Tx voltage value unstable

[Jiihoo]

I have 7 channel Cockpit 2.4 Ghz (older generation from 2014) where the transmitter battery voltage value does not stay stable; it varies suddenly from for instance 8.18 V to 7.93 volts and then jumps back to 8.10V within seconds. Battery is brand new (original 6/2100 mAh MPX NiMh battery) . It did the same with old battery. This feature has come to my radio lately so it has not been always like that.

Is this a typical for older Cockpit radios ?

I suspect that there is something wrong with the circuit which measures the voltage of the radio.

In practice it is a problem when battery is low and it is difficult to know if it is really empty if voltage display varies between 7.3 V -7.1V and low battery alarm is at 7.1V.

Regards/Grusse,
Jussi

[aeroparts]

Hi, my does the same thing. One time it even went down to start warning but then the warning disappeared and the voltage went back to the normal unstable measuring.

[Jiihoo]

Ok, this can mean that the component measuring voltage is not always stable in these radio models.

MPX guys: what are your comments to this?

Jussi

[AndreasJ]

Dear Sir, a difference of about 0,2V is normal. It is because the M-Link system is sending in intervalls.... So the voltage breaks in a little when the transmitter is sending information.

Best regards

[Jiihoo]

Hi Andreas,

Ok, thanks for your answer.
But do you know why this same does not happen in Royal SX which I also have. There the voltage is always stable and goes down linear when voltage drops.

Regards,
Jussi

[AndreasJ]

If you are using the royal,
the voltage will also drop about some 100mV...
Maybe it is a little bit better, but the behavior also depends on the internal resistant of the used batteries.
So if you are using batteries with "eneloop" technologie, like the multiplex 156051 battery pack, it could be a little bit more....

[Jiihoo]

Yes, I am using 156051 in both radios.
It is also so that in Royal the voltage is shown with one decimal if I remember right, so the variation does not show so easily as in Cocpit which has two decimals.

The positive thing is that the battery lasts long in Coxkpit and Royal (>10 h).

ps It is great that MPX people are following this forum also during weekends and give their comments to the questions fast. I think this has a big impact why many use MPX products in general.

Jussi