Lipo in my DX3R?
 

How much voltage is the radio rated for? Should i use a 2s or 3s? When u take the stock battery tray out, how much room is there in the radio?

Anybody?

Brian had a post about this awhile back...it's not as easy as the DX2.0 and DX3.0 because the DX3R runs on 4 AA cells or 4.8 volts. 2S is way too much. I am with you though...I hope you figure it out and post your findings...I'd like to upgrade my radio someday but I am not going to do it until somebody figures out a 4.8V lipo conversion for all the newer radios. I did the 3S lipo conversion to my DX3.0 and I really like it. One charge seems to last forever.

4 dry AA cells are 6V so lipo + good voltage regulator should do.
bu why bother with lipo when 4x2700mah sanyo nimh cells last ages

???

4 AA cells are 4.8Volts

4 X 1.2V = 4.8V

I suppose when they are new you can get 1.5V each, but that performance doesn't last long compared to lipo.

i just put a 3s 2200mAH flightmax lipo in my DX2.0, works fine.

here's my post: http://www.rc-monster.com/forum/showthread.php?t=19233

edit: i forgot that the DX3r uses only 4 double a's, but i have seen people convert it to use 6 or 8 IIRC, im sure you could use a 3s, but i would check with the manufacturer to be sure that it won't mess anything up.

I ran with the same four AA Duracells in my DX3R all last race season. They showed 6V for the first couple weekends and then showed between 5.8/5.5 for the longest time. I still have them in the radio and just used it today, they are now at 4.8. Time for a new set. I got Sanyo 2700 mah nimh cells to use for this race season.

Well with a lipo i can get more runtime and voltage for the same or less weight compared to my 4 AA 2500mah batteries.

I agree that you will, I was just stating that the DX3R is not power hungry and 4 AAs last a long time. But if you use your RC a lot and for long periods of time then go ahead with the lipo upgrade. Be sure to post pics of your set up.

Yea, it is uncommon for me to use my radio 5 or more hours at a time.

AA alkaline batteries are 1.5V/cell versus Nixx at 1.2V/cell. I would guess the radio can prolly handle at least 6.5V. I took mine apart to see how much room is in there, there is actually alot of room! I ran 2500mah Energizer nimh for awhile but after about an hour I can notice a drop in range and the voltage is down to 4.8V. For the fall carpet season at my lhs I ran Duracell ProCell batteries and got a season and a half out of them plus all the bashing I do, I won't bother with rechargeables anymore, $5 worth of Duracells last me about 6 months, have a higher voltage and better range.

I wasn't sure what the effects of running just 4.8v (4 X NiMH cells) was, so modded the radio tray to use 5 NiMH cells (6v) to match what 4 alkaline AAs would put out voltage-wise. The voltage of 5 freshly peaked NiMH cells is closer to 6.5v, but hasn't harmed my radio yet.

To use lipo, you could go a couple of routes:

1: Use 2s lipo with a linear voltage regulator. An LM7805 linear regulator would work fine, but only gives 5v. You can easily boost it with the addition of a couple of resistors to get 6v though. And since radio current draw is small, you shouldn't need a heatsink. I figure 400mA worst case current draw (judging by the runtime I get on 2500mAh NiMHs), which equates to 0.96w when the lipo is at 4.2v/cell, and 0.4w when the lipo is at 3/5v/cell. I wouldn't run the lipos down much beyond that because at low current draws, you have much less voltage "rebound" when you remove the load. And at that point, there isn't much runtime left anyhow.

2: Use whatever cell count lipo you want and hook that to a switching BEC. The higher voltage you go, the lower current draw from the lipos. If you use 4s lipo, current draw will be around 200mA if the radio is drawing 400mA @ 6v. The trouble with this setup is that if the BEC fails, it could send full battery voltage to your radio. Not good. So, I would use something like the CCBEC with a programmable output, set it to something like 7.2v, and then use a linear regulator to take it the rest of the way down to 6v. Power loss on the linear regulator will be minimal since the delta voltage is small, yet it provides protection if the BEC should fail. The worst that will happen if the BEC failed is that the linear reg would heat up and thermal, which should be a good indication that something is wrong. Despite the poor efficiency of linear regs, they are pretty bulletproof; you really have to try to break them.

