Pro's & Con's of 3S vs 4S Batteries

[mrwestern]

I am a newbie here, having just built my first F550 (stock motors and blades). I was hoping someone (in the know how) could shed some light on the Pros' and Cons' of using 3S vs 4S batteries.

My observations so far are (This is for the same mAh):
Price: 3S cheaper than 4S
Weight: 3S lighter than 4S
Flight time: 3S longer than 4S (That is what the sales guy at the Hobbyshop told me - using 8"props for 4S and 10" props for 3S - so this needs to be substanciated )
Revs: 3S lower than 4S (Prolonged life for motors? Less heat and wear and tear)

I would appreciate your informed views, if you could add factors to the list or refute it that would be appreciated! Thanks.

 

[rilot]

Pros for 4S:

More power
More lifting capability

Once your F550 gets above 2kg you'll struggle with 3S as you'll have very little power in reserve.

 

[mrwestern]

Pros for 4S:

More power
More lifting capability

Once your F550 gets above 2kg you'll struggle with 3S as you'll have very little power in reserve.

Thanks Rilot for the response. DJI recommend using 8" props for the 4S - I assume because the revs are higher on the motors and 10" props will put too much strain on the motors? What are the most efficient props, to increase flight time?

 

[Motopreserve]

If you head over to eCalc you can swap batteries and props and see the relationship and effects these changes have. Might not be perfect, but it's great for researching these types of choices.

Good luck!

 

[rilot]

I use Graupner 10x5 props on the stock motors on 4S. No heat issues and plenty of lift.

 

[Silverburn]

Thanks Rilot for the response. DJI recommend using 8" props for the 4S - I assume because the revs are higher on the motors and 10" props will put too much strain on the motors? What are the most efficient props, to increase flight time?

Bigger props, turned slower = better flight times.

I prefer to think of 3S = "endurance", and 4S = "performance". Hardly scientific, but there you go.

Re: heat etc - it's more a factor what props you're asking a motor to turn. An underpowered/undertorqued motor will heat up more trying to turn a prop that's too big for it. Bearing life is negligible, all things considered - your crashing will damage them more than any 3S/4S load mixes.

 

[DucktileMedia]

One thing to keep on mind is that it is much harder to tune 3s/10" props to keep jello out of the gopro. I found on almost all my small quad builds that the frequency the motors needed to spin to hover was just right in that area that showed the worst jello. Spinning a smaller prop faster immediately got rid of the jello. Also an 8" APC sf has about the same area as a 9" graupner. Which is why spinning 10" graupners on stock DJI motors works ok, its also nice because the hub fits perfectly over the notched motor shafts without needing to be bored. But 4s on smaller props will reduce the flight time. A lot of this has to do with balancing and disc loading. If your f550 is carrying a gopro and you put 4s,2216's and 10" props on it, you better have things perfectly dialed or it is gonna be squirrely in the air.

 

[Bowley]

One thing to keep on mind is that it is much harder to tune 3s/10" props to keep jello out of the gopro. I found on almost all my small quad builds that the frequency the motors needed to spin to hover was just right in that area that showed the worst jello. Spinning a smaller prop faster immediately got rid of the jello. Also an 8" APC sf has about the same area as a 9" graupner. Which is why spinning 10" graupners on stock DJI motors works ok, its also nice because the hub fits perfectly over the notched motor shafts without needing to be bored. But 4s on smaller props will reduce the flight time. A lot of this has to do with balancing and disc loading. If your f550 is carrying a gopro and you put 4s,2216's and 10" props on it, you better have things perfectly dialed or it is gonna be squirrely in the air.

+1.

 

[farmerfred]

I have a 3s 5500mah and use 10" props and it's a perfect combination. Think my f550 is about 2kg.

What combination you choose is all dependant on weight of your machine. To start with 8" props are great and your f550 will be nice and manoeuvrable but as you add more wight like fpv stuff you'll notice your motors are working harder as they are louder...
That's when your ready to switch to 10" props... Not as manoeuvrable but more stable and the motors don't have to work quite so hard...
Then when you add more weight you might want to buy a 4s for more grunt and to maintain decent flight times.

But for me 3s and 10" works well.

 

[el gwiz]

Thanks all, that's a great help, was thinking of changing prop/battery combination but won't bother now.

 

[mrwestern]

Thank you to all who have contributed, a lot of wise words here!!

I have decided to order some 4s 8000mAh 30C and will switch to the 10" props (for now). I will look for some Gauptner 10" Carbon Fibre props going forward, unfortunately I have not been able to find any in South Africa? Looked at their website and the supplier details for South Africa seem to be fly by nighters. Anyway if anyway has suggestions on alternative props (as I cant seem to find Gauptners) then that would be just great!! BTW my F550 will have the following gear on it (so it wil be a bit heavy):
- Naza V2 etc
- iOSD mini
- DJI Videolink
- DJI Datalink
- H3 2D gimbal
- Carbon legs (no name brand!)
View attachment 15918
Here is a shot I took today:

 

[DucktileMedia]

you might be better off ordering 4000's as you will not only have the option to run 1 4000 but you have some sort of redundancy with your lipos if one should fail mid flight.

 

[Motopreserve]

you might be better off ordering 4000's as you will not only have the option to run 1 4000 but you have some sort of redundancy with your lipos if one should fail mid flight.

+1.

 

[mrwestern]

you might be better off ordering 4000's as you will not only have the option to run 1 4000 but you have some sort of redundancy with your lipos if one should fail mid flight.

Good point IrisAerial!! Will see what I can do, as I have already paid for them.