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Lipo for Rapidstrike with 180 motors


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#1 Speedr117

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Posted 24 March 2017 - 08:12 PM

Hello! I am new to nerfhaven, but not to nerf modding. I have done a few electrical mods before and decided it was time to make a primary. I have ordered two mtb hellcats and one wolverine that I plan on installing in a rapidstrike. The rapidstrike will have bodywork similar to Torok's tacmod. Now I was going to order a lipo, specifically, this one (https://hobbyking.co...-lipo-pack.html). Then I heard that a pair of hellcats draw 45 amps and a wolverine draws 50. According to my calculations I would need a battery like this (https://hobbyking.com/en_us/graphene-2200mah-3s-65c-w-xt60.html). This cannot be right. Was my first battery ok, or should I get something else.
TL;DR What lipo to get for a mtb rapidstrike.
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#2 SirBrass

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Posted 24 March 2017 - 09:51 PM

Edit: For the tl;dr, use a 3240 (aka blade 180) for the pusher. It'll do just as well on 3s as a wolverine will do on 2s but without the obscene current draw.

Okay, don't use triple wolverines without mosfets. Period. Way too much current draw. It's not that you won't find a suitable battery but the stress on 10A microswitches from that much current is not a good thing.

Hellcats draw much less current at stall. You'll want to have about 60A discharge available for burst for a tri-blade or triple hellcat build according to the data sheet compiled by ssgt at britnerf.

A 1000mAh 3S 65C Turnigy Graphene battery will have plenty of discharge capability & capacity for a triple hellcat build. For a tri-blade, a 1000mAh 2S 65C Graphene is also more than sufficient.

For my tri-blade stryfe (xsw full auto kit powered by a blade 180), I use a Zippy Compact 2200mah 2S 60C battery. It has massive overkill in discharge capability (60C continuous, which with 2.2AH is 132A, and 130C burst) but the size is fine and it doesn't even drop to 8.0V from 8.4V after a full day of battling with it. The 1AH 2S Graphene powering the same blaster before it was modified with the fa kit but with blades as flywheel motors was a few tenths of a volt away from storage level from 8.4 after a full day of play.

So the capacity of the battery is important. If you have a 2S or 3S (depending on if you go tri-blade or triple hellcat) 2AH (2000mAh) battery that'll work well for the RS for a full day. With 2AH, you'll only need about 25C minimum discharge (50A continuous will probably have at least 60A or higher burst, which covers you perfectly fine) for the battery.

If you want maximum battery longevity over the day, 3S motors and a 3S battery will get you better current usage than a similarly speced 2S system due to more of the power being driven by voltage and thus less current (P=IV in a dc circuit, so if P is constant, then as V increases I decreases). In which case you could get away with play all day on a 1AH battery with sufficient current discharge capability (60C burst capability). That would let you use a smaller battery (the bigger the capacity the bigger the battery).

Edit: with a wolverine as the pusher, you WILL need diodes to drop the voltage from the 3S battery. You will need 3S to drive the hellcats. But the wolverine at 7.4 volts draws 40A at stall!

With 2 hellcat flywheels, you will need EIGHTY AMPS discharge capability at stall (if you start all 3 motors within a few tenths of a second of each other). That's over 4 times what the dc2 micros are rated for if you wire the pusher to only activate when the flywheels are powered.

Basically wolverines are current hogs and simply not needed for the performance they offer.

Edited by SirBrass, 24 March 2017 - 10:17 PM.

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#3 Speedr117

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Posted 25 March 2017 - 07:07 AM

Thanks for the quick response. So my first lipo is ok for a triple hellcat setup. I may order that and another hellcat. However, I want the best rof with this build.
Can a use a 3240 on a 3s with hellcat flywheels?
Would I need a diode?
Could I use the same battery?
Do you have a link to 3240's that aren't gonna break the bank?
Also, with hellcats I can do live center, right?
But on a blade 180 do I need dead center.
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#4 jwasko

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Posted 26 March 2017 - 03:49 PM

If I'm doing the math right based on the motor database, your 2 Hellcats plus a Wolverine would be 114 Amps at total stall right?

