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LiPo Battery Warning!!!


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#301 UKBananas

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Posted 25 July 2012 - 01:00 PM

No response to the voltage question?

#302 niko_gpsy

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Posted 25 July 2012 - 02:49 PM

A main concern with out-of-spec lipo batteries in terms of "C" rating is that too much current flow in high voltage batteries can cause severe arcing between the trigger contacts and can burn them out prematurely. It can also "over-clock" your motor (sort of speak) and cause super cycling which can lead to over cycling and premature wear of the internal system.
A 7.4V can still spike and arc but with less severity and due to lower cycling speed it may spare your gun from accelerated wear and tear.  And the "C" rating on a 7.4 along with the storage capacity (mah) doesn't matter so much due to the low voltage, hence the ability of the voltage to push the current through a circuit is not very high compared to that of 11.1V lipos since it is the voltage (force) that pushes current through a system.

#303 UKBananas

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Posted 26 July 2012 - 08:16 AM

View Postniko_gpsy, on 25 July 2012 - 02:49 PM, said:

A main concern with out-of-spec lipo batteries in terms of "C" rating is that too much current flow in high voltage batteries can cause severe arcing between the trigger contacts and can burn them out prematurely. It can also "over-clock" your motor (sort of speak) and cause super cycling which can lead to over cycling and premature wear of the internal system.
A 7.4V can still spike and arc but with less severity and due to lower cycling speed it may spare your gun from accelerated wear and tear.  And the "C" rating on a 7.4 along with the storage capacity (mah) doesn't matter so much due to the low voltage, hence the ability of the voltage to push the current through a circuit is not very high compared to that of 11.1V lipos since it is the voltage (force) that pushes current through a system.
Great response thanks, so as the main purpose of a MOSFET is to reduce arcing on the trigger, if I install one I could go with a 7.4v higher C rating battery without too much risk.
I guess related to this question which I need to research, are there MOSFETs which also manage the power to the motor (stop 'overclocking').

#304 philsaudio

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Posted 27 July 2012 - 04:02 AM

View PostUKBananas, on 26 July 2012 - 08:16 AM, said:

<snip>
I guess related to this question which I need to research, are there MOSFETs which also manage the power to the motor (stop 'overclocking').

If you do see a FET design that reports to lower the voltage at the motor terminals expect to see a rather large heat sink on it, similar in size to RC electronic speed controller. If it were to drop the voltage it would do it through dissipation where the power (heat) not being consumed in the motor would have to be consumed by the FET. Review series DC circuits to understand this concept.

The low C LiPO is, in effect, a series circuit with the motor; where the motor is part of the load and the LiPO internal resistance is the other part of the series load. The more current drawn by the motor the more voltage drop by the internal resistance, which in effect causes the voltage across the load (motor) to drop as more and more current is drawn.

The voltage divider rule is another search you can use to research what is happening with your battery. The higher the C rating the lower the battery's internal resistance therefore the "stiffer" the supply and the less prone it is to voltage drop under load.

To avoid overloading the motor just get a lower voltage LiPO.

You may want to re-read this post earlier in this thread.
http://kwausa.com/fo...indpost&p=80596


Peace

#305 UKBananas

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Posted 27 July 2012 - 10:17 AM

View Postphilsaudio, on 27 July 2012 - 04:02 AM, said:


If you do see a FET design that reports to lower the voltage at the motor terminals expect to see a rather large heat sink on it, similar in size to RC electronic speed controller. If it were to drop the voltage it would do it through dissipation where the power (heat) not being consumed in the motor would have to be consumed by the FET. Review series DC circuits to understand this concept.

The low C LiPO is, in effect, a series circuit with the motor; where the motor is part of the load and the LiPO internal resistance is the other part of the series load. The more current drawn by the motor the more voltage drop by the internal resistance, which in effect causes the voltage across the load (motor) to drop as more and more current is drawn.

The voltage divider rule is another search you can use to research what is happening with your battery. The higher the C rating the lower the battery's internal resistance therefore the "stiffer" the supply and the less prone it is to voltage drop under load.

To avoid overloading the motor just get a lower voltage LiPO.

You may want to re-read this post earlier in this thread.
http://kwausa.com/fo...indpost&p=80596


Peace

Wow high quality responses on this board, thanks a lot.

