mike07

i am planing on building a new plane a 50cc plane right now i am using nicd i see alot of people using nimh and lipo and li ions what would be the best i am looking at 2700 or better in amps don't want to use a reg if i dont have to will be use hitech 7955 servos and spekum ar 7000 recv. any help thanks

MinnFlyer

My Feedback: (4)

At least:

http://www.horizonhobby.com/Products...rodID=JRPB5008

Wouldn't hurt:

http://www.horizonhobby.com/Products...rodID=JRPB4550

dignlivn

I would use 2 of the ones minnflyer recommended.
The second one that is. 2 batteries and 2 swithches for
the Rx. Then you'll need a pac for the IE also. Maybe a
sub C size over the AA size.

Bob

bkdavy

My Feedback: (1)

This question will recieve many different answers depending on the responders personal preferences. I recently went through this exercise, and here's what I ended up with.

All electrical power is provided by a 2s1p A123 cell (2300 mah, 6.6 volts nominal, 7.2 volts max). The battery is connected to two separate switches for reciever power, and a third switch for ignition power. With two switches wired to the receiver it can easily supply 8 amps steady if needed. Servos are 5 HS-7955TG (2 elevator, 2 aileron, 1 rudder) and 1 HS-425BB (throttle). Ignition power goes to a 5 volt LDO linear regulator (cost about $4 to assemble myself).

This system draws about 200 mah out of the battery in a 10 minute flight doing IMAC pattern moves. The A123 battery can be fully recharged in 30 minutes or less.

Brad

mike07

ok guys these a123 battery what kind of charger need for these batterys also will i need to but a bat share in line with the batterys to the recv. and they wire in with a y harness to the recv.? on my 29% texas hurricane that i am flying now i have on 6 volt ni cad on the servos they are hitech 645's and a 4.8 bat on ign...

bkdavy

My Feedback: (1)

You need a charger thats capable of handling A123. Its a lithium chemistry, but not the same as the LiPo. I use the FMA CellPro 4s. Charges A123 at 4 amps to 7.2 volts, then ramps current rate down holding voltage constant.

I got my cells by scavenging a new Dewalt 36 volt pack (10 cells, 2300 mah, $130) I ended up with 5 battery packs, so about $25/pack.

I don't use a battery share. Just two switches on the same battery. Its easy to check that each switch is functioning when I turn the plane on. One switch goes to the battery connection on the reciever, the other goes to a Y harness on another channel.

I just wired both receiver switches and the ignition power switch to a deans connector, and then use the deans connector to connect the battery. Ignition power is then routed through a second switch that is mechanically attached to another micro-servo. That micro servo is operated by the throttle cut function. Yeah, its old school, but effective.

Brad

mike07

ok guys i think i am going with the a123 batterys i am going to run two on the servos and one on ign

bkdavy

My Feedback: (1)

You're missing the point. You don't need 3 batteries. That will just be extra weight. And yes, even though you'll have a 50cc engine, you still want to be light where you can so you can add reinforcement where you need to (fire wall for example). A 2300 mah A123 pack powers my 30% YAK with 5 hi torque digital servos for about 6 flights. If I wanted to, I could recharge the battery from one flight in the time it takes me to refuel.

Since the switches are a more failure likely component, it makes sense to have two reciever switches in parallel, but they can both come off the same battery with no additional risk of failure.

Brad

FrankFuss

If you are thinking about running two batteries for redundancy, then consider the Spektrum AR9100 receiver with two 2000mAh or 1350mAh LiPos, or two heavier A123 batteries. There are no in-line switches to fail. You can run the Hitec 7955TG servos unregulated. You would only need a servo regulator for your throttle servo.

http://www.horizonhobby.com/Products...odID=SPMAR9100
http://www.horizonhobby.com/Products...dID=SPMB2000LP
http://www.horizonhobby.com/Products...dID=SPMB1350LP
http://www.smart-fly.com/Products/Regulator/4.htm

This setup may be a little overkill, but so are the Hitec 7955TG servos for a smaller gas model. BTW, this is also the setup I will be using in my 35cc Aeroworks Extra 260 with a DA-50.

mike07

why would i need the 9 ch recv, could i use just one 2700mah nich battery for this and maybe a 1700 or 2000 mah for ign and for get all bout setting up for two battery and all or this other stuff

bkdavy

My Feedback: (1)

You CAN use those batteries. But why? You battery selection should be optimized for the performance you're looking for. As I've tried to show earlier, a typical aerobatic 50cc setup (thats with 5 of the 7955TGs) will draw approximately 300-400 mah out of the electrical system in a 10-minute flight. The ignition system is probably pulling about 400 ma. That means in your proposed setup, you'll have sufficient power in the reciever battery for about 60-70 minutes of flight time, and the ignition battery will have about 4 hours of flight time.

Now if you're using those batteries because you have them laying around not doing anything, go for it. Just make sure the components you're using are rated for the entire range of voltages you'll be giving them. In otherwords, make sure they won't burn out from a fully charged battery.NiCd 6v pack on ignition will be fully charged over 7 volts and may cause trouble. A 4 cell (4.8 v nominal) NiCd battery will be fully charged below 6 volts is OK, but you'll use less than half the battery capacity before it drops below 4.8 volts, which is typically the lowest recommended voltage for the ignition system. Using a regulator will help provide more consistent performance across the entire range.

Brad