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[cos918]

Hi all
I put my model of Finnjet on the water a few days a go and she was to heavy,she need's to lose weight.
2 areas I have found were big weight savings can be made are motors and battery.

On the battery front. I was going to use a 4.8V NI-MH pack this is to heavy. I have look in to LIPO battery's and they are so much lighter. I have seen a 3.7v 1000mah that weighs only 37 g. Will a battery of 3.7 volts power a receiver as it is 1.1v less than the normal 4.8v pack?

I am thinking of using the Action ESC that plug in to the reciver and get there power from the reiver.

will this new set up work.

John

 

[FullLeatherJacket]

I am thinking of using the Action ESC that plug in to the receiver and get their power from the receiver.

John
Tell me which ESC and what type of motor and I'll check it on 3.7v when I get back to "the factory". BTW you can get a 4 cell NiMH AAA pack which only weighs 52g, and you won't need a special charger for it.
FLJ

[wombat]

I would be cautious about using 3.7V to power the reciever for a couple of reasons

1/. If you have a 2.4GHz reciever then it will probably be OK on 3.7V (internally the Rx runs at 3.3V typically) but it could be vulnerable to any shifts in voltage caused by battery voltage variations or noise on the system. If you are running on 40MHz it is more likely that the reciever will be desiggned for 4.8V operation and may suffer from reduced range and vulnerability to interference.

2/. The reciever is used to power the servos - these are usually designed to run on 4.8V. Running on a lower voltage could significantly reduce the response time of the servo and reduce its torque - this could affect the control of the boat under load.

If the ESC is one of the P9x series then it will function on 3.8V, however there is a risk that the MOSFETs that provide the motor drive will not be turned on as fully as they would be if the system is running on 4.8V which will mean that they could run hotter than on the higher voltage. This may mean that you need to provide more heatsinking or water cooling to control the temperature.

If you really cannot support a 4.8V reciever battery pack on the system, then I suggest using a BEC (e.g. ACTion P19) from the main battery.


Wom

[cos918]

Hi Dave
I was Intending of using X2 P68A ESC and X1 P82 mixer.

 That AAA 800mah pack at 51g  I had seen . It is only an extra 14g so It could be an option.
The big problem I am having is weight. When i tried her she sat to low. the motors and battery pack came in at 181g. there was still radio to add to this.
I have some other motors that weigh 18g each your esc\mixer weigh 13g each or 7g out of the case rx is about the same. so new motors + electronics= 88g+ battery51g =131g .I will do some trials.
One question is ok with your electronics to run them out of the case and stuck down on servo tape as this will give me an extra 18g to play with.

John  

[cos918]

Hi Wom
thanks for that. I am going to use 2.4ghz
The reason I was thinking of lipo was for weight saving and from what I can see they come in 3.7v 7.4v 11.1v etc not sure were a P19 would go on the circuit


John