Adding a Flightpower 3s LiPo to the DX7

[dennis22g]

My logic is make it reverseable if possible. I never like drilling holes if there is another way. Changing to a LIPO on my DX7 was simple. If anyone needs to know how to setup the LiPo battery or install an ON indicator with simple plug-in plug-out modifications I will be happy to put up some pix. But here it is in text form.
A simple description of what I did is: http://www.hobbycity.com/hobbycity/s...idProduct=5280
[Battery comes with an inbuilt CPM (Cell Protection Module) which stops the pack from being over-discharged due to slow residual drain.]
1.Purchase a battery from Hobbycity.
2.Slice off the plug and splice on the plug from your NiMh battery.(heat shirink joints)
3.Include in series a GP diode or 1N4001 will suffice (only needs to carry 100ma)
4.Plug it in to existing socket and pack in some foam to leave in TX, no need to remove for charging. Normal socket will not work because of diode.(no accidents)
5.Connect balance lead to charger.
6.Modify balance lead by connecting main power leads to each side of balance plug.(works well on my BC6)

Indicator light. One bright coloured LED with suitable resistor for 12v (250 ohm to 680 ohm - depending on your led. mine is bright on 12ma)
Very light connecting wire maximum 15cm - (6") long with resistor on opp end to led.
1.Cut some stiff wire from one side of the resistor and solder to one lead.
2.Solder the resistor to the other lead and leaving the wire long enough to act as a plug.
3.Plug both wires into the power socket on the upper circuit board in the back of the DX7.(No probs removing cover- manual tells how to adjust tension by removing cover)

Because of the resistor and the fact the led is polarised just plug in till it lights. This power is direct from the main switch, so it is a POWER ON indicator. The led is then sandwiched between the case sides just next to the aerial. This position gives a perfect on light without pointing the led into your face. It is perfect when you are packing your TX away because you cant miss it.

If anyone disagrees please let me know.. no one is perfect (I think)
I am only too happy to answer any questions.
I have already received an untold amount of help myself from this group.

Dennis

[gww528]

quote from http://myhobbycity.com/showthread.php?t=833&page=3

Hi guys,

this discussion has gone the wrong direction as it's based on wrong assumptions not backuped by manufacturers' data.

99% of today's transmitters are perfectly happy when powered from any solid current source ranging from 9 to 12V. The key word is "solid" and voltage itself is of no importance as long as it stays within 9 to 12V.

Output RF power is constant and clean in that voltage range thanks to various stabilizer circuits implemented for simple reason: FCC rules conformity.

And there is a simple reason transmitter copes with 12V source with ease: It must accept primary cells (carbon-zinc and alkaline) in case rechargeable batteries are not at hand.

Sometimes, you can find in users manual manufacturers don't recommend using primary cells but this is not because of to high voltage expected. On contrary, this is because to low voltage can emerge from low quality carbon-zinc batteries due to their high internal impendance loaded at 200-250 mA transmitters usually draw.

Besides, to high battery internal resistance frequently cause transmitter output circuitry instability, interference and low output power. Sensitivity to high power supply impendance makes use of diodes connected in series with battery (as proposed by someone in this thread) a no-no since this raises the impendance to dangerous values.

Alll the above are based on manufacturers' service and users manuals as well on 30 years of radio gear repair experience.
So guys just relax and enjoy using 11V Lipoly TX packs. The only real problem you'll have is weight imballance due to much lower Lipoly pack weight.
I've solved the problem by using 2.4 GHz RF module which calls for taking out standard antenna.

Regards, Miljenko

Hi Denis,

Thank you for the additional info. I went to My Hobby City and read the reviews about the battery. There was a reference to a thread about the use a lipos in TX. The above quote is from there. My question is about using the diode because of the following statement "Sensitivity to high power supply impedance makes use of diodes connected in series with battery (as proposed by someone in this thread) a no-no since this raises the impedance to dangerous values." Do you have any thoughts on this?

Thank you for your reply with the additional info about your installation

[dennis22g]

There must be some ulterior motive by people against diodes on LiPo batteries.
There are some fairytales going around just to persuade people to seek incorrect alternate paths. A diode has certain properties in its makeup. (P & N properties for those technically minded.) These properties act as a non return valve for electricity (electron flow).
A bi-product of this action of non-return is a voltage drop of around .6 of a volt.
The first benefit derived in our case on the DX7 is the lowering of the battery voltage from 12.6v to 12v (in a fully charged state for the LiPo).(The DX7 only sees this lower voltage and doesnt know you are using a diode). The second benefit is a safety valve protecting the battery from accidental use of the standard charger.

