Tired of blowing cells.. - RC-Monster Forums

J57ltr · 12.28.2009, 12:59 AM

When I first got my mamba max and 7700 I ran Duratrax 4200's and they did ok as long as I was geared 87/15 in my rustler on the street when I went to a 17 tooth I actually popped one of the cells. The hobby shop replaced it under warranty. I got an eagle tree data logger and found out I was pulling 126 amps and pulling the pack down below 5V. For a while I still ran this setup but more closely monitered the temps. I still managed to kill a second pack. After that I got a different motor to tame it down a bit. I still run it from time to time but switched to A123 batteries and just run speed runs with it.

Jeff

HomeGrown · 01:54 PM

Quote:

Originally Posted by J57ltr

When I first got my mamba max and 7700 I ran Duratrax 4200's and they did ok as long as I was geared 87/15 in my rustler on the street when I went to a 17 tooth I actually popped one of the cells. The hobby shop replaced it under warranty. I got an eagle tree data logger and found out I was pulling 126 amps and pulling the pack down below 5V. For a while I still ran this setup but more closely monitered the temps. I still managed to kill a second pack. After that I got a different motor to tame it down a bit. I still run it from time to time but switched to A123 batteries and just run speed runs with it.

Jeff

i was running DTX 4200s i've blown like 6 cells of them.. never really had temp problems..

on another note i have a buddy that would trade my 7700 for a 5700 mamba.. think i should do so?.. and if i do wouldn't i be losing speed and torque? i love poppin wheelies on demand.. i only bash but race cars up my street often.. i like to see their

when my RC passes them..

i guess i'll opt for the 40c packs.. does it make a difference with a hardcase? because i bash the hell outta my truck and hardcase just seems logical.. whats the pros and cons of a hardcased lipo?

also if i swap motors i could go bigger then just 2s.. i think that 5700 is rated for 5s or 6s lipo..

_paralyzed_ · 12.28.2009, 02:54 PM

the 7700 refers to how many rpm's per volt the motor turns. On 2s the motor spins at 56980 rpm (7700kvx7.4v=56980rpm)

The 5700 on 5s would be 105450rpm (5700kvx18.5v=105450rpm)

that's way too much! You don't want to run the castle motors past 60,000rpm. You could go 3s on the 5700.

With the 5700 you would GAIN torque and lose speed. A lower kv motor has more torque than a similar higher kv motor.

The 5700 would still do what you want on 2s (wheelies at will) and run much cooler than the 7700.

I would sell off the 7700 and get a bigger motor(not castle).

J57ltr · 12.29.2009, 12:53 AM

Quote:

Originally Posted by HomeGrown

i was running DTX 4200s i've blown like 6 cells of them.. never really had temp problems..

on another note i have a buddy that would trade my 7700 for a 5700 mamba.. think i should do so?.. and if i do wouldn't i be losing speed and torque? i love poppin wheelies on demand.. i only bash but race cars up my street often.. i like to see their

when my RC passes them..

i guess i'll opt for the 40c packs.. does it make a difference with a hardcase? because i bash the hell outta my truck and hardcase just seems logical.. whats the pros and cons of a hardcased lipo?

also if i swap motors i could go bigger then just 2s.. i think that 5700 is rated for 5s or 6s lipo..

I bet it was one of the cells opposite the battery leads.

I got the batteries real hot one time. We had a pile of dirt where a house was being built next door and a friend and I were climbing to the top. I was running the 7700 and it was geared pretty low (87/12) and I was also using my eagle tree with a temp sensor on the battery, ESC and motor. The motor and ESC was pretty warm around 130 and the batteries stopped at 200 at about 3 minutes into the 6 minute run. I have no idea how it really got because I had accidently set the upper limit to 200. That was measured under the wrap.

I used a Feigao motor (4436Kv) and they are just about identical to the castle cm36 motors. Like the guys said 5-6S would be death, although you can usually get away with it a time or 2. I have run the 7700 on 3S2P A123 and it cranks out some serious power. It's real hard to keep it from flipping a rustler on it's lid and it's kinda like going over a cliff, you still hit those brakes.

I also have a Nemesis blue 6 turn motor (5915 Kv?) and it does very well also. I would say it's probably right along with the CM36 and Feigao motors. I have run it on up to 4S2P A123 and it flies. I have run all these motors on Nimh and wouldn't recomend the 7700 with them. I run mostly on the street which is a little easier on batteries, so if you run offroad a lot you should probably try to get that 5700 or lower when you can.

Jeff

_paralyzed_ · 12.29.2009, 01:39 AM

Quote:

Originally Posted by J57ltr

I also have a Nemesis blue 6 turn motor (5915 Kv?) and it does very well also. I would say it's probably right along with the CM36 and Feigao motors.
Jeff

nemesis blue is just a feigao that chris fine from fine designs put a sticker on. isn't capitalism spiffy?

J57ltr · 12.29.2009, 02:29 AM

It's not hard to tell just by the way they are constructed. Rebranding isn't so bad as long as you know what's out there. I remember in the 90's Autotek, Hifonics, Rodek, Earthquake, and at least 3 other "manufacturers" had amplifiers that were all made/designed by a single company. They were all good amps they wern't Nakamichi or A/D/S but they were powerful and pretty good quality.

You have to think that when you are coming over from brushed even the entry level motors are fast. A Neu is nice but a Nemesis is.... ah hell I got nothing...

Jeff