Lipo conversion in your Tx/Rx

[concretejungle]

When i first got into RC and i purchased a crawler online the guy i purchased the rig from had switched the radio over to use a 3s lipo. At first i thought how strange, but i soon realized it was a great idea. The radio would last forever and it was easy and quick to charge with the rest of my crawler batteries.

From what i could tell he opened up the radio and pulled the two power wires out and soldered a deans connector on them.

So, now i have a new to me dx3c and i am using rechargeable batteries (energizer). They don't last for crap and i'm constantly having to recharge them. I was thinking about trying to convert my radio over to use a 3s.

Anyone done this and any suggestions? Bad idea?

[braq]

Originally Posted by concretejungle

When i first got into RC and i purchased a crawler online the guy i purchased the rig from had switched the radio over to use a 3s lipo. At first i thought how strange, but i soon realized it was a great idea. The radio would last forever and it was easy and quick to charge with the rest of my crawler batteries.

From what i could tell he opened up the radio and pulled the two power wires out and soldered a deans connector on them.

So, now i have a new to me dx3c and i am using rechargeable batteries (energizer). They don't last for crap and i'm constantly having to recharge them. I was thinking about trying to convert my radio over to use a 3s.

Anyone done this and any suggestions? Bad idea?

Even better, go with 2s. Either lighter for the same amphours or more running time with higher amphours.

Today's Tx mostly run on 5V (and some circuits on the board itself at 3.3V).
When you follow the battery leads to the mainboard you will find a device with three legs (much like a MosFet or Transistor, typically TO220 housing) that scales your input voltage to 5V. A sure telltale is the imprint 7805, but there are others in use as well.

With 7.4V the standard regulators will have a hard time fullfilling their job, most need those 2.5V between input and outpu.
I change my Txs to 2s by replacing those standard regulators with low drop type regulators. some like the turnigy 9x have a 2nd regulator on the module as well. For very simple ones (like the 3 CH ones that come with kits) I will keep their standard regulators and they will give a low batt alarm at some point, but still work.

Other than that just reprogramm the low voltage alarm (or change the according resistor value if that is used to measure low voltage) and you are good for 10 ish hours of Tx usage ,

cheers

braq

[concretejungle]

awesome thanks!

[TrailDawg362]

I like the idea of going to lipo power for my DX3R, wouldn't a CCBEC work for a small 2 cell and set to the proper voltage? Now you got my wheels turning!

[braq]

not really, why would you want to reduce the voltage before it goes into the Txs internal regulator? As pointed out, in some cases the internal regulator will get at its limits (simple ones like to have 2.5V minimum between input and output) and cut off. That is why I switched to low drop regulators in some of my Txs.

I have looked into my older FM type Txs, they had holders for 6 AA cells, and to increase runtime we would drop a used 7.2V NiCd battery (that would not deliver high amps anymore but still do well delivering a small current).

The question is why they ever went to holders for 8 cells, only reason I can imagine now is a conspiracy of battery manufacturers to increase their turnover

cheers

braq

[braq]

here is an example for the turnigy 9x (I keep my simple pistol grip type Txs with the stock regulator, the give optican low bat alarm but work fine)

Neuer 9-Kanal-Sender für 70,--$ aus Hongkong - Seite 74 - Fernsteuerungen (Sender und Empfänger) - RCLine Modellbau Forum

a couple of pics, first find the stock voltage regulator



desolder (cut legs off?)



take a multimeter and follow your plus lead from the battery (along the power switch, sometimes there is a diode for protection against reversing polarity), usually it also the red wire on the connector on the mainboard until you find it (in many cases it will say 7805 in some form, if it is different just input the inscription, check the internet and verify it is a voltage regulator).
You need to identify three ports, input, GND and output.

Get a replacement one, this is just one I used, there are tons of other out there
NCP1117DT50G ON Semiconductor | Mouser

Take a look at its datasheet,sometime the pin arrangement for input, GND and output is switched, sometimes you can flip it (top-bottom) or just connect with wire.

Solder in



for the turnigy 9x there is a 2nd regulator on the transmission module



cut off and solder new one in on the other side of the board





I have no GTB or DX, so please somebody else open these and identify the regulator positions.

Again, it is worth trying just with the lower voltage (and ignoring low batt alarm if there is any at all or setting the alarm voltage to an appropiate value (7.0V in case of 2s?) before changing out the regulators.

cheers

braq