View Single Post
  #18  
Old 07-17-2006, 07:42 AM
ccarey75
Guest
 
Posts: n/a
I did some more measurements tonight with the other packs (again all tests are wheels-in-the-air). This time I extended the run times to 20 seconds - mostly so I could see what the cells did over a period of high load.

Overall the GP1100's fared ok (better than last time although I can't explain why). The SC1700's were fine and dandy (although not enough cells to be fun) and the LiPo caused a very small thermonuclear meltdown inside the ESC.

I need a higher current ESC I think... Anyone heard anything good about the bigger Mamba escs?

GP1100 x 9
- voltage fully charged (unloaded) : 12.12V
- voltage @ full throttle (20 sec) : 9.6V
- unloaded voltage after 20 sec run : 11.63V
- ESC temp after 20 sec run : 60C
- current draw @ full throttle: 20A
- est. speed (from venom meter) 85 km/h
- glitch? : not as bad as when i did the first set of measurements for some reason but still present. Only difference this time is that the pack was seperated from the car so the electronics were a good 3 inches away.

SC1700 x 6
- voltage fully charged (unloaded) : 7.74V
- voltage @ full throttle (20 sec) : 7.02V
- unloaded voltage after 20 sec run : 7.46V
- ESC temp after 20 sec run : 33C
- current draw @ full throttle: 15A
- est. speed (from venom meter) 62 km/h
- glitch? : no

3S Lipo 1800MAh
- voltage fully charged (unloaded) : 12.46V
- voltage @ full throttle (20 sec) : 11V
- unloaded voltage after 20 sec run : 12.23V
- ESC temp after 20 sec run : 98C
- current draw @ full throttle: ??A
- est. speed (from venom meter) ??km/h
- glitch? : not unless you count a meltdown


I ran into some trouble with the LiPo pack this time - because i was testing over 20 sec rather than 10 sec (like the last set). I wasn't monitoring the ESC temp during the run - just measuring it after so this last test was cut short after I smelled smoke (and the ESC insulation started visibly smouldering). It would seem that 10 seconds was about the maximum amount of time the ESC would tolerate the load from the lipo/400 combo.... Talk about finding out the hard way.

The temp reading was taken a little late too - allow for about 20 seconds cool-down (and a lot of swearing) before I had the presence of mind to point the temp gun at it.

I pulled the power immediately at that point so I didn't get a chance to do a current reading or check the RPM from the venom meter. Since the VSM is basically an RPM guage with a multiplier on it, though I calculate the measurement at around 97km/h (8km/h per volt as consistent with the other two measurements).

At that point I unplugged everything and set it aside to cool down -- fingers crossed it still works (I'm working up the courage to try it again).

soooo..... i have no idea why the 1100 pack ran nicer today since nothing else about the car has changed. I've got it on a discharge cycle as I type this to see what the cell voltages are when discharged... maybe that will tell me something?

The run with the LiPo pack was a frightening thing to behold. Smoke aside, all 4 wheels were ballooning to about 150% of their usual diameter with the high rpm and the noise was pretty amazing. I think next time I'd prefer not to be holding it in my hand - I had visions of trying to explain to a surgeon why there was a 20T pinion embedded 3 inches into my face.
Reply With Quote