Sorry. Could not find a Li-Ion hardware Discussion.

Got a large Li-ion battery from iFlight for my Chimera 7. 22.2V/6S2P 8000 mAh FULLSENT LR.

This is my first Li-ion battery in a model. Use to large Lipo's

Need to answer the following in Betaflight Power & Battery.

Minimum Cell Voltage
Maximum Cell Voltage
Warning Cell Voltage

Any thoughts on some good values?

I know the web says Li-ion normal is 3.7 per cell and 2.4 to 3.0 min. Not sure I want my long range quad way out at or near minimums.

Thanks.

Mike.

With Li-ions, you need to operate them to fairly low voltage to get the rated capacity from them. According to iFlight, they use Samsung INR21700-40T cells in this pack, which are good 21700 sized cells. Here is some test data from them:
https://lygte-info.dk/review/batteries20...%20UK.html



As you can see from the discharge curve, under load the voltage drops fairly linearly between 4.0v and 3.2v, and below 3.2v the voltage drops off quickly. If you want to be conservative, I would use the following values:

Minimum Cell Voltage: 2.9v
Maximum Cell Voltage: 4.25v
Warning Cell Voltage: 3.4v

Depending on your flying style, you may want to increase or decrease the warning cell voltage a bit. I'd probably use 3.25 or 3.3v.

Thanks for the great info. I'll plug it in and go fly.

Mike.

highly informative piece from iflight about the 21700 packets they use!?

If you know the brand and model of the cells, you can usually find a reliable discharge curve, manufacturer spec sheet, as well as reliable cycle life test data, and anything else you want to know about the cells. Unlike lipos, liions often have detailed specs and perform very close to the stated specs (for the big brands at least), not some imaginary marketing C number that you find on lipos.
If you know the amp draw of your setup, match it to the respective discharge curve, and that will let you know the realistic flight time to expect and also what the voltage reading under load would be at different levels of capacity remaining.

The Samsung 40T was a great cell that served me well for many years. but today you want a Molicel P45B wich outperforms the 40T by miles. make sure you have enough cooling if you stress your batteries. the max cell V can be left at 4.2V but you want to lower the min cell V down to 2.5V. i have my warning at 2.8V. the true power of a Li-Ion is between 3.8-2.8V above and below they drop quite quickly. Occasionally i fly mine down all the way to 2.5V but you have to be careful as below 2.8V they drop very quickly. if you want your batteries to live long then it's best if you stay between 4.15V-2.8V. If you need the extra punch you can go up to 4.25V and all the way down to 2.5V but that will shorten the lifespan. Molicel promises 500 cycles on their new cells.. i never had a battery with 500 cycles on it, so i abuse mine quite a bit expecting to reach 200 cycles which is totally ok for me.
don't forget to disable LVC on your ESC!!!

(25-Jan-2024, 05:32 PM)StuweFPV Wrote: don't forget to disable LVC on your ESC!!!

Do any drone ESCs still have LVC? I thought this was removed years ago? There is a minimum voltage below which the MCU will not power up, but I believe that would only come into play for 1-2S, and you would have to do some hardware mod for that?

(25-Jan-2024, 07:19 PM)mstc Wrote: Do any drone ESCs still have LVC? I thought this was removed years ago? There is a minimum voltage below which the MCU will not power up, but I believe that would only come into play for 1-2S, and you would have to do some hardware mod for that?

yes they do. at least the ones i use do.. but the true features of your ESC is only revealed once bl_heli has read the ESC. connect bl_heli suite and check. It usually gives you the option to lower the V or turn it off completely. I always turn it off as i rather loose a battery than a plane.. and i had some flights comming home with 1.8V left on a cell..
the other problem with LVC is, that usually it start cutting power before reaching the limit. if you set your LVC i.e. 3V it will start reducing power somewhere around 3.4-3.3V already, gradually reducing the power until the cutt-off comes at 3V. I prefer to be the judge of the power depending on the situation and not having a computer override me. up to you

The screenshot is showing Blheli v14.0, which I believe was released 9 years back. I'm not sure any of the recent drone ESC firmwares still have this setting? But yes if you are using an older ESC, it would be wise to double-check.

yeah i know.. I'm sorry i just pickt the first pic on the internet and did not go in the shop, connected a plane and took a screenshot just to post it here... i currently use version 32.9.0.3 and the LVC shows on all my ESC's (Holybro, IFlight, Flycolor and APD) which are maybe 1 year old and some older. but they all have it. but hey if yours does not have it then just forget about it - no sweat. it was just to point out that if you fly Li-Ion and per default have LVC on at 3.6V, you're not benefiting from the new technology. I'd actually be worse than a lipo and you'd woder why..

Hmmm... interesting, I wonder if it has to do with the version of your configurator? I hooked up a Blheli32 quad and did not see that setting either?




Once in a while my drones hang themselves in trees for several days, and I am surprised when they finally come down that the lipo is not completely dead. I wonder if the LVC feature is secretly enabled and I'm just not able to see the settings? Or maybe simply the AIO stops drawing power below its rated voltage.

yeah i see.. interesting.. maybe my esc's are too old as you've suggested.. but i'm not complaining i like to control that for sure