Originally Posted by Johnnyspeed

Mike Mayberry, maybe you could chime in here, I think a lot of us myself included are going for the lighter weight option of running one servo vs two and the lightest option is the powersafe receivers with the 7950's, if you are having a problem with this combination could you let us know. I have 8 7950's and a couple power safe receivers on hold at my LHS for over a month now at least show us some courtesy and let us know if you are looking into this so that I can weigh my options.
Thanks
Johnny V.

I agree although Hitec is not responsible for other manufacturers compatibility a lot of guys are considering the power safe receiver with the Hitec HV's. It would be good to know if an issue exists.

I'm putting together a 42% Dalton and purchased 8 - 7950TH servos for it.
I called Hitec about this issue last week and was told by the Tech that the issue was most likely due to using
Li-Ion batteries. He even used the FROMECO brand name and I use FROMECO batteries. He said Li-Ions do not output enough like a NI-Cad or Li-Po batteries do. He said the 7950TH requires a lot of juice. Does this make sense to the battery guru's.

Below was copies from Hitec web site:
"Hitec's strongest servo period, the "Ultra Torque" HS-7950TH is designed to operate on a two cell LiPo Pack."
http://www.hitecrcd.com/servos/show?name=HS-7950TH

I'm not an expert in electronics or batteries but I was always under the impression that Li-Ions output more then Ni-Cad.

So the folks who were have the issue, what batteries are you using?

r/clm
I am often wrong when I was sure I was right

Originally Posted by clm

I'm putting together a 42% Dalton and purchased 8 - 7950TH servos for it.
I called Hitec about this issue last week and was told by the Tech that the issue was most likely due to using
Li-Ion batteries. He even used the FROMECO brand name and I use FROMECO batteries. He said Li-Ions do not output enough like a NI-Cad or Li-Po batteries do. He said the 7950TH requires a lot of juice. Does this make sense to the battery guru's.

Below was copies from Hitec web site:
"Hitec's strongest servo period, the "Ultra Torque" HS-7950TH is designed to operate on a two cell LiPo Pack."
http://www.hitecrcd.com/servos/show?name=HS-7950TH

I'm not an expert in electronics or batteries but I was always under the impression that Li-Ions output more then Ni-Cad.

So the folks who were have the issue, what batteries are you using?

r/clm
I am often wrong when I was sure I was right

I would tend to agree with the point that multiple HV servos can outstrip the capability of a li-ion battery to keep up. A 2 cell li-ion can put out about 4 amps continuously which multiple HV servos can exceed easily.

2600 mah

Specifications and Requirements

Application
Charging Specs

Chemistry TypeLithium Ion or Lithium PolymerMax Charge Rate2.6Number of Cells2
Connector Specs
Connector Max "RATED" Amperage3ampsConnector TypeJR
Electrical Specs
Max Amperage4Max Voltage8.4Operating Voltage7.4

5200mah
Specifications and Requirements
Application
Charging Specs
Chemistry TypeLithium Ion or Lithium PolymerMax Charge Rate5.2Number of Cells4
Connector Specs
Connector Max "RATED" Amperage3Connector TypeJR
Electrical Specs
Max Amperage8Max Voltage8.4Operating Voltage7.4

unless you go with the 5200 there isnt much rated amp output

Originally Posted by crash-n-burn

I would tend to agree with the point that multiple HV servos can outstrip the capability of a li-ion battery to keep up. A 2 cell li-ion can put out about 4 amps continuously which multiple HV servos can exceed easily.

Tex is flying his Dalton with 8 8711HV and a 8717HV on the throttle and choke. With Fromeco 5200 li-ion batteries. I will be using their li-polymer in mine. They can handle the amps.

Originally Posted by crash-n-burn

I would tend to agree with the point that multiple HV servos can outstrip the capability of a li-ion battery to keep up. A 2 cell li-ion can put out about 4 amps continuously which multiple HV servos can exceed easily.

This is exactly why I have switched everything over to A123's,,, 60amp continious rating,, of course you would melt wires and such,, but the pack can take it,, just face it Lithiums are old technology since A123's have came out,, especially on recievers,, no regs, less weight, cheaper,, won't burn your house down, etc,etc,,

I'll drink to that!

Guys, I had a similar issue also with my 7950s running 2S 20C lipo x 2 with the Spektrum AR9100 receiver.

on 2S lipo, it glitches like mad on the ailerons. But if I hook up the wing to the tail extension, 5 ft away, the glitching stopped. So I tried a partially charged 2S LiFe, and all glitching STOPPED. So going to LiFe with the lower voltage helps.

I find, through the help of a friend, that if you increase your deadband to 3 instead of 1, the twitching goes away. The reasoning is that the deadband is influenced by the speed of the motor, which in turn, is influenced by the voltage.

I do have two out of the 8 servos that I will need to turn back to Hitec since they glitch at all setting. It's likely the same problem that Karl had with his 7950

Originally Posted by BoneDoc

Guys, I had a similar issue also with my 7950s running 2S 20C lipo x 2 with the Spektrum AR9100 receiver.

on 2S lipo, it glitches like mad on the ailerons. But if I hook up the wing to the tail extension, 5 ft away, the glitching stopped. So I tried a partially charged 2S LiFe, and all glitching STOPPED. So going to LiFe with the lower voltage helps.

