Tired of AA's... - Page 2 - RC-Monster Forums

rawfuls · 07.17.2009, 02:50 PM

4 actually.

nitrostarter · 07.17.2009, 02:54 PM

4 or 5 cells.

So would a fully charged 2s pack be too much voltage? If not, they should fit in there.

rawfuls · 07.17.2009, 03:00 PM

Probably.... Probably not.

lincpimp · 07.17.2009, 03:00 PM

Small 2s lipo and a ccbec, the radio may be able to handle the voltage if the bec fails, so you should be covered. Not sure what to use as a lvc though, someone makes a regulator designed to be used with a 2s lipo as a nitro rx pack that has a lvc. Not too sure who though, maybe novak?

lincpimp · 07.17.2009, 03:01 PM

Or just use 2 of the 1100 a123 cells in series. Around 6v, so it should work great. No need for a lvc either, if you leave it on it will not melt the radio. May even be able to fit a 2s2p pack in there.

sikeston34m · 07.17.2009, 03:09 PM

Quote:

Originally Posted by lincpimp

Or just use 2 of the 1100 a123 cells in series. Around 6v, so it should work great. No need for a lvc either, if you leave it on it will not melt the radio. May even be able to fit a 2s2p pack in there.

Yes, in the case of 6v input. Some other Battery Chemistry would be the way to go.

Or like you said, use a voltage regulator.

It's really hard on any battery to completely kill it though.

J57ltr · 07.17.2009, 03:15 PM

Don't most radios already have a low battery warning? The Traxxas blinks (IDK what voltage) and my MX3 shuts off at 9V and warnins at 9.1V which is perfect for my setup.

Jeff

Bondonutz · 07.17.2009, 03:17 PM

Quote:

Originally Posted by Arct1k

Now someone do it for the DX3R?

http://www.rc-monster.com/forum/showthread.php?t=22091

BrianG · 07.17.2009, 03:24 PM

We kinda went over this before for the DX3r, but here goes anyway:

Wondering about "raw" 2s voltage, I emailed Spektrum. They said it would not like 7.4v, not to mention a fully "peaked" lipo is 8.4v. So, we're shooting for 6v to 6.5v MAX here.

Yeah, a switching BEC could be employed, but it will be about as efficient as a linear regulator on 2s. So, to get the switching BEC to be efficient, you need over 2s. Otherwise a linear regulator would actually be better. For example, a switch regulator is around 80% efficient at lower currents. Assuming the radio is drawing 200mA @ 6v, and the battery is 7.4v: That would mean a switching regulator would bes drawing 203mA from the battery. A linear regulator will only draw 200mA, so the linear one is actually more efficient on 2s.

To reap the benefits of high switching BEC efficiency, you need higher voltage, which means 3s+ is the minimum voltage. But, if the regulator goes out, that means the radio will receive the full 11.1v. The radio MAY survive 2s for a short time, but I doubt it will survive 11.1v. Another plus for the linear regulators; they are all but bulletproof. You really have to try to break one.

And, most any regulators of any kind need at least 0.5v (for LDO types) or 1.0v (for regular types) above the rated output to work right, which would be troublesome near LVC. To get around this, you could get a LDO style rated for 6v (or get an adjustable one and fix it at 6v), or a regular regulator like an LM7805 (5v).

Then, you need some kind of LVC/LVA, or some kind of indicator showing the voltage level of the actual battery.

So, after this is all said and done, it seems more trouble than it's worth. But, if you insist on using lipos, the best/safest/most efficient setup IMO is 2s using a 5v linear regulator with an LVA/LVC.

nitrostarter · 07.17.2009, 03:45 PM

Thank you for that explanation professor... lol

I'll go ahead and use my TQ4 with pride because I can easily use Lipo's!

J57ltr · 07.17.2009, 03:46 PM

When does the TQ's start to flash anyway? If no one knows I'll try it tonight.

Jeff

nitrostarter · 07.17.2009, 04:06 PM

Quote:

Originally Posted by J57ltr

When does the TQ's start to flash anyway? If no one knows I'll try it tonight.

Jeff

Just got off the phone with Traxxas on this issue. He said he was never asked that question before and he was discussing it with another guy there. The best he could say was it's around 10v. I told him I was trying to see when at what voltage the light started blinking so that I could possibly use that as a LVC. He actually suggested the smart thing in saying to get a LVC for 3s and be safe that way.

So Jeff, if you wouldn't mind trying to see at which voltage it will start to blink that would be nice. I would like to know as well. My cells have internal cut offs tho.

zeropointbug · 04:17 PM

I made this pack last week... dremeled a slot for the wire to come out from (soldered onto the lead springs inside), and I just used a Deans connector because that's the one that was on the pack in the first place. I also am running a 2s M1 receiver pack as well(I don't trust BEC's for racing), but I would like to get something lighter...

It's a 4s A123 pack, if you couldn't figure it out. Runs at 12.7 volts for the entire runtime, of which is over 24 hours! I have alot more range as well, about 1/3 mile now.

Although I would like to get some 18650 A123 cells for lighter weight, but it's not bad, it makes it stable i guess for at the track.

HERE you can get the G3 LiFe receiver packs, they are brand new, just became available two days ago.

zeropointbug · 07.17.2009, 04:18 PM

Does the DX2.0 have a voltage regulator? Because it holds 12.7 for almost the entire runtime, and the M1 cell would normally hold 3.2volts average over the discharge.

redshift · 07.17.2009, 04:24 PM

jtr and nitro, easiet way is to remove 1 AA, jumper the tabs, remove another, repeat until you get the flash.

ZP that is awesome and I want to do the same with my DX3.0.

Does anyone know what voltage the alarm sounds on a DX7? I am trying to convince a buddy to ditch his Nixx's and use an older TP 3S 2100- but he's all scared he'll leave the TX on and puff a cell or worse.... anyone?