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Old Jul 01, 2011, 04:36 AM
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Joined Jun 2011
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What is 3S1P???

This is all very complicated:

I'm looking at this plane: http://www.rcgroups.com/forums/showthread.php?t=1377470 and it needs a battery.

The battery recommended for it is a 1300 mAh 3S1P battery.

The battery compartment on the plane could hold two 1300's.

So I want to upload to 2200 mAh.

I have found the battery: http://www.hobbyking.com/hobbycity/s...dproduct=14668

BUT

The top output model of a 1300mAh is 20C.

The battery I want is 25C.

My question is:

Does it really matter what output the battery gives? There is a 15C 3S1P, as well as a 20C. Will a 25C hurt the motor?

Thanks so much for your time
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Old Jul 01, 2011, 05:39 AM
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whitecrest's Avatar
Orleans, MA
Joined Feb 2007
2,060 Posts
3S1P means a battery is comprised of 3 lipo cells connected in series. If you were to take 3 more lipo cells, also connected in series, and connect these two units in parallel, your battery would then be designated 3S2P.

The C-rating (15C, 20C, 25C...) is merely an indication of how much burst current a battery can theoretically provide beyond its base rating (1C). For example, a 1300mAh battery has a 1C rating of 1.3 amps (decimal 3 places to the left). If it is rated 25C, then it can theoretically provide 32.5 amps (1.3 x 25) if demanded by the motor/prop combination installed on your plane. Think of it as having a wider pipe which can deliver more water volume if required. The motor/prop combination determines how much current is pulled from the battery. The battery's total voltage and C-rating determines how easy or hard it is to pull current from the battery.

For most practical power systems, you will rarely approach a battery's maximum C-rating. For reasonable flight times and power levels, you will probably need only around 10C most of the time. A 10C draw at full throttle will provide about 6 minutes of run time. If you are not running full throttle all the time, you should easily achieve around 10 minutes of flight time.
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Old Jul 01, 2011, 06:22 AM
Retired CFI Helicopter
Hughes500Bob's Avatar
Southeast PA
Joined Jun 2007
1,609 Posts
http://www.scriptasylum.com/rc_speed/lipo.html > Will show you any configuration.
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Old Jul 01, 2011, 07:04 AM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,718 Posts
2 other concerns you need to have about changing the battery size.

#1 - Will it fit? Packs are usually a little bigger than the size listed, mostly because of the wires sticking out of one end. May add up to 3/4" to the length.
#2 - Will you be able to meet the cg specification? If the battery is not on the cg, a heavier battery is going to move the cg unless it can be moved.
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Old Jul 01, 2011, 10:38 AM
Garry
Tumble weed country Eastern Washington
Joined Aug 2004
530 Posts
One other thing, will the plane handle the extra weight of the bigger battery.
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Old Jul 01, 2011, 10:58 AM
Fly Safe !!
Cape Town
Joined Jul 2007
440 Posts
As to the mass of the battery - it could make a huge difference or hardly any difference to the planes flying if you increase the size of the battery it all depends on the resultant wing loading . On a small wingspan plane you are going to increase the wing load drastically but on a large wingspan plane there is not going to be that much of a differece.
On a plane like a cessna wih a wingspan of 38" I would stick to a 1300mAh battery maybe try a 1800mAh battery but anything larger would give a negative result unless you increase the size of the motor etc etc - you may as well buy a different plane

20C is fine for that plane - remember your ESC must be able to handle the extra power that will be needed to pull the extra mass.

Fly the recommended setup first and then change if you are not happy.
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Old Jul 01, 2011, 03:14 PM
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Joined Jun 2011
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Thanks!

btw my ESC is 25A and my battery is 25C does that mean I would need a 30A ESC atleast?
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Old Jul 01, 2011, 03:56 PM
Space Coast USA
hoppy's Avatar
Space Coast
Joined Oct 2000
20,718 Posts
No
In general, you need an ESC capable of handling the current drawn by the motor/prop combination.
If the current needed was 20A, you could use any ESC larger than 25A (a little safety margin) and any lipo pack capable of supplying 20A continuously. It could be a 50C pack or a 15C pack as long as it can supply 20A continuously. The ESC could be rated for 25A or 50A as long as it was above the current needed by the motor/prop.
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Old Jul 02, 2011, 03:55 PM
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Gerry__'s Avatar
United Kingdom, London
Joined Jan 2005
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Quote:
Originally Posted by ljmrules View Post
This is all very complicated:

I'm looking at this plane: http://www.rcgroups.com/forums/showthread.php?t=1377470 and it needs a battery.

The battery recommended for it is a 1300 mAh 3S1P battery.

The battery compartment on the plane could hold two 1300's.

So I want to upload to 2200 mAh.

I have found the battery: http://www.hobbyking.com/hobbycity/s...dproduct=14668

BUT

The top output model of a 1300mAh is 20C.

The battery I want is 25C.

My question is:

Does it really matter what output the battery gives? There is a 15C 3S1P, as well as a 20C. Will a 25C hurt the motor?

Thanks so much for your time
You'd be better off sticking to the recommended specs to begin with.
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Old Jul 03, 2011, 02:39 AM
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lipoflyer's Avatar
Australia
Joined Nov 2010
2,876 Posts
actually you're generally better off ignoring the vendors advice and reading the reviews. most offten the reviews for HK planes will say DON'T use recommended battery as it will be too tail heavy.
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Old Jul 03, 2011, 11:17 AM
Fly Safe !!
Cape Town
Joined Jul 2007
440 Posts
Must admit that reviews usually are the better option but then in some reviews some guys tend to go over the top - bigger motor bigger battery bigger esc - you may as well buy the correct plane 1st time arround.

When a new plane comes onto the market I usually wait a few weeks till a few reviews have been posted and then decide.
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Last edited by porqui; Jul 03, 2011 at 11:19 AM. Reason: grammar
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Old Jul 04, 2011, 10:54 AM
Bye Bye VP Aug 2010 - Aug 2012
Gerry__'s Avatar
United Kingdom, London
Joined Jan 2005
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Quote:
Originally Posted by lipoflyer View Post
actually you're generally better off ignoring the vendors advice and reading the reviews. most offten the reviews for HK planes will say DON'T use recommended battery as it will be too tail heavy.
Not in this case though.
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Last edited by Gerry__; Jul 04, 2011 at 04:05 PM.
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