Hello.
I needed of a small, cheap and easy to carry, drone to do some generic VLOS training; not too fast, with alt-hold, loiter and telemetry trough FPV camera.
I was worried about autonomy so I decided to try some Li-ion batteries.
I am pretty satisfied with the results: it’s a 5", 550g AUW (1.2 libs) and can fly for 18-20 minutes.
The issue with li-ions is the low discharge current compared to Lipos, I’m using Sony Murata vtc6 and maximum suggested current is 15Amps, you can draw up to 30Amps if the temperature does not rise over 80 deg Celsius (176 Fahrenheit)
Loiter and alt-hold modes are not a problem, it hovers with 6 to 9 amps.
If I keep max throttle and wobble frantically pitch, roll and yaw to their maximum ranges the current stays under 20 amps.
However a simple throttle punch in stabilize mode will immediately draw over 30 amps.
I would like to keep stabilize aviable as a mode but I cannot risk to damage the batteries, I’d like a maximum current draw around 20-25 amps in stabilize.
I’ve thought of 3 possible solutions:
MOT_BATT_CURR_MAX
It’s already set to 25 amps but it takes 5 seconds to activate.
I’ve noticed the parameter MOT_BAT_CURR_TC, if I set it to 0 will the current limiting activate immediately or the minimum value is 1 second? (cannot find documentation)
THROTTLE CURVE / ENDPOINTS
I can modify the throttle curve on the radio to avoid going over a certain threshold but I think this will mess up alt hold and loiter mode.
MOT_SPIN_MAX
I could lower this value and keep checking logs until I find a sweet spot.
Will this cause problems while manuvering?
What course of action do you suggest?
Thank you for your time.
Same thing now I’m doing in current project only problem with li-ion discharge rate it’s tooooo low , so now I’m doing is 4s2p or may-be 6s1p and throttle cut on somewhere
Are you sure ??? , Because in my case it’s only 8min and max 10 and with 200g load 4 to 5 max
Li-ions batteries are used in a multitude of devices and have a wider range of specs compared to lipos.
You need to check rewievs sites, tests reports and technical sheets provided by the manifacturer of your batteries.
My, sony-murata vtc6, batteries have:
Maximum voltage charge 4.25 volts
(some li-ions have 4.1 max voltage and you cannot charge them with lipo settings)
Cut off voltage: 2 volts, if current is under 1 amp.
Cut off voltage with current over 1 amp: 2.5 Volts
Rated capacity: 3000 mAh
I use a 4s1p pack from 16.8V to 11.5V (2.87 per cell).
My first alarm is at 11.8V, 2.95V per cell. (under load)
I could go lower but I don’t need a longer flying time, it’s a boring drone.
A reminder: be sure to have low voltage cutoff disabled in the ESC settings.
There is no limit to the time constant parameter. Looks like setting it to 0 will cause an immediate reduction in throttle if the current goes over the limit. Setting it to any positive value will cause the throttle to gradually decrease for as long as the current is higher than the limit; a smaller TC value makes it decrease faster.
It might not be a good idea to use 0, though - I speculate that it might cause the throttle to oscillate in some situations. A small TC of 0.5 or something would work, I think. Then again, the parameter says the recommended range is 0-10, so maybe 0 is fine.
I’ve used the VTC6 as well, it’s a very good cell. As far as Li-ion cells go, it actually has a pretty high discharge rate, but one thing I did to reduce current demand is increase cell count. That was also useful for increasing the bottom-end voltage for performance reasons, since lion cells can go much lower than lipos. Might be worth considering if your ESCs handle 5S or 6S voltage.
I have lg 3000mah on 15A burst 20A
And I’m charging at lipo method it’s correct ?
Because when I purchase cell then seller say charging method look like lipo don’t forget it , why this message say to me , I’m too confused.
And in flight my pack is too hot during only 5min and surprise things is when I disconnect to the fpv then rise temperature quickly , this is out of my head
My pack is warm after flight but I’ll not define that as HOT, however the terminology HOT is quite subjective.
You should check the logs and take a look at your amp draw, if they get really hot you are drawing too much current, in that case the capacity decreases and you get reduced flight time.
Yuppp , and also lg icr18650hb2 1500mah it’s rated 30A and 40A burst
And when I testing then after 6min my pack is soo hot and 2min later I checked in charger then cell voltage ia 3.60v and overall current draw nearly 10 to 18A
So your issue is specifically with punching out in stabilize mode? To me this indicates a bad tune, with your motors wasting amps fighting each other and oscillating between full and off rapidly. Motor efficiency is nonlinear in throttle, so going full throttle with 50% duty cycle is way less efficient than holding 50% throttle. You can check individual motor throttle in the onboard logs.
I had this issue with a quad I designed that incidentally used Li-ion as well: pre-tune it drew 2x the current I was expected, but autotune fixed it right up.
The thing is with Li-Ions that you won´t get any benefits if your aircrafts flight time with regular Li-Po batteries is below 30 min. Manufacturers usually list Li-ion rated and burst currents, but at those discharge rates you woun´t be able to discharge the batteries to theit full capacity and this is why LiPos work better at these lower flight times.
Try to look up discharge curves of your cells and you will be able to determine how much usable capacity you have at a given discharge rate.
Yeah that’s why I made 1 3000mah 20A burst 30A and 2 1500mah 30A burst 35to40A and those 2 pack together with XT60 and this 2 XT60 to 1 XT60 given main point ,
yeah but this experiment work in progress
The discharge curve is more banded on voltage drop to 4.18 to direct 3.60 in 3000mah cell because amps rating is too low and I only nearly 1700mah pull out from my pack and talk about 1500mah cell it’s surprising 1100mah pull out from pack after its very hot “Both”
This value on 9" in standard F450 frame
And lipo battery hard to receive in my country mostly fpv battery
Sure. When I built my Li-ion quad I used the motor efficiency data (g/W) and the total mass to calculate the hover current, but when I tested it I was getting really bad controllability and double the current draw I expected, so I thought “I guess something is wrong with the Li-ions and I should have used LiPo”. It was just flyable enough to get it up in the air and run Arducopter’s autotune. After that I got hover at my expected current draw.
Looking at your new crashes I think you do have a new issue. I’ve have yet to experience crashes like that fortunately.
Last 3 days to i mark , there is so much voltage drop on little punch or something similar to do then altitude and performance are bad at that time , it’s because voltage drop is big praposnal to discharge rating is to low.
Maybe Li-ions not for fpv it’s perfect for big copter like (in my experience) 8 to 13inch
Ok I didn’t know how you were trying to fly. If you’re doing acro or manual flight and you might want to punch out or avoid an obstacle, you will sag and heat your battery and potentially cause the flight controller to shut down due to low voltage. Li-ions are great if you fly in FBW modes only.
Yeah I know but same setup same motor , ESC , frame , receiver only difference between fc now I choose beta flight F4 fc and it’s gives morE then 15min on acro mode this is my out of world
