Renegade_2k

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Hello all..

I originally posted this in the Hitec radio support section of RCU.. possibly that was the wrong area?? Can anyone help me with this?

I recently purchased a SP-1801N (stock number 41801S) speed control with ESC from my LHS. I went to the Hitec website, but the only information I could find was a .pdf that turned out to be the instruction sheet included with the unit.

The instructions on the box are clear, as to the maximum number of cells the unit will handle (5 to 7), but the max pulsed current (720 A) and the continuous drain current (180 A) specs seem to be way above the specs for todays offerings. I understand some basic concepts of current, with respect to cell/motor/prop combinations, but I need a little guidance here.

My question is this. What is the maximum size motor I can use, and assuming a 7 cell pack, about what size (MAH) should the pack be for a reasonable flight time. I am unfamiliar with electric flight. I have been flying R/C for about 31 yrs, and I am interested in trying this. My goal is to utilize the speed control to its fullest, by using the largest motor it will accommodate, in (hopefully) a large aerobatic electric scratch built plane, maybe even a bipe!

Thank you in advance for your response.

Harry.

Matt Kirsch

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Yes, the Hitec radio support forum was not a good place to put this question. That forum is for issues directly relating to products and product support.

I'm sorry to break this to you, but the 1801N is a CAR speed control, not an airplane speed control. They rate car speed controls differently because cars and airplanes are very different in how they operate. In cars, there is a quick high-current burst as the car accelerates, then it coasts, using very little current. In airplanes, the current load is continuous.

If the shop owner sold it to you as an airplane speed control, get your money back and never do business with that shop again. Whoever sold you that speed control lied to you.

It can be used in an airplane, but it is not a good idea, as it is very limited in how many cells it can use, and has a reverse that can be disastrous for an airplane.

Airplanes need a certain amount of power to fly well, depending on the airplane. This is generally about 75 Watts per pound for sport planes. If you limit yourself to 7 cells, the amount of current required to make that power is very high, which means flight times will be very short, and the batteries will be very hot. Only very small park fliers use 6 or 7 cells, and your speed control is much too heavy for those.

Renegade_2k

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Hello..

Thank you for the answer. The box the control came in does however say it is for aircraft. The included instruction sheet also has the information on how to hook it up, and has separate information for cars, along with the model number for the car control. The Aircraft model is SP-1801 and the car version is SP-1802.

The information you gave me is very informative though. I have noticed that most of the aircraft controls are using more than 7 cells.. which is why I posted here. I just figured there was some secret that I wasn't finding, regarding a motor that used 7 large cells, and used them efficiently. Perhaps this is why Hitec discontinued this particular model of speed control. There is a link on Hitechs page for this model, but it is only to a .pdf file of the paper instruction sheet that came with the controller. The link is http://www.hitecrcd.com/Support/Manuals/Sp1801.pdf or here

I'm thinking that maybe the speed control was a car model, that was electronically re-worked, and the reverse taken out for aircraft use?? Perhaps for a glider, where it would be used intermittently? Who knows..

Thanks anyway for the other information. It really helped out with some other things I hadn't thought of. The information on the wattage required was especially helpful.

Harry.

sierra gold

Hi Harry,

I found your ESC listed at Hobby People. It is indeed an airplane ESC, but has very "unusual specifications" as you have mentioned. Hobby People show it as back-ordered which may mean it is no longer available from Hitec. I had never heard of it until your post here. The URL is:

http://www.hobbypeople.net/gallery/759851.asp

Steve Lewin

Car type ESCs have nasty habit of giving the current rating based on the total rating of the output devices i.e. the sort of thing that would only be true if they were on a huge heatsink in a really good airflow. It's normal to de-rate them by anything up to about 1/8th so I'd say that's about a 20-25A ESC. Since it appears to be developed from a car ESC it's almost certainly intended for car motors, roughly speaking Speed 600 sizes.

I'm afraid you're not going to fly a very large or aerobatic plane on 7 cells and 20A. It's probably possible to fly something around 36-42" span that's fairly aerobatic. If you use 3000mAh cells you should get a reasonable duration.

If you have a plane specification in mind you might want to start again from there and let the experts give you some ideas as to what equipment you would really need to achieve your ambitions.

Steve

Renegade_2k

My Feedback: (1)

Hello all..

I'd like to thank everyone for the posts, and information. Looks like this particular control wasn't quite the deal I thought it was... though it will work for something smaller than I had in mind.

Well, back to the drawing board! :tired:

Mhale71

wait, lol, i use the sp-1801n in my helicopter at 8 cells and its fine !!