What factors would affect a drone's flight time? Battery capacity? Weight? Anything else?
I'd watch out for several factors:
Drop any additional weight that you don't absolutely need for functioning. This may mean downsizing to smaller motors, which obviously means that you have to balance weight vs. power; you may be able to get your flight time much longer but at the expense of speed.
Obviously the more juice you got, the longer you can go for. Again, though it's going to be a balance between the weight of your battery... go for lighter technologies like LiPo.
Also, make sure you've got new batteries on your drone; as your batteries age, they'll lose juice and capacity.
If you really want to increase the flight time... go for lighter less powerful motors. Of course, you won't be able to go as far, so that may not be a tradeoff you want to make.
Make sure you're flying your drone in dry weather... Condensation or water droplets will both add resistance to any moving parts and weight. Also, when the weather is well below freezing you'll notice that your batteries will start performing less well, as well as having increased friction.
Keep all moving parts well greased! As friction increases, the amount of battery power you use will increase in consequence.
Also, make sure all contacts remain solid. Though it's not a big issue with newer drones, rust in the contacts / loose contacts will eat power.
All of the things you mentioned will affect flight time.
Here is a synopsis:
The batteries you use will have a very large impact.
Firstly, your battery chemistry. Li-ion generally has a larger capacity for the same weight but can provide a lower current. This means that if you are doing slow or cinematic flying, it is worth looking at lithium ion batteries.
Capacity also has a lot to do with it. Generally, greater capacity provides greater flight time, however this only works up to a point. If I use a 300mAh 2S LiPo on my toothpick, it will provide less flight time than a 450mAh 2S LiPo. However, an 800mAh would probably not give that great a flight time as the added mass takes more energy to lift than the battery can provide.
Finally, the cell count has an impact. One of the reasons that people like to fly 6S is that it reduces battery sag, and this means that you can fly for longer before your voltage drops too low.
Propellers and motors
Generally, larger propellers and low KV motors are more efficient. This is why long range builds commonly use 7inch props.
Also, lower pitch props produce less power but are also more efficient so will increase flight time.
Flying 2 blade props is also generally more efficient.
All up weight
Obviously, a heavier quad will take more energy.
Mathematically this is because F=MA, and more energy is required to create a greater force for the same acceleration.
Flying style and conditions
Flying in windy conditions will often drain batteries more quickly as you have to spin up the motors to fight against the wind.
Batteries also perform worse in cold conditions.
If you fly more acrobatically or race, you will drain your battery more quickly than if you are just cruising around.
Sometimes, changing settings in your software can improve flight time.
For example, setting your ESCs to 48KHz on tiny whoops and toothpicks can greatly increase flight time.
I hope this helps, feel free to ask for any clarification or if you feel I’ve missed anything.
Flight time is all about efficiency. The more efficient your drone, the longer it can fly given the amount of stored energy it carries.
There are a couple things you can do to improve efficiency. The biggest one is to reduce weight. The less the drone weighs compared to the energy source ( battery etc. ). The longer it can fly. You can add larger batteries to increase flight time, but there are diminishing returns there. Eventually you have to increase the size of everything to compensate for the larger battery.
The other thing you can do to improve efficiency is to use the most efficient propellers you can. In general larger propellers are more efficient as are propellers with fewer blades. Many racing drones use propellers with 3 blades because they improve maneuverability, but that comes at the cost of decreased efficiency.
Weight - the less the drone weighs, the less energy needs to be used to lift it so it will fly for longer on the same charge.
Battery Capacity - The more charge the drone can carry, the longer it can fly. However increasing battery capacity increases the weight (for the same battery technology)
Battery Technology - As an extension of the above two, some batteries weigh less than others for the same stored charge - this is called the specific energy. a higher specific energy lets you have more battery capacity for the same weight.
Aerodynamics - this is more important for fixed wing drones, but does apply to multirotors. The less obstruction you have to airflow - be it over the fuselage, or around the motor arms - the less drag will be experienced so less force (and so energy) is needed to sustain flight.
Altitude (above sea level) - as the air density decreases, the motors need to spin faster to move sufficient air to stay aloft. Some manufacturers produce high altitude propellers to improve efficiency
Propellers - more blades on a propeller reduces efficiency, as each blade is subject to more wake turbulance from the one ahead. However, as the blades get longer the force needed to rotate them increases; so there is a trade-off to balance.
The main thing to Remember is never to go below min voltage on say a 4 s 14.9 volts this will keep your battery in good condition and increase the life of your battery I would say flight time depends on what type of drone you are flying freestyle about 3 to 4 mins on a 4s battery the main thing is never go beyond the min voltage the battery is the most used piece of equipment and also very expensive so I would advise battery halt before increased time flying