What the Heck is C-Rating? Why it matters for AEG.
Short Answer - It's all about the Amps, not about the C-Rating
Using a battery’s C rating alone to determine if it can work for your gun is not enough as it’s only half the equation. The other half is how many mAh the battery has. These two together (mAh and C rating) determine how many Amps the battery can push. Because Titans carry about twice the mAh of the average AEG LiPo and have about half the C rating, they can push on average the same Amps, and still offer 2x the capacity, so you get 2x the shots with the same power.
A 1300mAh 20C LiPo can push 26 amps and has 1300mAh
A 2600mAh 10C Titan can push 26 amps and has 2600mAh (2x as much!)
**FULL NERD WARNING**
What is C rating?
- C rating measures how fast a battery can discharge its energy.
- The higher the C rating - the faster the power can leave the battery to turn motors, power a light bulb, etc.
- Some electronics can use batteries with lower C ratings (most flashlights, radios, etc.) while others need high C rating batteries (electric vehicles, drones, etc.).
- A very low C rating battery (like a standard Alkaline AA) is like a bottle of syrup. The bottle might be full (like a fully charged battery), but it can’t empty very quickly because the syrup is so thick. This is okay for an alarm clock that will empty the battery over many months, but not okay for starting a car. A very high C rating battery is like a bottle of water with no lid, you can tip it over and empty the whole bottle (like a fully charged battery) in a few seconds. This allows high power electric motors to turn quickly.
What does the C rating number actually mean?
- The C rating number is the number of times the battery can discharge in one hour without overheating or damaging the battery.
- For example, a battery with 1C can discharge it's entire capacity in 1 hour, while;
- 6C battery can in 10 minutes (60min / 6C = 10min)
- 20C battery can in 5 minutes (60min / 20C = 5min)
- 60C battery can in 1 minute (60min / 60C = 1min)
What is Constant? What is Burst?
- Every battery has two C ratings, Constant and Burst.
- Constant is how fast it can discharge at a constant rate until it's empty. Examples of a constant discharge are flashlights, remote control airplanes or drones, etc. Things that use their batteries for for minutes or hours straight without stopping.
- Burst measures how much power the battery can give for a few seconds and still keep it’s voltage up. Examples are AEG, an RC airplane during take off, starting a car or truck, etc.
Which C Rating matters to AEG's?
The Burst C Rating of a battery is more important to AEG's than it’s Constant C Rating. This is because most AEG's are only used for a few seconds or less at a time, not for a constant 10 minutes for example.
How do AEG's use batteries?
- There are two stages of battery drain for an AEG, the initial inrush and the constant draw.
- The initial inrush lasts for just hundreths of a second and is the power needed to start the motor turning. Smaller AEG's need about 30 Amps while larger ones can need over 100 Amps. As this lasts for such a short time, this stage has very little effect on a battery’s charge.
- After the motor starts turning, the constant draw is the power needed to keep the motor turning, and lasts much longer and is a better measurement of how much power it will need.
How does a battery get it's C Rating?
- Unfortunately there is no standard for defining C rating. Because of this, many manufactures often overstate their battery’s C Rating.
- In principle, Burst C is the Amp rate the battery can discharge and still keep its voltage above it’s minimum (typically 3.0v for LiPo’s, 2.5v for Lithium Ion)
- Constant C is the Amp rate that the battery can discharge until it’s empty without overheating at the end (Titan uses 140F / 60C as it’s max temperature. Lithium Ion cells don't get dangerous until much higher).
C Rating Math
- You can use the capacity of the battery (like 1500mAh) and the C rating of the battery (like 10C) to calculate how many amps it can constantly discharge until it's empty.
- A 1500mAh battery is actually a 1.5Ah battery (mAh means milliamp hours, or 1 thousandths of an Amp hour). If you take 1.5Ah and multiply it by it's C rating (in this case 10C) you get 15A, or 15 amps. So this battery can discharge 15A for 6 minutes until it's totally empty without overheating.
- Other examples are:
- 1500mAh 10C = 15A for 6 min (1.5Ah * 10C = 15A) then (60min / 10C = 6min)
- 800mAh 5C = 4A for 12 min (0.8Ah * 5C = 4A) then (60min / 5C = 12min)
- 2600mAh 3C = 8A for 20 min (2.6Ah * 3C = 8A) then (60min / 3C = 20min)
- One interesting result from this: two batteries that have different capacities (mAh) and different C Ratings can actually have the same discharge capability. For example:
- 2000mAh 5C = 15A (2.0Ah * 5C = 10A)
- 1000mAh 10C = 4A (1.0Ah * 10C = 10A)
- However, they won’t last the same amount of time!
- 2000mAh 5C = 12min (60min / 5C = 12min)
- 1000mAh 10C = 6min (60min / 10C = 6min)