Planes > Park Flyers / Foamies

Li Po Batteries

<< < (6/8) > >>

Ron:
Where is the Hall in Middleton...... :?
Apart from being in Middleton of course  :oops:

Happy Days:
Aidan, please allow me to correct you slightly re Li-Po voltages.

3.7V is the cells nominal voltage.
It’s fully discharged voltage is 2.7v although most people would say 2.75 to be on the safe side.
And to be even more safe most LVC’s cut the power at 3v/cell.

Yes, I know I’m a pedantic old bastard :evil: ……………….but I can’t help it! :lol:

K.

Ron:
You and me both Keith.
I used to be just a pedantic bastard, but now I'm an pedantic old bastard :lol:  :lol:  :lol:

Ron

Aidan:

--- Quote from: "Happy Days" ---Aidan, please allow me to correct you slightly re Li-Po voltages.

3.7V is the cells nominal voltage.
It’s fully discharged voltage is 2.7v although most people would say 2.75 to be on the safe side.
And to be even more safe most LVC’s cut the power at 3v/cell.

Yes, I know I’m a pedantic old bastard :evil: ……………….but I can’t help it! :lol:

K.
--- End quote ---

I have to disagree with your disagreement Keith!

Those voltages refer to the loaded voltage not the resting voltage which is what I was discussing. The resting voltage of a discharged cell is 3.7V. They should normally be stored at about 3.85V which equates to approx half charge. Full charge is 4.23V.
Under load the voltage will "sag". How much depends entirely on the size of the load, the capability of the cells, the charge state and the temperature. If you're at the limit of the cell's output the sag can be pretty significant.

LVC limits early on in lipo use were typically around 2.7V but that was because the cells available could only barely deliver the currents needed and sagged A LOT! A typical 6C or 8C lipo operating at it's limit might trip the LVC at 2.7V under load but would come back up to about 3.7V at rest. However newer cells don't sag nearly as much so an LVC set at 2.7V would allow the cells over-discharge enough to damage them.
An LVC of about 3V is still normal practice but for high C rate cells it's often suggested that this be raised to 3.2V or so.
As far as I know there is no "correct" LVC value. It all depends on the resting voltage you end up with and that depends on all the factors listed above... and more.

Well - I've got to get off my ass now and go finish a new plane for Middleton and charge all my lipos for some indoor fun.

By the way - in case it helps persuade you to come along tomorrow - Ralph usually brings cakes! :clap:

Aidan

Happy Days:
What, What, WHAT! You disagree! :shock:  :shock:

Hmmmmm :?: …….. I like a person that stands their ground. :D

Well Aidan, purely as an exercise, and from one gentleman to another;
To quote from your posting.....

--- Quote ---When a lipo cell is fully charged it should not exceed 4.23V per cell and when it's fully discharged it shouldn't be below 3.7V per cell.
--- End quote ---


It has always been my understanding that the term ‘Discharged battery voltage’ refers to the potential across a battery’s terminals, at it’s lowest safe working voltage, while connected to a load of 1C. Therefore, to quote from  Wikipedia

“The voltage of a Li-poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged).”

What you refer to as “Resting voltage” I’ve understood to called the “Nominal voltage.”

Maybe the confusion has occurred in translation?


Either way, whether we choose to agree or disagree about this matter  I assure you that I fully respect you point of view and I’ve found this discussion very stimulating indeed. Thank you.

(Actually, we used to have an encyclopaedia in our house, but we found we didn‘t need it…………my wife knows everything!) :lol:

Alas I won’t be at the fly-in tomorrow. I used up all my brownie point by flying off Mt. Lienster this afternoon.
Enjoy your day and I’ll look forward to meeting up with you again at some future venue.

K.

Navigation

[0] Message Index

[#] Next page

[*] Previous page