4.8v Futaba Servos

[bert baker]

I have purchased plane and it’s got some old Futaba S9404 core less servos

It looks to me that they are only rated at 4.8v

It’s what I believe to be a mk1 pre built and covered one piece wing

Glens Cap 232,, it’s in extraordinarily good condition,,

It has been put together with all the carb bends and recommendations,

so does also have the SM Services Battery backer,,,

I have exercised the servos with my servo tester they seem ok,,,my dilemma is whether to go for 4.8 battery packs or go bigger and fit a inline regulator to the receiver

[bert baker]

In the manual for the plane Above 5kg servos was recommend.

the Futaba S9404 At 4.8 are 5.7kg

so they should be ok

[Paul Marsh]

If using Spektrum, have a 6v battery, wouldn't use a 4 cell battery on that. Maybe fit a regulator just for the servos, or use a separate battery for rx/servos.

[Former Member]

[This posting has been removed]

[Former Member]

[This posting has been removed]

[bert baker]

I plan to use a JR 921 receiver

Just been reading that the SM Services backer is for 5 cell packs,

now wondering if the servos have been ran at 6v, so now not sure if they are still safe to use.

Hmm, probably end up replacing them 

 

Edited By bert baker on 19/06/2020 16:42:44

[cymaz]

Have a look on servodatabase and see what what there is

[Engine Doctor]

Hi Bert . The Futaba servos will be fine at 6v . Use a decent battery that can handle the current draw as they do use quite a current compared to the standard Futaba servos .Similarly if you go for bigger battery with regulator , make sure it can give enough current and still keep your receiver happy  Only servos that I knew of that let the smoke out on 6v were the JR servos .

Edited By Engine Doctor on 19/06/2020 16:55:34

[Frank Skilbeck]

My vote would be to use a 4 cell sub C pack, Sub C cells seem to be better at maintaining voltage under load than high capacity AA cells.

[bert baker]

Posted by Frank Skilbeck on 19/06/2020 17:48:46:

My vote would be to use a 4 cell sub C pack, Sub C cells seem to be better at maintaining voltage under load than high capacity AA cells.

Hi many thanks but but the Battery Backer needs 5 cell input

And many thanks to all comments

[Engine Doctor]

Posted by bert baker on 19/06/2020 17:58:43:

Posted by Frank Skilbeck on 19/06/2020 17:48:46:

My vote would be to use a 4 cell sub C pack, Sub C cells seem to be better at maintaining voltage under load than high capacity AA cells.

Hi many thanks but but the Battery Backer needs 5 cell input

The S&M Services battery backer uses Schottky diodes to stop batteries balancing or discharging through one another . This drops the voltage slightly hence the need for a 5 cell pack. You can create your own by fitting two batteries with their own switch harness and a Schottky diode in each feed wire . It will take about 0.5 volt from the power .

[bert baker]

Cheers ED,

I have tested with a reciver and 5 cell 2200 pack,just to see if i got smoke,, I did not plug in the Backer at this stage,

All looks ok,,,, I think my next thing to do is to check voltage pre and post Backer.

I normally would just crack on and not worry, but I think age is becoming to be against me and turning into my Dad

I have noticed that the rudder servo has been moved to the back,

I will relocate the rudder servo where it should be,,, inside the fuz and reinstae the closed loop

[Phil Green]

Posted by Engine Doctor on 20/06/2020 11:12:41:

The S&M Services battery backer uses Schottky diodes...

Really? thats poor design. Powerfets in an ideal-diode configuration would give a higher current capacity and no voltage drop

Cheers
Phil

[Peter Christy]

I've been using Spektrum receivers since they first came out. Although I've now moved away from Spektrum, I still have a few models with Spektrum receivers on board, including one large, petrol powered scale helicopter.

I have never run them on anything other than 4-cells, AA on smaller models and sub-Cs on larger ones (as recommended by Frank S above). This is mainly due to having a LOT of JR servos that don't like higher voltages.

I have yet to experience a "brown-out".

I do use good quality switch harnesses.

I have, however, both experienced and witnessed far more issues with regulators and battery backers than I have ever seen or heard of from running Spektrum on 4-cell packs.

A *well-maintained* 4-cell pack and a decent switch harness (NOT one that incorporates a charge socket in the switch!) will be perfectly fine, in my experience.

The more you insert between the battery and the receiver, the more there is to go wrong! Keep It Simple!

Bert: Is your dad Barry, who used to fly up at Little Haldon in the 60's?

--

Pete

[Cuban8]

Out of idle curiosity, I see that on none of the datasheets including Servo databse website, is there any mention of the Futaba S9404 's performance at 6V only at 4.8V. I guess you have to read into that what you will, but I'd not be inclined to possibly stress the servo at 6V and risk a 'magic smoke ' failure at an inconvenient moment if the specs don't give 6V perfomance.

I run 6V myself these days, but for 4.8V, for a decent quality Sub C pack.