Mini Quad: 3S, 4S Setups Comparison and Migration

In this post we will have a look at the difference of mini quad running 3S and 4S lipo batteries. Many who are building their first mini quad might struggle to decide which setup to go for, I hope this post can answer some of the questions. Also I will talk about how to move from a 3S mini quad setup to 4S, as I was asked a few times from FPV’ers who want more power and speed.

I am new, Should I start from 3S or 4S?

4S is now a standard voltage level  for a mini quad to run, so you should just start on 4S. There are just so much extra investment both in time and money goes to waste when migrating from 3S to 4S later on.

Difference between a 3S and 4S Setup for Mini Quadcopter

It’s kind of obvious, the main difference is voltage that powers the motors.

Let’s say we have a 2300KV motor, when powered under 3S lipo (12.6V), RPM (rotation per minute) is 2300 x 12.6 = 28900 (in theory). That means the motor spins 28,900 times a minute without any propellers. When you power the same motor with 4S lipo (16.4V), the RPM is 2300 x 16.4 = 37720, that’s a significant increase in RPM.

Increase in RPM means more thrust, more power, and your quadcopter flies faster and throttle becomes more sensitive and harder to control.

Also note that 4S setup are usually a little heavier than 3S, because of the additional weight of the voltage regulator, and heavier batteries.

But if you think a 4S mini quad is too powerful and hard to control, you can always adjust your throttle output range to 75% or even 50% to tame it down. (Mixer page in Taranis, reduce weight to 75 or 50, and adjust offset so the range start at -100)

Upgrading from 3S to 4S

Here are some tips in case you are getting bored of 3S, and want a faster mini quad. If you can afford it, you might also consider building another quad purely designed for 4S LiPo. It’s not a bad idea to have two quads when one is down for maintenance.

Motor and ESC

First question to ask is: can your motor and ESC handle 4S? For both increased voltage and current.

Popular 3S motors such as DYS 1806, EMAX 1806, T-Motor MN1806, Cobra 2204 2300KV and so on have been tested on 4S and seems okay. Of course you do it at your own risk, motors rated for 3S are not really designed for 4S, but it gives you the immediate results. It would be ideal to upgrade your motors to 22xx class with lower KV around 2000 whenever you can. (for example Cobra 2204 1960KV, or Cobra 2208 2000KV)

But be aware try not to run anything larger or higher pitch than 5030 on 4S with 1806 motors (which are usually rated for 2S-3S). When current gets too high, the little motor and thin motor windings will start to gather heat. If you keep pushing it, the enamel on the motor windings will burn off, causing electrical shorts inside the motor, between poles. Eventually it will lead to fatal power loss, and the motor will fail while your quad is travelling at top speed. And BANG! Your quad crashed into pieces.

Most 12A ESCs these days can run on 4S such as Afro, Blue Series ESC or KISS ESC, but it’s always worth checking first. When voltage increases, current draw will also go up. So make sure the motor and propeller combination you are planning to use would not exceed the current rating on your ESC. In some cases it’s necessary to upgrade your ESCs from 12A to 18A / 20A.

VTX / FPV camera / OSD

It’s very likely that either your video transmitter or FPV camera or both does not support 16V input. In which case a voltage regulator or a BEC is required to convert 16V to 12V (4S to 3S). I have been using this mini voltage regulator since I first built my 4S setup, it has never disappointed me.

Also make sure your OSD can read / be powered by 4S lipo. I made this mistake when I bought the Hobbyking E-OSD, and listened to some “rumour” that it can run on 4S although it’s rated for 3S. Spending $10 to watch some magic smoke is really not worth it. :) Since I have been using Super Simple OSD that takes 2S-4S, I like it because it’s plug and play, no configuration required.

18 thoughts on “Mini Quad: 3S, 4S Setups Comparison and Migration

  1. Modzel

    “When voltage increases, current draw will also go up.” How is it possible? sudden change in laws of physics?

