Which Lipo?

[Bigmax]

I've been looking at lipo batteries and not sure what to do...

I'm going to be converting to a brushless / lipo setup... currently looking at the Ammo 28-35-3900 motor and I've got a 40A esc I'm going to try. What kind of currents am I likely to see with this motor? It seems like in order to get a high enough mah/C rating to give me ~30-40 amps that the packs are too big (3.75 - 4+ inches long) to fit in the hull. I'm planning on sticking with the stock prop to keep things simple (and cheap) so what kind of current is realistic and what mah & C rating can I get away with?

Also, any reason not to use a Feigao HXT motor (other than it's a 28.2mm instead of 28mm)? http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4200

Thanks,

Chad

[mtgoat]

The specs for the ammo motor you mention can be found here (http://www.electrifly.com/powersystem/motors/motors-ammo-28-35.html). A 40 amp ESC might not be enough as the manufacturer recommends a 45 amp ESC.

Maybe you could try the 28-35-2700 and go with the 3s lipo (part number GPMP0709 from the same manufacturer). It would fit exactly in the stock battery location and probably weigh half as much. It's only 910mAh 15-20C, but it would be better than the stock battery.

[Bigmax]

Thanks for the reply mtgoat.

I'm still a little confused though... Here's the specs on 3 of the Ammo motors:

28-35-2700 constant: 15A Max: 30A
28-35-3900 constant: 22A Max: 45A
28-35-5100 constant: 30A Max: 50A

Do I need to be overly concerned with the Max Amps or just go by the constant current? What makes be wonder is when I see someone like Wingnut running a 28-35-5100 with a 25A ESC. I realize that the prop selection will dictate a lot of the total current but what's reasonable to expect if it's not over propped (ie. I'm assuming the stock prop would not be over propped)? It just seems like if you go by the name plate values that it's excessive compared to what some people are running.

And on the battery... a 910mAh 20C battery should only be good for 18.2 Amps... if the motor and ESC are rated for sized for say ~30A, wouldn't that be too much for this pack? Not having much real world experience (and not wanting to spend a fortune getting one :) ) is what makes this confusing because it seems like most people aren't just sizing things off of the name plate values which lead me to believe it's more of an art instead of a science.