Spektrum DX3r Battery Mod

[BrianG]

It's nice that the Spektrum DX3r only uses 4 batteries, but the voltage gets a little low when using NiXX vs Alkaline. Maybe on a peaked charge, the NiXX might get to 1.4v/cell, but I don't peak my Tx batteries that high, so maybe 1.3v. At 4 cells, that's only 5.2v. Sooo, I decided to add an extra NiXX cell in there to get the full 6v. Peaked, it might see around 6.5v, but Alkalines aren't exactly 1.5v/cell either...

I opened her up, disconnected the power wires, and took out the battery tray. Nothing magical here, but that block of plastic intrigued me....



So I ripped it out. And 'lo and behold, two more battery slots! However, there are no actual battery contacts. Poo.



Well, I'm sure we all have at least one or two of these laying around. Makes a good donor for a battery contact terminal!



The battery area without the tray. Looks empty.



It was just a matter of creating another set of battery contacts in the next empty slot and completing the circuit. I did have to extend the wires a bit to give me room to work - Spektrum doesn't give you much wire slack!

I should have taken more pics, but I forgot about the camera and got over excited, so all you get to see is the finished tray with 5 cells. Sorry!



And of course it works! Note the voltage of 5 freshly charged NiMH Duracell AA's.



Before you go tearing up your $300 radio, let me say getting the switch and power jack back where they needed to go was a PITA. My fingers are too big for such small work. Nevertheless, it IS possible, but don't blame me if you wreck your radio!

[bdebde]

Very nice Brian.

[jnev]

So how do you like your DX3R over your old DX3.0? I will soon run out of model space on my DX3.0 and was thinking about upgrading. Is it easy to use? Can you run the same receivers on the DX3R as you do on the DX3.0?

Nice job on installing the 5 cells btw.

[gixxer]

nice to see that the battery tray already has two extra slots. not sure I want to take apart my new radio though.

[BrianG]

jnev: I like it a lot. I really only got it for the multiple model memories, but the menu system is pretty cool, it's lighter, and balanced better. Works with the older Spektrum receivers, but they only work in DSM1 mode, not DSM2 (no big deal since I can't tell the difference anyway). One thing I will say: If you reset the parameters, make sure to recalibrate the throttle and steering throws! Failure to do this leads to undesirable operation!

gixxer: Yeah, I can understand that. But I wanted a more stable voltage more than I wanted a warranty. If I needed to do a warranty claim, I can always add a jumper in that last cell spot and put that plastic box back in and no one would be the wiser. But I would only do this if it broke because of something unrelated to what I did.

[gixxer]

Originally Posted by BrianG

But I would only do this if it broke because of something unrelated to what I did.

I like it and might have someone I know do it to my controller but myself I dont like to soldier stuff that small. In stock form the batteries last pretty good but the extra voltage would make it great. Would probably last as long as the lipo did in my z-1 then.

[BrianG]

I toyed with the idea of using lipos on a UBEC with a custom LVC circuit, but didn't like that idea too much. For one, I already had the batteries, so the mod was "free". Two, if out playing and don't want to stop, I can run down NiXXs lower than I would normally without too much adverse affects, but lipos...

Spektrum says the lower overall voltage doesn't affect range, and that makes sense if everythig was designed for 6v. But if the battery goes as low as 4.5-5v, that's gotta affect the range somewhat I would think. This just makes sure I have a solid 6v no matter what. Even at 1.1v/cell "cutoff", I'd still have 5.5v minimum.

[MetalMan]

Originally Posted by BrianG

I toyed with the idea of using lipos on a UBEC with a custom LVC circuit, but didn't like that idea too much. For one, I already had the batteries, so the mod was "free". Two, if out playing and don't want to stop, I can run down NiXXs lower than I would normally without too much adverse affects, but lipos...

