LiPo upgrades...

[Devildog]

I have a CA M4 UAC, with it I use a 9.6v 4200 mAh NiMh battery (a beast with 1 inch cells that barely fits in the stock), along with a CA high torque motor, an M120 spring, 18:1 CA proline gearset, 70 duro sorbo, and 18 Ga wiring. The gun currently fires at about 23 RPS and roughly 400 FPS. The dilemma is that the battery is huge and wires keep breaking because I have to cram it into the stock.
Although I like the ROF the big battery gives me, I want to try and use a little smaller battery whilst keeping my RPS at about 23 minimum.

So I had two ideas:

A): Install a MOSFET to protect the trigger switch, a high speed motor (maybe a neo magnet one), and/or a 16:1 gearset, and a 7.4v 25-50c 2200 mAh LiPo (does amperage increase ROF with LiPos?).

B): Install a MOSFET to protect the trigger switch, use the CA high torque motor and the 18:1 gearset, a wire harness larger than 18GA, and an 11.1v 25-50c 1500 mAh LiPo.

I would prefer not to go any higher than 23 or 25 RPS. So with that said, does anyone have any recommendations or advice? Do these ideas sound relevant?

[Kjones]

The 7.4v lipo will have a wattage of 407 and a burst of 814, The NiMh will be about 483. The 7.4 will give you about the same results as your current 9.6v with out changing any internals. The lipo will also give you better trigger response even at the lower voltage.

[Devildog]

I did try using a 7.4v 1500 mAh 25-50c LiPo and found the the ROF and trigger response to be much lower than the 4200 mAh NiMh I currently use. Would I have to get a 7.4v LiPo with higher amperage?

[X]

Oct 7, 2013 7:35:57 GMT -5 Devildog said:

I did try using a 7.4v 1500 mAh 25-50c LiPo and found the the ROF and trigger response to be much lower than the 4200 mAh NiMh I currently use. Would I have to get a 7.4v LiPo with higher amperage?

No, that will probably not help. Think of it like this. The current that a battery can put out (calculated from the C-Rating) will only limit a motor's output if there's not enough. So once you hit a certain point increasing the C Rating will not increase the ROF. However, voltage is directly linked to the output of the motor. So in your case you stepped down from a battery that was supplying the necessary current to a battery with a lower voltage that also supplies the necessary current.

Kjones was basing his advise on the fact that most people have small 9.6v batteries which limit the output of the motor. When those people step down in voltage and up in amperage they usually end up seeing similar performance because their old batteries were not able to meet the current requirements of the motor.

Now I haven't played around with gearsets so please don't take the following as fact, but I believe what you want to do is put in a 16:1 gearset, keep the high torque motor, and use the 7.4v lipo. By increasing the torque demand on the motor you should raise the required current and ROF. Since the 7.4v lipo has a shit load of current you should net an increased ROF over the recent 7.4v results. However, I don't know if that will be more or less than the 9.6v (with 18:1 gears).

Sent from my XT1080 using proboards

[Tank]

Oct 7, 2013 7:35:57 GMT -5 Devildog said:

I did try using a 7.4v 1500 mAh 25-50c LiPo and found the the ROF and trigger response to be much lower than the 4200 mAh NiMh I currently use. Would I have to get a 7.4v LiPo with higher amperage?

There are three factors that come into play.
The current your motor wants, the capacity of your battery, and your battery's discharge rate.

If you have a battery with a 20c discharge rate and the capacity is 1000mAh, the current your battery can supply is 20A. If your motor wants 25A, then you will be holding it back from its true potential. In this scenario, you can change with the capacity of the battery or the discharge rate of the battery and get get more from your gun. A 1500mAh battery, with the same discharge rate, would give you 30A ability. A 1000mAh battery with a 25c battery would give you 25A capability. Either change would have you realizing the full capability of your motor.

The load your motor will put on your battery will vary from gun to gun. Measuring it is difficult, without special equipment. The easiest way would be to try out a few peoples' batteries, knowing their capacity and discharge rate, then go from there. At some point, you will stop seeing RPS and trigger response getting faster. At that point, you will have a rough idea what your motor needs.

Edit: X is right, I didn't notice the high capacity 9.6V. You will never see as fast of a response with a 7.4V as you do with that 9.6V, without changing your gearing.

[Devildog]

At one point I upgraded to a 16:1 gearset with the high cap 9.6v, and found that the ROF went up by maybe 1 but no more. Would I get better results with a 7.4v LiPo instead?

I think my understanding of batteries needs to be a little upgraded.
Say I have a 7.4v 1500 mAh 25c LiPo.

7.4v= voltage (how much the battery holds)

1500 mAh= capacity (how much comes out each time the trigger is pulled)

25c= discharge rate (how fast it comes out when the trigger is pulled)
Are these calculations right? If not please correct me.

[X]

Oct 7, 2013 8:50:11 GMT -5 Devildog said:

At one point I upgraded to a 16:1 gearset with the high cap 9.6v, and found that the ROF went up by maybe 1 but no more. Would I get better results with a 7.4v LiPo instead?

I think my understanding of batteries needs to be a little upgraded.
Say I have a 7.4v 1500 mAh 25c LiPo.

7.4v= voltage (how much the battery holds)

1500 mAh= capacity (how much comes out each time the trigger is pulled)

25c= discharge rate (how fast it comes out when the trigger is pulled)
Are these calculations right? If not please correct me.

MMM not really.

Electricity relates to water pretty well. so... Think of it like a big water tank with a hose.

Voltage = Pressure of the water tank (how hard the water pushes coming out)

mAH = How big the water tank is.

Discharge current = How big around the hose is.

C Rating isn't really useful on it's own. See my sticky here to understand what it means.

EDIT: I didn't run your numbers initially, but here's some food for thought.

Your Lipo that you tried...

7.4V
1.5 Ah
25C
37.6 A Continuous Discharge
75.2 A Burst


Your NIMH battery...

9.6v
4.2 Ah
~12C
50.4 A Continuous Discharge
Burst, but based on random info from the web I would guess 80 A (20C)

That Lipo is without a doubt going to be slower. Like Tank said I would try finding someone who has different battery. Look for something that has over 100 A burst. It will still be slower than your 9.6V, but you may be happier with the results. The real issue here is we have no idea what your gun needs. It's possible that with the 16:1 gears you were drawing more than the 80 A your NIMH could supply, but I'm sort of doubting it. I once measured my TM SR-16 (with M120 spring) at roughly 20 A continuous in full auto. The problem is that we really need to know what the burst requirements are and without expensive equipment it's hard to get that info.

If you can make it to the No Limits Game in two weeks I have a large lipo you can try.

[helix]

If you want really crisp trigger response you can wire inline capacitors. That can burst as much current as your motor can handle.

[Gimpalong]

Helix,

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