Laminator

Hi @ll,

I have just bougt a couple of digital HiTec servos.
I want to use them on my Aeroworks extra 300l.
A friend of mine told me that these servos are not made for a 5 cell nicad pack.

Does anybody use theese servos with 5cells?
Are there any problems?

edge_fanatic

My Feedback: (4)

This page shows a 6.0V torque and speed rating, thus providing support for a 5 cell pack being fine here.


http://www.servocity.com/Products/Hi..._coreless.html

visioneer_one

My Feedback: (506)

6 volts is OK.

They don't like the 7+ volts that a freshly-charged 5-cell pack puts out, though. Most digital servos are that way.

Use a regulator and you'll have no problems.

Gary Retterbush

Most companies mean 6.0V as in 4 X 1.5V cells; not 5 Nicads.

edge_fanatic

My Feedback: (4)

If companies mean 6.0= 4 X 1.5 v cells, then they must also not be referring to a 4 cell nicad system either, when they provide 4.8v numbers, since the charged voltage for a 4-cell nicad system is rarely as low as 4.8v.

It wouldn't make sense not to be consistent. I think they really mean that the 5 nicad systems should be used with a regulator. Or perhaps, they are using the "minimum" voltage for such nicad systems.

I've often wondered whether the companies that produce the numbers are doing anything that is actually used in the industry. what caused you to form the conclusion that the companies are talking about dry cells rather than nicads?

Just curious.

Gary Retterbush

Reading their catalogs.

edge_fanatic

My Feedback: (4)

I have a hitec catalog, and don't see the info. Please provide a direct quote.

Their sales rep says it is okay to use a 5-cell nicad pack without a regulator.

Thanks!

Gary Retterbush

I did NOT say Hitec did or did not, I spoke in general terms and still do.

However, I quote from the Graupner catalog:
"4.8V = 4 NC Cells, 6V = 4 drycell batteries 1.5V"

As far as I know, Multiplex is the only one that clearly says yes or no to 5 NC cells for each of their servos. They publish specs for 4 cells and 5 cells.

It would be nice if others who officially approve 5 NC cells would so state in black and white.

BTW, I see you posted a direct question to Mike about this subject on the subforum and that there is no answer as of yet.

Have a nice day,
Gary

mglavin

My Feedback: (31)

4 NiCad cells @ 1.2v = 4.8v

4 dry cells such alkalines @ 1.5v = 6.0v

5 NiCad cells @1.2v = 6.0v

Problem is most cells less the dry cells deliver more than the rated capacity for a short time, more so when the come directly from the charger. Some equipment just plain does not like the elevated voltage which is often over 7.0v.

It's generally accepted practice to use the five cell packs without benefit of a regulator, however some equipment for whatever reason reacts adversely to the higher voltage.

The Hitec's work fine on Duralites which are rated at 6.0v plus and all other 5-cell batteries that I am aware of. I've been doing this for years without regulator's.

Gary Retterbush

Mike, I'm fully aware of everything you stated. The point really is that not many companies CLEARLY state their official position on using 5 full charged NC's.

I frequently use 5 cells and have never had a problem but that does not mean the company approved it.

The present day battery/voltage specs for servos seem to go back to the middle ages and have never been updated. The 6V was orginally there to officially okay using 4 X drycell 1.5V which in the early days was done a lot.

edge_fanatic

My Feedback: (4)

Thanks for the response...I realize you didn't specify hitec, and I assumed it, because the original poster directed the question to a particular Hitec servo, and I thought you were responding to that question.

I feel that the manufacturers are the most reliable source of info about their products, and therefore posed the question both to Hitec and Futaba. Incidentally, Futaba responded last night (Sunday!) with respect to a particular servo of theirs (9252) and they said an unregulated 5-cell nicad pack would be fine with that servo.

Forgues Research

My Feedback: (7)

A fully charged NiCd is 1.33 volts/cell which would be 6.65 volts for 5 cells.
Right out of the charger, it will be even higher then this but only for a few minutes untill it stabilizes.

