Electric RC Jets Discuss rc electric ducted fan or radio control prop jets here.

Hot battery

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Old 10-20-2012, 06:48 AM
  #1
xcz5785
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Default Hot battery

Running up my new jet (Concept X) on full power on the ground for two min. the battery gets really hot (coffe mug hot). ESC is above room temp. It has a 40a ESC and 1300 mah 3s 25c lipo. I did cut a vent in the nose that lets air run through the battery compartment and out the tail. When it's running it does suck air through there quite well. Are the C's too low possibly? Is it just not getting enough air on the ground and will cool off more in the air.
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Old 10-22-2012, 06:24 AM
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Bill G
 
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Default RE: Hot battery

While cooler is better, a good lipo should be able to withstand a bit of heat. If you can hold onto the lipo for any length of time, it is below the 140F borderline. At 140F, you can't hold onto it for more than a second, if that.
Air cooling is overrated in two ways: First, an EDF flight is likely near it's end, before good ventilation starts to make a significant difference in battery temp. It's not as if the flight goes 10-15 minutes, where you could actually reach a steady state condition. Second, the inner cells don't cool well, whether vented or not. The physical size and IR of the batt will mostly determine how well it can deliver power and not heat up. The battery is probably just too small for the job. I was heavily into smaller jets at one time, and found mostly all the smaller batts in the 1300 and smaller range to be overrated. At the time, the TP 3s-1320 was the only one that would actually fly some of my jets, such as a 50mm AR234 and 40mm ME262 twin. I still question if there are any true 25C 1300mAh lipos, that aren't simply larger lipos that are derated, to have a good C rating at 1300mAh.
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Old 10-22-2012, 06:26 AM
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Default RE: Hot battery

How many amps are you pulling from battery?

Without basic info is hard to tell.

You can nowdays get a wattmeter very cheap, a esencial tool for eletrics.

I think your batterry is to small in capacity, and you have a high amp draw. You won't know until you measure the amps.

Solutions
Increase capacity
Increase c rating of battery
Both of the above.




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Old 10-22-2012, 08:32 AM
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Default RE: Hot battery

Too small capacity and/ or C rating on the battery for the application.
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Old 10-22-2012, 10:34 AM
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Default RE: Hot battery

Thanks! I am just learning about electrics. I thought it might be too small a C rating. That was the suggested minimum. I'll try a 30-40C. I do need to get a meter. 1300 is about all the battery compartment will take without mods. It's shoved back as far as it can go to balance the plane.
What is the balance between watts and amps, that's what I don't get. Do you want as much as you can on both? Or low? I need a Lipo/fan/Motor, ESC for dummies book!
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Old 11-03-2012, 04:38 PM
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Default RE: Hot battery

Watts = volts x amps... obviously you want as many watts as you can get, safely..........as far as limits go, you need to make sure your amp draw does not exceed the rated limits for battery, ESC or motor.... since you are using a certain voltage (3s), watts take care of themselves as long as amp limits aren't exceeded.

Since, per usual, Nitroplanes is selling a model with no information about the motor they use (weight, Io, Rm, max. amps etc... I did see in one ad that it is a 2604-3000 whatever that is) you are somewhat in the dark... but since THEY suggest 4s, and you are running 3s, your amp draw should be nowhere near the limit for ESC or motor.. but your pack is probably good for only 26A at best... so you might be too near that for comfort.
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Old 11-13-2012, 07:02 AM
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Default RE: Hot battery

Why are you running at full power for two minutes on the ground? I never run full power for more than 10-15 seconds if that. And thats with the aircraft in the air and well broken in batteries. If your cells are below 3.7 volts at rest after a normal flight you are pushing to hard, flight is to long or you need more capacity. The majority of heat is generated at the end of batts capacity. But you should never get there. You want to use a max of 80-85% of mah leaving 20%. never run till low voltage cutoff.
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Old 11-13-2012, 07:13 AM
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Default RE: Hot battery

Im an electric and EDF nube. I was running it to see if it would get hot, it did. After running it in the air it was normal temp. Nube mistake. I now run it with 40c. I know better now.
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Old 11-13-2012, 07:40 AM
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Default RE: Hot battery

Keep an eye on those batts if you pushed them to the brink. Good luck......Doug
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