# What is C Rating of LiPo Battery FPV Drones

C rating is one of the most important factors to consider when buying LiPo batteries for your FPV drone. In this tutorial I will explain what C rating is, the significance of C-rating and how it’s calculated.

Make sure to check out my tutorial about LiPo batteries for FPV Drone, it has everything you need to know about LiPo.

# What’s LiPo Battery C Rating

C Rating is an indicator of the continuous and burst discharge rate of a LiPo battery. It allows users to easily calculate the maximum current you can draw from the LiPo safely without damaging the battery.

`Max Current Draw = Capacity x C-Rating`

For example, if you have a 3S 1000mah 20C LiPo battery, the safe maximum current draw would be 1000ma x 20C = 20A.

You might wonder, can I draw more amperage than the above figure (i.e. higher the 20A given in the example)? You could, but it’s not recommended.

Discharging a battery at a rate higher than its specification – the battery will overheat and that will increase the internal resistance of the cells faster, which subsequently shortens battery lifespan or even damage it.

# What Affects C-Rating

The following factors affects the C-rating of a LiPo battery:

• internal resistance of the cells – chemicals, battery construction, age etc…
• connector
• thickness of the wires

The biggest factor is usually internal resistance (IR), it limits the max current output of a LiPo battery.

If your battery has a low C-rating, it has high internal resistance, voltage of the battery will drop as you increase throttle – a common issue as known as “voltage sag”. And with voltage decrease, the motor will lose RPM and ultimately the drone would feel less powerful. (This is an over-simplified explanation of battery would affect the performance of a drone)

Energy that is lost to resistance will turn into heat, and this is why the battery gets warm when it’s discharging.

# Higher C Rating Battery Is Bigger and Heavier?

Batteries of the same capacity, the one with higher discharge rate is normally bigger.

Both of these batteries are 4S 650mAh, but the one on the left only weighs 60g, while the one on the right weighs over 86g and much bigger.

And yes, the bigger battery has much better performance and able to output much higher current without getting overheat. But I wouldn’t say one necessarily better than the other. For a less powerful drone, it might not need all that potential power. A lower C-rating battery could be more beneficial because it’s lighter, cheaper, more efficient and actually gives you longer flight time. It all depends on the application.

# Can You Trust C Rating?

No you can’t.

C rating can be a useful tool to help you select a LiPo battery, unfortunately many RC LiPo manufacturers nowadays use inflated C-rating numbers for marketing. Therefore, while C rating is an indication of how good a LiPo is, you should only take it as a grain of salt..

Check out my testing and reviews if you are not sure what batteries to buy.

# Charging Your Batteries at 1C

C rating is also used to refer to how quickly you should charge a LiPo battery (or how much current to pump into the LiPo when charging).

You might have heard of a common saying “charge your LiPo at 1C”. This means charging the battery at a current equals to its capacity*1C.

For example to charge an 4S 1500mAh at 1C, simply multiply 1500mA by 1, which is 1.5A. At 2C, that would be 1.5A x 2 = 3A.

It’s worth knowing that if you charge a battery at 1C, it will take exactly one hour to fully charge it (regardless the capacity), at 2C that would be 30mins, and at 6C, 10mins.

Higher quality batteries can handle higher charge rates at little to no degradation over time, but lower grade cells will overheat if you charge them with too much current. For safety, it’s recommended to charge at 1C whenever possible. Or stick to the recommendations from manufacturer to prolong battery life and performance.

# Edit History

• Feb 2015 – Article Created
• Jan 2018 – Updated

## 40 thoughts on “What is C Rating of LiPo Battery FPV Drones”

1. Manjunath S

I am building quadcopter at my home,
Using FPV 450 frame
Kk2 board
Esc 30a 4nos
2212 1400kv bldc motors 4no.
1045 pro propellers
What battery need to buy. And help me about c rating and mah if battery

1. Oscar Post author

In theory, higher C rating gives you higher max discharge current while it increases the battery weight and cost.

