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

Picture of 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.
 
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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.

Step 2: Removing the back case

Picture of Removing the back case
Spektrum DX3 008.jpg
There are 8 phillips screws, as indicated in the picture. Remove them. You do not need to remove them all the way from the case if your good. If you don't think your skills can pay the bills--remove them, and put them somewhere safe. Preferably inside something you can close so they won't scatter under the workbench. If I had a nickel for every screw I lost...

Also, you will want to be very careful about the antenna wire, which is attached to the antenna which is attached to the back of the case. I don't know why (I think it's an engineering flaw, myself) but such is life. It's very thin and fragile. Well, it's not really that fragile but you can break it if you gorilla it too much. Just remove the back and you'll see a grey wire going to a small golden connector on the PCB.

Using your fingernail, put it just under where the wire meets the connector at the PCB, and pull straight up. The connector will come off easily (if not, don't force it! just wiggle it and it will pop off) and then put the whole back case off to the side. See how you don't need to remove the screws? I told you I was good...

Step 3: Find the Linear Regulator

Picture of Find the Linear Regulator
It's pretty easy to spot... It's pretty much staring you in the face. Its the black square with three legs next to where the antenna was connected, and right above the bind button.

About the bind button... It's kinda right in the way of where we are going to be working... but you can't remove it. You may want to put some layers of tape on it so you don't end up melting it. I only singed it a little, but it still works. Plus, it's not like anybody sees it anyway...

Step 4: De-solder the Linear Regulator legs

Picture of De-solder the Linear Regulator legs
Spektrum DX3 012.jpg
First, you tin up the legs. All electronics sold in the USA have to be RoHS Compliant. What that means for us is that there is no lead in any of the solder. That means that it sucks for re-soldering. So tin up the legs with your new solder. Just because they can't be sold in the USA without being RoHS compliant dosen't mean that we have to use use PBFree Solder. (PB is the symbol for Lead.)

Now wedge your needle nose pliers under the first leg and gently pull up on it while putting the iron on the leg. You will hear it pop (or make a scrunchy sound.) which is normal. At this same time, you'll see it move up. DON'T PANIC. Just keep a firm grip on the leg and move it up and out of the way.

If you got a big solder-bridge, two things may have happened:

1. You had too much solder on the leg.
2. You didin't move the leg up enough.

Just heat up the solder and with any luck, it will come free. If not, get out your solder-sucker and suck the excess solder up. If you don't have a solder-sucker then just wipe off the tip of your iron and wipe it through the solder. And get a solder-sucker. Soon.

Step 5: Removing the Linear Regulator from the PCB.

Picture of Removing the Linear Regulator from the PCB.
C:\Documents and Settings\E039758\Desktop\Spektrum DX3 016.jpg
This involves heating up the bigger end and melting the solder under it. It is a seperate step, because unless you de-solder the legs first, you'll never get the unit off the PCB.

The PCB is the heatsink for this part. And, I did some tests with my temperature probe--this sucker got HOT. All that wasted energy as heat means your batteries are going bye-bye. To remove the regulator, simply put your iron on the large flat metal piece and feed some solder into it. Push up against the part and you'll likely send it flying across your workbench. Don't worry--you shant need it again. Let it keep the dust bunnies company with it's radiating warmth and lack of efficiency at high voltages. They'll appreciate the company.

Step 6: Tin the regulator pads on the PCB

Picture of Tin the regulator pads on the PCB
A small step, but a crucial one. Without this step, you'll have a very hard time getting the new regulator on the pads. Trust me. I hate PBFree solder.

Step 7: Inserting the new Regulator into the circuit

Picture of Inserting the new Regulator into the circuit
Spektrum DX3 011.jpg
C:\Documents and Settings\E039758\Desktop\Spektrum DX3 023.jpg
C:\Documents and Settings\E039758\Desktop\Spektrum DX3 022.jpg
This the only really, truly difficult step. And even this one isin't that bad.

There's not enough room on the PCB to have the new regulator fit where the old one was. There is also not quite enough room to have it sticking over the edge. What to do! Luckily, we do not live in a flat world!

My solution is to slightly angle it and have it up in the air. Good for cooling (the regulator hardly gets warm at all--also tested) and more importantly: It lets it fit!

Tack down one leg (making sure to check the polarity) by pressing the iron to the leg and NOT the pad. As you should all know, you heat the component not the solder.

With the extra solder already on the pad, once the leg heats up it should flow easily and stick the component down. Ah, good old lead solder. Then solder the other leg, and then the other-other leg. Easy.

I had to clip off a little of the legs to make it fit without touching the ground-plane. That's the big silver area where the old regulator used to be. You may not need to. Just don't let them touch the ground-plane that the other regulator was stuck to. Sparks and the factory packaged smoke may be released. BAD!

Also, you could also use a little bit of wire and stuff it down into the body of the radio. I don't like things rattling around inside my radio--so I chose not to do this. You make your own decisions, and stick with them.