I'm sure you are aware that I'm running Lipo/UBEC in my Nomadio React. TBH, I don't think you could really understand all of the benefits of this setup until you actually use it . No self-discharge, easy charging, super-long runtime (NiMh doesn't always put out what it's rated for...), and the ability to say "my TX runs a Lipo, and yours doesn't!". As for running rechargable AAs too low, my React actually stops functioning at about 4.5v, all the while the vibrate/audible alerts are going haywire. The Lipo is just so much better, with a switch between the Lipo and the UBEC, and an audible low-voltage warning hooked up to the UBEC input.

Originally Posted by BrianG

Spektrum says the lower overall voltage doesn't affect range, and that makes sense if everythig was designed for 6v. But if the battery goes as low as 4.5-5v, that's gotta affect the range somewhat I would think. This just makes sure I have a solid 6v no matter what. Even at 1.1v/cell "cutoff", I'd still have 5.5v minimum.

This makes me wonder - the React runs 4 rechargable AAs stock. Granted, it's not "DSM", but still. And the React is supposed to have a 10x greater output power than the Spektrum radios. Ideas?

[Mike_D]

Brian i just did this to my DX3R and it was really easy. Thanks for the great directions. Now you or somebody needs to figure out how to install a backlight.

[DRIFT_BUGGY]

Well done, that is a top mod

[jhautz]

Great mod Brian!

Quick question.... With the tray removed did it look like there would be anough room to fit 2 a123 cells in there? I have been toying with the idea for a while, but havent gotten around to tearing up the radio to check out feasability. I'm sick of buying AA cells and I agree I didnt like the lower voltage of the NiMH when it was only 4 of them. Now that I see its not that hard I may get to it. I would love to make a couple 2s a123 packs that would fit with an normal JST plug or something like that. What are your thoughts on fitting it in there?

[BrianG]

Well, the tray (with the "box" removed) fits 6 AA cells. The thickness of the cells may give you some trouble though. There is a little room above the tray, but not sure how much, or enough for the A123 cells.

Then, what about the voltage? Peaked, 2s A123 cells are 7.2v (a bit high), nominal at 6.6v (probably ok, but still a teeny bit high), and LVC at ~5v. A UBEC (or even a linear regulator) has too much drop-out voltage to use it effectively (esp at LVC), and besides, a switching BEC would be wasted here due to the low differential voltage and relatively low current. If I were to use 2s A123s or lipos, I'd probably use a diode in series with the + line to drop a consitent ~0.7v. True, at LVC, that will be quite low, but A123's drop fast though. Just set the radio voltage alert for ~5.6-5.8v.

[jhautz]

Originally Posted by BrianG

Well, the tray (with the "box" removed) fits 6 AA cells. The thickness of the cells may give you some trouble though. There is a little room above the tray, but not sure how much, or enough for the A123 cells.

Then, what about the voltage? Peaked, 2s A123 cells are 7.2v (a bit high), nominal at 6.6v (probably ok, but still a teeny bit high), and LVC at ~5v. A UBEC (or even a linear regulator) has too much drop-out voltage to use it effectively (esp at LVC), and besides, a switching BEC would be wasted here due to the low differential voltage and relatively low current. If I were to use 2s A123s or lipos, I'd probably use a diode in series with the + line to drop a consitent ~0.7v. True, at LVC, that will be quite low, but A123's drop fast though. Just set the radio voltage alert for ~5.6-5.8v.

Just thinking about this again. If you are using 5 NiMH cells they are 1.4 to 1.5v peaked so 5 of them is 7.0 to 7.5v and 2 x a123 cells are only 7.3v peaked (3.65 x 2) I might try hooking upa 2s a123 pack to the radio just using aligator clips on the inputs just to make sure I dont toast the thing before I tear it apart and make any modifications.

[lincpimp]

I guess that a 2s2p pack of the 1100 a123 cells would fit in there? Just an observation...

[t-maxxracer32]

i just bought a dx3r and am anxious to try this out.

brian if i wanted to get a lipo in there are there any options that i could look at?