permissible voltage differences when using several cells

[CMK]

Hi everyone,

I hope that the question has not been asked too often and that this is not the umpteenth question:
When using several cells, it is normal to a certain extent that they age differently or have aged differently. Which (open circuit) voltage difference between the individual cells can be regarded as problem-free with regard to the risk of deep discharge of the weakest cell?

As an example, I have 2 cells here and now with a total battery level of 30%.
Cell 1: 3.66V
Cell 2: 3.54V
Both the same cell type / manufacturer.

In my other pairings, the individual voltages are a maximum of 0.02V apart.

Do I have to worry now?

[Wayneo]

I have personally seen about a .17v difference between 2 cells. The board IMHO uses the volts of the the lowest cell to trigger the 'weak' and 'check' battery warnings.

No need to worry, but externally charging will bring both back up to their full charge much quicker than internally charging.
 

[CMK]

vor 25 Minuten schrieb Wayneo:

The board IMHO uses the volts of the the lowest cell to trigger the 'weak' and 'check' battery warnings.

Ok, that's the crucial piece of information, at least in terms of 250c

(100c: "The DNA 100 Colour is powered by a single lithium cell and can also be wired in parallel configuration") 

 

vor 25 Minuten schrieb Wayneo:

... but externally charging will bring both back up to their full charge much quicker than internally charging.

Basically, I always have a few cells ready in the charger, in the mod I actually only charge when I'm traveling.  Internal charging is actually only prohibited with the 75c and more than 1 cell (e.g. Therion 75c, or Paranormal 75c).  However, I don't know anything about non-C chipsets. 

Edited August 12, 2021 by gwyar

[Wayneo]

That difference was seen on a 3S LiPo battery. On round cells it could also be seen by dirty contacts. When it's a round cell, I've thrown a cheap sticker on the offending cell to help differentiate between mod contacts or cell itself.

 

20 minutes ago, gwyar said:

Internal charging is actually only prohibited with the 75c and more than 1 cell (e.g. Therion 75c, or Paranormal 75c). 

I have never heard that before.

20 minutes ago, gwyar said:

However, I don't know anything about non-C chipsets. 

All their serial boards follow what I said before, so that's all 2xx

[CMK]

vor 26 Minuten schrieb Wayneo:

vor 47 Minuten schrieb gwyar:

Internal charging is actually only prohibited with the 75c and more than 1 cell (e.g. Therion 75c, or Paranormal 75c). 

I have never heard that before.

Not forbidden in the sense of "Evolv did not allow it", but if more than 1 battery cell is used, the batteries of the 75C (100C?) Are operated in parallel. They are not evaluated individually and therefore cannot be loaded reliably. In the extreme case - 1 new cell + 1 deeply discharged cell - an explosion can occur.

[Wayneo]

The DNA60, 75, 75C, 100C are all parallel boards. And yes, do appear as 1 cell to the board. Most use round cells and can be monitored via external charging. Some can even be operated with a single cell in a 2 cell setup. There are 2S and 3S Lipo's wired in parallel in use. And of course battery safety should always be a concern. Great thing about choice 

[retird]

That's why multiple cells in a device should be "mated for life" and only used together....  but we already know that... just saying in case a new vapor drops by...🙂

[zark]

Я пользователь Triade 250c. Более трёх лет заряжаю батареи только внутренней зарядкой, блоком питания на 2.5 A с функцией быстрой зарядки (отдельной внешней зарядки вообще не имею) . Батареи извлекаю, только для того, чтобы заменить на новые. Разница напряжений в пределах +\- 0.007V. комплекта из трёх элементов хватает примерно на 1 год. Никаких проблем с доской не было (правда, одна доска вышла из строя, но это произошло по моей вине)

[zark]

29 minutes ago, zark said:

комплекта из трёх элементов хватает примерно на 1 год

Я посмотрел свои записи. Это второй комплект, а первого хватило на два года

[CMK]

vor 2 Stunden schrieb zark:

Я посмотрел свои записи. Это второй комплект, а первого хватило на два года

I looked at my notes. This is the second set, and the first one was enough for two years

The set of 2, which I was talking about at the beginning, is almost 3 years old ... So I don't complain if the capacities of the two deviate from each other as described.

[HankStarr]

Hi....Assuming after use, one cell is routinely 2.8 and the other 3.6, the battery is harmed and should be supplanted. Cells ought to never be released beneath 3.0v, ideally way off the mark to 3.0v

It may be the case that one battery began with an awful cell yet by interfacing them all together on an equal board you are pulling down the cells on different batteries as well, and have now harmed them moreover.

The main inquiry would be how are you checking the voltage? In the event that you are utilizing a little module cell checker, their exactness is problematic.

In solution to your unique inquiry, subsequent to adjusting the cells ought to be inside about 0.02v of one another.

[Wayneo]

Welcome to the forum @HankStarr 👋

4 hours ago, HankStarr said:

Cells ought to never be released beneath 3.0v, ideally way off the mark to 3.0v

I don't know where you heard this, because many cells have a 'Fully discharged' value of 2.5v, a few 2.3v, and IIRC one is 2.0v. The 250C, regardless has a 3.0v minimum standing/unloaded voltage for each cell.