fallingleaf

My Feedback: (1)

Hi All. I am about to build a Carl Goldberg Ultimate Biplane kit and plan to be using 5x Hitec HS-645MG High-Torque 2BB Metal Gear Servos and one standard fuaba servo for throttle. I am wondering what sort of reciever batter pack I should be using to power all 6 servos adequately. I have a new 4.8v futaba 1500mah nicd...will this be enough? or should I be looking for a high amped Nimh like 2500mah etc? I plan on going with 4.8v rather than 6v just to reduce complications, and have enough torque on the hitecs at that voltage (103.5oz).

I don't have a lipo charger by the way and dont want to go down that road....more $$$$!

Thanks!

carlosponti

My Feedback: (1)

those 645's will work just fine with a 4.8v since they are already high torqued. what complications are you talking about when comparing 6v nimh to 4.8 nicad? its not really that different from the other when it comes to basic charging. the only thing that changes is how long before you cycle them. i got a 1500 mah nimh 6v for my 60 sized yak just for the extra charge. the only thing you have to worry about is mainly the mah rating of the battery because a 600 or 700 will be depleted too early but the 1500 you have will work just fine. they also have 6v nicads as well if you look around.


ps lipo is overkill for your setup because you would just need a voltage regulator in the airplane to step down voltage to 6 volt anyhow.

Jonathan Ott

My Feedback: (25)

Check out www.radicalrc.com and look at the differnt batteries that Dave has there. I've usually gone with a 5 cell, 1650 (or so) mAh NiMH battery from him. Great battery, great price.

The 5 cell 1650 NiMH will give you many great flights in an outing, and will help you servos to produce the power you want and the speed you need. Personally, I would not go with a 4 cell pack in a 90 size plane...too much load on the larger surfaces for a 4.8v battery.

My opinion, but I think Dave Thacker would back me on it. Check 'em out.

Jon

fallingleaf

My Feedback: (1)

Thanks for that carlosponti. Regarding 4.8 v 6 it simply meant the higher voltage may wear out the servos slightly faster than normal...that is only a sweeping statement I heard in some other thread so whether it has substance I am not sure. I guess going with 6v would give me about 20% more torque in the 645's too so could be a good idea....can never have too much torque I guess. I will see how it goes with the 4.8v 1500 nicd I have and go from there. It sounds as though it should be sweet.

Is there any real difference between Nicd and Nimh aside from the obviously larger Mah rating that Nimh's seem to have?

fallingleaf

My Feedback: (1)

Xtreeme, that was what my intial thoughts were. WHile I do not fly like a maniac I will have a large engine on the plane (120ax) so I am taking no chances with flutter issues etc. There is far greater torque and speed with those servos too if I use a 6v....I think I am now answering my own questions. If 1600 mah roundabouts works fine then I will look into that.

Interested to know the differences in Nicd and Nimh though!

carlosponti

My Feedback: (1)

nimh you can go longer without cycling which means you dont have to discharge and recharge to condition the battery. also they are better longer lasting batteries than nicad. they also lose more charge when left unattended per amount of time than nicad. i hadnt heard 6v wears your servos out quicker. thought there is some truth to it but i doubt it is that kind of concern where you cant use 6v. you are talking a small percentage of degradation in the circuits if anything at all. the only servos you want to be careful of are those that dont have a 6v volt rating because those will wear out quickly if not immediately. I dont think with the hitec 645's you will have a problem or experience anything xtreme mentioned because 645's are used in large gassers on 6v and a 90 size is way smaller. you may find outside of sport flying however when you need more control throw the 6v will give needed umph for the larger throws. then i would say get the 6v. i looked into the radical rc and they are a little cheaper than the 6v i bought. i bought a 1650 or so 6v for 29.99 with connector.

fallingleaf

My Feedback: (1)

Yeah I am looking to do some pretty crazy snaps and lomcevac's, iverted death spins and what not once I figure out how to execute tham properly! So perhaps a good 6v will be good. At least now I know I can also use my new 1500 nicd for simple sport flying initiall to get accquainted with the model, and then have it as a suitable backup to the 6v. I wish batteries were cheaper though!

fallingleaf

My Feedback: (1)

One more question!...In an ultimate bipe (90 sized goldberg) would it be beneficial to have two reciever batteries? (i.e. 2x 2000mah 6v nimh's). I have read afew tales of peoples switches shorting out, one on a biplane like I am building and it has put the heebie jeebies up me! I anticipate to of these batteries would weigh about 10oz. I am over killing this, or would it be prudent? I figure the weight isn't too much of a prob but others may have a different take?

Also, running two 6v's into the reciever isn't going to overload it is it? will it still be 6v? (you can probably tell i'm not too clued up on electronics in terms of volts, amps and all that!)

Thanks for the help!

carlosponti

My Feedback: (1)

if this were a 50cc bipe i would say don't scrimp but 90 size is just personal preference and a bit overkill IMO. there are some examples on the internet on how to set one up that you might look into anyhow just so you know what it entails. giant scale guys do it all the time with two batteries and two switches. Also it leads to a more difficult handling of your airplane because you have to charge two batteries.

David Bathe

The CG Ultimate.90 is a totally standard small sized plane and can be equipped accordingly. Nothing to worry about. Use what us have and use a battery checker.
What you should concern you're self with is weight, keep it as light as possible. Two batteries and switches isn't going to contribute anything positive.
Enjoy it for what it is. A great flying plane.

fallingleaf

My Feedback: (1)

Yeah it does seem abit hardout to me. in terms of switches i guess I could have two connections soldered to my battery and two switches, such that if one shorted out (heaven forbid!) there will still be a soild connectinon to power the plane?

David Bathe

No, two stitches, two batteries... plugged into two receiver slots!
I have flown model planes since the early 70s and have never had a switch short out.
Just set it up as normal and stop worrying. The chances that you'll crash through pilot error, yours or somebody else are infinitely bigger than a switch failure.

carlosponti

My Feedback: (1)

the setup like david mentions is basically two batteries in parallel which doesn't mean more voltage is going into the radio just more milliamp hours. if they were connected in serial that would contribute to more voltage. ie two batteries chained to the same channel with one switch.

fallingleaf

My Feedback: (1)

Ah choice, I will just do the normal old setup then. I have heard of people with two terminals coming out of a single battery going into two switches...there is a thread on it somewhere here and it sounded like a good idea to me. Yes I am paranoid but money is tight! I will just use the switch I have in my ultrasport. It has never given any problems and at least I have faith in that particular switch. Its a standard switch nothing heavy duty...I assume a heavy duty futaba switch is also over kill even with just 6 high torque servos?

carlosponti

My Feedback: (1)

standard switch should do well yes.

fallingleaf

My Feedback: (1)

I just read that the Hitec HS-645MG servos I am using (5 of them) suck the battery juice like crazy. Is there substance to this? In which case is a single 1500 Mah battery or even 2000mah sufficient?

Yes I know I am being paranoid but I don't like having to change batteries on a bipe after every 2-3 flights etc! Anyone have experience with these servos and their supposed current draw?