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Sr7 Li-Po Choices


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#1 Aaron556

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Posted 09 August 2011 - 07:48 AM

Just purchased my first KWA...the KM4 SR7 DEVGRU. I've been researching and learning about Li-Po batteries and I "think" I've found some good choices. The only thing I'm confused about is the discharge ratings. I've read in the manual that 15C is used, but I didn't read that it MUST be used. I'm not even sure about what the letter in the discharge rate means (A, C, etc).

My two choices are as follows, both of which are for sale in the ProShop:

1. Kong Power 7.4v 2000mAh 15C LiPo / Brick Style

2. RA-Tech High Rate Lipo Battery 7.4V / 2000mAh / 40A


Will #2 serve me better since it has a 40A discharge rate? Can I even use it?
I've decided to stay away from 11.1v (for now) to allow the gears to last longer. Am I correct in my thinking?

Are there better battery choices out there?

#2 Hitman07

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Posted 09 August 2011 - 09:15 AM

Get the Tenergy 11.1v 1600mAh 20c. I have it for my G36 and I take it apart on a monthly basis and everytime the gears look great. I have had the gun since Dec. 2010 and have put close to 100k rounds through it.

#3 Aaron556

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Posted 09 August 2011 - 02:43 PM

Why is 20C not recommended?

#4 niko_gpsy

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Posted 09 August 2011 - 02:50 PM

View PostAaron556, on 09 August 2011 - 02:43 PM, said:

Why is 20C not recommended?
Because a 20C at 1600 MaH will put you at 32A which is over recommended spec.  But with that said many do use a 20C batteries including myself with no problems.  Keep in mind though that a high Amp battery will accelerate wear on your gun.

#5 Aaron556

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Posted 09 August 2011 - 03:41 PM

View Postniko_gpsy, on 09 August 2011 - 02:50 PM, said:

Because a 20C at 1600 MaH will put you at 32A which is over recommended spec.  But with that said many do use a 20C batteries including myself with no problems.  Keep in mind though that a high Amp battery will accelerate wear on your gun.

Thanks niko_gpsy.

What is the difference between A and C?

What is your opinion on the Kong Power 7.4v 2000mAh 15C Li-Po? Would 7.4v 2200mAh 20C be too hard on the gun?

If this was your gun what would you go with?

Edited by Aaron556, 09 August 2011 - 03:42 PM.


#6 gcw360

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Posted 09 August 2011 - 04:47 PM

"C" is a number used to explain the ability of a battery to dump charge.  The higher the C rating the more continuous amps can be delivered by a battery.  Then continous amps delivered are determined by multiplying the C rating by mAh/1000 (simplified).  So, as Niko stated, "20C at 1600 mAh will put you at 32A" continuous or 20C x 1600/1000=32A

The batteries that you mention above are as follows:

15C x 2000mAh/1000 = 30 amps continuous

and

20C x 2200mAh/1000 = 44 amps continuous

You are better off with the Kong Power at 30 amps. KWA recommends the C rating not exceed 15C and has typically listed batteries above 20amps continuous as out of spec.  There are a host of reasons for this that are posted throughout the Forum.  Suffice it to say, if you buy the batteries recommended by KWA or ones with similar specs, you should be fine.

#7 niko_gpsy

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Posted 09 August 2011 - 05:09 PM

View PostAaron556, on 09 August 2011 - 03:41 PM, said:

Thanks niko_gpsy.

What is the difference between A and C?

What is your opinion on the Kong Power 7.4v 2000mAh 15C Li-Po? Would 7.4v 2200mAh 20C be too hard on the gun?

If this was your gun what would you go with?

C is the rate at which a battery discharges current so amp is somewhat a different way of quantitatively describing current discharge and the relationship is as what gcw360 has already told you.

C(Rate of discharge) x capacity of battery in Ah (in amp hours) = Discharge rate in amps

#8 Aaron556

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Posted 09 August 2011 - 05:38 PM

Looks like I'll be getting two of the Kong Power 7.4v 2000mAh 15C Li-Po. Would it be OK to use a M120 or 130 spring with this battery? Would it lessen the life?

#9 gcw360

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Posted 09 August 2011 - 05:54 PM

If you are going to upgrade the spring I would seriously consider an 11.1 LiPo for both trigger response and ROF.  :gun:

#10 Aaron556

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Posted 09 August 2011 - 06:00 PM

View Postgcw360, on 09 August 2011 - 05:54 PM, said:

If you are going to upgrade the spring I would seriously consider an 11.1 LiPo for both trigger response and ROF.  :gun:

11.1v LiPo suggestions would be greatly appreciated.

