ESC, Motor, LiPo help. - RC-Monster Forums

rustnpede · 06:12 PM

Well I was waiting until February to buy the electronics to finish my BL Revo (stock chassis and single speed), but this holiday sale is too good to pass up.

I want a 7xl with a 9920 but where I live the temps are usually around mid 90’s from late spring all the way through mid fall. How much hotter is a 7xl compared to a 8xl? Should I go with a 8xl or even a 9xl to keep temps cool? With the 9920 I will need a Li-Saver right?

I don’t know a thing when it comes to LiPo. At first I was thinking 4s and running them parallel but then I figured if went 2s and hooked them up in series then I would be able to use the packs seperately in other low voltage escs. Is there any advantage in parallel vs series?

What is the difference between TP taps and Hyperion taps? I have a superbrain 997, will any balancer work with it? I know if I go 4s then Ill need a different charger.

Thanks for taking the time to help a New-B.

rustnpede · 12.11.2006, 04:31 PM

Also how much hotter will electronics run on 5s vs 4s?

riceman · 12.11.2006, 04:40 PM

I'll let some of the other pros here answer you lipo questions. I will chime in here becuase the 9920/7XL setup is exactly what I have powering my 12 pound MGT conversion here in lo-Cal. Take a look at it run here. After figuring out my gearing and with the 25mm fan I have yet to have any temperature issues.

rustnpede · 12.11.2006, 06:13 PM

Quote:

Originally Posted by riceman

I'll let some of the other pros here answer you lipo questions. I will chime in here becuase the 9920/7XL setup is exactly what I have powering my 12 pound MGT conversion here in lo-Cal. Take a look at it run here. After figuring out my gearing and with the 25mm fan I have yet to have any temperature issues.

Good to know.

Your vid credits 5s 4000. I cant completely see the voltage on the top pack. Looks like another 7.4. So are you running 4s now? What charger and what balancer are you using?

Is your fan running off of a reciever pack?

I live in Moreno Valley. What part of california are you?

riceman · 12.11.2006, 06:35 PM

Yeah - the pictures show two 2S cells but I've got a 2S and 3S in it now. I'm running a Li-Saver LVC. Torque is great. The center diff keeps the wheelies in check. I have a Duratrax Ice charger and using a Hyperion LBA 6 balancer which works with the Maxamps standard taps. I plan on getting a single 5S pack so I have an Astro Flight 109 on the way since the Ice will only do up to 4S. Yes - fan and servos are running off receiver pack.

Procharged5.0 · 12.11.2006, 05:36 PM

Nice Conversion!

Are you happy with the torque of your combo?

neweuser · 06:02 PM

I would run the 4s in series. More power. And with the 7xl, you would have heat issues i would think on 5s

rustnpede · 02:41 PM

Quote:

Originally Posted by neweuser

I would run the 4s in series. More power. And with the 7xl, you would have heat issues i would think on 5s

I dont get it. 4s in series = more power than 5s? Hows that?

Quote:

Originally Posted by riceman

I'm running a Li-Saver LVC.

I understand that the Li-saver gos between the Rx and the ESC and the ESC and the battery, but where does the fan get power from? EDIT: nevermind, missed that last line

riceman · 12.12.2006, 07:19 PM

No problem - In fact I wondered where to draw the current for the fan. One of the airplane guys at my LHS recommended that I splice in prior to the esc and reciever. Use a 12 volt fan and draw directly from the batteries. His reasoning was that any fluctuation in current produced by the fan may lead to glitching if it was being drawn from the reciever. Since I already had a 5 volt fan I went ahead and plugged it into channel 3 of the receiver and haven't had any glitching yet. My LST2 conversion is put together the same way and I haven't had any issues there either.

rustnpede · 12.13.2006, 03:31 AM

I have a 12 volt fan, maybe Ill take your guys advice. Should tap into the Li-saver or have a seperate set of deans and wires to go between the Li-Saver and batterys?
Is there any advantage in parallel vs series when total voltage is the same? Is there more resistance when wired in series? More heat?

riceman · 11:46 AM

The 12 volt hookup to the batteries work if one of them is 3S. Otherwise will need a 5 volt fan to wire to the reciever.

look here for wiring diagram

put the lvc between the batteries and esc.

BrianG · 12.13.2006, 11:55 AM

Hmmm. Maybe I should add an external LVC diagram to my page...

riceman · 12.13.2006, 12:06 PM

I thought about contacting you with that. that would be cool :027:

There are also a bunch of guys doing LST2 conversions. I have all the ratios already memorized so I don't need them in the calculator pull downs. I do point a few of the guys on the LST forums to your calculator. If you think it worthwhile to add I can try to get exact tooth count on each of the gearing combos. The sad part is a lot of the guys on the LST forums are doing the Fine Design conversions and have no idea what the motor rating is.

BrianG · 12.13.2006, 12:18 PM

If you let me know the LST gear tooth counts, I'll add them. You can either PM them to me or post in the stickied thread. What would be really nice is a seperate tooth count for the diff and each tranny speed. Also, only two tooth counts for each ratio. Sometimes, there are more than two gears in the tranny, so just let me know what they are. I'll just have to convert that to only two "output gear" and "input gear" tooth counts.

coolhandcountry · 12.13.2006, 04:54 PM

The holiday sale is a good buy. Hard to pass it up if you plan to buy.