#306 Standard4130

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Posted 27 July 2012 - 11:44 AM

With more HP in your race car comes more maintenance.........After all these are "guns" and guns of all types require maintenance on a regular basis. How much maintenance you are willing to do should sway your decision on battery choice......... You want no problems? Chose a low powered battery................... You want max performance? Learn how to work on & maintain your gun.....This usually cost money as with race cars....LOL. I really don't see a disadvantage to mosfeting other than the cost & them being non submersible. Which if you are running Lipo then it's non submersible anyways.

#307 philsaudio

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Posted 28 July 2012 - 05:15 AM

I thought of a way to make a two speed. Using a 3 cell LiPO a circuit can be built to switch 2 or 3 of the cells to the motor when the trigger is pulled. This could be as simple as a break-before-make DPDT switch or relay.

If one cell is open then there would be no need to drop the voltage for it, just switch it in and out.

This would preclude any balancing of the cells.

#308 niko_gpsy

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Posted 28 July 2012 - 01:28 PM

View Postphilsaudio, on 28 July 2012 - 05:15 AM, said:

I thought of a way to make a two speed. Using a 3 cell LiPO a circuit can be built to switch 2 or 3 of the cells to the motor when the trigger is pulled. This could be as simple as a break-before-make DPDT switch or relay.

If one cell is open then there would be no need to drop the voltage for it, just switch it in and out.

This would preclude any balancing of the cells.
I personally would like to see this built into an AEG.  But size and space has always been a limiting factor I think.

#309 airsoftmatthias

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Posted 15 August 2012 - 09:34 AM

I know for a fact that a couple of these LiPos are out of spec, but since I use an AWS Raptor MOSFET, I'm not overly worried about the excessive wear and tear since I can control the ROF (and the warranty is 2 years expired...). I am more concerned about longevity and performance though. I will be using this battery inside a handguard and crane stock, so the dimensions have to be right for both. Which will fit?

http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...RSOFT_Pack.html

#310 manglepop

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Posted 21 August 2012 - 01:19 PM

Since the CQR series are lipo ready, Using a 11.1v 1400mah 15c will not damage the gearbox in the long run, correct? This is my first time purchasing a lipo battery for my CQR MOD2.

#311 ga mercs

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Posted 21 August 2012 - 05:02 PM

that will work,,, i run a 2000mah 11.1v 15-25c lipo in my cqb and have not had any electrical issues as of yet .....over 100000 rounds.......i still dont understand the whole out of spec concept... i know what they are saying but it makes no sense ,,,,,you can lead a horse to water but you cant make him drink,,,,what i mean is the lipo that i run will technically  dump 30 amps constant and up to 50 amps in burst but the gun has a 20amp fuse that has not blown to date so if a 20amp fuse is holding the motor can not be drawing more than 20 amps ..please correct me if i am misunderstanding the concept

#312 ga mercs

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Posted 21 August 2012 - 05:07 PM

View Postairsoftmatthias, on 15 August 2012 - 09:34 AM, said:

I know for a fact that a couple of these LiPos are out of spec, but since I use an AWS Raptor MOSFET, I'm not overly worried about the excessive wear and tear since I can control the ROF (and the warranty is 2 years expired...). I am more concerned about longevity and performance though. I will be using this battery inside a handguard and crane stock, so the dimensions have to be right for both. Which will fit?

http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...RSOFT_Pack.

http://www.hobbyking...RSOFT_Pack.html
http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...0mah_3S_15_25C_

these will fit in the handguard   i run them in my cqb with no mosfet

#313 manglepop

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Posted 21 August 2012 - 09:34 PM

View Postga mercs, on 21 August 2012 - 05:07 PM, said:

http://www.hobbyking...RSOFT_Pack.html

http://www.hobbyking...0mah_3S_15_25C_

these will fit in the handguard   i run them in my cqb with no mosfet

I just brought the http://www.hobbyking...RSOFT_Pack.html for my CQR MOD2

#314 philsaudio

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Posted 22 August 2012 - 03:30 AM

View Postga mercs, on 21 August 2012 - 05:02 PM, said:

that will work,,, i run a 2000mah 11.1v 15-25c lipo in my cqb and have not had any electrical issues as of yet .....over 100000 rounds.......i still dont understand the whole out of spec concept... i know what they are saying but it makes no sense ,,,,,you can lead a horse to water but you cant make him drink,,,,what i mean is the lipo that i run will technically  dump 30 amps constant and up to 50 amps in burst but the gun has a 20amp fuse that has not blown to date so if a 20amp fuse is holding the motor can not be drawing more than 20 amps ..please correct me if i am misunderstanding the concept

Your fuse could be letting in excess of 20 amps flow, for a short time that is, without blowing. The time to blow chart below can shed some light on that fact.
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#315 Chuck S

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Posted 22 August 2012 - 04:22 AM

Hi Guys --

Forgive what may be a stupid question.  What am I missing here?  Why would I want to use a Lipo battery rather than a NiMh battery?  We talking Rate of Fire?

