A quick Lipo question

[Gate88]

As I'm now dabbling in the mysterious world of leccy's I'm looking round for Lipo's (lots of 'em) and I'm a bit confused. I know my TR450 should have an 11.1v battery, it has 3 cells, and I know that the higher the mAh number the longer it'll run the motor, but what does 20c 25c 30c mean? And what do they mean by "Burst"?

[JeromeF]

The numbers you mention with the C at the end relate to the 'Discharge Rate' of the battery.

You will usually find two numbers: The constant and burst. Burst is higher than the constant, and can be withheld for a certain time - some batts say 10secs, some 30secs...

If you would like to work out the figures, use this as an example:

SuperLipo 11.1v 3S1P 2000mAh 25C Constant / 50C Burst

2000/2 x 25 = 50amp
2000/2 x 50 = 100amp

So that given pack with 2000mAh capacity and 25C Constant rate gives 50amps and 100amp max/burst over a short period of time.

Hope this makes sense

[Gate88]

Errrmmm? So for take off's, climb out's etc the higher the C rating the longer I get to crank it up?

[JeromeF]

Errrmmm? So for take off's, climb out's etc the higher the C rating the longer I get to crank it up?

The higher the C rating the more power you will get as such, but the same given time usually with the same capacity on a less discharge pack.

You can notice the difference when using better, higher quality lipos... I remember using old tired 15-20C lipos on my first 450 and then bought a new 25C pack and was amazed at the difference!

[mikeyp]

I saw somewhere explained that the "C" rating is like the size of the tap on the battery, the bigger the "C" rating the more current can flow through at one time to the motor..

For gentle flying you won't feel much difference but as you punch the power the higher "C" battery will deliver the power as you need it..

Mike

[Brian Gifford]

I saw somewhere explained that the "C" rating is like the size of the tap on the battery, the bigger the "C" rating the more current can flow through at one time to the motor..

For gentle flying you won't feel much difference but as you punch the power the higher "C" battery will deliver the power as you need it..

Mike

Good analogy, Mike.

[spunkmyer]

The higher the C rating the more power you will get as such, but the same given time usually with the same capacity on a less discharge pack.

You can notice the difference when using better, higher quality lipos... I remember using old tired 15-20C lipos on my first 450 and then bought a new 25C pack and was amazed at the difference!

Thats make sence to me, thanks for that.

[whirlybird]

Hi Mike

Couple of added thoughts. The 'C' rating of a LiPo is a multiple of the total capacity.
So, an 1800 20c Lipo will have a maximum current output of 36 amps. A 2200 20c liPo will have a maximum current output of 44amps.
If you need more current capacity, might try a bigger battery, rather than a higher C rating.
Also, be aware 'C' ratings are not standard, each manufacturer has their own way of measuring, and some are optimistic.
What is apparent is that using a LiPo at or near its maximum current will shorten it's service life.
What you need to do, is work out the average current your heli is using, and then aim for a battery where this current is, say, 15c for a 20c battery.
Foe example, if your heli takes, on average, 30 amps in flight, you need a battery of
at least 2000Ma 20c.
This will give you a good margin, and should make your LiPo's last longer.
Also check the temperature after a flight.
Your Lipo should be only warm. if it is so hot you cannot comfortably hold your finger on it, sure sign you are working them too hard.
Hope this helps
Jeff