Howard

My Feedback: (55)

Krysta/Bax,

I was recently asked by a fellow flying buddy for some assistance in selecting new servos for his next plane. We discussed a broad number of potential candidates and he seems to have settled on the Futaba brand. When he did his research on each candidate he discovered information that seemed to question the use of either Nimh or Lipo batteries with the servos. Sure enough when I looked into the information provided on the Futaba website and the Tower website I found the following:

Quoted from both the Futaba and Tower websites

S3305
This is the Futaba S3305 High Torque, Metal Gear Servo. per Futaba this servo is approved for use with NiCd batteries ONLY!
This servo can produce high-current draw from your batteries.If using NiMH or LiPo batteries, make sure they are capable of delivering sufficient amps

S3010
This servo can produce high-current draw from your batteries. If using NiMH or LiPo batteries, make sure they are capable of delivering approximately 2A for each servo

S3004
This servo can produce high-current draw from your batteries. If using NiMH or LiPo batteries, make sure they are capable of delivering sufficient amps.

S3001
This servo can produce high-current draw from your batteries. If using NiMH or LiPo batteries, make sure they are capable of delivering sufficient amps.

There are a number of areas where I have issues with these statements but, my primary concern is why Futaba is calling into question the use of Nimh or Lipo batteries and in one case requiring the use of Nicd only. Some of the new Nimh batteries with low internal impedance are exceptional airborne packs and easily exceed many parameters available in Nicd batteries. Other than Lipo high voltage concerns I am not aware of other parameters that could be detremental to Futaba servos. If high voltage is a concern then I think it would be better to say that.

In any case I am posing this issue so that I can learn from it - your insights and knowlege are appreciated.

Thanks

Howard

Bax

My Feedback: (11)

The statements are there because many people have NiMH or LiPO battery packs that simply cannot deliver the current necessary to drive a number of the large servos. Therefore the caution. Would you have us not caution you about the fact that high-current draw can cause damage to NiMH or LiPO battery packs that are not able to handle the loads? NiCd battery packs are well-proven through decades of use to be able to provide high levels of current, provided they are of sufficient capacity to give you the duration you need, and that you use wiring of sufficient gauge to prevent voltage drop.

Howard

My Feedback: (55)

OK - I understand the motivation and agree with you that providing a caution to the potential buyer is beneficial. Where I might disagree, by way of example, would be that an S 3001 is is a high current draw servo as well as the others, and that there are many variations of Nicd airborn packs that fall into the same category as the Nimh packs that you mention - many people have Nicd packs not capable of delivering the current necesary to drive large servos. Based on your response I believe your customers would be better served if the caution read something like "be sure that your airborne battery pack is capable of providing the high current required by this servo" rather than unintentionally leaving the reader with the feeling that Nimh or Lipo batteries are suspect as compared to Nicd - becuase they are not.

I certainly applaud the motivation and intent however, the impact (I think) may be different than you intended. Just a thought. If you told me your attorney wrote the caution then I would really understand. Thanks for getting back to me so quickly, your presence and contributions make a very positive difference and lots of us appreciate it.

Howard

F22Mech

Does Futaba publish current draw on their servos? I could not find this on futaba's web site.

Bax

My Feedback: (11)

That information isn't published.