I find, through the help of a friend, that if you increase your deadband to 3 instead of 1, the twitching goes away. The reasoning is that the deadband is influenced by the speed of the motor, which in turn, is influenced by the voltage.

I do have two out of the 8 servos that I will need to turn back to Hitec since they glitch at all setting. It's likely the same problem that Karl had with his 7950

Thanks for posting your results, I am going to set my deadband to 3 on mine then reprogram them for the rudder of my 35%. I will also hook up an ampmeter to test the draw on each servo.

Originally Posted by khedge

Thanks for posting your results, I am going to set my deadband to 3 on mine then reprogram them for the rudder of my 35%. I will also hook up an ampmeter to test the draw on each servo.

That would be interesting. Let us know the results when you find out.

Originally Posted by rcgood

That would be interesting. Let us know the results when you find out.

Will do

I emailed FROMECO asking about their batteries amp draw.

Question asked:
What is the Amp rating of the 2600 and the 5200 li-Ion? I would like to use 8 of the new Hitec 7950TH high volt (7.4v) servos in a 42% plane and want to ensure the batteries have enough through put.


Reply:
Hello Curt,

The manufactured amperage rating for our cells is 4 amps. This is for 24/7 365 use on applications such as Lap Tops and the like. This is what we post. Please understand the harshness of Lap Top service is severe; unknown temps, cycles, vibration etc. Samsung our cell manufacture has to be very conservative in their ratings, they must account for harsh conditions. De-rating them creates scenario where the batteries have a better chance of survival since they are not running balls out.

We have our own lab, our ratings “not posted” is 11.5 amps per cell. This rating is repeatable 100% of the time, they can actually go slightly higher, however manufacturing tolerances start to play a roll. As a group we take much better care of our batteries than the “majority” with lap tops do. One of the other factors that play a roll in this rating is Voltage. @ 11.5 amps on a 2600 and 23 on a 5200 your constant voltage will be 6.2 volts.

So to answer your question, we comfortably rate our cells “via phone and e-mail correspondence”, at 11.5amps for a 2600 and 23amps for a 5200. I can tell you that dual 5200’s on your 42% will work just fine with the set up that you are looking to use. We already have pilots flying that configuration.

Hope this is what you were looking for.

Kurt Cook
Fromeco Scale Avionics LLC
www.fromeco.org
kurt@fromeco.org
503.715.0020


I'm not an electronic guru or a battery expert by any means but this is looking more and more like the 7950TH issue is not the amp draw like Hitec is indicating but a voltage issue as others have indicated.

r/Curt Myers

Originally Posted by clm

I emailed FROMECO asking about their batteries amp draw.

Question asked:
What is the Amp rating of the 2600 and the 5200 li-Ion? I would like to use 8 of the new Hitec 7950TH high volt (7.4v) servos in a 42% plane and want to ensure the batteries have enough through put.


Reply:
Hello Curt,

The manufactured amperage rating for our cells is 4 amps. This is for 24/7 365 use on applications such as Lap Tops and the like. This is what we post. Please understand the harshness of Lap Top service is severe; unknown temps, cycles, vibration etc. Samsung our cell manufacture has to be very conservative in their ratings, they must account for harsh conditions. De-rating them creates scenario where the batteries have a better chance of survival since they are not running balls out.

We have our own lab, our ratings “not posted” is 11.5 amps per cell. This rating is repeatable 100% of the time, they can actually go slightly higher, however manufacturing tolerances start to play a roll. As a group we take much better care of our batteries than the “majority” with lap tops do. One of the other factors that play a roll in this rating is Voltage. @ 11.5 amps on a 2600 and 23 on a 5200 your constant voltage will be 6.2 volts.

So to answer your question, we comfortably rate our cells “via phone and e-mail correspondence”, at 11.5amps for a 2600 and 23amps for a 5200. I can tell you that dual 5200’s on your 42% will work just fine with the set up that you are looking to use. We already have pilots flying that configuration.

Hope this is what you were looking for.

Kurt Cook
Gases Engineering
Microchip Technologies


I'm not an electronic guru or a battery expert by any means but this is looking more and more like the 7950TH issue is not the amp draw like Hitec is indicating but a voltage issue as others have indicated.

r/Curt Myers

Gotta love fromeco there number 1 for a reason

Originally Posted by clm

I'm not an electronic guru or a battery expert by any means but this is looking more and more like the 7950TH issue is not the amp draw like Hitec is indicating but a voltage issue as others have indicated.

As you already figured the glitching occurs on the ground just wiggeling the sticks it's pretty obvious that it isn't an amp draw issue.

Originally Posted by crash-n-burn

Hitec is not responsible for other manufacturers compatibility

I have not read the instructions for the servos, maybe they say that the servos are only compatable with Hitec Rx's. If so you are right.