What size cells?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> Electric Aircraft Universe >> Electric Training >> What size cells?
Page: [1]

Login
Message << Older Topic   Newer Topic >>
What size cells? - 8/24/2003 6:49:45 PM   
Snowball1952


 

Posts: 82
Joined: 5/28/2002
From: Dousman, WI, USA
Status: offline 		You always hear about how many cells, but how do you determine what size?
Thanks
Kevin
       Post #: 1

What size cells? - 8/24/2003 7:37:09 PM   
sierra gold


 

Posts: 341
Joined: 1/8/2003
From: Foresthill, CA, USA
Status: offline 		The mah rating of cells determines the "size of the tank" of the battery pack. Thus, how long a pack will fly a given airplane and motor/prop.

If you're referring to your Slow Stick, you probably want 7-8 cells in the 800-1100 mah size. With the stock motor, an 1100 mah pack should give 10-15 mins. of flight.

(in reply to Snowball1952)
       Post #: 2

cell size aa-Sub-C and so on. - 8/24/2003 10:09:31 PM   
Snowball1952


 

Posts: 82
Joined: 5/28/2002
From: Dousman, WI, USA
Status: offline 		I understand that. I was wondering like AA -Sub-C and so on.
Thanks
Kevin

(in reply to Snowball1952)
       Post #: 3

What size cells? - 8/24/2003 11:09:22 PM   
sierra gold


 

Posts: 341
Joined: 1/8/2003
From: Foresthill, CA, USA
Status: offline 		I find the "size" you are referring to as quite confusing also.

I therefore don't try to remember them. I go by the mah rating. The higher the mah, the larger the cell is. Each mah rating corresponds to a cell size - AA, AAA, 4/5C, etc. I buy my cells by mah rating.

A quick browsing of any Web site that sells batteries will show the relationship.

(in reply to Snowball1952)
       Post #: 4

ok Thanks - 8/25/2003 12:15:27 AM   
Snowball1952


 

Posts: 82
Joined: 5/28/2002
From: Dousman, WI, USA
Status: offline 		Thanks

(in reply to Snowball1952)
       Post #: 5

What size cells? - 8/27/2003 3:56:48 AM   
red91sit


 

Posts: 237
Joined: 8/19/2003
From: Red Lake Falls, MN, USA
Status: offline 		but nimh are smaller and have the same mah. but u can use them in place of nicd of same mah and you'll end up with a lighter plane :-D or use nimh of same weight and get longer run time :-D

(in reply to Snowball1952)
       Post #: 6

What size cells? - 8/27/2003 4:25:36 AM   
Dr Kiwi


 

Posts: 1153
Joined: 12/4/2002
From: Chattanooga, TN, USA
Status: offline 		Here is a useful link giving sizes for batteries of all sorts!

http://www.powerstream.com/index.html

Good luck in sorting out all of it!

Cheers, Phil

_____________________________

Dr Phil Millener, Chattanooga, TN

(in reply to Snowball1952)
       Post #: 7

What size cells? - 8/27/2003 5:17:10 PM   
Matt Kirsch



Posts: 7043
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline 		[QUOTE]Originally posted by red91sit
but nimh are smaller and have the same mah. but u can use them in place of nicd of same mah and you'll end up with a lighter plane :-D [/QUOTE]

Incorrect, most of the time. The physical size of the cell is a good indicator of its internal resistance, which in turn is a good indicator of how much current it can produce. Bigger cell == lower internal resistance == higher current.

We are often pushing NiCd cells to their limits as far as draining current from them. If you replace a NiCd cell with a smaller NiMH of the same capacity, you often end up with a NiMH that can't handle the current (Amps) your motor/gearbox/prop setup is drawing. You will notice that you don't have as much power as you did with the NiCds. You will notice that the batteries are VERY HOT after a flight. You will notice that the NiMH cells will no longer hold a charge after a few flights like this.

As a general rule of thumb, you should replace NiCds with NiMH cells of the same PHYSICAL SIZE, that is a 2/3A NiCd should be replaced with a 2/3A NiMH. The advantage is not lighter weight, but additional flying time...

[QUOTE]Originally posted by red91sit
or use nimh of same weight and get longer run time :-D [/QUOTE]

There ya go

(in reply to Snowball1952)
       Post #: 8

What size cells? - 8/27/2003 11:14:31 PM   
red91sit


 

Posts: 237
Joined: 8/19/2003
From: Red Lake Falls, MN, USA
Status: offline 		oops good to know i was just about to buy a 8 cell aaa pack :EDIT: to replace my 8 AA pack

(in reply to Snowball1952)
       Post #: 9

What size cells? - 8/28/2003 3:11:19 AM   
Dr Kiwi


 

Posts: 1153
Joined: 12/4/2002
From: Chattanooga, TN, USA
Status: offline 		Another rule of thumb - because NiMH cells, even of the same physical size as NiCd, have higher internal resistance [i.e. don't give up their electrons as readily], you should replace a 6-cell NiCd pack with a 7-cell NiMh pack, and a 7-cell NiCd pack with an 8-cell NiMh pack................


Cheers, Phil

_____________________________

Dr Phil Millener, Chattanooga, TN

(in reply to Snowball1952)
       Post #: 10

What size cells? - 8/28/2003 5:10:38 PM   
Matt Kirsch



Posts: 7043
Joined: 7/5/2002
From: Rochester, NY, USA
Status: offline 		Again, another myth that won't die

That used to be true with older NiMH cells, but the most popular NiMH cells these days actually have LOWER internal resistance than their NiCd counterparts. Adding the extra cell is generally not necessary.

KAN1050's, for example, have a punch that's as good as or better than the 600AR/600AE NiCds they'd be replacing.

(in reply to Snowball1952)
       Post #: 11

Page:   [1]
All Forums >> Electric Aircraft Universe >> Electric Training >> What size cells?
Page: [1]





Jump to: