Links to useful articles:

Using a Watt Meter

AMA LiPo Battery Safety

HorizonHobby-BeginnerSeries