Beginner Series - Batteries and Safety

by FliteTest | December 4, 2013 | (39) Posted in How To

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


  • 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.

    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





shermanhartman on December 4, 2013
Finally. A video that actually explains how C rating works. Awesome. Thanks.
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lracnolip on December 4, 2013
good info
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Mat Dockerty on December 5, 2013
Well done, again, guys. I learned a lot of this the hard way (including some spectacular fires). Not sure if you were really struggling with the definition of C rating but it's probably current, aka amps.
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William Smith on December 5, 2013
Josh S: Math is not my friend either.
Thanks for the video. I know a lot more about batteries then I did before.
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Willsonman on December 5, 2013
When installing your batteries in your plane make sure there are no obstructions that could puncture the battery in the event of a small crash. Learned this one the hard way. I actually had a battery fall out of a plane and it survived. Then another plane that went in from 10 ft up. Got a small puncture from a screw. Fireball.
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sambrown300 on December 5, 2013
I had that happen with a parkzone corsair. No fire though:)

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Christopher14 on December 5, 2013
The C rating on a LiPo battery is the number of milliamps times the C rating, so a 1100mah battery with a 25C rating could discharge at a rate of 27 amps safely, also a 1100mah with a 45C rating could safely discharge at a rate of 49 amps safely, so again the safe number of amps you could discharge from a LiPo battery is determined by the the C rating times the number milliamps = the number of amps you can safely discharge without permanently damaging the battery.
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petedotnl on December 5, 2013
C rating stands for Capacity of charging or discharging your battery defined by the manufacturer.
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Marker on December 5, 2013
Question. What should I do with a battery (LiPo) that I crashed in a fresh water pond?
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caseMasterxL on December 6, 2013
I am pretty new to flying RC planes. From day one I have used Turnigy Nano-Tech batteries from HobbyKing. I have all of my ESCs set to "soft-cut" mode meaning that the power delivered to the motor is reduced when 3.2 volts is reached. When flying, I land as soon as I experience lethargic throttle response. I have never puffed a battery using this approach.

One thing I have noticed though is that charging rate has a definite impact on flight time. If I charge at 2C or 3C the battery provides less flight time than if I charge it at 1C. In fact if I charge the battery at approximately 0.8C I get nearly 25% better flight time.

For example, I charge my 3S 1300mAh 25C Nano-Tech at 2.6Ah (2C), I get about 8 minutes of flight with liberal throttle. If I charge the same battery at 1.0Ah (~0.8C) I get about 10 minutes of similar flight.

This is consistent across the range of batteries I use, ranging from 850mah to 3300mah.

I have managed to puff a Nano-Tech (3S 5000mAh 35C) but that was in a 1/8 scale truggy that was geared too steep in HOT weather AND I drained it to ~3.0/cell. Even that battery hasn't shown signs of lost capacity despite it's puffiness but I only charge it at 0.8C - 1.0C for safety.
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o0Jack0o on December 9, 2013
Where are the battery calculator links you mentioned in the episode???
The AMA link is to their home page...?

You guys are busy I know. Thank you in advance for fixing the problem.

Great job, easily the best and most complete and informative lipo article/episode :) on the web today!!! Keep `em coming
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clough42 on December 12, 2013
My favorite motor/prop/ESC/battery calculator is here:
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sgrocker576 on December 22, 2013
rookie question: So I'm slightly confused, if i have a 3200mah 3s 20c rated battery then in order to charge at 1C as recommended then i should set my charger to 3.2amps? any help would be great! thanks!
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TheWW1FlyingAce on December 28, 2013
You got it right. 3200mAH is 3.2AH. 1C of 3.2AH is 3.2A. If you want to determine how many amps you can get from your battery when flying, take 20C times 3.2AH and you get 64A. That's the most you can discharge your pack at.
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TheWW1FlyingAce on December 28, 2013
Please, please, PLEASE do not recommend using salt water to dispose of LiPOs. This is an urban legend that took on a life of its own. When actually put to the test, it was found that the salt water corroded the contacts on the battery before the battery had a chance to discharge fully, so the battery remained partially charged and unsafe.

The best way to discharge a battery for disposal is to use automobile taillights. Solder your favorite connector to some wire, solder the other end of the wire to one (for up to 3 cells) or two (for up to 6 cells) taillights in series, plug your battery into the newly created discharger for a few hours. Then check the battery voltage to ensure it's close to 0, cut off the connector, strip the wires and twist them together to ensure that any bounceback voltage goes away, and discard the pack.
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hunterradiocontrol on December 29, 2013
how do you get the power source for the charge?? do you connect the charger to a car battery?? pls help.

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TheWW1FlyingAce on December 29, 2013
You can do that, but you won't be able to charge too many batteries before the car battery is discharged. The better option is to purchase a 12V power supply. If you have a cheap 50W charger, you'll be looking for a 60W power supply (chargers are usually about 80% efficient, so you need more power in that out.) 60W is 5A at 12V, so look for a 12V power supply with at least 5A output - more amps is better, since then you can hook up multiple chargers (or larger chargers) to charge more packs or charge your current packs faster.
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hunterradiocontrol on January 1, 2014
can anybody please tell me a power source of the battery charger??? pls help
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TheWW1FlyingAce on January 17, 2014
eBay is an option - search for "12V 5A" and you'll get a listing of power supplies that would work fine for a 50W charger. Another option is to go down to your local thrift store and see if they have a section with power supplies - you might be able to pick up a 12V/5A laptop power supply for $5 or so. Note that it's fine to go higher on the amperage, so a 12V/10A power supply would be even better.

If you upgrade to a bigger charger (and you will, believe me) you'll need a more powerful supply. The one I use is an HP DPS-600PB server power supply - 12.5V/47A. These are available on eBay for around $20 shipped. Using this supply does require some soldering skills, but gives you a lot of headroom to either use a bigger charger or multiple small chargers simultaneously.

I recommend reading for a lot more detail on selecting a charger and power supply.
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jefforig on April 4, 2014
Can you create a more in depth video on choosing a charger, power supply, lipo bag, and properly setting it all up? I researched a bunch of different sites to learn but still don't feel very confident I have it right. Also, can you recommend some decent choices on these items? Please post those items on this page as well: Thanks!
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DAG__DAG on April 8, 2017
totaly agree
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travman on June 8, 2014
this helped a lot thanks flite test :)
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Andrewmacor on June 30, 2014
What does the s after the battery mah ?
And if a BEC calls for 1 AMP can I use a 3 amp lipo battery?
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a8med on August 1, 2014
i am having a problem and i think it is the battery's. Running a home built quad from HK parts and using 4x NTM 2830 1100-kv motors and 30A esc. Powering that whit a 3s 3700mah 25c battery. I nead to have the throttle at about 75% for lift and have therefore not much to controll or fly around whit. Quad is about 1,3kg total and the motors is supposed to lift 1kg each at 16 amps.
The battery should be able to deliver 25*3,7=92,5 amps that means about 23A for each motor.
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Flite test for life! on May 21, 2015
What is the best charger for a

Turnigy 1000mAh 3S 25C Lipo Pack

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mikeporterinmd on February 6, 2016
You may want to consider adding information about storage charging the batteries. It's not uncommon for me to charge a bunch of batteries, but not use them for any number of reasons. They need to be discharged and then storage charged. I'm sure you know all this, but these videos are a little older now and perhaps need a bit of updating? Thanks for the video!

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akashpsinghal on July 30, 2020
I am a beginner in the rc hobby and need a very Rookie advice. If I have funds to buy only one or two batteries, which should I buy in order to run the maximum number of FT models?
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Beginner Series - Batteries and Safety