RCCrawler Forums

Ty · 10-04-2009, 08:39 PM

I just go my old RC10T running and don't want to buy a new battery for it. I ran my 3s 35C 1100 Hyperion in it for a few mins and the batt was warm. The truck has a 27 pro motor and a old Novak racer esc. I was looking at Maxamps site and they talk about the surge watts of the motor needing to be less than that of the batt. What would be the surge watts of my 27 turn motor? I would think if that Hyperion battery can run my Losi moa with Holmes HH 35t's it would run one 27 turn motor. I would like to use my current batteries if I can. Thanks for the help

Manning · 10-05-2009, 07:05 PM

That 27 turn motor will pull more amps than the 35. Quite a bit more. Depends on how fast it's geared, and if there is traction or not.

I'll go out on a limb and say it will be somewhere in the area of 40 amps, so 40 amps x 10 volts (under load) = 400 watts for the car during acceleration. That battery is rated for 35c, so 35 x 1100mA = 31800 mA or 31.8 amps....so 31.8 x 10 = 318 watts.

It'll be marginal at best.

clockworks · 10-06-2009, 12:43 AM

Solid info on the amp draw of motors is hard to find, so I can only offer advice from my own experience.
When I first started in RC, I ran a 14T motor in a 1/10 touring car. The ESC that I used (Speedmaster) had a 40amp blade fuse wired in-line with the battery positive wire.
In many hours of serious abuse, the fuse never blew.
A couple of the 27T motors that I've owned came with dyno printouts. IIRC, they were pulling around 90 watts on 6 cells, which is 12.5A. The startup or stall current will be significantly higher, maybe double.

Maybe someone should test various car/truck motors with a watt meter? I do this with all my electric planes, to check that the motor, battery and ESC aren't overloaded by the prop, and to make sure that I've got enough power to actually fly.
It's easy to run these tests on a plane, as the prop puts more load on the motor with the plane stationary than when it's flying.
With a car/truck, you'd have to drive it with the meter connected.

Manning · 10-06-2009, 05:13 AM

Just FYI, fuses don't blow at their rated current. It takes 50% or more over the rating to open "quickly".

So your car could have been pulling 60 amps momentarily, or 50 amps for many seconds, and not blow the fuse. A 40 amp fuse won't blow for a long time, if ever, while passing 45 amps.

A "stock" racing motor will pull lots of amps if there is traction.

Ty · 10-06-2009, 01:42 PM

Thanks for the info guys! I was looking in the Shortcoarse section and alot of those guys are running 20c 40 burst packs. I dont know if this is with brushed or brushless. Those packs are all around the 5000mah range. Thanks for the help

JohnRobHolmes · 10-06-2009, 01:51 PM

I would want at least 40a continous, but 60a or 80a would allow the pack to run cooler.

Ty · 10-06-2009, 05:11 PM

Cool I will see if I can find something to take care of that. Maybe it has no effect on the amps, but a 35c 5000 mah pack would work right? I am just going by the math that Manning did for me. Thanks again

JohnRobHolmes · 10-06-2009, 06:07 PM

Yep. ThAT should do it. I like to use a batt that can run continuously at the peak loads. So if the motor is geared for 80 amps burst I would run a 4000 mah 20c.

Ty · 10-06-2009, 07:44 PM

Thanks again for your help, Ty

10-04-2009, 08:39 PM	#1
Ty Quarry Creeper Join Date: Apr 2009 Location: Lincoln Posts: 371	surge watts I just go my old RC10T running and don't want to buy a new battery for it. I ran my 3s 35C 1100 Hyperion in it for a few mins and the batt was warm. The truck has a 27 pro motor and a old Novak racer esc. I was looking at Maxamps site and they talk about the surge watts of the motor needing to be less than that of the batt. What would be the surge watts of my 27 turn motor? I would think if that Hyperion battery can run my Losi moa with Holmes HH 35t's it would run one 27 turn motor. I would like to use my current batteries if I can. Thanks for the help

10-06-2009, 01:42 PM	#5
Ty Quarry Creeper Join Date: Apr 2009 Location: Lincoln Posts: 371	Thanks Thanks for the info guys! I was looking in the Shortcoarse section and alot of those guys are running 20c 40 burst packs. I dont know if this is with brushed or brushless. Those packs are all around the 5000mah range. Thanks for the help

10-06-2009, 05:11 PM	#7
Ty Quarry Creeper Join Date: Apr 2009 Location: Lincoln Posts: 371	Cool I will see if I can find something to take care of that. Maybe it has no effect on the amps, but a 35c 5000 mah pack would work right? I am just going by the math that Manning did for me. Thanks again Last edited by Ty; 10-06-2009 at 05:14 PM.

10-05-2009, 07:05 PM	#2
Manning RCC Addict Join Date: Nov 2006 Location: Lowell, Arkansas Posts: 1,307	That 27 turn motor will pull more amps than the 35. Quite a bit more. Depends on how fast it's geared, and if there is traction or not. I'll go out on a limb and say it will be somewhere in the area of 40 amps, so 40 amps x 10 volts (under load) = 400 watts for the car during acceleration. That battery is rated for 35c, so 35 x 1100mA = 31800 mA or 31.8 amps....so 31.8 x 10 = 318 watts. It'll be marginal at best.

10-06-2009, 12:43 AM	#3
clockworks Rock Crawler Join Date: Feb 2008 Location: UK Posts: 818	Solid info on the amp draw of motors is hard to find, so I can only offer advice from my own experience. When I first started in RC, I ran a 14T motor in a 1/10 touring car. The ESC that I used (Speedmaster) had a 40amp blade fuse wired in-line with the battery positive wire. In many hours of serious abuse, the fuse never blew. A couple of the 27T motors that I've owned came with dyno printouts. IIRC, they were pulling around 90 watts on 6 cells, which is 12.5A. The startup or stall current will be significantly higher, maybe double. Maybe someone should test various car/truck motors with a watt meter? I do this with all my electric planes, to check that the motor, battery and ESC aren't overloaded by the prop, and to make sure that I've got enough power to actually fly. It's easy to run these tests on a plane, as the prop puts more load on the motor with the plane stationary than when it's flying. With a car/truck, you'd have to drive it with the meter connected.

10-06-2009, 05:13 AM	#4
Manning RCC Addict Join Date: Nov 2006 Location: Lowell, Arkansas Posts: 1,307	Just FYI, fuses don't blow at their rated current. It takes 50% or more over the rating to open "quickly". So your car could have been pulling 60 amps momentarily, or 50 amps for many seconds, and not blow the fuse. A 40 amp fuse won't blow for a long time, if ever, while passing 45 amps. A "stock" racing motor will pull lots of amps if there is traction.

10-06-2009, 01:51 PM	#6
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	I would want at least 40a continous, but 60a or 80a would allow the pack to run cooler.

10-06-2009, 06:07 PM	#8
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	Yep. ThAT should do it. I like to use a batt that can run continuously at the peak loads. So if the motor is geared for 80 amps burst I would run a 4000 mah 20c.

10-06-2009, 07:44 PM	#9
Ty Quarry Creeper Join Date: Apr 2009 Location: Lincoln Posts: 371	Thanks again for your help, Ty

Sponsored Links

RCCrawler Forums

Thread: surge watts