425 and 5s battery

[Gasser Steve]

Can i use a 5s battery in the Gaui 425.
I recently traded some stuff to my friend for a 425.
I am not into electrics that much, i fly mostly gassers. But, electrics are convenient if i want to run over to the park for a couple of flights.
This 425 has the battery tray mod, so it can take a single pack. I have a few 5s batteries, and if i can use them it would save me the expense of buying the 6 cells. I am also a sport flyer. No 3D
The heli. is stock
50t Front Main
19t One Way
61t Rear Main
15t pinion
The motor is a Typhoon 500. Not sure about KV maybe 1800
So, if i can use 5s batteries, what would i need to change. Thanks

[SQRT(-2)]

The voltage would be lower so the head speed would be lower. About 85% of the head speed with 6 cells I would think. It will probably fly it would just be more docile. You may be able to adjust the gearing to compensate, that is beyond me though. Also the throttle curve could be adjusted to bump the head speed up a bit. Both these would cost you some flight time though.

I would try it with the 5 cell, make the flight short and easy and see what happens.

[Jerrymac]

It would likely fly fine, just a little under powered. Probably bog the motor without a light touch on the collective. If the motor you have is actually a 1800kv motor you won't really need to change anything as that gearing would give you a head speed of around 2800 to 3000 on 5s batteries. If the motor is a lesser kv then you may need to change the gearing to get the desired head speed. A head speed of 2600 is the recommended minimum.

What size 5s batteries are you planning on running? For 6s I use 2650mah 30c at the least. For 5s you might need something a little bigger, maybe 3000mah or more.