Instructables

Double the battery life of the DX3 Radio from Spektrum for under $20

I first got the idea for this over on the thread for the DX6/7 on RCGRoups.com forums. I run nitro cars, so I bought a DX3. I used the radio for a while, and my battery life was on the better side of most radios--but the DX7 owners were getting like 5-6 hours of runtime after the mod. Now that's what I'm talking about! I figured that the DX3 and the DX6/7 might be using the same regulator chip, due to the fact that the chip design and internal circuitry shoulden't have changed that much. Less PCB tooling and all that.

Turns out, I was right.

I would harbor a guess that the DX2 (new and old) use the same regulator inside. However, I have not tested those and the innards may be a little different. Check your parts, and make sure your soldering it in the right way. Best case, it doesn't work. Worse case, you release the factory-packaged smoke and you get to buy a new radio. Not fun.

The mod is about as easy as it can get: De-solder a component, tin the pads, put the other component on. Done.

Here's a picture-by-picture diagram on what to do. As with everything on the Internet: I take no responsibility on your actions. This worked for me. It may not for you. Don't do it if you can't solder.

Step 1: Assemble your tools

Picture of Assemble your tools
Step one: Assemble your tools. As with any good mod/hack, get your tools together before you start modding. Also a good rule for life, I suppose... At any rate, I ended up using:

Phillips Screwdriver
Needle Nose Pliers
Soldering Iron
Solder, sponge, etc.
 
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The older weller soldering guns were terrible.
aero0075 years ago
(removed by author or community request)
Spokehedz (author)  aero0075 years ago
Yes. As you can see in the pictures, the two caps have traces that you can solder back to. But, this is pretty tricky and I recommend practicing on some other broken electronics first so that you can learn how to do this.
Could you please tell me the model number of regulator that you put in the DX3???.Thank You,.........
Spokehedz (author)  Gunny683 years ago
it is from Dimension Engineering, and the model number is DE-SW033

http://www.dimensionengineering.com/DE-SW033.htm
Thank You Very much.......
aero0075 years ago
Not all understood. the 3s lipo is 115 grams each ( not bad, half the weight of the 2600mah nimh i have), to be charged to, say, 4.0V per cell. 3s packs are common to use even on dx3. comments on several sites say it lasts for months, compared to nimh where i have to charge every time, and its a drag..

I plan to solder wires on the lower print at the opposite side of the lower print that has the white plug with black and red wire.

there isnt much difference in 8 x aa(max 12V) and 3s lipo(max 12.4v), why would it matter with the DM regulator, its good up to way above 12V right ?

were you talking about the fuse ? the picture shows the location, could it be possible to use a 3a fuse there just like that, or even use a resettable fuse called 'polyswitch' or..? spektrum/jr have spare fuses, but probably not suited for a DX3.0

yep, you can have the pics, heres some more.

this show closeup of old regulator
http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/spektrum/DSCN1500.jpg

this pic show the lower print and where to wire up a plug for battery connector
http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/spektrum/DSCN1498.jpg

this show lower print on dx3.0, you can see there is no diode, but a wire connection instead
http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/DSCN9282.jpg

overview pic of dx3.0 inside
http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/DSCN9283.jpg

