Battery drain with 815 servo

by **Dave Mains** » Sat Mar 11, 2006 8:22 am

My Hitec 815 sail servo causes me to go through a 2000MAH 6V battery pack in about an hour and a half (if there is a decent wind). It's also not nearly strong enough to hold the sails in a moderate wind. I have seen posts here where people have put in a pair of 815's to handle the sails. I assume its 1 for the main and 1 for the jib. I can do that. My question is, how does this affect battery drain? Theory would be that the 2 servos would draw less than just 1 trying to do the job by itself. I'm trying me best not to go to a winch if I can. Don't ask, I'd just rather stay with the swing arm(s).

Dave
Orange Park, FL
#1566

by **Doug Wotring** » Sat Mar 11, 2006 9:16 pm

HI Dave, I beleive your servo is way underpowered for the application ( without looking up it's perf. specs.

Also the use of twin servos is not class legal with my interpretation

Best bet get yourself a winch.

Another option is the new digital servo that Futaba or Hitec is making.....has more torrque than a 1/4 scale servo

by **Doug Wotring** » Sat Mar 11, 2006 9:47 pm

Off Tower Hobbies Website for the Hitec 815:

This servo consumes 800mAh UNLOADED 

Produces 231 in/oz of torque at 6v...

thats a bit over 2 hours no load ( no wind)

For comparison,

RMG 280DL produces 14kg/cm torque at 6v. I didn't bother doing the conversion

by **Rick West** » Sat Mar 11, 2006 10:16 pm

The 100 to 135 torque servos have done the job for a long time for trim where the load is directly from the sheetline. The use of this category servo for the rudder increased dramatically a few years back when it was found they could control most attempts to broach on a run.

The Ozmun swing arm winch and the RMG drum designs have been trouble free and reliable when installed correctly. The RMG is constantly being upgraded as new technology and radios systems arrive. It is a professional quality unit for a very reasonable price.

Battery drain is not a problem to the degree it is not thought of. I have been using the Apak 1600ma 6v batteries since 2000 with a fast charger. I am still using some of the original ones. Point is though, that with all the changes that have come along in winch design and the use of higher torque servos, my time on one single pack for the whole system has not changed...that is one pack in the morning and one in the afternoon and another if sailing after 1600. I check a battery when it goes in and it is changed on time only, not when near depletion.

One would thing that digital servos would embody all it touts. It does and then beyond. Here is a disturbing story:
Two boats became intangled during a rules infraction (strange?). The jib trim servo with the jib sheetline passing through the long arm could not return to its instructed position and while trying, went into a high amperage dump that started wires and the sub C batteries smoking by the time it arrived at the shore. Fortunately, it did not catch fire. The loss was several hundred dollars and a smelly bilge.

What catch my eye in this topic is that competitive racing 3000 miles from home requires reliable equipment and proper deligence before an event. There is too much at stake and for my having fun. So, we share this with all on the building site. Part of having fun is that your playmates are also even if you grind your teeth a bit.

...94 [8D]

by **Dave Mains** » Sun Mar 12, 2006 10:26 am

Good info guys. Thanks.
The Osmond swing arm system interests me. Can someone who uses it tell me if it is strong enough in a moderate wind, is it fast/slow, and how is it on battery drain? I know I could look up the specs but I don't think I could tell from that what you could tell me from experience.

Thanks,

Dave

Dave
Orange Park, FL
#1566

by **Rick West** » Sun Mar 12, 2006 1:11 pm

Dave,
For those that are looking for the simplicity of the swing arm system, the Ozmun Designs unit is the best in the hobby. It is built of the frame design of the old ProBar that was from the 70's. This was the one with the blasted micro switches to make it "Proportional." Ray Ozmun used a processor controlled circuit board to operate the driving motor, which turned it all into a servo that has multiple big gears with more power that a quarter-scale.

Battery drain calculations can make an EE major dizzy with all the variables including the demands of the hobbyist. I have no idea the specifications or ratings if there are such. All I know is that the unit has proven its place in the EC12. I have built three boats with this system for those that specifically wanted them. We sail at Delta in winds up to 18 mph sometimes when we have to get through the day.

Battery maintenance and disipline is always needed. To know battery drain for certain conditions indicates use of a system out to its limits. In a hobby that is fun, my personal approach was to stay away from the limits with frequent changes, as indicated in the above post. To sail in an event out to the limits of power is risky if not foolish and defeating the reason for being there. This is not a JPL controlled spacecraft but a toy boat.

