Different battery size

[extreme_stu2@yahoo.com]

Would a 2200 mah battery change the CG in a plane that much?I am referring to one that suggests a 1300mah battery?I'm referring to a 1200mm,48 in span plane.

[fhhuber]

Depends on the airplane...

The Parkzone Radian simply does not have the space to shove a bigger battery rearward and thus the appx 70% extra battery weight would significantly shift CG forward.
You can't cut the foam out to make it work without weakening the fuselage excessively.

The Dynam P-51 which calls for a 2200 mah 3S can easily carry a 3300 mah 4S with minor foam cutting and put the CG exactly where it needs to be for best performance.

[xviper]

It also depends on the battery. Different brands, models and series of batteries of the same mah can weigh vastly different. A Turnigy "blue", high C, "heavy duty" battery can weight a lot more than a low C Turnigy battery. I've stuffed 1800mah, 3s bats into my Radian, while some of my buddies use 2200mah. I've also got a load of GPS, Return Home and stabilizer equipment in my Radian. I need to attach coins to the tail to make it fly right.

[doctormike]

I use an 1800 mah in my Radian in low wind for better thermaling. In higher wind, I use an 2200 mah with high c rating for better penetration. Doc

[Aerodale]

If the battery location is centered on the CG than going to a heavier battery will not change the CG.

[xviper]

If the battery location is centered on the CG than going to a heavier battery will not change the CG.

I'm not sure if the stock battery is centered on the CG but no matter, it's "bottomed out". The stock 1300mah battery goes down the hole as far as it will go for the proper balance. All other batteries (1800 or 2200) still goes as far down as possible but a significant amount of the battery sticks forward of where the stock battery begins. Whether or not the stock battery is centered, a bigger, longer battery can't be centered. It has no place to go.

[KitBuilder]

Your battery is no where near the CG. It's in the nose area to assist with balance.
You can remove some foam if your comfortable doing that but you don't want to thin things out to much.

[xviper]

My #6 post was referring to the Radian, in case we're getting confused here. The first poster did not say what kind of plane he's talking about, but it's not a Radian at 1200mm wingspan. Funny that he's not come back to continue the discussion. In the Radian, the battery is not located at it's CG. However, in a plane that the battery was located exactly at the CG, then going to a bigger battery would not change anything except the wing loading. That said, the further away from the CG, any change in weight of the battery will alter the balance of the plane more. If the battery position can't be shifted to maintain the same balance, then weight will have to be added and in this case of going to a heavier battery, the weight will need to go in or at the tail.