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18650 Batteries in the 9XR Pro

Posted: Sun May 19, 2019 11:08 am
by Rad
Hi guys, I am swaping my LIPO batteries to 18650s, and I wonder if it is possible to fit them in the 9XR Pro.

Would the radio work with just 2? And the most important part, can I just plug them in the radio? And in which pins? I am very afraid of reverse polarity problems.

Re: 18650 Batteries in the 9XR Pro

Posted: Sun May 19, 2019 1:47 pm
by MikeB
The radio should be fine with 2, I've been using 6 NiMh cells OK.
For the wiring, just check the red and black wires of your existing battery. I can't tell specifically as both my 'PROs are pre-production and have non-standard power connectors.

Mike

Re: 18650 Batteries in the 9XR Pro

Posted: Sun May 19, 2019 5:51 pm
by Rad
Ok, thanks!

Re: 18650 Batteries in the 9XR Pro

Posted: Thu Nov 21, 2019 10:24 pm
by rsilk49
What is the operating voltage range for the 9XR Pro?
I am currently using a 3S LiFe battery connected to the radio via the balance port lead.

Re: 18650 Batteries in the 9XR Pro

Posted: Thu Nov 21, 2019 10:39 pm
by jhsa
Not less than 7V if that is what you want to know.. Maximum for the regulator, if the datasheet I am looking at is correct, is 36V

João

Re: 18650 Batteries in the 9XR Pro

Posted: Fri Nov 22, 2019 4:34 pm
by rsilk49
So 7-36v then.
In reality it is best to use any type of 3S battery so that the built-in 3S balance connecter can be used.

Re: 18650 Batteries in the 9XR Pro

Posted: Fri Nov 22, 2019 4:40 pm
by jhsa
I would say so :)

João

Re: 18650 Batteries in the 9XR Pro

Posted: Fri Nov 22, 2019 11:50 pm
by MikeB
The voltage regulation in the 'PRO is in two stages. The first stage, a switching regulator, provides 5V for the audio output, and 5V is also then passed to a linear 3.3V regulator for the processor. There is a schottky diode in series with the battery for reverse polarity protection. This does drop a small voltage 0.2-0.3V.
The 'PRO I use for testing is usually powered from a 6-cell NiMh battery, so 7.2V nominal. If this battery drops low, then the audio may lose volume, but the processor still gets the 3.3V OK.
You also need to check the voltage requirement of any RF module. The module power is also the battery voltage after a (different) schottky diode.

Mike

Re: 18650 Batteries in the 9XR Pro

Posted: Sat Nov 23, 2019 2:23 am
by jhsa
But it seems that under 7V the regulator might not regulate to 5V well anymore. I didn't check the dropout voltage of the 3.3V regulator, but if it is high enough, and if the 5V regulators aren't regulating well, you could also see the 3.3V voltage dropping, I think. Even using 7.2V nominal, better not to let it go under 7V. This is the alarm setting on my PRO. :)

João

Re: 18650 Batteries in the 9XR Pro

Posted: Sun Nov 24, 2019 12:31 am
by MikeB
The 3.3V regulator dropout voltage is 1.3V at 800mA, less for the lower current the Tx uses.
So as long as it gets 4.6V it is fine. I would say that the 5V regulator would therefore be OK at 6.6V input.
Still, using 7V as your alarm would be OK, and the battery is probably fairly used up by then anyway.

Mike

Re: 18650 Batteries in the 9XR Pro

Posted: Sun Nov 24, 2019 3:48 am
by jhsa
Thanks Mike, as I said, I wasn't sure about the 3.3V regulator.. :) Then the limit could very well be the minimum voltage the RF module needs.

João