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All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> SUB-C or AA
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SUB-C or AA - 4/4/2003 7:31:42 AM   
r_rich


 

Posts: 7
Joined: 1/7/2003
From: Kansas City, MO, USA
Status: offline 		I have a question I keep getting different answers on.

Weight is NOT a factor, I need a receiver pack to power 6 Hitec 422's and 1 hitec 605BB. in my Ultra Stick .60.

Will I get more fly time (flights) on a single charge out of a:

1. 6V 2400mAh SUB-C pack
or
2. 6V 2400mAh AA pack

Again I DON"T care about weight I have 2oz. and a 6V pack on the tail now. It would be no problem with the added weight from the SUB-C's.

I know there is somebody who can set me straight.

Thanks,
Rich
       Post #: 1

SUB-C or AA - 4/4/2003 7:52:27 AM   
strato911



Posts: 1479
Joined: 9/17/2002
From: Winnipeg, MB, CANADA
Status: offline 		In theory, both packs should give approximately the same flight times. However, in practice it's not quite so cut and dry.

Are both Packs NiMh?, or are the sub-C's NiCd?

Since the sub-C's have a lower internal resistance than AA's (especially if they are NiCd), they will waste less energy overcoming the internal resistance (identified as heat), and provide a slightly longer flight time.

Why not just give it a try and see? I assume you are using some means to check your pack's voltage between flights...


_____________________________

I try to learn from other people's mistakes...
I won't live long enough to make them all myself.

(in reply to r_rich)
       Post #: 2

SUB-C or AA - 4/4/2003 4:47:08 PM   
rscamp



Posts: 242
Joined: 6/22/2002
From: Dundas, ON, CANADA
Status: offline 		There is some information missing here - i.e. the battery chemistries. Sounds like the AAs would be NiMH and the sub Cs NiCd fast charge type (SCR).

As pointed out, the AAs would have a higher internal resistance and be a poorer choice for high current applications. If the above assumptions are true, the following points can also be considered:

- the AAs will have a shorter life and be MUCH more delicate
- the sub Cs can be charged MUCH faster
- the sub Cs will benefit greatly from periodic cycling

Rob

(in reply to r_rich)
       Post #: 3

SUB-C or AA - 4/4/2003 10:41:32 PM   
TopShelf



Posts: 651
Joined: 12/6/2001
From: West Linn, OR, USA
Status: offline 		I asked a similar question some time ago and the answer that I got is basically that the only difference is the longevity of the pack. To get the same 2400mah capacity packed into the smaller package of the AA cell means the membranes are thinner etc. Do a search for my earlier thread to get all the details.

_____________________________

He Who is a Slave to the Compass has the Freedom of the Sky.
www.TopShelfRC.com

(in reply to r_rich)
       Post #: 4

SUB-C or AA - 4/5/2003 5:18:10 AM   
smokingcrater


 

Posts: 2353
Joined: 9/20/2002
From: Up north, ND, USA
Status: offline 		Didn't think AA's went above 2000 or so? What kind? Is this a serial-parallel pack of 1200 AA's?

(in reply to r_rich)
       Post #: 5

SUB-C or AA - 4/5/2003 9:11:23 AM   
Ed


 

Posts: 1812
Joined: 12/5/2001
From: Bemis, , USA
Status: offline 		How do they get 1000 - 2000 mah into what use to be a 500 mah NiCd package ? They use a thinner substrate, and wrap them a hell of a lot tighter. It's kinda like stuffing 5 lbs. of fertilizer into a 2 lb. bag. Opens up all kinds of bad reliability problems, worst of all, internal shorts. I have had bad luck with AA NiCd's over 1000 mah, much shorter life span. I have since switched to 1300 sub C's for much more predictable, and superior performance.

For what it's worth.

> Jim

< Message edited by GeeBeeJim-RCU -- Apr 5 2003 6:25PM >

(in reply to r_rich)
       Post #: 6

SUB-C or AA - 4/6/2003 9:25:46 PM   
RCP57


 

Posts: 374
Joined: 3/3/2002
From: Magnolia, TX, USA
Status: offline 		Rather than quote old past information about NiMH batteries let me give you my personal experience. I use nothing but Sanyo NiMH batteries in all my airplanes, and have for some time. I even use them for my nitro T-Maxx receiver/servos. Right now I’m using Sanyo HR-AU batteries that are "A" size, 2700 mAh in my airplanes. I use them in both 6 volt and 4.8 volt configurations. They are used to power the receiver/servos and the electronic ignition in my gas planes. I have never had a single problem with their use. All this talk about internal resistance, longevity, performance, and all the other statements don’t mean anything to me. I use the batteries in everything from my fun-fly plane all the way up to and including my giant scale 35% planes which have 9 servos. I run JR DS8411 digital servos on everything but the rudder on my giant scale planes where I use a pair of Futaba 5301 analog servos. I even use JR DS811 digital servos in my fun fly. Then there is the statement that you should not charge NiMH batteries and leave them sit because they will loose their energy. I charged two 6 volt 2700 mAh packs at C10 rate, then let them sit for SIX months. The batteries were charged on September 17, 2002 for 24 hours, and then sat idle in my closet until March 26, 2003. I then discharged them using a Sirius SuperTest at a rate of 500 mAh. Both packs had just over 2360 mAh remaining. So I guess the “you have to fly immediately after charging the pack” theory goes out the window.

These NiMH batteries should NOT be treated the same as NiCad batteries. They are more sensitive to heat and need to be charged with more care. I always completely discharge my batteries before putting them on a C10 rate, and did that with NiCad batteries also. Just use some common sense and get to know your batteries, then learn how to charge them based on their usage. I suggest purchasing a good peak charger like the Triton. Program the unit for a slower C5 to C10 rate so that the batteries are not pounded into a fully charged state. You can use the Triton just like your overnight charger, it does not have to be a quick charger.

_____________________________

Later,
Mike

(in reply to r_rich)
       Post #: 7

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