A 4 cell pack will be 5.32 volts and again a bit higher right out of the charger which will stabilize after a few minutes.

Gary Retterbush

You read the reply differently than I did. The reply said it was okay for unregulated 6 volts; not 5 cells. Now it could well be that I am wrong but I think you got an answer which beat around the bush about your question.

We all take 6 volts as being 5 cells but it isn't and that is the point of this discussion. Why can't the companies say yes or no to the question if 5 cells unregulated are approved for their servos.

BTW, I'm not trying to be a pain in the butt about this but since we got on the subject, let's get it straighten out for each company. MPX prints their stand very plainly with specs for both 4 and 5 cell packs. I wish the rest would be so kind as to do the same.

Laminator

Thats exactly the point.

The main problem is that the specifications for 6 V are really meant for 6V not for 5 cells!

I want to use the servos with a DPSI ( Dual Power Servo Interface )
I´m not sure if you guys have that system in the US but it is frequently used in bigger aircraft here in Europe.

You can find it on the internet www.flugschau.de/shop.html

A data sheet in english (pdf file is avaiable there too)

if you use a dpsi you have the full voltage available for the servos and a stabilized voltage of 5 V for the receiver.

So what i want to know is if there is anybody using the 5945 with 5 cells without a regulator?

does that work without any problems?

Gary Retterbush

Just for kicks I did a little test this evening (per cell):
Fresh off the charger = 1.42 V
After 15 minutes = 1.405 V
After 30 minutes = 1.3975 V
After 1 hour 15 minutes = 1.39 V

Got busy doing other things and gave up. I was a little surprised that it didn't drop more quickly. At this rate, a 5 cell pack is going to be way over 6 V for quite some time. Of course these are no load figures so with a few wiggles it will drop more quickly.

For what ever its worth....

edge_fanatic

My Feedback: (4)

I agree that the answer I received didn't address the specifics of my question. but I did say that I was using 5-nicad cells, and Ann Marie said I could do it (sort of...).

Mike of Hitec was direct, and told me that an unregulated system was acceptable with their 5945's. (So, I didn't spend all that money for nothing after all...hehe)

Forgues Research

My Feedback: (7)

Hmmmm... Interesting, I haven't tested for a while, maybe things have changed.
Thanks for the head's up on this.

Gary Retterbush

The type of answer Mike gave is the kind we should be getting; direct and to the point, period. Score one for Hitec.

I see that JR has also been asked, so we'll see what they have to say.

aerografixs, I was not questioning your data at all. I simply wanted to see how quickly the voltage dropped. As I said, I was surprised to find how slowly it was. Again, those figures were no load. Guess I should do it again but with a 100-200 ma load.

visioneer_one

My Feedback: (506)

Not necessarily.

The voltage per cell at the end of a peak-charge will vary depending on the capacity of that cell. AA/A-sized cells rated 1000 mAh or less will show a terminal voltage of ~1.35-1.4V; cells rated over that can show up to 1.47V. Those of you running 1700 mAh+ sub-c nicad cells in your flight packs can see terminal voltage spikes well over 1.6V!

These elevated voltage levels drop pretty quickly to the ~1.3V/cell nominal rate once the pack under load, and is unlikely to *instantly* smoke anything. (Unless you are unlucky enough to have a jammed servo. The amperage soars and *POOF* out comes the Magic Smoke.)

The components in your flight pack are only rated for so many volts and so many amps. Exceed those specifications for any period of time, and *something* will fatigue.

The short answer: gear run in an unregulated system will have a shorter life than gear run at lower voltages. Guaranteed.

Gary Retterbush

JR and Futaba joined Hitec and MPX with an okay for using 5 NiCd cells without a regulator. So, now we know officially that it is perfectly okay to use them. Nice to know that I've been "legal" all this time.

Edited:

Forgot to mention that the battery is 1.3475 volts. It is hanging right in there.