LiPo batteries are difficult to deal and maintain, Can I use Li-ion batteries?
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LiPo batteries are difficult to deal and maintain, Can I use Li-ion batteries?
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It dropped from 3.6v in the lowest cell to nothing in a matter of seconds (our low voltage alarm for landing is 3.4v). The battery had only completed three cycles!
Why don't you cycle your battery packs of-the-air ?
My apologies, I'm having difficulty understanding your question. The lipo pack in question had undergone three charge/discharge cycles whilst flying in the aircraft. It had previously shown no issues before the last flight yesterday, when one cell completely failed.
Hi Martin,
what I mean is off-the-air cycling a new battery pack (charging / discharging) out of the box on your desk to diagnose any faulty cell in advance as to not risk your aircraft to fall to the ground.
Thanks mate, got it now! Yes we do cycle the batteries through when brand new before flying. This lipo showed no issues at all, cells balanced, internal resistance ok and good charge/discharge. It had three flying cycles before this event with no problems.
Wow, that's looks promising :) ; you have to open a post with your advances I think that is no problem in this forum if you show your product when it look's usefull for the rest of the community and you help others with your knowledge, you can PM to a moderator to ask. ;)
Li-Ion, Li-Po, LiFePo4... all lithium ion of sorts
Interesting subject, battery tech is the first and foremost issue surrounding further commercial development of a lot of things, be it drones, internet of things or just your average smart device. EV is a big driver for development of course, big pushes being made.
Anyhow, a recent development that a few people may have heard,
http://www.nature.com/ncomms/2015/150805/ncomms8872/abs/ncomms8872....
This is the egg/yolk thing that’s been banded around various news outlets. I'm not a chemical Scientist but my engineering mind figures they have essentially been able to create an anode/electrode using aluminium nano-spheres with a titanium dioxide shell which mitigates fatigue from charge / discharge cycles. An aluminium based anode is cited as being one of the holy grails of battery tech but generally not feasible due to fatigue problems. The TiO2 shell mitigates this.
Looking at what they did, commercial available aluminium nano-spheres, aqueous TiO2 and some acid, they were able to convert what is a problem (aluminium oxide layers on everything aluminium) into a beneficial and easy step in producing a stable TiO2 aluminium centred sphere. Well worth a read. The big take-home on this is it is a process that is simple and straight forward, ideal for these guys who are already making LiPO'S
If this materialises, perhaps a 2 or 3, maybe 4 times increase in capacities.
With regard to the li-Po vs Li-Ion debate, it would be worth describing it in a more definitive manner, there are a few constitutions of Lithium Ion cells, lithium cobalt oxide, lithium manganese, LiFePo4, etc...
http://batteryuniversity.com/learn/article/types_of_lithium_ion
The LiPo batteries we refer to will be some sort of make-up from the above in a prismatic structure. The Multistar High Capacity cells are likely to be different to a nano-tech 65C jobby.
I'm running a fair few different batteries now and plan on doing some more testing. I've recently bought Zippy flightmax 4s LiFePo4 cells (supposedly 30C…) and will be trying them out on my 560 alien with 570kv motors, 1760g total frame + gimbal + gopro weight.
With Zippy 5800mah LiPo 4S 30C (+568g) I get about 13:30 mostly hover time (3.6 alarm)
With Multistar 8000mah LiPo 4S 10C (+663g) I get about 18:30 mostly hover time (3.6v alarm)
With the 4200mah LiFePo4 4S 30C (+488g) I'm banking on about 8mins flight time based on static testing…. Not great compared to typical LiPo compositions but compared to Lithium Cobalt type compounds found in typical LiPo's I won't be constantly worrying if things are about to go up in fire! LiFePo4 type cells will be great for me heading abroad with Claude the Drone and not having to worry too much about inferno.
Did tour Australia and New Zealand for two months with my first drone and two Turnigy Hardcase LiPo's without problem but I was always spot on with the charging and not so clued up with all the horror stories of LiPo fires…
Anyhow, some potentially big changes coming if the recent discoveries make some head way….
UPDATE:
Ok, just thought I would share an update on my recently purchased Zippy Flightmax 4200mah 4S LiFePo4 cells.
I estimated about 8mins flight time with these but in reality managed to get a little more. The flights were done in Loiter, moving around, up down and general video shooting at low speed movement - no fast runs, nice a smooth video.
I managed to get between 8:30 and 9:30 out of the batteries before the 2.9v low voltage alarm went off.
When static testing with these cells and giving them a bit of hell whilst monitoring current draw via mission planner, I see that once the cells reach 2.85v they really have trouble giving out more than 30amps full throttle. My tests show with a full pack I can pull around 50amps full throttle out of these cells. My hover amps with these cells is around 22 - 25 amps, so a good 2:1 ratio can be achieved with these cells when they are charged, but anything below 3v and things start getting saggy.
LiFePo4 is a cell that would be problematic to fly on if you didn't understand the rapid drop off below 3v. I notice that once at 3v I have about 3 mins before 2.9v is reached, which then gives me about 1.5 mins to land before I am at a level where the hover amps exceeds what can be pulled from the cells.
I don't intend to push these cells too hard but from what I have read and my own limited testing, I have a feeling they will be very robust. I would never dare push a LiPo to a state where it is sagging so much it can't supply hover power (about 275 watts) but I have this feeling with the LiFePo4's that doing this isn't the end of the world. I read about a lot of people pulling these cells down to 2.5v. Interesting to note that when the load is removed from these cells, they bounce right back up to about 3.22 volts and will take back about 3300mah. I guess I could eek out about another minute of hovering if I let the volts drop to around 2.8v, but at that point I have very little ability to climb. I am considering trying to get hold of a 5S version of this battery which may give me a little more leeway.
Another interesting thing to note regarding the multistar high capacity, I have the 4S 8000mah version. In loiter mode just moving around a little I can happily stay up for over 18mins until 3.6v alarm goes off. Trying to be more demanding and just doing 1 hard full speed run in alt hold mode in a full 4.2v battery resulted in the 3.6v low voltage alarm going off! realistically that's about 60 - 80 amps I guess which collapses the cell voltage!
It recovers quite quickly when hovering again but I don't see these cells being useful for anything other than slow video captures.
My Zippy compacts 30C cells are really good though for high speed runs. Absolutely hammering these things time and time again in Alt Hold mode at full speed and they don't complain and still give over 12 mins hard flying... Excellent batteries for more demanding work.
Anyway, LiFePo4 batteries for me have an endearing quality that I like, the fact I can leave them fully charged without doing too much damage, that I can charge them in the house and not worry too much about spontaneous combustion, and can have them stored in my backpack with my drone ready to go flying at a moments notice. Yes, the flight time is awful compared to LiPo's, but, for what I want, 9 minutes of video in one location is more than enough? I have never had the need to spend more than 5 minutes filming something, I like the idea of multiple short captures edited together nicely as opposed to the same spot for 10 minutes?
What are others views on this?
I did a short test with my Y6 using both the 12800 mAh LiIon and the 10000 mAh LiPo. As you can see in the logs the average voltage of the LiIon cell is almost 2 V lower than the LiPo. So I reach the same flighttime (25 min) using only 9700 mAh compared to 10800 with the LiIon. FS voltage was 10,1 V (LiIon) / 13,4 V (LiPo)
Weight of the cells is almost the same (810 g) but the capacity of the cheap 10C Multistar is impressive.
I found this interesting blog about LiIon cells with a lot of tests.
this is a nice video on using Lithium Ion, its a plane tho
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