 

Couple batteries in between the two that you posted:

https://hobbyking.co...-lipo-pack.html70C burst x 2.2A capacity = 154 Amps available at burst

https://hobbyking.co...-lipo-pack.html90C burst x 2.2A capacity = 198 Amps available at burst

 

Continuous ratings for those would be 77Amps and 99Amps respectively.

 

I would definitely never buy that 20C (looks like 30C burst in the picture?) LiPo except maybe for a stryfe build with 2 Rhinos...it only gives you like 60Amps burst.

 

Based on the numbers I think you might be okay with the 45C~90C one, especially since you're only using one Wolverine. I think people really do recommend Graphene sometimes though.

 

 

3240s/blades can run on 3S but you may need a diode if wiring live center...I can't recall. Again, I'd get one of the batteries I linked at minimum even if using a 3240.


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#5 SirBrass

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Posted 26 March 2017 - 09:34 PM

Problem with that much current at stall is the switches holding up for long. That's massively over what they're rated for and while 10A dc2's have stood up well to 40A stalls with about 8.5A continuous, the wolverine is 10A continuous by itself.

You'll need a very beefy trigger switch (at least a full sized omron 21A) for the pusher. The dc2 will be fine for switching on 2 hellcats as long as you don't make it so the acceleration trigger must be closed & flywheels spinning for the pusher to activate (it'd mean all motor current for all 3 motors flows through that switch). Even with a mosfet you're begging for something to pop much sooner rather than later.

If you want that kind of "flamethrower" power, go with an xp180 (as modified by MTB to have a longer shaft) as the pusher & step down the voltage going to it with 3 diodes to bring the voltage going to it to near 2S levels. That's if you want reliable pusher control. If you're just wanting pure mag dump capability, go with a honeybadger pusher on 3S and watch your RS be an absolute beastly dart hose.

jw, no need for that kind of overkill on blade 180s. They're 22A at stall, so a tri-blade will need a battery that can do 50A burst for the whole blaster. That'd be accomplished with a 25C (burst) 2200mah 2s lipo. You can get a 1000mAh 65C 2s Graphene easily on hobbyking for not much money (around $12). It's a tiny battery and more than capable of powering the tri-blade burst current with its continuous current rating.

No need for a battery with 154A burst capability.

Edited by SirBrass, 26 March 2017 - 09:41 PM.

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#6 jwasko

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Posted 27 March 2017 - 07:37 PM

jw, no need for that kind of overkill on blade 180s. They're 22A at stall, so a tri-blade will need a battery that can do 50A burst for the whole blaster. That'd be accomplished with a 25C (burst) 2200mah 2s lipo. You can get a 1000mAh 65C 2s Graphene easily on hobbyking for not much money (around $12). It's a tiny battery and more than capable of powering the tri-blade burst current with its continuous current rating.

No need for a battery with 154A burst capability.


Triblade = 22A x 3 motors = 66Amps, right? 25C burst/2200mAh seems to be cutting it close.

Yes 154A is overkill especially for Triblade at 2S but I was mainly suggesting LiPos that could handle a 3S hellcat/wolverine build.

Edited by jwasko, 27 March 2017 - 07:41 PM.

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#7 Speedr117

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Posted 28 March 2017 - 10:38 AM

https://hobbyking.co...45c-w-xt60.html
I decided to purchase this one since people like graphene battery's.
https://hobbyking.co...-lipo-pack.html
This one is similar while being a tad smaller. Any difference
They are both small with more than enough power for my blaster, I think? The both battery's have only one Ah so do you recommend a bigger battery for twice the cost. Or just get two of them.
Edit: P.S. I forgot to mention going for triple hellcats.
Edit 2: I decided against the small lipo and get this one https://hobbyking.co...45c-w-xt60.html more than enough c rating and capacity. Going to design and print a custom holder under the barrel.

Edited by Speedr117, 29 March 2017 - 08:52 AM.

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