Direct servo/battery connection. How to article

[Climate]

Direct servo/battery connection. How to article


We get a lot of customers asking us how to hook their sail winch servos up to their batteries directly.
The main advantage in hooking up a winch this way is that it gets the full capacity from the battery pack before the power gets branched out to other parts of the radio system.
This method can increase servo speed and strength considerably.

Give it a try on your next boat. You will be pleased with the results.

Here is a link to how it is done.

http://climateboatworks.bizland.com/store/media/direct%20battery%20hook%20up.gif

Peter R.
www.climatemodels.com

[jmat101]

I have done just this, as per the instructions that came with my sail servo, but I am experencing problem with it(sailservo). I will tell you what I have & have done, You help me trouble shoot...PLease...

I am wired just like the wiring diagram on the link you posted. It is also the same diagram that came with the sailservo.

sailservo=HiTech HS-815BB mega sail servo 1/4 scale
servo2 (rudder)= Hobbico commander cs-72 BB 1/4 scale
receiver= Futaba FP-R122JE BEC type am 2 channel
Battery= 4 AA 1.5v (energizer)= 6V
BOTH SERVOS ARE NEW OUT OF BOX

I am having the sailservo cut in and out, sometimes not functioning, sometimes functioning fine but only for a short time. Servo2 is functioning fine. I have servo2 in channel 1 & sailservo in channel 2. I have tried switching them but the problem is still there with the sailservo.

My theory is that running (2) 1/4 scale servos, 6 volts is not enough power. I could increase to 9 volts by adding 2 more AA Batteries or go to a 9.6V nicad. I'm just worried about burning something up or out(eg; receiver).

And Yes I'm kinda new at this.

Got any Ideas, can you or someone else help...PLEASE...........JIM

[Doc]

Hmm. The diagram shows a 'direct' connection to the battery external to the receiver. The 'normal way of hooking up a servo is exactly the same except that the battery connection is on th receiver's buss. I'm sorry, but I don't see the point. The only difference would be the size of the connection's trace inside the receiver, which is typically large enough for any 1/4 scale servo, and I would think the same holds true for a sail winch. So, what am I missing?
- 'Doc

[jmat101]

According to the info given with the sailservo " with a BEC receiver, Do not plug into the battery terminal other wise no matter how large the capacity battery is used it WILL not help". BEC= Battery Eliminator Circuit, with that in mind useing a Y harness makes sense, but it still is not working. If servo2 is 1/4 scale I am lead to beleive both should be on a Y harness but how is that possible? no instuctions came with this servo it. & Should or Could I increase the voltage? & if I increase the voltage will it burn anything out? Is any one or has anyone exprinced a similar problem and what was the fix. Is any one running (2) 1/4 scale servos on 6 volts or more?

[Climate]

You are sort of thinking along the right path, but are off track a bit.
It is not the voltage that is causing the problem, it is the amperage.
The sail winch servo draws about 800 mA. when it is idle. When it is working, that draw can go up close to 2 Amps.
Remember that as Amperage goes up, voltage goes down.
Your little 4.8 Volt AA receiver battery pack is not capable of a sustained high amp draw. The cells just can not put out the juice needed to run the large servo and your receiver at the same time. This is not a Voltage problem, but is an Amperage problem.
When you put the load on the battery pack, the sail winch servo takes the most draw from the pack. The receiver is left with whatever remains. This is often not enough to run the receiver and other servo, so it shuts down.

The solution is to use a higher capacity battery pack.
Your AA cells will probably be rated at a nominal 1.2 Volts with a 600 mAh capacity.
That is, they will deliver 1.2 Volts for one hour at a 600 mA load.
You are probably pulling close to 1 Amp out of them just while the boat is sitting still. (800 mA for the sail servo, 150 mA for the receiver an other servo.)

I would suggest nothing less than a 2000 mAh pack for any large servo.

I use 3300 mAh cells on most of my boats and have never had a problem.

Peter R.
www.climatemodels.com

[jmat101]

I knew logic would prevail! Thank you!

Now,
Off hand do you know if a 9.6v commonly used in RTRs give me the amps I need and/or will it damage my receiver? I have several of these around so I don't have to buy something I might already have. I can't find any amp rateing on them or the charger.

Next space & weight are an issue. The Boat is a Victor model Wild Cat, a catamaran. Too big a battery may not fit into the compartment & too heavy I will have to adjust the ballist so that both hull sit even at the waterline (this can be a headache). Not to menchon I don't want to sacrafice speed, which is the most appealling things about a multihull. When it works this baby is fast,fast,fast and will out run most electric (motor)RTRs. She doesn't sail in a light breeze, She needs wind, So if she gets heavier she'll need heavier wind. Something I want to avoid is more weight.

***whoo, Google must be reading these, someone placed a link for batteries at the top of the page. After checking some of these out I better understand what you where talking about &, weight & space are not an issue.

If I am reading this stuff right I can get 4 aa sized NiNH batteries to pump the amps I need? However My original quest about the 9.6v NiCd still applies, Could this be a fix?

PS Thanks Peter You really seam to know your stuff....Jim M. Orlando,FL

[Climate]

Without seeing the batteries that you have, I can not comment on their capacity.
Sometimes the cell size will give you an indication of what they are.

Typically higher capacity cells are in the "Sub C" category. They range from 1200 mAh to 3700 mAh.

I would be looking at a cell that will provide at least 1100mAh for your needs.
That sail servo will kill anything less pretty fast.

Weight should not be that much of an issue. I know it seams like it would be, but once a cat gets flying on one hull, the extra weight can actually help damp some of the faster oscillations that would effect a lighter hull.

Peter R.
www.climatemodels.com

[jmat101]

I edited my last. And again sir "hats off to ya". You are familiar with multihulls! Not many are. I have sailed Cats & Tri's for many years. Once I found a R/C Cat I had to have it. Do you think Climate Models may venture to Multihulls, if you do one, you may email me directly.

Back on topic.

If I try the NiCd 9.6v could it hurt the receiver?

Since you can't see it I'll give the best description I can...they are;
9.6v eztec NiCd #3702...it looks like 8 aa sized batteries wrapped togather w/one + & one - lead. Commonly purchased at Toys R Us or Walmart. Used in alot of RTRs.

Hope this helps, if not thanks for your help anyway. I've been beating my mind senseless over this & your responces were knowlegible and eased my fog.

[Climate]

Do not run 9.6 Volts to the servo or receiver. 6 Volts is about as high as you want. The servo will not safely work on much more.
You can cut the battery pack you have apart and remove a few cells to give you the pack you need.
Each cell should be about 1.2 volts.
If you do the math you will see that a 5 cell pack will give you 6 volts.
Under load this may go down to 5.5V or lower.

I would doubt that the pack you have is a very high capacity if the cells are AA sized. At best it might be 1000 mA. Still on the low side for the power you require.
If it came from Wal-Mart or Toys are us, the quality will be less than good as well.
Good batteries cost money. Cheap batteries are exactly that...Cheap!

Peter R.
www.climatemodels.com

[jmat101]

I will heed your words. & thank you for all the help. I'll just have to wait for my next sea trial.