2. Nash Ortiz

Try looking for batteries with at least 10 *AMPS* (important amps not C rating) higher than the constant draw from your motor(s).
Example: Motor @ Max 25Amp
Then Batt: *1500mAh *25C = 37.5 Amp
(1500×25/100) (or1.5×25) = 37.5
Batt #2: 1300mAh 30C = 39 Amp
(1.3×30) = 39

2. Kostas

Hi Oscar.
I found your articles very usefull.
I am building a fishing boat (5-6 kilos with the batteries) the motor that i am going to use is the xerun 4274sd 1800kv 1300watts and i am intending to use 4s 10000mah baterries.2 of them
I want to ask you which c rating should my baterries have for economical use.I dont want to drive it fast only for fishing
Thanx a loy

1. Oscar Post author

We wouldn’t know until you have the motor tested in the water with propeller on. I have no previous experience with RC boats.

3. Jim D.

Hey Oscar!
Great info for us rookies! Thanks for that!
I definitely understand more having read a couple of these posts from you!
A friend and I started with some Aeris Shadows (To get a Cheap feel for flying) and are currently building our own using:
A Realacc Phoenix frame
Racerstar 2205 (2300kv-friend, 2600kv-myself) motors
Dal Cyclones t5045 props
30a v2 x4 ESC’s
Evo F3 FC
Plus a few other bits
We’re planning on running Runcam Owls, probably 2plus’..
My/Our question is, what size would you recommend for us? We’re considering 2200mah 65c’s for the obvious advantage of MORE POWER!! but we understand our drones may not be beefy enough..
Thanks again!
Jim D

1. Oscar Post author

I think 1300mah – 1600mah is the best size for your quad. 2200 is way too heavy you will lose a lot of agility over that :)

4. Wasantha Weerawarna

Hi Oscar,

Very nice article. Could you clarify bit more of whatvyou said to choose the correct battery for me pls.

Hexacopter with DJI Naza M V2.

Motors – 4114 400kv 4-8s motors (max current draw is 25.6A) Max Thrust is 2980g
ESC: hobbywing 40A 6s Opto. This is only recommendation I found that is compatible with Naza M V2.
I have a Multistar 5200mAH 10C battery.

And with the given calculations, is not good enough? If not what would be the best battery in terms of discharge rate?

I prefer to buy another of the above battery and add more flight time if I can use it. Can you pls advice? Since ESC supports only 6s is this possible? I mean coupling the two batteries? Or do you advice me to buy a 6s high capacity battery with higher C rating?

Expect a favourable response.

Cheers

WAS

1. Oscar Post author

according to your information, the max current draw that can happen in your setup is about 150A.
5200mah 10C in theory can only supply 52A max continuously, or 104A at burst (burst C rating is usually double of the continuous rating, but double check and confirm with your battery)
So it’s not quite enough IMO, I would probably get something higher than 20C, that should give you 100A+ current and 200A at burst, given you might use 100% throttle during flight, and it doesn’t happen longer than 10 seconds.

5. James V

Hi Oscar,

It’d be helpful to know exactly how much power a cell would lose under a certain load.
Is it possible to calculate the voltage drop or internal resistance of a cell from the C rating and capacity?

Thanks.

6. Ashvini Kumar Sharma

Hello Oscar , I am using A2212/13T motor which have a max current rating is 13A, I am building a quadcopter , I bought 30 A ESC and 3600mAh 25C lipo battery ? Is this a good choice because my quad is not lifting up one motor runs faster than the other three, please help me

1. Echo246

Hi,
Try calibrating your ESCs if you are using an analogue protocol (i.e oneshot 125 or multishot)

7. Aliff Nuriman

Hi Oscar,I need help.Im about to choose LiPo battery,i calculated my maximum current draw on 100% is 58A.If i choose LiPo that is calculated (4A*15C)=60A.Is that okay if choose that?

1. Oscar Post author

you are using 4000mah 15C battery? if so the calculation looks okay, but be careful of weight.

8. ponnex

I have DYS 1306 3100KV motor in which its draws around 8A to 10A based on specification. It’s safe for me to assume that my set up will draw max of 40A only(10A per motor x 4)? And I can make it to 45C LiPo giving an extra window? As well as I can assume that having a 65C LiPo will be the same with 45C since I wont be drawing close up to 65C?

This question relates to LiPo weight and total efficiency.

1. Oscar Post author

it depends on the props, if you are using the same props in the data sheet then yes you can assume the max current draw is 40A. Having higher C rating battery doesn’t hurt.