raw weight of a dx3.0 w/o batteries:
http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/spektrum/DSCN1495.jpg
Spokehedz (author)  aero0075 years ago
What is the mAh of the Lipo pack? That is what determines how long it will last. You have the voltage, which on a 3s is somewhere around 11.1v but you never said what the mAh of the Lipo pack is. I have no idea about the fuse, as I don't even have the option on mine. The regulator won't care what type of battery you use--you could connect it to a 12v car battery and it should still work just fine. Just not while the car is running. :P
they are 2200mah 3s, actually arrived with a 0.09V reading on one cell and other were really low as well.. oki. i did not ask 'how long will they last'. they cant possibly last shorter than the 700 or 2600mah i have already. Being that i also count in 'OFF' time, meaning not having to charge all the time. in place of the fuse is a little smd or something whatever it is its small..
Spokehedz (author)  aero0075 years ago
If your NiMh are draining in a day, then your controller is not really off or your batteries are really terrible. I can leave mine sitting for more than a month and I will still have charge for a little time for testing. The little chip that you see is called a 'jumper' and it is essentially a zero-ohm resistor--or a wire. If you want to use the fuse, you need to remove that first. But it won't work until you put either a fuse or that resistor back.
that jumper/zero ohm fuse, may have some limit right ? if a lipo pack would burn it up, its hard to replace. i have bought some fuse clips and see what i can do there..would it make sense to place a .500mah or 1a fuse in place ?
Spokehedz (author)  aero0075 years ago
I would measure the amp-draw on your radio and rate your fuse accordingly. I do not think that the radio is drawing an amp, but I think that it might draw at least 500ma. I have no idea on how to rate fuses though.
aero0075 years ago
spokedhez, i found this on the internet:

>For Spektrum DX7 users. Most all electronic circuits use some form of voltage regulator to take the various incoming voltage and regultate it to a constant voltage. I opened my DX7 and found the voltage regulator chip and it is labeld LM2937-3.3 Search for this part number on the internet you will find the data sheet for this chip. This voltage regulator is rated for a 26V input and has an output voltage of 3.3V So a 12.6V battery is not going to be a problem. People with other transmitters just need to find the voltage regulator chip and look up the data sheet to see if thier transmitter can handle the voltage. The voltage regulator is usually a 3 pin chip with a large metal heat sink. For surface mount boards it is usually one of the larger chips.

another interesting post:

>I have been using this battery in my Futaba 7C and 6EX transmitters for the last 6 months. I charge it to 12.6 volts (4.20 x 3). No problems whatsoever. Remember, some AA batteries can be as high as 1.6v. Do the math, 8 x 1.6v = 12.8v. This is .2v above the full charge of a 3S lipo. People are worrying for no reason.Travis 05/06/09

--

Can i put a 1s4p or 2s2p lipo pack inside the dx3.0 ? if the voltage regulator needs 3.3v only .. ? another post make me think it needs 5V internally:

>You will notice that many of the new 2.4GHz radios (Futaba 12/14 for example) now come with a 2-cell lithium battery (not a 3S).
This is because 2.4GHz systems need only 5V internally so a 2S lithium is perfect for the job. Unfortunately, a transmitter that expects a 9.6V NiMH/Nicad pack will beep low-voltage if you try to use a 2S Lipo ** however, in the case of the Turnigy 9X, the addition of a single resistor can fix that problem and allow a good-sized 2S LiPo to be fitted. That would give about a 30% longer run-time than when using a 3S lipo of the same physical size and also keep the internals (regulators) running much cooler.
Spokehedz (author)  aero0075 years ago
I never said it would not work, I am saying that it would provide no benefit whatsoever and you would have to be careful as the potential to over-drain the batteries would be there. And Lipos do not like being drained. The biggest current draw in the TX is the radio module--which is what the 3.3v regulator is for. That is why it is so close to the radio module, as the 3.3v drops signifigantly over copper traces. And it is the only part of the radio that uses it, so it makes a lot of engineering sense to put it there. Now, when we replace the Lin-reg with the switch-reg, that power requirement doesn't change--it is going to draw the same amount of mAh no matter what we do--but what we used to waste in heat going from 12v to 3.3v is now gained by the radio. Now what matters to how long a pack runs is not the type of pack (NiCad, NiMh, Li-Ion, etc) but the capacity of the pack. I have some good quality AA batteries that are 2600mAh. They cost me all of $20 for 8 of them. They last me almost all day when I am out burning up the nitro. I have a good quality 3s Lipo that is also 2600mAh. It cost me almost $60. While the pack capacity is the same (2600mAh) I cannot drain the Lipo nearly as much and therefore it runs for less time than my NiMh pack does. Not only that, since it is a Lipo I have to use my Lipo charger to charge it--and not the TX charger that is built into the radio. The key is to remember this: More volts is not a longer run-time. mAh (Milli-Amp Hours) is what tells you if a pack is going to run longer. If you wanted to get longer run-time you will have to increase your mAh and the only way to do that is to get another pack and put it in parallel (I know some crazy racers who do this just so they won't lose a radio from a bad set of batteries) or get a higher capacity pack. I get all day with a set of 2600mAh batteries. I don't know what else you would need.
aero0075 years ago
My DX3.0 has that regulator sitting far from the bind button, and i think the new regulator will fit fine in. thank you for helping. the instrutable was great as is, but you make it greater by well explaining things. Makes me wonder why there are no other comments.

