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Old Sep 24, 2012, 02:37 PM
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jsf135pal1's Avatar
United States, CT, Plainville
Joined Aug 2012
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Help!
Mini Super cub battery upgrade questions

I just bought a 7.4v 950Mah 25c 2s Lipo for this plane and the LHS said it would be safe to use for the stock motor it came with.
However, this battery is a tad longer than the stock battery by about 3/4". My questions are:
1. Willl this in fact be safe to use and will it burn out the motor?
2. I would need to cut the foam in the battery compartment, which looks like only one way, and that's towards the tail. I presume I would use an exacto knife.
3. What will this due to the CG? What is the CG for this plane? I hear 2 3/8" from leading edge.

Any help would be much appreciated.
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Old Sep 24, 2012, 03:10 PM
RvE
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Canada, ON, Toronto
Joined May 2012
134 Posts
The larger battery will not hurt the motor since it is the same voltage (7.4v) as the stock battery. The only change is the battery capacity and that just increases the run time.

I run my MSC with Rhino 460 mAHr packs for around 10 minutes and the motor is not even warm. I guess with 950 mAHr you can run for nearly 20 minutes, but that is a long, long time to run the plane (you might be bored by then). So I would recommend trying say 10 minutes and see how the motor and battery feels (likely stone cold) and then increase run time in increments of 2 minutes and check battery consumption and motor temp after each flight. Keep increasing until you are bored or the motor is warm or the packs are 80% discharged (eg you put 750-800 mAHr back into them). This assumes you have a charger that displays the battery capacity (not the stock charger).


The CofG is a more important issue (I cant recall the correct dimension but I am pretty sure it is stated in the manual). I would not move the battery to the back, as it might make the plane tail heavy (these are such light planes). It might be prudent to try to centre the battery in its current location. I know there is some room to slide the battery forward in the existing compartment. Not sure how thick the 950 mAHr is. If it is much thicker than stock , you may need to dig out some foam from the battery box.

By the way, the 460 mAHr Rhino (from Hobby King) is an exact fit into the existing stock battery box and flies identical to the stock battery.

I am a 4 Ch beginner, but I still enjoy flying this 3 ch plane at the smaller fields.

RvE
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Old Sep 24, 2012, 06:45 PM
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United States, CT, Plainville
Joined Aug 2012
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Quote:
Originally Posted by RvE View Post
The larger battery will not hurt the motor since it is the same voltage (7.4v) as the stock battery. The only change is the battery capacity and that just increases the run time.

I run my MSC with Rhino 460 mAHr packs for around 10 minutes and the motor is not even warm. I guess with 950 mAHr you can run for nearly 20 minutes, but that is a long, long time to run the plane (you might be bored by then). So I would recommend trying say 10 minutes and see how the motor and battery feels (likely stone cold) and then increase run time in increments of 2 minutes and check battery consumption and motor temp after each flight. Keep increasing until you are bored or the motor is warm or the packs are 80% discharged (eg you put 750-800 mAHr back into them). This assumes you have a charger that displays the battery capacity (not the stock charger).


The CofG is a more important issue (I cant recall the correct dimension but I am pretty sure it is stated in the manual). I would not move the battery to the back, as it might make the plane tail heavy (these are such light planes). It might be prudent to try to centre the battery in its current location. I know there is some room to slide the battery forward in the existing compartment. Not sure how thick the 950 mAHr is. If it is much thicker than stock , you may need to dig out some foam from the battery box.

By the way, the 460 mAHr Rhino (from Hobby King) is an exact fit into the existing stock battery box and flies identical to the stock battery.

I am a 4 Ch beginner, but I still enjoy flying this 3 ch plane at the smaller fields.

RvE
Thanks RvE. I was actually planning on using the existing battery compartment but cutting it longer towards the back. As far as thickness goes, the new battery is thicker but the compartment is plenty deep enough.
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Old Sep 24, 2012, 08:21 PM
RvE
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Canada, ON, Toronto
Joined May 2012
134 Posts
I was trying to suggest NOT cutting the back of the compartment. The plane tends to drift upwards on throttle, and that may be exaggerated if the battery weight is at the back and that might make the plane tail heavy. Perhap you can slide the battery partially foraward under the front battery box edge, and only cut a small portion of the back of the compartment, thereby "centering" the new battery within the battery box.

Good luck with it, RvE
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