700 Battery C rating for Trex 700E Pro DFC Combo

[Erfan]

Hi guys

Looking at buying the Trex 700E Pro DFC Super Combo.
It comes with the "Castle EDGE HV 120 Brushless ESC" and "800MX Brushless Motor(520KV), 5100w).

I have read some threads here by Tony and watched his videos about choosing the right battery for a specific ESC and motor.
I think I understood what he tried to explain, but I'm not sure

So my question is what kind of C rating do I need with the above combination? I will not fly 3D anytime soon, perhaps couple of loops and inverted fly...

The heli needs 2 x 6s 4500-5200mAh, I was thinking of getting 5000mAh and it should be enough with 30C, no?

5000 x 30 = 15000 / 1000 = 150Amps (Both ESC and motor needs less).
even
4500 x 30 = 13500 / 1000 ) = 135Amps should work as well?

Have I understood this correctly or do I need more C?
I can for just a few dollars more get a 45C so perhaps that's even better?

 

[Slobberdog]

With these bigger helis your probably better getting the larger C rating,

just a word on your workings, they look right but your never gonna be flying using 30c for the duration that's gonna be small peaks not constant.....

 

[Erfan]

Ok, so 45C is the way to go?
Will I need more anytime soon, considering that I don't think there will be any 3D anytime soon (just been flying for around 8 months).

 

[Lee]

30C would be fine. The 45C will just not have to work as hard, which would extend its life. So if price is no issue get the 45C, but don't stress if 30C is what you can get.

 

[pvolcko]

Yeah, 30-45C will do it. I've got turnigy 25C packs I think to and they fly it fine even through some mild 3D. A 30C pack will usually have a peak discharge C rating of around double that, and the 120A draw on a stock TRex 700 is going to be peak. Normally you're going to be 30-60A draw, so 30C is great for what you'll be throwing at it.

 

[RandyDSok]

Just to be clear about it... this isn't about the C rating per se. It is about how many amps your setup needs and you use a battery packs C rating to help determine how many amps that pack can provide based on the capacity of the pack as the math shown indicates. Let me explain using two battery sizes but with different C ratings to help explain.

A 5000mah battery with a 30C rating can provide up to 150A of current at peak. Yet a 6000mah battery with a 25C rating can also provide that same 150A of power even though the C rating is lower. So it isn't the C rating itself... but the resulting current ( amperage )

I do like to use slightly more of a battery that can provide more current than I usually need so I'm not working the batteries as hard but you still need to be conservative because that also comes at a price of being a heavier load that the aircraft must carry which can limit the aircraft's performance and flight characteristics.

 

[Erfan]

Thx for all the answers guys, it made things clearer! One step closer to buying my first 700 size heli

 

[Graham Lawrie]

Looking forward to the build Batteries are much of a muchness. £$ being the deciding factor with most of us There are a lot of batteries on the market, a lot of the cheaper ones get bad press, but I have not found a bad one yet

 

[Erfan]

Me too!
Hopefully I will have it in couple of weeks and a maiden in Maj.

I agree concerning cheap batteries, at least for my type of flying I have not noticed any difference, perhaps they wont have as many charge cycles as more expensive? I don't know and for now it does not matter much...

 

[Graham Lawrie]

I have a cheap 3s that is out performing the dearer ones