The current draw for a stable power platform for the DX7 (which allows continuous steady transmission) is between 100 to 200 milliamps.(This does not depend on the size of your model or how fast you fly!)
The diode will allow 1000 milliamps continuous and a surge to 50,000 milliamps.(yes 50 amps) (1N4001)

There is no problem using a diode when a direct current (DC) power source is required.
EVERY DC powersupply (apart from batteries) has them.

My DX7 has been fitted with a Lipo + diode for 4 months, and an LED on indicatior for 3 months without any problems. The only thing I notice is bloody thing never needs charging.
As well as the great yellow light if I put it in the carry box still turned on.


Dennis

[gww528]

Hi Dennis,

LED: Do you have it sticking outside the case, standing / sandwiched between the cover next to the antenna? Did you cut the case?

Thanks again for the update,
grant

Originally Posted by dennis22g

<snip>

Because of the resistor and the fact the led is polarised just plug in till it lights. This power is direct from the main switch, so it is a POWER ON indicator. The led is then sandwiched between the case sides just next to the aerial. This position gives a perfect on light without pointing the led into your face. It is perfect when you are packing your TX away because you cant miss it.t.

<snip>

Dennis

[marchambault]

Originally Posted by gww528

Horizon support states that a battery that is more than 11.5 volts will burn out the output transistor.

It's a linear voltage regulator. They did not use a copper heat sink as per the component spec sheet so it is prone to overheating. Warm to the touch at 10.5 V. Too hot to hold at 12.6V .... hence the switch to a dimension engineering 3.3 V switching regulator...

[Stolpe]

Lightning Power 2650mAh 4C 11.1V Transmitter Battery

http://www.helihobby.com/html/lithiu...l#PARTLP-B0106

What do you think about this battery? It seems to have connectors for both Futaba and Spektrum.

in my case I want to use it for my DX-7.

It should just be "plug & play" shouldn't it. And of course, I can't use the standard charger connection on the radio any more. I have to use the balance contact on the battry instead.

/ Stolpe

[marchambault]

TrueRC has a lipo that fits perfectly and it comes with the white JR connector. $30

[HeliSmith]

Originally Posted by Stolpe

Lightning Power 2650mAh 4C 11.1V Transmitter Battery

http://www.helihobby.com/html/lithiu...l#PARTLP-B0106

What do you think about this battery? It seems to have connectors for both Futaba and Spektrum.

in my case I want to use it for my DX-7.

It should just be "plug & play" shouldn't it. And of course, I can't use the standard charger connection on the radio any more. I have to use the balance contact on the battry instead.

/ Stolpe

I keep wanting to get this battery but then spending my money on other things. I am charging my transmitter after every day of flying now because I fly so much.

If you get this battery I want to hear about it too.

[apexc]

hi everyone, i am new to RC Heli flying...need some help here..
firstly i am sorry if i post this in the wrong thread...but i feel that this is the most suitable thread to post and obtain answers..


I own a Esky Lama V4, been flying for about 2 months, noticed that my radio batteries run out very fast as it is using 8AA alkaline batteries, so i decided to change it to 8AA Nicd batteries, but found out that 8AA Nicad batteries will only produce 9.6v as each one is only 1.2v at fully charged. I wont able to fly with that battery level.

through reading the forum found out that some of the members have tried changing their battery from Nicd battery pack(original) to 3s lipo 11.1v and have full satisfaction....

so my question is can i substitute my alkaline batteries(originally use) to a 3s Lipo 11.1v?

what should i do if i can substitute to 3s lipo 11.1v....can i follow the steps posted in this thread previously...

tq first for all the replies....

[Stolpe]

I bulid my own batterypack instead. Just bougt 8 AA batteries rechargable of course. I got the duracell 2650 mah on a local store. I also bought the mini JST connector to attach to the pack.

Then I soldered them together and now I have my own home made batterypack, the batterytime have been increased alot.

Take a look at theese two instructions and I thinkt that maybe you want to give it a try.

