Gregor32

My Feedback: (1)

i just bought ds8411 and ds8231 servos and there is no specifications for 6v only 4.8v ,
are these servos going to be ok with 6v (5cell pack) or do i have to use a 4cell pack?
thanks greg

Shok

My Feedback: (28)

I run mine on 6v

schroedm

My Feedback: (1)

Greg,

These servos are fine on 6v. However, do not confuse 6v with a 5 cell pack. A 5 cell pack hot off the charger can often shown over 7v for a few minutes. It is because of the possibility of damage being caused by this scenario that JR no longer quote specs at 6v. In the UK they come with a note to say only use with a 4.8v pack.

If you use a 5cell pack it is probably best to run through a 5.9 or 6v regulator to both protect the servo and ensure you servos see a constant voltage through the flight.

Rgds,
Mark
UK Comp-ARF Rep
www.composite-arf.co.uk

ddennison

My Feedback: (15)

FWIW - I have been running 8411 and 8611 and As on 5 cell NiMH for three years. NO PROBLEMS. My voltage off the charger is 7.0-7.1, drops to 6.8-6.9 in a few minutes but no jitters even at 7.0.
These are all on 40% Cardens.only servo problem I have had is a stripped gear.
DD

trioval00

My Feedback: (17)

I use the same set servos as DD in all my jets with NO problems. I run 2 - 6.0 volt pack useing Electro Dynamics battery backer system. after full charge I am at or near 7.0 for a very short time, and never a problem.

Mark

Gregor32

My Feedback: (1)

thanks to all for your input. it would seem that it is not recomended to use 5cell packs but people are doing it and getting away with it , what would be the simplest regulated batt set up?
thanks greg

trioval00

My Feedback: (17)

for 5 cells, you do NOT need a regulator. it's not that we are getting away with it. it is a common practice among alot of pilots. I have used the 5 cell 6.volt packs for years and never once did I have a problem.

Mark

amjflyer

There are two ways of looking at this. Why run with a 5-cell pack anyway? To get more power or speed out of the servo? Theres probably not much point as the 4.8v torque/speed is so good these days there is little point in theoretically overdriving the servo with 6v+, after all they are designed to run at the nominal 4.8v+ a little. If its for redundancy (ie if one cell quits/reverses, or if you inadvertenetly over discharge the pack) then your better off with a power bus management system that can drive the radio gear with two packs regulated to 5v. Most often people are running two 5-cell packs as the power bus or regulator chops off a few volts from the output through regulation so to maintain 5v you must use a 5-cell pack. Otherwise 2 x 4.8v packs would be fine.

However, in my experience its the receiver (esp JR) that is sensistive to overvoltage not the servos. Most bus power management systems provide isolated and regulated receiver voltage at the optimal 5v. The only other instance ive heard of is heli pilots with tail rotor servos (being fed fast feedback by the gyro). At 6v+ they simply end up overdriving the servo due to oversensitiity casued by the increase in voltage resulting in a kind of amplfiied feedback oscillation setup between gyro and digi tail rotor servo.

Of course the other issue is you may void your warrantee by running it at 6v, esp. in the uk where the servos are distributed with a note not to do so.

Kevin Greene

My Feedback: (85)

JR DOES reommend their servos for use with a 6 volt pack---Just go to the Horizon Hobby web site to see for yourselves...Why use a six volt pack??? It's easy to understand when you see the specs of the JR 8611 jump from 260 in ounces of torque on a 4.8 volt pack to 320 with a 6 volt pack---Not to mention the speed increase!!! Just use a 6 volt regulator!!! Any time you use a higher voltage battery pack the current use goes up subtantially---You must use a pack with a lot of mAh reserve.

Don't just stick a six volt pack in for the sake of it---Do some research as to what happens to the power #'s when you use a 6 volt pack.....Use the proper sized pack.....And use a regulator!!!!

I use 6 volt packs exclusively...

Kevin

Shok

My Feedback: (28)

I plug 2, 6v nimh packs direct to my JR rx, no regulator.

Never had any sort of a problem.


I use 6v packs because my Artes Falcon requires 6v to the ecu, plus I get gains in servo torque

Kevin Greene

My Feedback: (85)

Something that needs to be re-addressed is that JR lists that it is OK to run their equipment on 6 volts---Not a six volt pack--If you run an unregulated six volt pack I've seen them come hot off of a charger at OVER 7 volts...Just my .02---

Kevin

jason

My Feedback: (1)

I run 4 cell nicads on all my set ups without any problem. When my 4 cell packs come off charge I'm looking for some where between 6.15 and 6.34 volts, if there not peaking at this then I look for a problem.

Another point with 5 cell packs is that they actually discharge quicker than a 4 cell pack on the same set-up. Don't ask my why but they do.

