Having a hard time deciding.  

Drop an 03 Air unit in my 4s AOS 3.5 with BH 1504.5 3950kv motors.  Dial motor output to 75% and run a 6s 380mah battery 

or

Get an F3 Split, re use the motors and FC from the AOS also reducing motor output to 75% for 6s

I have never flown a 3" I have flown whoops, 2.5", 3.5", 4", and 5".  I love the feel of the sub 250 AOS 3.5 on the BH motors.  It has the kind of thrust and power I like.  But I want to add an 03.  Will it still have the power and thrust on dialed back motors with 6s?  Being used to 3.5" am I going to be dissapointed with 3"

If you are strictly trying to stay under 250g, does it make sense to go to 6s? Smaller cells tend to underperform and if you are looking at the GNB yellow 90C HV cells? in my experience those cells are great in being light, having excellent flight times, but clearly fantasy C ratings, will sag, and deteriorate or flat out die after a few cycles (I've even received some doa, never experienced with any other battery)..
I've not flown 6S so maybe I don't know what I'm talking about, but on my heavy 3.5" (not sub 250) 220g dry with Naked Gopro and 1604 motors, running a 4S 850 non-HV pack (RDQ but I believe GNB rebrand) in sub zero temps, get excellent performance - little sag, plenty of burst, and close to 6 minutes flight time. You will likely get better performance from a larger mah cell.

But as for a 3" O3 build, you will certainly lose some flight time compared to your 3.5", but depending on your flying style maybe you would still enjoy it. But again not sure 6S makes sense on 3" if you cannot get a decent battery?

(14-Feb-2024, 12:27 AM)mstc Wrote: If you are strictly trying to stay under 250g, does it make sense to go to 6s? Smaller cells tend to underperform and if you are looking at the GNB yellow 90C HV cells? in my experience those cells are great in being light, having excellent flight times, but clearly fantasy C ratings, will sag, and deteriorate or flat out die after a few cycles (I've even received some doa, never experienced with any other battery)..
I've not flown 6S so maybe I don't know what I'm talking about, but on my heavy 3.5" (not sub 250) 220g dry with Naked Gopro and 1604 motors, running a 4S 850 non-HV pack (RDQ but I believe GNB rebrand) in sub zero temps, get excellent performance - little sag, plenty of burst, and close to 6 minutes flight time. You will likely get better performance from a larger mah cell.

But as for a 3" O3 build, you will certainly lose some flight time compared to your 3.5", but depending on your flying style maybe you would still enjoy it. But again not sure 6S makes sense on 3" if you cannot get a decent battery?

I say 6s becuase in the 03 sub 250 builds i have seen with claimed 3-4 minute flight times, that is the only difference in specs than what I have now. With the walsknail 1s VTX and a 4s 850mah battery I get about 2.5 min, 3 if idont go full send. I sit right at 245grams and so I know the BH 1504.5 motors handle that weight well. If I swap in an 03 air unit I will go to 270-280 gram territory. I "could" use a 4s 550mah lipo to get weight back down to under 250 but with those batteries I only get 2 minutes, sometimes less. The 6s 380mah hour lipos weigh about the same as the 550mah 4s lipos. Only thing I can figure is the higher voltage uses less current? More efficient for longer flight time? I dont know.

I have only flown 1100-1300 6s on my 5" I have never flown a super small 6s so I dont know either. But I have actually had good luck with the GNB's I have several that i use regularly. Its my CNHL Blacks that die most lol

I have lots of CNHL orange packs, despite being HV and sold for dirt cheap, those have all lasted even if they probably don't give as much flight time as before, at least none of the cells have died. I have a lot of GNB packs too and always thought they were a good brand, but I have too many dead GNB HV cells, I don't baby my packs, but I don't really fly hard either.

I had pretty bad flight times with my 1604 3.5" build at the start, probably 3 to 4 min only, but that RDQ 4S 850 really did wonders. You probably fly at higher throttle and warmer weather = thinner air so maybe thats why you get such short flight times. With the flight times you are getting now, going down to 3" you will lose efficiency, add more weight (at least drone:battery), so maybe looking at under 2.5 or even under 2 min flight time?! If its just the cost a frame, it might be worth a try, then you can move the O3 back to the 3.5" and put a walksnail on the 3".

So just be aware that CNHL Lipos tend to be heavier than say equivalent GNB or Tattu packs. I have tons of CNHL lipos lying around and they are good, but if you compare say a CNHL 2S 450 HV to a GNB 2S 450 HV, the CNHL is heavier and I don't think they last as long, nor keep you in the air as long. Those GNB yellow 380's aren't so good either. I bought 10x 2S of them when I first started and none lasted the first year. The 2S 660's are still running over 2 years later. The CNHL I definitely have lost capacity on the 2S packs, but I have flown them many times. For me the Tattu packs are worth the extra money if you are looking for max performance and power, but they are a premium battery and you can usually get somewhere near double the number of batteries for the same price with CNHL and on occasion, possibly more in the deals. So it's a bit swings and roundabouts. If you don't mind having a battery that is slightly heavier, doesn't give as much flight time, but you can buy two of for the price of one premium battery, then the CNHL are often the best deal. I use them because whether I take say 10 Tattu packs or 20 CNHL is irrelevant to me. If I have to change the battery more, so be it.

fwiw...

Extra voltage driving 5" props is nice vs sag, I felt a larger jump going from 4S to 5S than from 5S to 6S flying 5 & 6"ers in the past.

Smaller disc area of 3" props vs 5" props are really better suited for lower weight, not just spinning faster. You can make a very fling-able brick but it won't be prone for more flight time.