R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric Off-Road

Reply
 
Thread Tools Search this Thread
Old 10-14-2008, 09:17 PM   #1
Tech Regular
 
RCRat's Avatar
 
Join Date: May 2008
Location: Martinsburg, WV
Posts: 348
Trader Rating: 3 (100%+)
Send a message via AIM to RCRat Send a message via Skype™ to RCRat
Default Amp ratings on BL Systems....???

Can someone help me understand the Amp rating systems on BL systems?

For example I have seen some that say 35A...but they can handle a 3S lipo.
And I've seen others that say 200A that can't......

or does it not have anything to do with voltage?
RCRat is offline   Reply With Quote
Old 10-14-2008, 09:26 PM   #2
Tech Adept
 
Join Date: Feb 2008
Posts: 242
Trader Rating: 14 (100%+)
Default

It depends on what type of motor you are running and what volts. If you are running a high KV motor with low voltage (ex 2 cell lipo 7.4) then you will pull more amps than say with a lower KV motor with higher voltage to acheive the same RPM's. Some esc's are rated 3 cell (11.1) lipos with a lower kv motor and only 2 cell with a higher KV motor due to the higher amps. Esc's experience the highest amps when accelerating and trying to push the motor from 0 to top speed, but usually it's only brief. In general you want to try to put the highest voltage with the lowest KV motor to reduce the amps, some motors are higher kv to get the most out of the batteries that may be limited to the size of the chassis of the rc, but the trade off is a higher amp load on the batteries and esc, which ends with more heat.

Hope this helps.
spcpicard is offline   Reply With Quote
Old 10-14-2008, 09:33 PM   #3
Tech Regular
 
RCRat's Avatar
 
Join Date: May 2008
Location: Martinsburg, WV
Posts: 348
Trader Rating: 3 (100%+)
Send a message via AIM to RCRat Send a message via Skype™ to RCRat
Default

Okay so an example is a 35A ESC with a 4300KV motor running a 2S (4000mah)

I'm just worried it will get to hot and burn up...or that it is a dog and doesn't want to move a Slash around.
RCRat is offline   Reply With Quote
Old 10-14-2008, 09:43 PM   #4
Tech Adept
 
Join Date: Feb 2008
Posts: 242
Trader Rating: 14 (100%+)
Default

35amp is kinda low, I would suggest going with atleat a CC sidewinder esc, they are pretty cheap and are rated at 75 amps I think. In all of my 1/10 scales I've always used the CC mamba max esc's and they never missed a beat, but that esc is kinda pricey. If you gear correctly you should be fine, on the slash I would think 16/86 would be a good start, tighten your spur fully and back it off 1/4 of a turn. I am guessing the slash comes with an 86 spur, check your temps and you should be okay, if you are running on a high traction surface you may need to gear down more. BTW the losi pinions work the best with the traxxas spurs, I've tried the Robinson racing and traxxas ones and they sharpen really quick.
spcpicard is offline   Reply With Quote
Old 10-15-2008, 08:33 PM   #5
Tech Elite
 
Drifting101's Avatar
 
Join Date: Oct 2007
Location: Melbourne, Aus
Posts: 2,199
Trader Rating: 8 (100%+)
Default

Quote:
Originally Posted by VVRC View Post
Okay so an example is a 35A ESC with a 4300KV motor running a 2S (4000mah)

I'm just worried it will get to hot and burn up...or that it is a dog and doesn't want to move a Slash around.
So its the hobby wing system right?

I am running the 10t not the 9t but i have a 5000 mah lipo in it and when the ground temp is 46 degrees(C) (so its hot) the esc only hit 65 degrees (C) and the motor hit 80 degrees (C) wich is about right for a senserless

This is in a T4
__________________
::Mi4::17.5::::::M03R::HW 3000kv::::::T4::7.5::::::HB Cyclone D4::5.5::

"Why follow, when you can lead?"
Schumacher
Drifting101 is offline   Reply With Quote
Old 10-15-2008, 08:51 PM   #6
Tech Regular
 
RCRat's Avatar
 
Join Date: May 2008
Location: Martinsburg, WV
Posts: 348
Trader Rating: 3 (100%+)
Send a message via AIM to RCRat Send a message via Skype™ to RCRat
Default

Quote:
Originally Posted by Drifting101 View Post
So its the hobby wing system right?

I am running the 10t not the 9t but i have a 5000 mah lipo in it and when the ground temp is 46 degrees(C) (so its hot) the esc only hit 65 degrees (C) and the motor hit 80 degrees (C) wich is about right for a senserless

This is in a T4
Yep it is the Hobbywing system....you like it?
RCRat is offline   Reply With Quote
Old 10-15-2008, 08:55 PM   #7
Tech Elite
 
Drifting101's Avatar
 
Join Date: Oct 2007
Location: Melbourne, Aus
Posts: 2,199
Trader Rating: 8 (100%+)
Default

Quote:
Originally Posted by VVRC View Post
Yep it is the Hobbywing system....you like it?
Yes i like it better than my GTB....the only problem is that there is a small cogging but the is un noticable unless you hold the throttle so little (other than nutral) that a normal motor wouldnt even move
__________________
::Mi4::17.5::::::M03R::HW 3000kv::::::T4::7.5::::::HB Cyclone D4::5.5::

"Why follow, when you can lead?"
Schumacher
Drifting101 is offline   Reply With Quote
Old 10-15-2008, 09:17 PM   #8
Tech Fanatic
 
94eg!'s Avatar
 
Join Date: Jan 2008
Posts: 832
Trader Rating: 17 (100%+)
Default

Voltage and amperage are two separate things. Together they make power. Volts (charge) x Amps (current) = watts (power). To get more power, you need more of one or both...

BTW: The eZRun system (35A/9T combo) has been purchased by many many people, and I've still yet to hear any real bad news. The only thing to watch out for is the cheap on/off switch. Some have removed and soldered the wires so it's always on when the battery is plugged in...
94eg! is offline   Reply With Quote
Old 10-15-2008, 09:20 PM   #9
Tech Master
 
Join Date: Oct 2002
Location: KY
Posts: 1,152
Trader Rating: 95 (99%+)
Default

Amp rating has nothing to do with how many cells a speed control will handle.

I've heard many good things about the hobbywing esc.

The other thing you have to look at when looking at amp rating are the giving you the actually continuous operating rate or the peak operating rate.

For example that 35 amp speedo has a peak current rate of 190 amps. Once you have your vehicle moving it draws very little amperage but when you take off, climb over a pipe, or any thing else that puts a heavy load on the motor you can easily get over the 35 amp rating but only for a second or so. The electronics have no problem handling that heavy load for a very short period.
__________________
www.rcrcr.com --------> B-Mag free since fall '07
RobbieS is offline   Reply With Quote
Old 10-15-2008, 09:27 PM   #10
Tech Elite
 
Drifting101's Avatar
 
Join Date: Oct 2007
Location: Melbourne, Aus
Posts: 2,199
Trader Rating: 8 (100%+)
Default

I have also heard that the switches are very hit and miss. Mine is good it actually fell of a went under my truck it is scratched but fine
__________________
::Mi4::17.5::::::M03R::HW 3000kv::::::T4::7.5::::::HB Cyclone D4::5.5::

"Why follow, when you can lead?"
Schumacher
Drifting101 is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Electric Touring / On-Road RC Screaming Wind Manila Racers 32167 05-02-2017 11:20 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 02:16 AM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net