Before we get started, let me tell you the specs of my quadcopter.
Frame S500 with carbon fibre landing gear
Motors Racerstar 920kv
ESC 30A Simonk
Onboard computer: Odroid XU4
Gimbal (To be added later) Tarot 2D
GPS uBlox NEO 8N
Currently I am using Gens ace 5000 mah 3S 11.1V battery and the current flight time of my drone is roughly 6-7 mins. The battery itself weighs about 400g. Any tips on how to get a better flight time i.e. around 10 mins if thats possible?
Is this battery good enough or do I need another one that is lightweight? What battery do you recommend?
[quote=“hassan, post:1, topic:49515”]
Motors Racerstar 920kv
The performance data isn’t very detailed, but it looks like you could try a 4s battery. What props are you running?
Thanks for the reply
It’s Racerstar BR2312 960KV Brushless Motor with 1045 carbon fibre props. The thrust pull of each motor is 845g
Your original post listed a Racestar 920kv motor, but I think the answer to your question is ultimately the same.
Usually the motor manufacture provides more data, at the very least specifications for thrust and current at various throttle and voltage combinations such as 25%, 50%, 75% and 100%, which would make it easier to assess the characteristics of the motor. In my experience, 9.2 amps is a lot of current for only 845 grams of thrust, so I am going to assume the specifications are for 100% throttle. For comparison, a T-Motor 380kv 4006 motor only draws 3.1 amps at 805 grams of thrust, although 6s and 15" prop. The general rule of lower kv, larger props and higher battery voltage usually, but not always applies.
In any case, looks like you gain 135 grams of thrust and reduce current draw by 1.4 amps per motor by going with a 4s battery. You will offset a certain amount the efficiency gained as a 4s battery of the same capacity will be heavier. It’s the first thing I would personally try to achieve longer flight times.
Currently I am using 40C 5000mah Gens ace 3S1P battery right now. Currently its powering pixhawk, motors, 30a esc and odroid (5V/2A). The weight of the battery is around 400g which I think is very heavy. What do you think?
What’s the all up weight of this craft with that battery?
It’s unlikely you will find a significantly lighter battery unless you go with less capacity. I would look at other factors to increase flight time, including a 4s battery. The physics of flight can’t be ignored, and as a favorite author of mine would say - there ain’t no such thing as a free lunch.
Start with your AUW - with battery - as @dkemxr has requested. This is probably the most important consideration in terms of selecting system components. Motor selection is usually made within the context of AUW, but in this case we will have to work with what you have.
Does you system include a calibrated current sensor so we have some idea of what current usage is at hover? Combined with AUW we could assess whether your configuration is up to the task.
Total weight of my drone w/ battery is ~1150g with gimbal and ~850 without gimbal.
But won’t a 4S battery be more heavier than 3S? Total weight of my drone w/ battery is ~1150g with gimbal and ~850g without gimbal.
No, I don’t have a calibrated current sensor at the moment. How do I find out the current usage at hover?
1st, it doesn’t make sense that you are only getting 6-7 minutes of flight time with that configuration. You should expect ~15min. How much mah did you put back in after this flight battery was charged? But let’s say you went to a 4S 5000mah battery anyway. A 25C version of this battery would weigh ~550g so the crafts all up weight would be 1300g. This would provide more power and a few more minutes of flight time. I have a 550 on 6S and wouldn’t do it any other way. The only down side is the expense of the battery.
The other option for you is to use 12" props but there is still something else wrong with the flight time you are reporting.
Agree with @dkemxr on all points.
Do you have more than one battery, and do you get the same results if you do?
I am of the opinion you have a problem battery, or the motors you have selected aren’t up to the task.
Please provide a bin log. I’d like to look at your throttle and requested power for each motor.