New Brushless System ?'s
 

Recently installed 9920/7XL into E-maxx w/ UBEC, geared 18/66.

What are some runtimes should I expect?

Also, my GP 3300's are measuring at 130 degrees. What are safe temps for the batts, controller and 9920?


P.S. - Love the system, thanks for all of your posts that helped me decide.

How many cells are you running with that gearing?

As of now, 12-14 cells

With that gearing and 14 cells you will be looking at around 10 minute racing run times and 20+ minute bashing.

130F sounds hot for the GP's,
The motor should not exceed 180F
I'm not positive about the controller temps but I wouldn't go much above 120F

I think it is about 160 f for the esc. The cooler the better though.

But why would the batts get hot? They have only been used about 10-12 runs.

The motor temp is 135 and controller at 95. Both have fans on them.

Could it be binding in the drivetrain?

The faster the discharge the hotter the batteries get. The 7xl will take some power. I had warm running batteries as well with the 7xl. Have you figured the run time. I didn't get a great deal with mine. Every one is different.

The controller can take about 180 deg. The batteries should be okay for up to 150 deg.

Have not timed the runs, but seem to be about 8-10 minutes of WOT. I stopped early on the last 2 runs because the batts were hot. I tested them and they had plenty of voltage to keep running.

You used a tempgun to measure the temp? your hands feel like burning at 50 degree C allready..

New system = extra cautious. Tempgun is good insurance, not wanting to fry anything the first few days...

i just thought you might find it interesting and valuable knowledge that 50 degree celsius allready feels like burning....

Thanks, now I know.....if 130F is too hot for batts?

130F is pretty much the limit for nimh's.

Any causes/preventions? Or, should I change batts more often?

Well if your saying you do 10minute WOT - that won't help at all. ;)

i think there's a tendency to do this at first with a new setup,while you revel in the new found power,i do it anyway.i think it will be fine in normal running though if you are running it up and down at WOT for 10 mins to hit 130F.Try driving it with a little sympathy for a pack,still plenty of WOT,and see what temps you're getting.

130 is a bit warm for the batteries, but not too terrible. I would be sure to let them rest/cool before running them again, though. You are drawing on the batts pretty good to get them that warm. Possibly a drop ingearing would spare them some agony and allow them to last longer. You could also add two cells and drop a couple teeth on the pinion. You would get similar speed, more power, longer runtimes and cooler batteries.