I am putting this in the Long Range section because Li-Ion batteries, specifically the 18650 ones, would likely only be used in Long Range applications; particularly quads in the 4 inch category.
 
As we strive to build a true sub-250 gram long range quad, an interesting discovery has been made that I certainly did not know and perhaps many others don’t know either, specifically:
 
Although not all ESCs have a voltage sensor or do not utilize it,
Most ESCs have a Low Voltage Cutoff set at 3.5 volts in order to prevent over discharging LiPo batteries.
AND
The Low Voltage Cutoff can be changed with BLHeli_32, but NOT with BLHeli_S.
 
Now, a Li-Ion, 18650, battery can be discharged down to about 2.5 Volts in order to fully utilize the battery’s potential, 
{and should be for Long Range flights}, however, this is not possible with a Low Voltage Cutoff set at 3.5 volts.
 
Since all of the 16x16 stacks and most of the 26x26 whoop boards come with BLHeli_S and have the Low Voltage Cutoff set at 3.5 volts,  it brings into question the suitability of using them in Long Range applications where 18650 Li-Ion packs will be used.
 
A notable exception appears to be the Flywoo boards that seem to have the LVC turned off so they can handle a Li-Ion battery for Long Range even though they come with BLHeli_S firmware.
 
My Conclusion:

If you want to run a Li-Ion battery, 18650 or other, THEN...
be sure that their is NO Low Voltage Cutoff to limit the discharge of the battery...
OR
that the ESC firmware is  BLHeli_32  so the LVC can be turned off.


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Related Links:

?? Voltage regulator to fix “LVC” problem on 2s ??   >   Last Post   >   My Post #5

[ESC] 2s li-ion discharge trick

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Right on , now what esc hardware runs BLHeli_32?

(22-Jan-2021, 12:59 PM)Joshua_A Wrote: Right on , now what esc hardware runs BLHeli_32?

I will update this list as we find them.

Although the list is short, at least there are some available options. 

I am only going to include FC AIO boards and stack/combos that will handle down to 2S in order to use a 2S 18650 pack,
have enough UARTS or support for the GPS and SmartAudio, 
have BLHeli_32, and that would be suitable for builds with the following criteria: 
sub-250g AUW, 30 minute Fly Time, 10k distance.


26x26  Whoop mounting format

Flywoo Goku GN745 2-6S AIO Whoop/Toothpick Flight Controller w/ 40A 32Bit 4in1 ESC

Flywoo Goku GNF4 2-6S AIO Whoop/Toothpick Flight Controller w/ 20A 32Bit 4in1 ESC

Flywoo Goku GNF4 2-6S AIO Whoop/Toothpick Stack/Combo (F411 FC / 20A 32Bit ESC / 25-600mW VTX)

BETAFPV F722 35A 2-6S AIO BLHeli_32 Brushless Flight Controller

CLRacing F7 32Bit Whoop AIO V2 Toothpick Flight Controller with 35A ESC  2-6S

16x16 mounting format

20x20 mounting format

GEPRC Stable Pro F7 Dual 20x20 Stack/Combo (Dual Gyro F7 FC, 35A, 500mW VTX)  2-6S

IFLIGHT SUCCEX-D MINI F7 TWING STACK (MINI F7+40A ESC)  2-6S

GOKU HD 745 EVO 40A AIO BL_32 DJI PLUS & PLAY （20mm X 20mm)  2-6S

I really believe that this can be addressed, but it will take compiling custom firmware that gives us the option to change or remove that setting. As BLHeli_S is still being actively updated, maybe it would be worth barraging the developers with requests to address the issue. If they are unwilling to do it, we need to start our own movement to create what we need. There is precedent, look to 48KHz firmwares for the older ESC's.

If we do not want to code in the ability to change it, then remove the limitation from the code entirely. This will mean that inattentive pilots will have to stop flying till their quads drop to the ground or risk destroying their flight packs.

The Tiny Talon is the only 16x16 32bit ESC I've found so far:
https://www.heli-nation.com/tiny-talon-1...eli-32-esc

Tiny TALON 16x16 BLHELI_32 ESC

ESC spec:
1. 2-4s Battery Input.
2. First 16x16 mounting 32bit ESC, running BLHELI_32
3. 15A continuous and 20A burst.
4. RPM filtering support
5. build in Current sensor
6. Only 3.1 Grams

In addition to the Whoop mount F745, Flywoo also has a 20x20 F7 AIO with a 32bit ESC:
https://flywoo.net/collections/goku-stac...-plus-play


The HGLRC Zeus F745 20x20 stack also has a 32bit ESC:
https://www.hglrc.com/products/hglrc-zeu...2-4in1-esc

(22-Jan-2021, 03:33 PM)kaitylynn Wrote: I really believe that this can be addressed, but it will take compiling custom firmware that gives us the option to change or remove that setting.  As BLHeli_S is still being actively updated, maybe it would be worth barraging the developers with requests to address the issue.  If they are unwilling to do it, we need to start our own movement to create what we need.  There is precedent, look to 48KHz firmwares for the older ESC's.

If we do not want to code in the ability to change it, then remove the limitation from the code entirely.  This will mean that inattentive pilots will have to stop flying till their quads drop to the ground or risk destroying their flight packs.

Hi Kaity,

Yes, this could be addressed by the developer, but will likely take awhile even if they decide to do it.

If they would just remove the Low Voltage Cutoff, that would be fine with me, however, what do others think about this.
The developers would probably want a lot of people requesting it with essentially no one opposing it. I'm not sure how we would want to approach this? Do you want to tackle it??

In the meantime, we just have to buy products that meet our requirements.

