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?

[ssspconcepts]

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.

[wallot]

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

[ssspconcepts]

???

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.

[shizzon]

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.

[mistercrash]

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.

[mistercrash]

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.

[E-Revonut]

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.

[BrianG]

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.....

[mistercrash]

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.

[BrianG]

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.