IIRC this is even a loading screen hint, but just in case anyone missed it (or is interested in the actual ratio), I decided to quickly test it.
| Zonai Charges | Capsules | Ratio |
|---|---|---|
| 1 small | 1 | 1 : 1 |
| 2 small | 3 | 1 : 1.5 |
| 3 small | 5 | 1: 1.6 |
| 4 small | 8 | 1 : 2 |
| 5 small | 12 | 1 : 2.4 |
| 1 big | 10 | 1 : 10 |
| 2 big | 22 | 1 : 11 |
| 3 big | 34 | 1 : 11.3 |
| 4 big | 47 | 1 : 11.75 |
| 5 big | 60 | 1 : 12 |
Conclusion: if you find a Zonai Device Dispenser with stuff you really like, feed it 5x Big Zonai Charges at once for maximum payout. The smaller Zonai Charges are best kept for other stuff, like checking what exactly a newly discovered dispenser spits out or refilling your battery in a pinch.
EDIT / ADDITION:
If you mix-and-match, you get the following output in capsules:
| Zonai Charges | 0 small | 1 small | 2 small | 3 small | 4 small | 5 small |
|---|---|---|---|---|---|---|
| 0 big | 0 | 1 | 3 | 5 | 8 | 12 |
| 1 big | 10 | 12 | 14 | 17 | 21 | |
| 2 big | 22 | 24 | 27 | 31 | ||
| 3 big | 34 | 37 | 40 | |||
| 4 big | 47 | 50 | ||||
| 5 big | 60 |
The blank squares are impossible as you can only put 5 items at once into the dispenser.
The Ratio:
| 1:X Ratio | 0 small | 1 small | 2 small | 3 small | 4 small | 5 small |
|---|---|---|---|---|---|---|
| 0 big | 1 | 1.5 | 1.6 | 2 | 2.4 | |
| 1 big | 10 | 6 | 4.6 | 4.25 | 4.2 | |
| 2 big | 11 | 8 | 6.75 | 6.2 | ||
| 3 big | 11.3 | 9.25 | 8 | |||
| 4 big | 11.75 | 10 | ||||
| 5 big | 12 |
What about Construct Horns?
These are always a 1:1 deal. Even if you put 5x Captain Construct IV Horns into the Device Dispenser at once, will you get 5x capsules in return.
All good info. At the time, I was actively avoiding looking things up, just trying to play as organically as possible. At some point I had stopped opening chests in the depths, because it seemed like the old map locations had the good loot and everything else just had charges or normal items. I wasn't sure if you needed a map before the good loot spawned (you do not) or if opening a chest before getting the map affected the contents (also no).
Was very much looking forward to a master mode replay using better resource management, but Nintendo rained on that parade. 😒