9. jordan

hi
I have just purchased a quadcopter and the battery is 3.7v 600mah however is does not tell me the c rating. I have just got 4 new batteries, they are all 3.7 600mah but have 25c on them. Now they do not last as long as the original battery so does this mean that the original battery has a higher c rating?

1. Oscar Post author

could be, when max continuous discharge current is below your usage, the voltage will drop more dramatically, and thus giving you shorter flight time.

So then what’s the difference between a 3000 mAh 20C battery and a 2000 mAh 30C battery? Both would have a max current draw of 60 A.

Hi, Oscar!
It’s my first time to build my homemade boat running with:
HobbyKing 60A ESC
Brushless 3100KV Motor, Max Amps: 56/38A
11.1 V 5200 mAh 10C

after 5min of my first test, the battery has gone Overheating.
what is the best battery to using for my boat?
what about if I connect tow batteries in parallel?

regards,

1. Oscar Post author

I think you are getting too close or even over the max current output on the battery.
To increase that, you can either up your total capacity or battery C rating.
So yes you can try putting another pack in parallel that way can up your total capacity.
or get some higher C rating battery (given it’s same capacity or higher capacity)

12. imran

Hi Oscar

My name is imran

It s my first time to build my zmr250 quad
Dys 1806 2300kv
Afro 12 a ESC
Naze 32
Marek pdb

But i don’t know which battery and how much c count to buy

13. Mehul Mahajan

Hi Oscar,
We have ordered a dys 3S 25C 2200 mah battery for our quadcopter but we dont know how much will be the flight time. can u please tell me the flight time of this battery. If u know any other battery which we can use plz tell me???

14. DoFPV

currently wait for shipment arf all rcx frame h250, rcx motor (not yet know the spec), esc blheli 20A

currently awaiting shipment my arf quad race arf rcx h250, rcx motor (not yet know the spec), esc blheli 20A, a friend offered me Dinogy 4S battery 14.8V 2250mAh 65C. is it proper ?

1. Oscar Post author

it should fly, but I think it’s a bit on the heavy side… i would prefer 1300mah to 1800mah..

15. collin

Hi Oscar
I’m not sure exactly how this correlates to my motors/escs. If I have six 20 amp escs at 11.1V what C rating do I need?

1. Oscar Post author

Hi Collin
You can work out the max current draw of your motor and propeller combination. Let’s say your motor/prop combo draws 17A current at 100% throttle for example, then your quadcopter can draw 17*4=68A max.
in that case, battery C rating = Max current / Battery capacity.

of course this is only theory, you can use lower C rating batteries within reasonable range.

16. Andrejs

Hi, Oscar!
I will have two 250quads with 1) Sunnysky X2207S KV2100 and 2) Sunnysky X2204 2300KV.
What battery I need to buy for both?

1. Andrejs

Yes, I want to buy 4S battery. But if I will by 2200mah? How much C i will need? 45-90C will be fine? Or 65-130C will be better?

2. Andrejs

17. Cogur

Hi Oscar,

First of all thanks for the work you done to make the RC community easier.

zmr250 carbonglass and DYS be1806 motors.
the max amp of the motors are 31a

I’m about to select the perfect battery for this build. I’m realy a beginer in the RC world and i would like to select a battery with which I can have long fly time. For now the agility is not that important.

Based on your articles I would need a battery with 35+ C rating to be able to handle additional stuffs with it later. and based on others comment Its recommended to use a 3s battery and It’s not recommended to use batterys largen than 2000Mah for a 250 sized quadcopter.

So I decided to by something like this:
hobbyking.com/hobbyking/store/__9937__ZIPPY_Flightmax_1800mAh_3S1P_40C.html
or that:
hobbyking.com/hobbyking/store/__11908__Turnigy_nano_tech_1800mah_3S_25_50C_Lipo_Pack.html

But I’m not sure what is the 20-50C rating means? It can discharge with 20 to save the battry life and with 50 if it’s necesarry?

Are those two batteries good choices for my purpose?

Thanks for the response.

1. Oscar Post author

HI Cogur,
that’s right, you don’t get much benefit from heavy battery. 1300mah to 1800mah is a good range for mini quad.
20-50C basically means 20C contant, 50C burst (max).
Both of them should be fine for your setup :)

For prompt technical support, please use our forum IntoFPV.com. I check blog comments weekly.