Hi,
I have a strange issue. I can fly my apm 3.1.15 quadcopter perfectly when i'm using my 5000mah Zippy 20C 3S battery. However when i put in the 1600mah zippy 20C 3S battery i can't take off without flipping the quadcopter and landing on it's back. I've tried three 1600mah batteries with the same result. but as soon as i put in the 5000mah all is good. I took a quick glance at the pids but they seem to be on default values. The only theory i could come up with in my head is that weight of the 5000mah battery was some how balancing the copter.
Bear in mind, i've ran the compass calibration, got respectible values, and i've also done compassmot and got very respectible values. i'm not too sure whats wrong. Any help would be appreciated.
Replies
I figured out what was happening. Turned out to be nothing to do with the mah of the battery. Mission planner was resetting the Battery "Sensor" setting in Mission planner to "other" even though i had selected 3DR power module. This seems to upset the quadcopter when trying to take off.
Your question is easy to answer:
Your quad need a lot of amps during take off when you give it some throttle.
The 5A 20C 3S lipo will give you a max of (5*20=) 100A.
Unfortunately your 1600mAh= 1,6A lipo just offers (1,6*20=) 32A max.
Just imagine each of your motors takes up 10A at the throttle you need to take off then you will need 40A on takeoff.
The 1,6A lipo just gives you 32A max.
You see the problem?
But, you could calculate what lipo you need to make it work:
Plan A:
To get the same 100A as the 5A lipo you need:
100A / 1,6 = 62,5C lipo (so: 1,6A lipo @ 62,5C : that is a lot)
or
100A / 3 = 33,3C lipo (3A lipo @ 33,3C : that is more doable)
So to get the same 100A the 5A lipo offers, you need to get a 3A 33C lipo.
Plan B:
use three lipos in parallel:
3x 1,6A 30C = 90A (almoust will give you the same amps as the 5A lipo.
or
2x 1,6A 50C = 100A
You see, just using 1,6A instead of 5A lipos won't do it. You need the C-rating into account, too.
Thanks for the reply CyberCrash, but my quadcopter used always work with the 1600s. It's a very light frame, Something happened lately to change that. I don't know if it's a mis setting in mission planner or the new 3.1.15 firmware.
It did fly with those 1600mAh 20C lipos?
Really?
Okay, then I guess your motors do use up more power. Maybe you had an accident and now a motor has more friction.
Use the 5A lipo, fly around for some minutes (just hover) and then touch the motors and find out if any of them is getting hotter than the others.
After updating firmware a few weeks ago on my main flyer I experienced simular problems. Turns out it was in + mode rather than x mode. I have no idea why it would have changed, but I popped it back into x mode and she was right as rain.
Ya, i noticed this myself a few days ago. Had to connect mission planner to it again to switch to X but, i had never set it to + in the first place. Weird. But don't think it's related to this instance.
I've actually had this happen to me as well. But this would not explain why the 5000 works while the 1600 does not.
Simple, the small batteries cannot supply the required current peaks, and you have brownouts.
Ok, what quad is that ?
Hi Gustav, i've had the quadcopter about 8 months and the 1600s were my first set of batteries. I was always able to fly it with the 1600s, something is after happening of late to change that. But i don't know what.
I'm betting on a much simpler answer... if it was tuned for a 5000, the quad is simply too light for the tuning you have with the 1600.
if this is right or wrong, it's easy to find out. tape some more weight on the quad so that it weighs the same as it does with the 5000 and try to take off. If it still flips it's something else... but if it flies, the tuning is simply too aggressive for the light weight you have with the 1600
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