My KM4-CQB currently has an unrealistic (compared to a 5.56mm M4 Carbine) ROF of 950rpm as it is with an "old technology" 8.4v (7 cell) NiMh battery.  And that rate measured with a battery that hasn't been charged in a couple of weeks and has a couple thousand test rounds thru her.  I should retest with a fresh charge but 950rpm is more than enough for any realism.

I guess I'm looking for "features and benefits."  Is LiPo just marketing buzz?

-- Chuck

#316 philsaudio

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Posted 22 August 2012 - 09:36 AM

View PostChuck S, on 22 August 2012 - 04:22 AM, said:

Hi Guys --

Forgive what may be a stupid question.  What am I missing here?  Why would I want to use a Lipo battery rather than a NiMh battery?  We talking Rate of Fire?

My KM4-CQB currently has an unrealistic (compared to a 5.56mm M4 Carbine) ROF of 950rpm as it is with an "old technology" 8.4v (7 cell) NiMh battery.  And that rate measured with a battery that hasn't been charged in a couple of weeks and has a couple thousand test rounds thru her.  I should retest with a fresh charge but 950rpm is more than enough for any realism.

I guess I'm looking for "features and benefits."  Is LiPo just marketing buzz?

-- Chuck


Whatever floats your boat.

LiPO are smaller, higher capacity, and cheaper than NiMH. Higher current overcomes inertia quicker and give a faster trigger response.

#317 Chuck S

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Posted 22 August 2012 - 02:05 PM

My boat really has little to do with this.  :)

I'm now confused regarding the "cheaper" note.  LiPo batteries are under $25? I paid $23 for a NiMH 8.4v 1600mah battery.

As noted earlier, I'm not in need of a hyper, unrealistic cyclic rate and after wading thru all 16 pages of this thread this seems to be the only benefit LIPO provides -- or did I miss something?  Just trying to understand the technology.  Gas is so simple!

-- Chuck

#318 ga mercs

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Posted 22 August 2012 - 02:18 PM

View PostChuck S, on 22 August 2012 - 04:22 AM, said:

Hi Guys --

Forgive what may be a stupid question.  What am I missing here?  Why would I want to use a Lipo battery rather than a NiMh battery?  We talking Rate of Fire?

My KM4-CQB currently has an unrealistic (compared to a 5.56mm M4 Carbine) ROF of 950rpm as it is with an "old technology" 8.4v (7 cell) NiMh battery.  And that rate measured with a battery that hasn't been charged in a couple of weeks and has a couple thousand test rounds thru her.  I should retest with a fresh charge but 950rpm is more than enough for any realism.

I guess I'm looking for "features and benefits."  Is LiPo just marketing buzz?

-- Chuck
well the lipos are cheaper ,,, the rate of fire will stay more consistent ,,, a 7.4v lipo rof will be between a 8.4v and a 9.6v.... i went to lipos because i had 3 -9.6v nunchucks and a 10.8v go bad in a 2 month period and all of them were less than 6 months old

#319 Standard4130

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Posted 22 August 2012 - 03:09 PM

Chuck S,
You can have a realistic fire rate with a adjustable mosfet and zero loss of trigger response. Trigger response in your case would be the major pro to going Lipo.  And yes, they are cheaper than ever now days if you purchase from the right place & don't mind soldering on your connector of choice. One gun of mine runs a 1600mah 14.8v 35c and can be adjusted from below 10 up to 35rps on a sp150 spring....... (540fps - non short stroked). This gun pops of rounds virtually instantly.........

#320 niko_gpsy

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Posted 23 August 2012 - 03:58 AM

There are fantastic lipos you can buy (Tenergy nano-tech lipo) on kinghobby.com for anywhere from $7-14.




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