# Info on Skyline 30 speed controller

• posted

I have a Skyline 30 (30 amp) speed controller, which is mfg by SJ PRopo. According to the info sheets supplied with this controller it has a low battery cutoff, and is suitable for an input voltage of 5 to

10 cells (their phrasing, not mine).

As I am thinking of using LiPo batteries - 2 or 3 cells - I need to know whether this controller is suitable

As I can see no way of changing the low batt cutoff I guess it must somehow set itself by sensing the input voltage, but....

The LHS can't help, and the SJPropo site is in Japanese, but anyway I couldn't find that model listed on their site - but perhaps it was, but in Japanese.

Any information or ideas greatly appreciated

David

• posted

| I have a Skyline 30 (30 amp) speed controller, which is mfg by SJ | PRopo. According to the info sheets supplied with this controller it | has a low battery cutoff, and is suitable for an input voltage of 5 to | 10 cells (their phrasing, not mine).

And it's a pretty common phrasing. It refers to NiCd/NiMH cells.

| As I am thinking of using LiPo batteries - 2 or 3 cells - I need to know | whether this controller is suitable

Well, work out the voltages.

5 cells = 5 * 1.4 volts = 7 volts. 10 cells = 14 volts. 2 Lipo cells = 2 * 4.2 = 8.4 volts 3 Lipo cells = = 12.6 volts

Since 8.4 and 12.6 volts are both between 7 and 14 volts, this controller is sutiable.

| As I can see no way of changing the low batt cutoff I guess it must | somehow set itself by sensing the input voltage, but....

... however, the low voltage cutoff may not be appropriate.

If there's really no way of changing it, the odds are good that it's not changable (profound, huh?) and so it'll probably be fixed at 6 volts or so. Which is too low for 3 LiPos but ok for 2 LiPos.

I've found that the low voltage cutoff is not that important, even for my planes with Lipos. When you start getting down to 3 volts/cell, the power drops off _a lot_ (power is porportional to voltage squared, so at 4.2 volts you get almost twice the power that you do at three volts.) If you pay attention to your plane, and land when you start losing power, you're almost certain to land before you get the cells below 3 volts/cell which is the point where you start doing damage.

But sorry, I can't give you a definitive answer on the cutoff question.

| The LHS can't help, and the SJPropo site is in Japanese, but anyway I | couldn't find that model listed on their site - but perhaps it was, but | in Japanese.

is snipped-for-privacy@prumail.co.kr ... so maybe it's actually Korean? Either way, I don't speak it. :)

Perhaps this URL will help --

http://216.239.39.104/translate_c?hl=en&u=

though it's amazing just _how_ bad the translation is. It looks like it's trying to be haiku or something :)

• posted

Thanks for the reply and info Doug.

Whoops of course the site was in Korean, not Japanese - I must be gettin old

It is only the cutoff point that concerned me. I figured that the controller must make some assumptions about the supply, and would assume that the cutoff point would be related to the number of cells - and if they were Nicad etc it might work on cutoff at 1.0v per cell - ie 5v for an input of 7 volts (5 cells)

By that reasoning it would assume that a 2cell lipo = 6 Nicads (6*1.4=8.4) and as you guessed? would cutoff at 6.0v

I tried a few translaters - NBG - a typical result was...

ccel Chass ccel ccayng ccalp Chass it is salty and the SKYLINE 30 (Chass the salty flag Mat) to be salty other ccel ccalp Chass it is salty, \$\$ln ccyang Chass it is salty Chass (the Size: 40 kb

Not sure about having a salty controller in my plane....

I might see if I can get a variable power supply and actually measure the point where the motor? cuts out, and also where the whole thing cuts out

Anyway, thanks again

David

Doug McLaren wrote:

• posted

| Whoops of course the site was in Korean, not Japanese - I must be | gettin old

Well, I don't speak either, so ...

| It is only the cutoff point that concerned me. I figured that the | controller must make some assumptions about the supply, and would assume | that the cutoff point would be related to the number of cells - and if | they were Nicad etc it might work on cutoff at 1.0v per | cell - ie 5v for an input of 7 volts (5 cells)

The controller doesn't know the number of cells. It only knows the voltage, though some OF THE VERY NEWEST ONES can guess at the number of cells from that and set the cutoff appropriately.

The motor cutoff has been around a lot longer than LiPos have. The initial purpose was to shut off your motor before your battery went so dead that your BEC couldn't even power your receiver and servos anymore.

Most older ESCs intended for NiCds or NiMH cells have the cutoff fixed at 5-6 volts, and you can't change it -- there was no real need to.

Helicopter ESCs generally don't seem to have motor cutoffs either -- after all, suddenly losing power in a helicopter is likely to cause a crash unless you're good at autorotations, are in a situation where one is possible, and your helicopter supports it. Better to risk ruining the battery. Some do have a light that comes on when it's time to land, however.

| By that reasoning it would assume that a 2cell lipo = 6 Nicads | (6*1.4=8.4) and as you guessed? would cutoff at 6.0v

Note that 1.4 v and 4.2 v are maximum voltages, not nominal or average. People usually use the figures 1.2 v and 3.6 v instead, but in this case calculating with the maximums made more sense.

| I tried a few translaters - NBG - a typical result was... | | ccel Chass ccel ccayng ccalp Chass it is salty and the SKYLINE 30 | (Chass the salty flag Mat) to be salty other ccel ccalp Chass it is | salty, \$\$ln ccyang Chass it is salty Chass (the Size: 40 kb | | Not sure about having a salty controller in my plane....

Heh. | I might see if I can get a variable power supply and actually | measure the point where the motor? cuts out, and also where the | whole thing cuts out

I wouldn't bother. It's pretty certain that it's around 5-6 volts -- the translation didn't seem to say anything about an adjustable cutoff.

Like I said, it'll work OK for your Lipos, but you'll have to just land when you start losing power if using the 3 cell packs. It'll be quite noticable as long as this isn't a plane that you like to `speck out' on a regular basis.

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