Overvoltage question

[Mrowka]

As you probably know, the MCPX circuit board will automatically shut off if voltage demands exceed a certain level, usually as a result of hard maneuvering.

If I install a tail motor with a lower KV rating (e.g. a 7mm), will this reduce voltage demands and thus reduce the incidence of shut-down due to overvoltage?

[dgoslee]

I have four MCPX with V1 main board, all with Micro Motor Warehouse CL-0720-14 motors (7mm, 14 KV). Never had a shutdown, ever. And it would be a over current, not a over voltage. Also have a stock MCPX-V1 that I fly with Hyperion high voltage LIPO. Never had an over voltage.
Dan

[JuanRodriguez]

Originally Posted by dgoslee

I have four MCPX Also have a stock MCPX-V1 that I fly with Hyperion high voltage LIPO. Never had an over voltage.
Dan

I thought you said over current, not over voltage ?????

[dgoslee]

Sorry, I shouldn't have mixed apples and oranges.

Too high a KV tail motor will draw extra current, potentially damaging the board, which has not happened to me.

My second point was a totally different case of input voltage. Imagine trying to run a MCPX meant for 1 cell (4.2V peak) on 2 cells (8.4 V peak). It would probably fry the board due to too much voltage, even without the motors even hooked up. My point was a HV lipo (4.35V peak) is fine (this would be over voltage).

I was trying to distinguish between over current and over voltage, but I just confused the issue.

[Smoggie]

Originally Posted by Mrowka

As you probably know, the MCPX circuit board will automatically shut off if voltage demands exceed a certain level, usually as a result of hard maneuvering.

If I install a tail motor with a lower KV rating (e.g. a 7mm), will this reduce voltage demands and thus reduce the incidence of shut-down due to overvoltage?

Do you mean 'under-voltage'

Speed controllers have a shut down facility that kicks in if the LiPo voltage falls too low. This is designed to prevent you from over-discharging and thus damaging the LiPo. As noted above, the only way you could achieve over-voltage is my installing a higher voltage battery (not recommended).

Under voltage may occur for a number of reasons:

1. Battery depleted (flown too long)
2. High current demand causes voltage to 'sag' under load.
3. Old and tired battery cant maintain voltage under load.

Fitting a lower kV tail rotor will reduce current so help with point 2 above, but only very slightly because the tail uses much less current than the main rotor anyway. By using lower kV motor tail RPM drops and tail hold will be worse... So i think it's a very bad idea.

[Mrowka]

Sorry, undervoltage. I have never attempted to use a 2S cell in an MCPX, nor would I do so.

In my experience, a 7mm tail motor (which has a lower KV rating than the stock 6mm) in place of the stock 6mm offers better tail holding.

[Smoggie]

Originally Posted by Mrowka

In my experience, a 7mm tail motor (which has a lower KV rating than the stock 6mm) in place of the stock 6mm offers better tail holding.

Lower RPM on the tail must reduce tail hold, it’s impossible that it would improve it

[Mrowka]

I'm pretty sure that a 7mm tail motor will hold better than a 6mm, simply because the bigger motor has more torque and consequently can change speeds more easily and quickly, even if it will not rev as high.