At this point, Flywoo seems to be ahead of the game; BetaFPV is in there and a few others.  Personally, I look for the manufacturers to be ahead of the BLHeli developers in putting out product, but that is just me 

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Keep the links coming... I will check them out and ADD the AIOs and Stack/combos to the list.

Is this an issue with 3s or higher? Is this a 6v shutoff for the 2s your having issues with or a problem with 3.0v / cell of any cell count?

(22-Jan-2021, 06:19 PM)EVILsteve Wrote: Is this an issue with 3s or higher? Is this a 6v shutoff for the 2s your having issues with or a problem with 3.0v / cell of any cell count?

That is a good question. I suppose the ESC could figure out the number of cells in the pack (and therefore cell voltage) assuming the starting voltage is somewhere between 3.5 and 4.35V/cell, but I haven't found any reports of people running into LVC on 3S or higher. I see this as mostly an issue with people planning <250g LR builds, as a 2S Li-ion pack makes the most sense in terms of weight. You'd have to be crazy to try it on 3S 

(22-Jan-2021, 06:19 PM)EVILsteve Wrote: Is this an issue with 3s or higher? Is this a 6v shutoff for the 2s your having issues with or a problem with 3.0v / cell of any cell count?

Hi EVILsteve,

The LVC is based on the per/cell voltage so the number of cells is pretty much irrelevant.
Also, the LVC is a safety mechanism for Li-Po batteries so pilots don't abuse their batteries. Sort of like training wheels 

Now, turning off the LVC is really ONLY relevant if you are using Li-Ion (18650) packs and want to run them down to about 2.5 volts which is quite a bit lower than what you would discharge a Li-Po battery. If you only use Li-Po batteries, no problems.

If you are racing or flying acro, you will likely NOT be using Li-Ion batteries since they are too heavy and don't recover fast enough for the hard throttle punches. These batteries are for easy cruise endurance and long fly times.

Considering that the goal is to build a quad that has a total All Up Weight less than 250 grams {with battery} that will fly for 30 minutes and cover a 10k distance, a 3S 18650 pack will likely be too heavy at 150 grams or more. That actually leaves less than 100 grams for the dry weight of the craft. Right now, I am looking at a weight of 88 grams for the electronics package and drive train {FC, VTX, Rx Receiver, Antennas, motors, props, and prop bolts...everything but a frame} so that leaves 12 grams for a frame and hardware. If I go over 100 grams then a 3S 18650 is simply out of the question. In order get that Fly Time, we need to push the 18650 3000 mAh cells down to the limit which is about 2.5 volts/cell. 

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I would venture to say that one reason you don't hear about this issue is that the Flywoo Explorer and some other long range quads do not appear to have a Low Voltage Cutoff; Not All ESCs are limited like this.  Perhaps they don't limit the ESCs so they can run Li-Ion packs and get really good Fly Times. Also notice that most of the people who review these new Long Range quads are running 4S 18650 packs which weigh about 200 grams so the AUW is definitely way over 250 grams. They also never tell you how far down that they discharged the battery. 

In my mind it is sort of cheating. You say you have a Flywoo Explorer sub 250 gram 4 inch Long Range. Fine, but it only weighs less than 250 grams with a 4S 650 mAh {or maybe a light weight 3S 1100 mAh GNB}, but this setup won't get you Long Range.

Now, strap on a 4S 18650 3000 mAh pack to get some real high Fly Times and Long Range and you have just blown the 250 gram AUW right out of the water. So, the quad is short range when under 250 grams, but over 250 grams when flying Long Range.    

(22-Jan-2021, 05:14 PM)V-22 Wrote: In addition to the Whoop mount F745, Flywoo also has a 20x20 F7 AIO with a 32bit ESC:
https://flywoo.net/collections/goku-stac...-plus-play


The HGLRC Zeus F745 20x20 stack also has a 32bit ESC:
https://www.hglrc.com/products/hglrc-zeu...2-4in1-esc

Hi V-22,

I included the Flywoo FC in the list. 

When I checked the link for the Zeus stack, it is listed as 3-6S so didn't add it. I am looking for 2S capable boards.


Thanks

Here’s my pick: https://flywoo.net/collections/goku-gn-f...5-5-x-25-5
But it’s $70.00
Edit: I just realized that you already have in on your list... (it’s so hard to find something you haven’t... great work )

(24-Jan-2021, 11:48 PM)Joshua_A Wrote: Here’s my pick:  https://flywoo.net/collections/goku-gn-f...5-5-x-25-5
 But it’s $70.00
Edit: I just realized that you already have in on your list... (it’s so hard to find something you haven’t... great work )

Hi Joshua,

Thanks. 

Yeah, I tried to buy that board, but it is out of stock pretty much everywhere. I must be a really HOT item. I could have ordered it direct from Flywoo, but I didn't want to wait that long for an FC for my current builds. I may get one anyway in the future, but right now my focus is on getting the current builds completed. 

(25-Jan-2021, 03:34 AM)iFly4rotors Wrote: Hi Joshua,

Thanks. 

Yeah, I tried to buy that board, but it is out of stock pretty much everywhere. I must be a really HOT item. I could have ordered it direct from Flywoo, but I didn't want to wait that long for an FC for my current builds. I may get one anyway in the future, but right now my focus is on getting the current builds completed. 

I got one from RDQ, came in a few days. I'm using it on my Phantom HD build. Looks like it's still in stock:
https://www.racedayquads.com/products/fl...1849&_ss=r

Looks like it is still in stock at RDQ. https://www.racedayquads.com/products/fl...77df&_ss=r