    Reply
    1. Oscar Post author

      Voltage increases RPM, and that leads to motor drawing more current. Just check thrust data and you will understand

      Reply
  2. landrieve

    hi oscar,
    when you go on the website of DYS, dys.hk/ProductShow.asp?ID=91, you can read that a 1806 2300kv, can run a 5045 without any problem and they never use 5030. Why?

    Luc, France

    Reply
    1. Oscar Post author

      they have changed the spec since. When they came out they were only supposed to run on 3S although some use it on 4S as well.

      Reply
  3. martteder

    Hi!

    How do You get OSD alarm work with both of battery types? Generaly You have to choose that you use 3S or 4S.

    Reply
  4. Jeremy

    Hi
    I have a question about the eachine 250 racer drone, i would like to upgrade the esc’s to 20a ones but the stock esc only has 6 conection points ( that must be including the servo wires )
    How to solder a new esc with more poles to it ?

    Ty

    Reply
  5. Mohammed

    I have t motors mn2204 2300kv and kiss 12a , Im thinking to give 4s a try , what do you think can i go with 4s ??

    Reply
    1. Benjamin

      definitely as long as your other gear can support it and you stay within a 5040 propeller. It will give you a lot more power.

      Reply
  6. Michael Anderson

    Hi Oscar

    Thank you for taking the time to make all of this information available. I enjoy reading it and I feel like I’m beginning to learn.

    I’m building my first quad – I’m not in any rush to get into the air. I’d really like to make sure I have a firm understanding of as much as I possibly can to begin with, and make sure I create a build with the greatest chance of success.

    I’ve begun purchasing the parts – I might have made some bad decisions. I hope you can find the time to give me your opinion.

    I’m building on the HobbyKing FPV250 Ghost Edition frame (with the cool looking LED lights). I’ve purchased the following setup:

    Cobra 2204 2300kv Motors
    Turnigy 18A ESCs
    Multiple sets of multiple propeller sizes for testing (all Gemfans, three sizes: 5030, 5045, and 6045)
    Turnigy 4S 20C 4000maH battery (this is now a source of concern at this point – worried it might be too big and heavy)

    I’m concerned that running that heavy of a setup (with that battery) might burn out the Cobras, especially if I try running the 6045s.

    For starters I will not be placing any FPV equipment on it, so the only other things will be a CC3D FC, the PDB that came with the frame, whatever wiring/velcro/sticky pads I will be using, my low battery warning beeper, and the receiver from my Turnigy 9X transmitter.

    The overall weight (even with the huge battery) will be coming in at around 800 and 900 grams, depending on solder/double-sided pads, velcro, etc.. (current weigh-in is 824 grams, but some wires will be trimmed down from ESCs and motors, and then the solder/velcro/etc… will be added).

    I’m considering purchasing a 3S 2200maH battery out of concern for burning out those Cobras. Any thoughts?

    Regards,

    Michael Anderson

    Reply
    1. Oscar Post author

      Hi Micheal.
      Motors and ESCs all look fine.
      As for props, 2300KV motors mostly runs 4 or 5 inch props, 5030 on 4S is good enough, with 5045, the thing is going to fly like a rocket! 6045 is probably too much i don’t recommend it.
      Yes the lipo is too big!, 1300mah-1800mah is a good range of capacity, while the weight isn’t too much.
      you should defintely check out this parts list
      and this cobra motor thrust tests

      Reply
      1. Michael Anderson

        Hi Oscar

        Thank you for the reply! I’m going to purchase a Turnigy Nano-Tech 4S 1800maH battery (hopefully they will be back in stock in the coming months) for this build.

        I am confused about one thing – I’m hoping you can answer this question for me:

        Every article I’ve read has suggested that the thrust power needs of a quadcopter is at least 2:1 in grams – some even suggest multiplying your quads weight by 2.2 and making sure you have a max thrust power at least equal to that (so if your quad weighs 1000 grams – multiply by 2.2 and you need a setup with a max thrust of at least 2200 grams, or 550 grams of thrust per motor). Easy enough to understand.