Jason

Woketman

My Feedback: (6)

I am not an electrical guy by any means. But I think the reason that its OK with > 7 volts off of a charge is because that is at about zero load, so no significant power is being expended. Once you draw just about any current, the voltage dips and you are lower than 7 volts. Then, of course, soon the battery is no longer hot off the charger and you are < 7. I use 2 5 cell packs with the MPX 7 channel receiver. The built in isolation circuit has some losses, so I am always < 7.

amjflyer

5-cell packs discharge quicker than 4-cell packs due to ohms law, amongst others. You dont get anything for nothing with electrics ultimately all must be in balance; current vs voltage vs pack mAh. So for arguments sake if your servo runs on 5v and produces 70oz of torque, or runs on 6v and produces 100oz of torque then it must be drawing more energy. Some of that energy comes from the extra 1v, but the rest comes from the fact that if you run an electric motor (which a servo of course is) at a higher voltage with the same load it generally draws more current (the same happens in electric flight, same motor on same prop at higher volts will draw more current as the higher voltage produces increased rpm due to increased electromagnetic forces created in the windings of the motor [armature)). So back to the original point, a 4-cell 2000mAh pack producing 5v into a 2A load will last 1 hour, a 5-cell 2000mAh pack producing 6v into a 3A load will only last 40mins, unsurprisingly.

On the point about 'hot off the charge packs', this is a characteristic of NiMH and NiCd cells when charged and then discharged for the first time. They will produce about 0.2v/cell more than nominal (of 1.2v), . All cells have slightly different 'off the charge' and discharge curves at different currents due to various factors (internal resistance, chemistry etc). Interestingly if you take for fresh of the charge pack and put a 1A+ load on it for a minute or two you will find that afterwards when used in the model it will be back to nominal voltage )) The voltage peak only effects the first discharge cycle, after that the chemistry changes subtly and the pack is back to nominal voltage (or thereabouts). In electric gliding competition (eslot etc) we use this property to effect.

siclick33

I had twin 5 cell packs in my Kangaroo. I was worried about all this talk (and the warnings suplied with the servo in the UK) about servo damage and did not want to use regulators so I took the 5 cell packs out and replaced them with 4 cell packs. I was a little worried about this due to the long(ish) servo leads but a quick check of the voltage at the end of the extensions showed that there was very little voltage drop in the leads.

Having flown the model again I cannot tell any difference in the flying characteristics between the two packs. Also, I was suprised at just how much capacity was used per flight on 4 cells (about 0.4 Amps on a 8 minute flight); as others have mentioned 5 cells would be even worse.

rcpete347

My Feedback: (251)

HI all, I"d like to know who these super pilots are that require the maxim power out of a servo for jets. Most jet control surfaces hardly move any way.
For Jets, I like to use the KISS theory, keep it simple, a large 4.8 pack, replaced every 2 years.
Most 10 minute flights consume about 300 mah.
Just my 2 cents worth.
Rcpete

amjflyer

Since some seem not to have seen the advice (or condition of use?) given in the UK ill provide a link. For the UK Macgregor is the main JR distributor. This is a link to a note on the 8417 servo which contains a general notice advising JR servos are not run on 6v. Ill let you come to your own view as to whether Macgregor makes any sense or not with this stipulation on their use.

http://www.macgregor.co.uk/faq/Servos/DS8417.htm

Doug Cronkhite

My Feedback: (34)

8411 and 8611's work just fine on a 5 cell pack. I actually ran my rudder servos on my Ultimate using an UNREGULATED Duralite Pro 8.4v pack as a test with no problems.

8417's should not be run on 6v as the motors just won't take it well. The 8417 is fast enough on 4.8v.

amjflyer

I wasnt actually drawing attention to the 8417 but the general JR note in that FAQ which says:

"Please note that JR servos should be used with 4 cell (4.8 volt) NiCad batteries only. 5 cell NiCads MUST NOT be used."

But I quite agree and know form my own experience that JR servos actually do run ok on 5 cells, as do Futaba, but Futaba do not issue such an instruction on pack used.

HarryC

My Feedback: (1)

This is another example of Macgregor's bizarre stipulations, like them sticking a label over the Saito instructions saying that castor must be used, when saito who probably know more than macgregor say castor must not be used.

Anyway, the official JR catalogue lists several 5 cell rx nicads, and states the speed and torque ratings for servos with both 4 and 5 cell packs where appropriate, or just with 4 cell packs for those servos not rated for 5 cells. Macgregors think they know better than JR and tell you that you can't use any JR rx and servos with batteries that JR list in their own catalogue! I know which one I believe.

Like JR, Futaba is specific about which servos are rated for 4 cell only or for both 4 and 5 cell. The Ripmax site tells you which servos are both, and which are 4 cell only
http://www.ripmax.com/catalogue.asp?page=268

Harry

amjflyer

Well i quite agree with that, running four strokes with castor, a perfect way to turn a lovely engine into a sticky brown mess...

Kevin Greene

My Feedback: (85)

Jeez Pete---Some of your posts lately are---Well---Hot off of the charger if ya know what I mean!!!...Someone been pissin' in your Wheaties again????

For me---Running a six volt pack depends upon the aircraft and my needs---Not due to being a super pilot... As far as control movements are concerned---Have you flown a EuroSport or a Rookie II lately????
Kevin