Choosing between 20C and 25C

[KingKow]

Hi,
I am relatively new to this electric scene and I am still trying to decide on my purchase for my extra batteries.

1.Should I get those with 20C or 25C if the price is about the same?
2.Since the battery is rated 25C continuous, does that mean that it will run out of energy faster than the 20C even if I am just hovering around?
3.Some of the batteries are rated with a higher burst C but others don't. Does that mean that if it does not specify a max burst C rating it will only run at the constant C?

Thanks for the input


:confused:

[Lastinch1]

Here's what I know ( which ain't much )
A higher C rated battery will be a little heavier then a lower C rated one
The C rating is the discharge rate the battery can handle ( a 20c 2000mah can discharge if needed @ 40,000 mah or 40 amps)
BURST is the MAX rating the battery can handle for a very short time ( a 20c 2000mah with a burst discharge rate of 25c would put out a burst 50,000 mah or 50 amps.

A 20C and a 25C rated battery will discharge at the same speed under the same load as long as the load doesn't exceed 20C
For longer run times you would choose a higher MAH rating
such as going from a 1500mah to 2000mah
However ther is a trade off, larger mah batteries weigh more and may decrease your flight time because of the increased weight.
For example
a 15C 1850mah 140 gram battery may give longer flight times than 25C 2000mah 205 gram battery
You'll need to figure out how much weight your Heli can carry and still fly efficiently.
motor and gear ratio will play a big part in your decision.
~ 10 motor turns : 1 Head rotor turns
A high gear 10:1 ratio will spin head faster and create more lift but will discharge a battery faster
A low gear 12:1 ratio will spin head slower and create less lift but with more torque and battery will last longer. Try to keep the load on the motor as low as possible to increase flight times ( things to try are smaller blades, smaller lighter batteries, use the lightest electronics, upgrade parts to carbon fibre, diferrent pinions)


Hope this helps
other opinions welcome

[TheBum]

I heard that higher C ratings will provide more consistent voltage and the batteries will run a bit cooler, but I don't have any evidence to back that up.

[Mercuriell]

Maximum C is how much current the pack can realistically deliver - continuous and in bursts. You will notice the difference if flying the heli at the limits of it's performance - if you don't you won't notice the difference. There shouldn't be any appreciable difference in duration for packs of the same capacity. It's to do with the formulation of the lipo and its internal resistance.

Sooo - if two C rating packs are nearly the same price, or you have to have best possible performance, go for the higher C although there is a lot of hype around C rating and some brands deliver more of what they promise than others