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batteries and flight times? - 12/14/2003 9:04:21 PM   
grant-RCU


 

Posts: 384
Joined: 1/11/2003
From: Plains, GA, USA
Status: offline 		What is the difference between LIpolys and LIions? Why are these better batteries than NiMh? I have a hobbico quick field charger capable of charging Liions. Will this charger charge LIpolys? What kind of flight time are you guys getting on these flat 3d planes? i was planning on using a gsw 350 motor with the D gear and 12x6 prop.

How long does it take to recharge the lipolys and liions? what size packs are you guys using?
       Post #: 1

RE: batteries and flight times? - 12/14/2003 9:15:47 PM   
low--flyers


 

Posts: 17
Joined: 8/30/2002
From: Chandler, AZ, USA
Status: offline 		if it is you go whith a li-polymer batt you will be about axactillt half the waight of a 8 cell ni metal batt pack.
also give you more flight time around 20 to thirty mins .

(in reply to grant-RCU)
       Post #: 2

RE: batteries and flight times? - 12/17/2003 3:10:42 PM   
bugleboy



Posts: 446
Joined: 1/8/2003
From: Lincoln, AR, USA
Status: offline 		You have asked a lot of questions.

Li-Polys are more stable than Li-Ion. Where Li-Ion might explode from overcharging or over discharging, Li-Polys may just swell. THIS DOES NOT MEAN THEY CANNOT CATCH FIRE! Carelessness and abuse have lead to lost planes, vehicles and ever homes. Lithium batteries require care to be used safely, but I have found it worth the trouble. I don't think I will ever go back to Nicads or NiMh. They are much light, as has already been said.

Flight time is still calculated just the same as with anyother battery: Ah of battery divided by Amp required by the motor. So a 1200 mah battery would get you approximately 12 minutes of flight time at 6 amps: 1.2 / 6 = 0.2 hours (12 minutes). Of course, since li-polys are much light, you may be able to fly the plane at a much lower throttle. Lets say at the lower throttle setting you are only consuming 4 amps. Now you will get 18 minutes of flight time: 1.2 / 4 = 0.3 hours (18 minutes).

The number of cells depends on the type of motor you are using. I use 2 cells in serial for my 300 size brushed motors such as the GWS 300C (On the GWS Slow Stick, GWS Mustang, etc.). I use 3 cells in serial for my small brushless motors such as the Razor 400.

On my Mountain Model (www.mountainmodel.com) Tantrum, I am getting 18 minutes with a 3s 1200 E-Tech pack. This is with a brushless motor, and of course they are a lot more efficient. With your 350, I would use a 2s pack.

All Lithium batteries are not made a like. Some can only discharge at 1-2 C and some can discharge at 20 C. So if a 1200 mah lithium battery says it can discharge at 7-8 C, that means you only want to run that pack on a motor and prop combination pulling 8.4-9.6 amps (1.2 x 7 = 8.4 amps).

As far as the charger you have, if it charges lithium ion batteries it should charge li-polys. HOWEVER, please contact the manufacture first. I would hate for you to lose your house in a fire or anything. Make sure not to charge lithium batteries at greater than 1C. Also make sure you can select the number of cells in your lithium pack on your charger. Many have a cell selector on the charger. Some, however, are only designed to charge 2s packs, and therefore they will not charge 3s packs. There should be more information in your charger's instruction manual.

I hope this helps at least a little. Let me know if you have any questions.

Jason
jasonc@uark.edu
http://www.bugleboy.rchomepage.com

(in reply to low--flyers)
       Post #: 3

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