I did find this:
High Performance 11.1V 15C 1800mAh Li-Poly Battery Pack (PTW / Crane Stock Type)
http://www.airsoftpo...oducts_id=33009

Edited by Aaron556, 09 August 2011 - 06:03 PM.


#11 gcw360

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Posted 09 August 2011 - 06:09 PM

View PostAaron556, on 09 August 2011 - 06:00 PM, said:

11.1v LiPo suggestions would be greatly appreciated.

I did find this:
High Performance 11.1V 15C 1800mAh Li-Poly Battery Pack (PTW / Crane Stock Type)
http://www.airsoftpo...oducts_id=33009

How about this one?  It's ten bucks less, KWA recommended and the shipping's free with "FREESHIP" code: http://store.kwausa....nchucklipo.aspx

:gun:

#12 Aaron556

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Posted 09 August 2011 - 06:19 PM

View Postgcw360, on 09 August 2011 - 06:09 PM, said:

How about this one?  It's ten bucks less, KWA recommended and the shipping's free with "FREESHIP" code: http://store.kwausa....nchucklipo.aspx

:gun:


Good eye! Is 1600mAh enough? This will fit in my Crane stock, right?

Edited by Aaron556, 09 August 2011 - 06:20 PM.


#13 gcw360

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Posted 09 August 2011 - 06:23 PM

Yes, that is why I recommended it.  1600mAh will give you 2000+ shots on a full charge.

#14 Aaron556

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Posted 10 August 2011 - 11:52 AM

Thanks for all the great advice fellas.

A friend of mine said I should look into the "Custom Battery Pack Builder" on CheapBatteryPacks.com. I emailed them and they said to go with 12V (10 cell) nunchuck pack made with the Elite 1500mAh 2/3A NiMh cells.

Question: Is 12V (or for that matter this configuration) SAFE to use? I read in the manual that 9.6v NiMh is used.

If it's safe, the builder asks what size wire to choose: 12, 14, 16, 18, 20, & 22AWG are the choices. Not sure which to choose.

I'm assuming the Small Female Tamiya is the plug I should choose?

Edited by Aaron556, 10 August 2011 - 11:57 AM.


#15 niko_gpsy

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Posted 10 August 2011 - 12:24 PM

12V. Is too much battery for your application unless you are planning on a MOSFET with active braking route. Highest voltage I would recommend is 11.1v to avoid excessive wear leading to premature failure.  Always good to use recommended batteries by manufacturer.

#16 Jesse Hammil

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Posted 18 December 2013 - 11:41 AM

I know this is an old thread, but I'm having trouble finding a in spec batter for my RIS. The pro shop doesn't seem to have any batteries anymore. Can anyone point me to a 11.1v lipo that will fit my gun?

Thanks

#17 Chuck S

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Posted 18 December 2013 - 03:46 PM

An 11.1v LiPO battery is 12+ volts when charged so I doubt a 12v NiMH will do any harm.  But LiPO seems a better battery and the prices have dropped significantly in the past couple of years.

RIS battery in a Crane stock? or M4 lower receiver extension?  Should be plenty of 11.1 LiPO batteries with loose cells that will fit.  Google is your friend.

-- Chuck

#18 Jesse Hammil

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Posted 18 December 2013 - 03:49 PM

I called our local shop, and they have a couple that fit. It's both are 11.1v 20c 1200mah.  That seems like it's out of spec. I thougt spec was 20A and that battery is 24A if I'm doing math correctly. Am I wrong on what is "in spec"?

#19 choochoo

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Posted 18 December 2013 - 04:35 PM

Check out www.hobbyking.com, I got this from there and fits nicely (albiet a little tight) in the crane stock.
http://www.hobbyking...idProduct=24203

#20 Jesse Hammil

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Posted 26 December 2013 - 01:35 PM

View Postchoochoo, on 18 December 2013 - 04:35 PM, said:

Check out www.hobbyking.com, I got this from there and fits nicely (albiet a little tight) in the crane stock.
http://www.hobbyking...idProduct=24203

Am I blind? I don't see the voltage on that.

Edited by Jesse Hammil, 26 December 2013 - 01:35 PM.





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