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Tanithlord

The 2S vs the 3S debate

I was just looking for pros and cons of 2s and 3s Lipos and wondered why people will chose one over the other. I know that size can play a major part in this and also i understand that its not advised to run a 3s via normal motors

James
Boff

It's not really a debate... It's 3S because it's what the mainstay motor du jour is designed to run on. If you're running MTB Rhinos on anything else, you're probably doing it wrong. The MTB 180 Hellcat was also designed around 3S so that people would have cross compatibility.

If you're not upgrading your motors then 2S for stock is fine however if you're over-volting then you're going to need to re-wire. You might as well then motor swap while you're there.
Franksie

i intend to do a rewire with 2S and stock motors first so i can get to know the blaster workings better.  Subconsciously i also feel as if FPS will be a bit lower with this setup for use against the kids and/or indoors.  Is there any real world fact in that assumption?! Laughing
Boff

You are correct: most 2S/stock motor builds don't clock much over 100FPS from memory. Compare that to a 3S LiPo MTB Rhino Stryfe that will shoot in the 110-115FPS range just fine.
UKNerfWar

Boff is bias because he only stocks 3S motors.

If you want an impartial answer to your question then it depends entirely on the motors you are going to be using in your build. Some work best on 2S, some on 3S so when deciding how to upgrade your blaster it's always best to start with the motors.

The size of the pack is another factor to consider. 2S packs are generally smaller in size for the same capacity so if you have a small battery compartment, a 2S pack will like permit you higher capacity. For example, without using an ugly tray expander you can fit a 850mah 2S pack in a Stryfe tray but the biggest 3S I have found to fit is 350mah (this may have changed with the introduction of 'graphine' packs but I've not used those yet). Using a lower capacity 3S isn't necessarily a problem though. All you need to do is make sure you carry a spare and swap packs should you loose power during the day.
OldNoob

As noted, size of packs, with 3s being bigger, is a factor.

The key with pack selection is to ensure its matched to the motors you are using, MTB have made this easier by pre setting the RPM to the optimal range at their recommended voltage, e.g. Rhinos freewheel at 33k @ 3s and Honeybadgers at 36k @ 2s. This has a knock on in the RS where you pick a Rate of Fire by RPM.
The next factor, after the pysical size of the pack and its resultant performance, is the current loads imposed by the motors. A motor producing a given torque at a LOWER voltage will demand more CURRENT than a motor of similar power output at a higher voltage. This is to do with the conservation of energy, TLDR- you can't make something out of nothing. 3s motors will thus typically have lower CURRENT demand compared to a similarly spec'd 2s motor.
This becomes more obvious in 180 motors (master race) where the greater physical size enables them to produce monster torque (good news) relative to weedier 130's. Take the MTB hellcat, it makes a whopping 67mNm of torque, THREE TIMES that of a Rhino. It does so with a stall current of 23A. The MTB Reaper, 2s 180 prototype makes about 70mNm of torque but at a whopping 41A stall load.
That load can be a factor in component choice and safety, for example 2 of the Reaper motors is 82A potential stall,which is 410 TIMES A LETHAL LEVEL for humans. That should make people consider MOSFETS and Fuses as far more essential in hi power builds than they do currently. A single MOSFET running the flywheel motors or a 40A master fuse would protect you in the event of a short during a  stall.

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