Step 8: Testing the Regulator

Picture of Testing the Regulator
Put a little more solder on the legs of the new regulator, and make sure that all connections are good. I do this by putting my DMM into Diode/beep mode and I touch the leg of the component near the component, and then another component that the trace runs to. On some circuits, this is easier said than done--but it is super easy on this one.

The two capacitors on each side of the old regulator gets a nice big trace to it. Simple touch the one probe of your meter to the regulator, follow the trace to the cap and touch the probe there. If it beeps or shows Zero-Ohm then your golden.

Next we get to test the radio. Turn on your receiver (RX) and wait for it to go into failsafe (3 sec). Then take your radio (TX) and put in the battery pack. You'll have to hold it in, as the bottom won't fit anymore.

Don't bother with the antenna or screwing on the back--just leave it off for now. Hold in the battery pack in and turn on the radio. Look at the display. Does it show a normal voltage between 11v and 10v? If it does, turn the knob and pull back on the throttle. If stuff moves, then your golden. Turn off the radio and the receiver, and put the battery pack off to the side once again.

If it dosen't, make sure your battery pack is charged and that you have it put in the right way. If it still dosen't work, go back and test your connections again. If it STILL dosen't work, then remove the regulator, clean the pads and the regulator legs of solder (solder-sucker!) and put new solder on.

Step 9: Putting it all back together

Picture of Putting it all back together
Take the antenna wire and find the connector on the radio. Yes, I know it's very small. Yes, you can do it. If I can do it with my big, fat fingers--you can too.

It's kinda tricky, but not too bad. The trick is getting it right over the connector. Put your pinky, or whatever you can under the floating PCB in the TX. Push down on the connector (gently!) and it will click/snap into place. Honest, it's a feather-touch here.

The connector will spin without popping off when it is on properly. Just don't go spinning it around in a circle like a goober. Once the antenna is back on, put the clear plastic bind button onto the LED that's sticking out of the black button, and put the case back on. If you angled your regulator correctly, you should be able to put the case back on and screw in the screws easily. If not... well... Go back and put it on correctly.

Don't go bending it like a hosehead either. You'll rip off the pads and then you will be up a certain creek without a paddle. so just don't do it. Re-soldering takes a minute, and it's easy.

Step 10: It's over!

Step ten: Sit back and feel accomplished! You did it! Now your batteries will last a LOT longer than they did before. I don't honestly know about how long they will, but it's noticeable.

I have 2600Mah batteries in there now, and before they would drop from 11v down to 9v really quick. I'd say, a good 2 hours of hard driving would really put a serious hurting on them. And alkaline batteries were almost useless--going dead within a matter of minutes. Now I charge up my batteries, and I can go all day without fear of my batteries going dead on me. I ran out of fuel before I ran out of batteries in my radio!

The RX on the other hand...

And before you start asking questions: No. The RX won't benefit as much from the new regulator as the TX does. The reason is kinda compliecated, but basically the old regulator was horribly inefficient at taking high voltages and stepping them down to the voltages that it outputs. This one output 3.3v and as you can see the batterpack has 8xAA batteries.

8AA * 1.2 = 9.6V (Ni-MH)
8AA * 1.5 = 12v (Alkaline)

Since the output (3.3v) is more than double (triple) than the input voltages, the inefficient regulator just burns up the batteries as heat.

The new regulator that we put in is a switching regulator, which has very high efficies at almost any voltage. Plus, it uses less current to operate. A bonus all around!

Step 11: Notes and afterthoughts

There you go! I hope this helps you as much as it did me. For as easy as this is, there is really no reason not to do this. I mean, other than the fact that you may break your radio... But that's never stopped me before! If anybody else comes up with information, or I need to change something I will make a note of it here.

And here's a video of it working. Why? Why not! Enjoy!


buckbanzai552 months ago

just want to add my 2 cents to this thread... Dimension engineering will make you a regulator for any radio and any radio running off a linear regulator needs this mod. you can disassemble any transmitter and look at the voltage regulator specs and get a switching regulator to match it. Furthermore, no need to de-solder the old regulator or even remove it. Just cut the legs in the middle, solder a BEC connector to the remaining legs coming off the board and you can even solder another bec connector on the old regulator should you ever have a problem and want to reconnect it. solder the female BEC to the DE switching regulator, plug in and good to go. On spektrum 3.0 there is a really nice spot for it on the left side of controller (looking at it from the back of course). While you are in there you should cut the backup battery off and solder a JST connector in there with a new CR2032 battery. If you change the backup battery before it dies, the controller will hold the memory for 10 min off a capacitor while you change it..

The older weller soldering guns were terrible.
aero0076 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)  aero0076 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)  aero0076 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)  aero0076 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.
aero0076 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)  aero0076 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.
aero0076 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)  aero0076 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.
aero0076 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)  aero0076 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.
bubba777 years ago
where did you get that soldering iron? i was looking and looking but cant find them anywhere : (
Spokehedz (author)  bubba776 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.
Ian018 years ago
The video has no sound.
bubba77 Ian017 years ago
it had sound when i watched it : D
Speed Metal8 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