That is my look on it. You will pay more for an Ozmun than any other winch but you will get a unit that you can depend on to do the job. History and experience has told us this and so it is passed.

I love to sail in the the rain in Jacksonville. There is something about standing dry under the elevated roadway and seeing water sheeting off the deck of an EC12 that reminds us what the real thing is like.

...94 [8D]

by **Skip Quinn** » Mon Mar 13, 2006 10:31 pm

Rick is right about the Ozman, it's a good winch. For a few dollars you can get a RMG 280DL. Much better in the long run. [8D]

by **Dave Mains** » Tue Mar 14, 2006 1:04 pm

Rick, come back to Jax anytime. I would love to meet you. I hate to end this tread because the info here has been great. However, the problem is solved. A buddy of mine here in Jax (Tom) is helping me install a RMG280 system. I didn't want the complications of the pulleys and stuff, but when he showed me his, it looked really good. So that's the solution. I was down in The Villages last Saturday and saw a couple of the Osmond systems. They look a lot simpler, but I'm doing the RMG. Thanks to all.

Dave
Orange Park, FL
#1566

by **Dave Mains** » Sat Mar 25, 2006 10:35 am

Just a follow up. I (Tom did all the work....and design....and supplied the beer) installed the RMG280 winch and I couldn't be happier. If you hear anyone else say they would rather not go to a winch, hit them over the head and make them do it anyway.

Taking it out this morning on the maiden voyage.[:D]

Thanks Tom.

Dave

Dave
Orange Park, FL
#1566

by **Rick West** » Sat Mar 25, 2006 12:29 pm

Glad you are about to go on the water. We try to not reinvent the wheel around here...innovation in another matter.

If you do not have it, there a programming checklist on the Electronics page of the building site. (copy and print) Steps 16-18 are very often missed. This is the sheet setting for the run position. Also, steps in 20 are not recommended.

I have never had a RMG deprogram but changing receivers is a good time to reprogram. Remember the audibles. The winch talks and lets you know when it is happy and at times unhappy.

Enjoy...it is the state of technolgy at the moment.

...94 [8D]

by **tag1945** » Sat Mar 25, 2006 6:53 pm

Your Welcome Dave! If Rick would get the info on the equipment board I made for Skip Hickman, other skippers that want to retrofit their boats can get it done without to much trouble!!!

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by OrangeParkDave

Just a follow up. I (Tom did all the work....and design....and supplied the beer) installed the RMG280 winch and I couldn't be happier. If you hear anyone else say they would rather not go to a winch, hit them over the head and make them do it anyway.

Taking it out this morning on the maiden voyage.[:D]

Thanks Tom.

Dave

Dave
Orange Park, FL
#1566
<hr height="1" noshade id="quote"></blockquote id="quote">

by **Rick West** » Sat Mar 25, 2006 10:11 pm

You are so right, Tom. The problem is I am retired and have little time for what I like to do...being in the shop. There sits your model...waiting.

...94 [8D]

by **tag1945** » Sat Mar 25, 2006 10:40 pm

Rick

I too am retired! The board that you have is not just a model but the actual equipment board. When you get a chance to view the CD and pictures, you will see how to assemble it and install it......

If you are going to try it in a boat, let me know as I have a couple of other ideas that make it better....

Priorities, something we all must establish..

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Rick West

You are so right, Tom. The problem is I am retired and have little time for what I like to do...being in the shop. There sits your model...waiting.

...94 [8D]

by **Dave Mains** » Sun Mar 26, 2006 11:14 am

OK. RMG280 test run completed. The winch is scary strong. Had it out for about an hour in a good blow. About all the wind the A set would want. No trouble sheeting in or holding. Didn't even slow down in a gust. When I brought her in, the battery was not even warm. My trusty V-300 battery tester indicated 80% remaining (I doubt that is really very accurate). However, with the old 815 servo in this kind of wind, I would be very close to the end of the charge. I'm guessing my rudder servo is using more power than the winch. I've still got a bit of a lead thumb on the rudder stick. Working on that.

Very pleased.

Dave
Orange Park, FL
#1566

by **greerdr** » Sun Mar 26, 2006 11:43 pm

You and everyone else using Bob Guyatt's winch.This guy is a BRAINIAC and we reap the benefit.Big BRAVO ZULU (U.S.Navy for great job)to the boy down under.

R.C.Greer

Battery drain with 815 servo

Battery drain with 815 servo

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