How low can you go?

How much do dare to discharge your cells before you consider them empty?

RC forums suggest that you should never get under 3.0-3.2 under load. Others claim that 3.7-3.8 is the minimum voltage level.

What do you say?

I let my BMS decide in my li-ion cells! :wink:

Good answer @tylerclark :slight_smile:

I use a LiPo 12S setup and would like to set “Fall back” and “Cut off” limits in the ESC that dont damage the batteries.

However, more riding time is nice!

That’s how I programmed my ESC:
LVC cutoff voltage: 3.2V
LVC mode: slow cutoff

That being said, each time I ride until the ESC stops and then i swim back and of course i have to try a few time to use the motor some more to save some swimming, and the pump and the rest of the electronic stay working.
That got the batteries very hot each time, and according to my log, i use the full 16Ah of the batteries.

In short, 3.2V works, but it might be better to stay above for safety and to preserve the life of the batteries. Also, keep in mind that different batteries might behave differently … mine are Turnigy MultiStar 6S 16000mAh 10C.

I aim for 3.6 volts which rebounds to 3.7 to 3.8 after 10 minutes of rest, this puts me at storage voltage.

I set the esc cutoff to 3.4 but never run to this level. I use a timer.

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Yeah. Think I will go for 3.4V cut off limit (40.8V on 12s). Fall back starts at 3.55V (42.6V).

I use 2 x Turnigy Graphene Professional 12000mah 15C

Planning on upgrading to 4x12000mah later.

You could use one of those “beepers” that connect to the balancing connector, they are adjustable. Might be annoying to listen to the noise but it could help to decide when it’s time to turn back to the shore.

For what i have seen and done , the best for lipo is to stop before the continious rating © you use of what is remaining in the cells …
You can go to the max C rated if not that is for Long Time ( 30s-2min…)

12a x15c = 180A
Lets say you use 50A to Cruise
You should stop at 30%
So 3,3v which is a good value for long terme use other wise i will start to swell and Heat …
Lower voltage = higher amp for the same power , lower rpm for take of ( pumping …)

You lipos are already empty at 3.55V. This can be a dangerous topic when people are talking about lipos and li-ion.
I ran my 12s tattu lipo 30ah pack to 43V and 5% once only. It generated a noticeable increase in battery temperatures. I stop riding when I get a 44V reading which leaves me with about 15-20% reamaining which is good for battery longevity.

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Correct my mistake , got 3,3v in my head from my 18650

30% is 3,77v/cell

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Interesting table @Alexandre where did you get it?

That looks like the table from batteryuniversity.com.
Great website for learning the finer details of batteries.

If you are looking for discharge behavior of different Li Ion 18650 i can suggest https://www.akkuline.de/test/18650-lithium-ion-zelle-vergleich

Got it in the net from à rc forum , the best is to note the voltage where you stop and how much you put when your charge them ( depending in brand …) and stop around 25-30% and c rating
So between 4.15 and 3,77 and not to much swelling and Heat shall be the best

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Lipos:
How can you use voltage to determine the state of charge while you are discharging with lets say 1C or 2C? So the shut down voltage of ESC must be much deeper, otherwise you can only use a small fraction of the capacity. Typically i reach 3.77V under load at the VESC already after using 20%. Even BMS with cell voltage measurement are not alarming above 3V. So serious builds use Ah counters. Swelling must be avoided under all circumstances, otherwise the cell is damaged seriously. Use a clamp frame, thats the best protection.

I typically use 80% of the capacity, sometimes 90%.

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I agree with the table shown , 3.5V as an absolute minimum

hello, basically you have to distinguish between lipo and li-ion. I usually fly my li-ion packs to 3.3 V per cell empty. the safety shutdown is set to 3V. then in the pack would be pretty much 10% capacity. but I use the technology to make it comfortable. that means i see during the flight exactly how many ampere hours were taken. the se values ​​are supplied by the esc to a module which then calculates the extracted capacity. So I set as an example: Battery has 15 S and 40 amp hours I want to use. real, the battery has 48 Ah. so my desired capacity always stays inside if I do not see the cockpit. I will use exactly the same technique with my e foil, which is currently under construction (the board). so you can then see the speed, A, V, GPS km / h max speed and so on. I will then also in the air in videos when e-foil fly the data in the video show. Please do not ask how it all works. as soon as i have time i will explain it to you. Here is an example where you can see the data. even as the voltage drops to 50 volts at 15 S battery. The battery (52 Ah) is now 4 years and has about 200 flights behind it. still has about 90% power. regards https://www.youtube.com/watch?v=u5QPIAW9GNE

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