http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/spektrum/DSCN1497.jpg
Do you know if there is a way to fit in a fuse in dx3.0 ? there is a place for it, and i intend to use 3s 2200mah lipo pack in this transmitter.

http://i204.photobucket.com/albums/bb51/aero007/RCstuff/esav/mods/spektrum/DSCN1503.jpg
Spokehedz (author)  aero0075 years ago
I would recommend against that, as the 3S battery pack would be putting out 11.1V which is within the range of the Dimension Engineering spec to regulate down to 3.3v but you wouldn't see any benefit from it. In fact, you might see a decrease in how long it runs, as Lipo batteries usually have no built-in protection circuit and you could drain them below the recommended voltages. As for making it lighter (which is the only thing I can possibly see you trying to use a LiPo pack for) you might be able to use a 2S pack but even that is kind of iffy as it is still going to drain the batteries below their 'safe' value. If it is okay with you, I would like to add your picture at the end of the instructable saying that it works for the DX3.0 as well. I would give you credit, of course.
aero0075 years ago
i might have used to LITTLE heat, or not get enough bond/solder legs w/ led tin, might have pulle a palte off the pcb with the pliars. worst case scenario..the iron was set to 300 celsius and i changed to a pin type soldering iron tip ok then i think i must solder wires onto those yellow caps, and the middle leg i can solder to the big flat ground plate right ? how much heat (celsius) do i need for the iron to be set ? i do not want to ruin those small caps, and a spektrum transmitter cost 300 dollars here, its terrible if this wont work..
Spokehedz (author)  aero0075 years ago
300C is fine. I keep mine at about 340-350C but then I know how long to hold the iron to make it flow but not burn up the component. Yes, the ground is the big flat area, so you should have no issues soldering there. In theory, these caps are just for reducing the amount of EMF that the old linear regulator throws out. The new switching regulator is much better about this, and it does not need them. This is all theory though. Find some wire, and tin the wire. Then put the wire onto the solder that is on the cap and press your iron onto the wire--not the actual solder. This will cause the wire to heat first, and then the solder on the cap. much safer method of soldering. You should be up and running in no time.
aero0075 years ago
(removed by author or community request)
Spokehedz (author)  aero0075 years ago
Use small lengths of wire to connect the pins to the pads on the caps. Also, if pads are coming off then you might have your iron set to hot.
bubba776 years ago
where did you get that soldering iron? i was looking and looking but cant find them anywhere : (
Spokehedz (author)  bubba775 years ago
That is my old butane soldering iron, and I have since moved on to a much better unit:

http://www.cooperhandtools.com/brands/CF_Files/model_detail.cfm?upc=037103191311

Which is not only much quicker to heat up, but also has temperature controlled so that it is much better to work with. Bigger items get more heat, whereas smaller items get less heat.

I am also experimenting with 'preheating' items with a hairdryer so that they solder quicker with less thermal shock.
Ian017 years ago
The video has no sound.
bubba77 Ian016 years ago
it had sound when i watched it : D
Speed Metal7 years ago
That's a great mod! I just love mods like this. Don't have a DX3 anymore but I still learned soemthing valuble and I enjoyed reading through these instructions. Thank you! regards speed metal