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Author Topic: ESC amp ratings  (Read 1192 times)

Online Brent Williams

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ESC amp ratings
« on: October 22, 2018, 08:20:11 PM »
I am contemplating using a Castle Talon 35 amp ESC in place of a Castle Edge lite 50 amp ESC.  There is an ounce of weight difference between these ESC's.  The motor is a Cobra 2820 which when run with a 4 cell battery, can (or is rated to) pull a maximum of 40 amps continuous.  However, we aren't running these setups at full power continuously.  Obviously the load changes with different maneuvers.  Using the APC 11x5.5 prop, I would anticipate a flight RPM of around 9500rpm, which is less than 70% of the full throttle RPM capability of the 970KV motor on a 4s battery.  (14.8v x 970kv =14,356 rpm potential.)

Would I be courting disaster to run the 35amp ESC, or would it be totally adequate?

My newly converted e-Gieseke Nobler weighs 44.5oz with the ThunderPower 4S/2800 battery and Hubin FM9 timer.  A swap to the Talon 35 ESC would drop an ounce off the nose.  After I gather some flight data, I may be able to move to a smaller 4s/2200 battery.  With a lighter battery and ESC combo, there is the potential to save around 2 to 2.5oz.  To bring the RTF weight down to around 42oz (battery installed) would be ideal, as it was flying great at 39.5oz(dry) with a Brodak 40.


Talon 35 amp rating info:*RC HOBBY APPLICATION RATING: 35 amps for the duration of a single 4,000 mAh battery pack with the ESC in contact with a 5 mph airflow of 25C (77F) or cooler air. Controller temperature must never exceed 100C (212F). Exceeding current or temperature ratings may damage components and may shorten the life of the ESC. Always verify system current draw at full-throttle. Decrease load or increase airflow to decrease the ESC’s operating temperature.
« Last Edit: October 23, 2018, 03:52:25 AM by Brent Williams »
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Offline Fred Underwood

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Re: ESC amp ratings
« Reply #1 on: October 22, 2018, 09:25:43 PM »
Did you datalog on the Castle 50?  You can have a fairly accurate picture of your peaks.  You average draw is fairly well approximated by replacement amps of a flight, and time of flight.
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Online Brent Williams

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Re: ESC amp ratings
« Reply #2 on: October 22, 2018, 09:50:45 PM »
I haven't data logged, but I guess that's a good reason to start.  It's a new setup.  I have no flights or data yet.

Thanks for the info.
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Offline TDM

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Re: ESC amp ratings
« Reply #3 on: October 23, 2018, 08:29:03 AM »
Do yo own a watt power analyzer? if yes you can put the motor on a test stand bolt to a piece of plywood and run on bench and check the max Amp if is under 35A then go with it.
Simpler answer small Amp ESC burn the ESC high amp ESC burn motor. If you look at the chart you are in the red zone. Options lighter prop XOAR 11x6 11x5 they weigh nothing 15g that will release some stress from the motor instantly. Because lower rpm you might be bellow the 35A. Expect a hot running system.
Cobra 2820-12 Look at prop chart for 4S 11x5.5 22.1A on a APC XOAR 11x6 you probably break even in power consumption. 44.7/60 x 6min= 4470mA so you night get by with a 4S 5600mA battery. 
Cobra 2826-12 might be a better best match looking at Amps used at 4S with that prop. Look at prop chart for 4S 11x5.5 22.1A on a APC XOAR 11x6 you probably break even in power consumption. 22.2/60 x 6min= 2220mA so you night get by with a 4S 2800mA battery.  That looks like a super option.

https://www.ebay.com/itm/XOAR-PJM-E-11x6-RC-Electric-Model-Airplane-Propeller-11-Inch-2-Blade-Wood-Prop/161743420313?epid=1745048545&hash=item25a8a8bb99:g:2UYAAOSwKIpV~HIO:sc:ShippingMethodStandard!30144!US!-1:rk:6:pf:0
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Online Howard Rush

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Re: ESC amp ratings
« Reply #4 on: October 23, 2018, 06:10:43 PM »
Put an ammeter between the battery and ESC on the ground with the motor, prop, and throttle setting you would use.  That would show max current you'd experience. 
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Offline Dane Martin

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Re: ESC amp ratings
« Reply #5 on: October 23, 2018, 06:56:23 PM »
Brent, if you don't have a watt meter, I'll mail you mine to test with. I've sent it to a few people to help out, it's always returned safely!

Online Crist Rigotti

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Re: ESC amp ratings
« Reply #6 on: October 23, 2018, 10:39:44 PM »
Brett,
Do not use a 35A ESC on a 45 ounce airplane using a 4S battery.  You'll need a 45A ESC to be safe.
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Online Brent Williams

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Re: ESC amp ratings
« Reply #7 on: October 23, 2018, 11:48:24 PM »
Thanks for the good info and generous offer.  I don't want to be greedy and jeapordize the system in an overzealous search for weight savings.  It will be very interesting to measure the amps on the ground and see what it reads at full load.

I just placed my order for a HobbyKing HK-010 Wattmeter & Voltage Analyzer.  Picked one up for around $10 on eBay.  I needed something like this anyway to check the battery level post-flight.
 
https://hobbyking.com/en_us/hobbyking-hk-010-wattmeter-voltage-analyzer.html

Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
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Offline John Rist

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Re: ESC amp ratings
« Reply #8 on: October 24, 2018, 02:00:25 AM »
Thanks for the good info and generous offer.  I don't want to be greedy and jeapordize the system in an overzealous search for weight savings.  It will be very interesting to measure the amps on the ground and see what it reads at full load.

I just placed my order for a HobbyKing HK-010 Wattmeter & Voltage Analyzer.  Picked one up for around $10 on eBay.  I needed something like this anyway to check the battery level post-flight.
 
https://hobbyking.com/en_us/hobbyking-hk-010-wattmeter-voltage-analyzer.html


Thanks for the tip.  I just ordered one from eBay
John Rist
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