In either case, you'll also need to add some sort of LVC, low voltage alarm, or small voltmeter panel (like this). Otherwise yoou run the risk of discharging the lipos too far.

So, I found it much easier to just stick with NiMHs in this case.

I use the Costco brand (Kirkland) alkaline AAs they are cheap and last a long time, I can see though if you have the lipo pack laying around gathering dust.....

BrianG,
I tried 5 cells when I got my DX3R a while back with old 2000 mah AAs I had. The 6.4 volts they pumped into the radio freaked me out a bit so I went back to 4 cells. How long have you been running with 5 cells? I'd like to go back to 5 cells if I was sure nothing bad would happen to the radio.
http://i177.photobucket.com/albums/w...h_53ba183a.jpghttp://i177.photobucket.com/albums/w...h_badde9cf.jpg

Probably around 6 months now - a few weeks after I got it. Granted, I don't get much use in the winter, so that translates to around 5-6 hours continuous operation.

5 cells
 

Yea I also bought one of those 5 cell NM packs off of TH, and plan on using it for my DX3R. With the guts removed from the battery tray it fits easily, and I am going to use a simple Tamyia plug for easy hookup and removal. Plus I have some laying around and don't plan on using them for anything else. I still need to figure out how I want to charge it up yet, but something will pan out. I was going to try and use the installed charging plug on the radio, but finding a 6v charger with low milliamp ratings that plugs right up to the radio proved to be too much work for me. Plus there was a warning about the leads being designed backwards with the negative wire in the center of the plug. I hate when these companies do propriatory designs. The Lipo batteries would be kind of cool, but like BG stated not worth the chance of frying the radio in my opinion due to low voltage on the Lipos, or some other failure issues that are inharent with Lipos. NMs are just the safer bet for my efforts.

the charger I got with my DX7 has that warning and thy provided a 16hr charger for me to use....its not much more than a cheap wall charger you might be able to get a good deal on one online somewhere

U don't have to use that rinky-dink wall charger, i've been using the same charger i use for everything else and charge through the built in plug for 5 years now with no problem. I just cut the end off of the wall charger that came with the radio and got a deans pigtail, and put the negative radio plug on the positive side of the deans and positive on negative, works great.

Yeah, I noticed that too. I just rewired the jack accordingly to have a negative sleeve/positive center pin (which is the way it should be). Then, I just used a RadioShack plug (size N or M - can't remember exactly now) and it fit perfectly in the stock jack. Then it was just a matter of wiring a small extension so I can use any NiMH charger.

Me to.
 

Yea I hear ya BG. I imagine that I will be doing the same thing with my DX3R as well. I guess since your radio is already done and in use, that it has not caused any collateral issues having the (+ & -) on the radio (charging jack)reversed? I will take a closer look at it this weekend and try to get it completed so I can start playing with my truck to. Thanks for the info Sir.

Like i said i have been using JR radios and the Spektrums since they came out (5 years total) using a made up adapter with no problems.

instead of rewiring the jack just swap the colors on 4mm bullets on the charge cord :)

Yeah, right! And the next time I just so happen to forget; poof!

Huh??
 

Now how does that help anyone find the right charger for this radio? And like BrianG stated I want something that is a permanent fix for the charging of my radio, with no chance of mixing anything up and killing my investment. Switching the jack leads on the radio is the simple and final answer in my opinion. Then all anyone has to do is find a 6volt charger with the right milliamp output, that will plug right in.

There's nothing to mix up.

I decided to go back to 5 cells in my DX3R. I use Sanyo 2700 mah nimh cells. They are new and when peaked they pumped out 6.9 volts when I turned on my radio, then after a minute dropped to 6.8V and stayed there. BrianG I'm freaking out again :lol:

http://i177.photobucket.com/albums/w...h_8056cbff.jpg http://i177.photobucket.com/albums/w...h_e0720d0a.jpg

Winner.
 

Sounds like a winner. I have the Hydromax 5 cell pack for mine. Now I just have to get the radio rigged up for direct charging so I do not have to remove the pack in order to charge it up, and then find the right plug in charger for it. I think it is a 2000 or 2200Mha pack.