/ Stolpe

http://www.yourzagi.com/battery.htm

Make a battery pack (6 min 31 sec)

[gww528]

Good information

[pxr5]

hi
i tried this mod using an 1800mah 11.1v lipo on the esky 6ch TX and ive noticed that the circuit board below the throttle stick gets REALLY hot, so hot i cant keep my thumb on it for more than a few seconds! is this just becuase esky is rubbish or do you think a 9.6v lipo would be best?

i used to have the DX7 and was gonna do this mod but after this discovery im not so sure 11.1v lipo is a good idea. id hate to fry the dx6i im about to get by doing this mod.
thanks

[HeliSmith]

Anything you can't hold your finger to for more than a few seconds is bad electronically. I would suggest a heat gun though so we can compare apples to green apples.

I have 2 chargeers both charge nimh. I have never flown so much in a day that I have drained my DX7. If you do so I will feel kind of lamish.

[Bigglesworth]

Originally Posted by Stolpe

Lightning Power 2650mAh 4C 11.1V Transmitter Battery

http://www.helihobby.com/html/lithiu...l#PARTLP-B0106

What do you think about this battery? It seems to have connectors for both Futaba and Spektrum.

in my case I want to use it for my DX-7.

It should just be "plug & play" shouldn't it. And of course, I can't use the standard charger connection on the radio any more. I have to use the balance contact on the battry instead.

/ Stolpe

I've used a GE Power RC pack (11.1V 2200mAh - Ebay), it fits like a glove.
I fitted a diode inline with the positive lead which means I can leave the DX7's charge jack alone with no risk of battery damage if the old charger gets plugged for some reason and it drops the max voltage to the system to 11.8V.

I also fitted a charging lead between the diode and the battery. I do drop the battery out of the tx to charge it but I leave it connected.

Works well for me.

[ualdrivr]

Originally Posted by Ticidytoc

I'm sure some of you have already done this and others thought about it. There are a few ways to do this, here is how I did my radio. Please use caution when doing this mod, if you have any doubts about soldering have someone that knows how help you.

First we need to remove the battery cover and battery. Next remove the 6 screws that hold the back cover on the radio.

I decided to remove the charge jack and covered the hole with a thin piece of carbon. You can simply flip the charge jack also.

What about this bulletin by Spectrum:http://www.spektrumrc.com/Articles/HobbyWire.aspx
check the first one on the top....

I think I am going to stick with a nice but bigger NiMh like this one:
http://www.maxamps.com/MA-2500-TX-JR-Brick.htm Plug n Play .

[marcgode]

LM2937-3.3

400mA and 500mA Voltage Regulator

Generic P/N 2937-3.3
Contents

General Description
Features
Datasheet
Package Availability, Models, Samples & Pricing


Positive Voltage - Fixed Family
Parametric Table
Multiple Output Capability No
On/Off Pin No
Error Flag No
Input Voltage, min (Volt) 4.75
Input Voltage, max (Volt) 26
Output Current, max 400 mA,500 mA
Quiescent Current, typ (mA) 2
Output Voltage (Volt) 3.30
Watchdog No

it only looses little power and has max 26 volt input

[fogger]

which regulator is used in the dx7?

[Quisp]

I asked this in another thread, but I just want to make sure I'm doing the right thing:

I have a 3 cell 11.1 v lipo coming for my DX7. I've read a few places about >12 v from the battery is not good for the transmitter regulator. I've also read some place a diode in series with the battery to drop the voltage, and I've seen others that replace the regulator itself.
My question, is it OK to just charge the lipo up to ~12 v or less and use it that way?

[gww528]

Originally Posted by Quisp

I asked this in another thread, but I just want to make sure I'm doing the right thing:

I have a 3 cell 11.1 v lipo coming for my DX7. I've read a few places about >12 v from the battery is not good for the transmitter regulator. I've also read some place a diode in series with the battery to drop the voltage, and I've seen others that replace the regulator itself.
My question, is it OK to just charge the lipo up to ~12 v or less and use it that way?

I myself use the diodes.

Replacing the regulator you will void the warranty.

You could charge to 12v but most likely you will charge it to full voltage while you do something else and forget about the charging.

[Quisp]

Originally Posted by gww528

I myself use the diodes.

Replacing the regulator you will void the warranty.

You could charge to 12v but most likely you will charge it to full voltage while you do something else and forget about the charging.

Looking at the picture above, you put the diode in the positive lead between the battery pack and the plug in the receiver, right?
The picture confused me a little because what I think I see is two white wires coming out of the battery pack.
Thanks!