        My question is this: if my current build weight is at max 900 grams even with that huge 4S 4000maH battery, and the Cobra 2204 2300kv motors with 5045 props on a 4S battery produce 710 grams of thrust per motor (by your own measurements) – then I would be at 2840 grams of thrust versus 900 grams total weight, with a thrust-to-weight ratio of over 3:1 – much greater than the suggested minimum of 2.2 times the total weight.

        Going only by that calculation, it seems like my quad should have more than enough power to be able to fly with that battery.

        However, virtually everything I’ve read says that it’s way too big (yourself included) – and everybody with similar builds to this is using much smaller batteries (like what you suggested 1100-1800 maH size) – what am I missing here?

        Please understand that I’m not doubting you, and like I said above I am ordering the smaller battery. I would just like to know what it is I’m not grasping about this – obviously I am missing something!

        Thanks again for your reply (and for providing a great web-site), I hope you are able to answer this as well.

        Regards,

        Michael Anderson

      2. Oscar Post author

        For mini quad, people generally use it for racing and fly really fast, so we want to achieve the greatest thrust:weight ratio possible.
        It’s not uncommon to find someone building a quad with thrust:weight ratio of 7:1 !!!
        the 2:1 or 2.2:1 is the bare minimum you should have on a multicopter, it flies… but it won’t go fast…

      3. Michael Anderson

        Hi Oscar,

        Update from last fall: I completed the 250 mini-quad (ended up going with a QAV-250 type frame, but everything else the same)… Amazingly, even with that 4000mah 4S battery, this thing is still crazy-fast. “eCalc” claims that the top speed with that battery and 5030 props is around 60mph, 85mph with 5045 (all GemFan), and a flight time of about 15 mins (AUW is around 815g).

        I can confirm the flight time, I flew for about 13 mins and my low-voltage buzzer had not gone off yet. I looked at the cell voltage when it landed, and it was still at about 3.72v per cell, then after rest it came back up to about 3.83v/cell, so pretty near storage. I have my buzzer set for 3.5. I can’t confirm the mph as I don’t have a radar – but I can say:

        You were right: this thing is FAST! (even with the massive battery)

        I was actually getting kind of stressed out flying it because it felt like it just wanted to run away from me. I had a lot of trouble just getting it to hover and stay in one spot – and the slightest pitch in any direction sent it flying off much faster than I was expecting. I did one punch-out for about 3 seconds and had to stop because I couldn’t believe how high it got, and how quickly it climbed! I’m going to try to correct the drifting with PID settings (I’ve read that the “I” setting might be able to help with that) – it’s a CC3D in “attitude” mode.

        I’m going to change to a 3S 2200mah battery. That will drop its weight down to the 560g range, and lower max speed down into the 40mph range on 5030’s (again – according to “eCalc”). I think that would probably be best for me right now, until I get a better handle on controlling this thing. It is NOTHING like my toy quad that I’ve been flying (a “UDI 818A”) – that’s like comparing a Ford Mustang to a go-cart. I can’t even imagine what it would be like to fly one of those professional racer quads (or a “WarpQuad”), topping 100mph. Just crazy! Honestly, at this point: I wouldn’t be able to handle it, since right now I can barely handle this, and I didn’t even push it that hard.

        At least I didn’t crash, lol… the worst thing that happened was I nicked up the props a little bit in a brief brush with the side of my house (bricks).

        Thank you again for all of your time and energy in making this blog available. It has been very helpful and educational to me as I was putting this thing together.

        Regards,

        Michael Anderson

  7. Tbotten

    I have a question regarding the relation between motor and ESC.
    As i understand, one should check the maximum A for a given motor to determine what minimum A an ESC should be, right?
    My question: is there any danger to use a much bigger A-ESC? > E.g.: if the motor specs indicate that maximum A is 23, we could state that a 25 or 30A ESC would be correct, but is it also okay to use a 40A?

    Thanks for your help regarding this.
    Greetings from Belgium,

    Thierry

    Reply
    1. Oscar Post author

      it’s okay to use “overkill” ESC :)
      the only drawback i can see would be the excessive weight.

      Reply

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