Turnigy 9x transmitter li-ion battery conversion

[JohnS]

Hello,
I love the battery mod and the expertise in this thread,
Could someone please explain why the 9x and others are designed to waste 12v down to the operating voltage of 5v/6v?
John

[BillGriffiths100]

Because the original transmitters used 35MHz ,72MHz (or whatever your local VHF frequency used to be) in the transmitting part of the transmitter, or module used these higher voltages.
The original 9x hardware was designed to take these VHF modules along with all the other Tx's that used VHF.
The modern 2.4GHz modules run from lower voltages and have therefore had incorporated in them voltage regulators which do indeed waste power, but make them compatible with the older Tx hardware.
The spektrum transmitters run from 4 dry or rechargeable cells but these were designed from the outset to use the lower voltages.
Undoubtedly new transmitters will change to use the lower supply voltage from the outset as the spektrums did.

[JohnS]

Thanks Bill,
Makes sense.

[borderlord]

Hi guys, need some help

Got a Turnigy 9x, saved from the reverse battery syndrome.
Just got the LiFe cells in to convert and they don't fit.
Ordered a pair from DealExtreme, as recommended by Bruce. These ordered 16th August and still waiting.
Meanwhile, got another pair from another source.
These are UltraFire 3000Ma, as offered as an alternative in Bruce's article.
Just tried them in the battery compartment at an angle, as suggested, and there is no way the cover will go on.
Not sure if I will ever receive the original order for the 2400's but research on the internet suggests that 18650 is a standard case size, so I would not expect the other type to be any smaller.
Any ideas?
Still like the idea of reducing the battery voltage to the minimum required, gives the electronics an easier time, so, if I can't get these to fit, thinking of a 6 cell pack of NiMh. What value resistor would I need if I went this way?
Would 5 cells work instead?

Thanks

Borderlord

[BillGriffiths100]

Yes five cells will work fine, I used five cells for several years in both my 9x's

[borderlord]

Hi Bill, thanks for that.
Would you know what value resistor I would need to fool the low battery alarm?
Cheers
Jeff

[BillGriffiths100]

Hi Jeff,
Probably better for the board not to do the resistor change, only as much work to re-flash with ER9x and less fiddly, since you can set the alarm voltage in the software.
Have a look at this how to video from Mr BMSWEB it's not too difficult and will solve a lot of problems and give you a much better radio.
http://www.youtube.com/watch?v=eXwVpabmICw
Lots more information here and on links from here:
http://code.google.com/p/er9x/
Regarding the resistor:
If you e-mail Bruce personally he might work out a resistor value for you.
Without pulling one of my TX's apart I can't tell you offhand.
Best wishes,
Bill

[borderlord]

Hi Bill

Thanks for your help on this one.
Thinking towards the 5 cell pack, since you have used them successfully.
These are nominal 1.2v per cell, or 6v fully charged.
As I understand it, the voltage regulators are 5v, so even with a fully charged pack, that's only 1v headroom.
I must be missing something since you use them. Could you enlighten me?
If you use a non standard battery pack, does the screen still show the actual battery voltage? In other words, does the resistor mod only fool the low voltage alarm?
Sorry for all the questions, as you can tell I'm no electronics guru.

Cheers

Jeff

[BillGriffiths100]

A fully charged cell gives 1.34 and for most of the discharge time above 1.25 giving more than 6.25 volts
So I set the low batt alarm at 6.4 volts but recharged when about 6.4 and never had a problem.
But I am using frsky tx modules with switched mode regulators that don't consume the current and have a much lower dropout voltage than the standard turnigy module
So I won't advocate it for everybody therefore I advise you to use six cells if you do the resistor change which will usually give you from 8.4 ish to 6.6 where they should definitely be recharged!
Regarding the voltage display I think the resistor change affects the displayed voltage that comes from an analogue to digital conversion off the power supply as there seem to have been some problems with it see this thread:
viewtopic.php?f=44&t=298&hilit=resistor+change#p2512
The resistor change was to fool the voltage detection circuit and therefore the voltage display also.
However probably the best solution is this that I currently use:
http://www.hobbyking.com/hobbyking/stor ... pack_.html
The pack operates at the same voltages as the nimh packs, but you will need a charger specifically for these type of cells like this one, set to LiFe charge.
http://www.hobbyking.com/hobbyking/stor ... ories.html
Some people advocate a higher capacity pack as below but mine lasts for at least a month.
http://www.hobbyking.com/hobbyking/stor ... ouse_.html

[borderlord]

Hi guys

Decision made, I'm going with a 6 cell NiMh pack (thanks Bill)
Couple of thoughts.
First, I think the value for the resistor mod (8.2K) should be ok for this as well. If not, any ideas?
Possibly one for Bruce if he happens to be lurking.
Second, I can make up my own soldered packs, so going with these
http://www.overlander.co.uk/batteries-c ... -cell.html
Looked on e-bay, and I found these
http://www.ebay.co.uk/itm/230897695578? ... 1497.l2649
These are sold as LiPo balance leads, but if you push the locking tab with a pin, you can slide the connector out and replace in the correct position to suit the Turnigy power connector.
A tip I picked up on another forum is to surround the plug with a piece of heatshrink. This means when you pull the plug out you are not pulling the wires and straining the connectors.
This especially with the 9x, where you can't easily reach the plug.

I actually heatshrink the whole plug, then cut the extra back with a sharp knife.
Doing this with all my LiPo's now, seems a good idea.
Finally, a puzzle (and the answer)
Would like to use the existing charge plug on the transmitter. Separated both halves to look at the resistor mod, while I was there, checked the polarity of the socket (centre pin positive, in case you were wondering)
Plugged it into my charger. and got voltage from charger plug to transmitter plug to diode to other end of diode, all the same.
However, no current flowing, ooh err!
Noticed that the other end of the diode did not go to the positive on the battery socket, as you would expect, but to the multi-plug that connects the two halves together. Odd that.
Anyway, upshot is connected both halves back again, and I have current flow, woo hoo.
So, if you are checking yours, you need both halves plugged together to get current flow.
This may help someone else

Cheers

Jeff