Ok , when they started talking about 3 volts I kind of got a little P****D
Look , each pack is made up of cells , the problem is - How well are these cells matched !
Some companies go to some effort to match the cells and some companies go to no effort to match the cells in the pack ..
The things that affect MATCHING , Discharge capability , the storage capacity , and cell quality .
As we all know , in manufacturing there is VARIANCE ! , So if a pack is made up of batteries from either extreme end of that variance , you may have imbalance .
Have I confused anyone ..
Here is an example ..
Cell one has an internal storage capacity of 1200mAh , and a discharge capability of 20Amps
Cell two has a internal storage capacity of 1100mAh , and a discharge capability of 25Amps
Does anyone see a problem ?
Now if we put these batteries together into a 2 cells pack ( 2s ) and lets say its a budget pack with a 1500mAh label on it ( very common ) .
Now under gentle discharge , lets say one amp . Both batteries may discharge well until around 3.5v or 3.6v .
The battery with less capacity , is going to start dropping voltage faster than the battery with more capacity ..
So by the time the better battery is at say 3v the battery with less capacity might be 2.5v .
Just let me say that over discharging Li-ion is BAD ! ( OK )
Now , under high load !
The battery that is capable of higher discharge and has a lower internal capacity is :
1) Discharge faster than the other battery
2) Going to deplete faster
3) Voltage will drop faster
4) Under high load there is a lot of voltage sag , so by the time ( under load ) one battery is say 3.3v the other might be 2.5v or lower under load ..
Am I explaining this well ?
The more cells you have in a pack , the more chance of FLAME CITY .
This is why I test my packs to see at what point the imbalance kicks in .
I have found 3.5v is the voltage region that most of my packs ( cheap ) develop imbalance ...
If you wait for 3v ( 6v for 2s - 9v for 3s ) then you may have waited too long .
Hence I use a battery monitor/alarm attached to my pack set to around 3.3 - 3.5v ...
Which ever cell reaches said voltage first triggers the alarm .
So monitor your batteries - Each cell ..
Check them after ( balance ) charging , check them after use and before charging - Be aware of what your battery is doing .
For a few $$ you can buy a battery voltage monitor / alarm .
It's this imbalance in the pack that causes FLAMES ...
And the inability of users to monitor such .
Packs can flame under HEAVY use , they can flame when charged FAST ..
I dont charge big packs with more than 1 Amp , yes it takes a while but I like to take care of my batteries .
I also balance charge , because if there is a bad / weak cell , you dont want to create imbalance whilst charging ..
A) You need to be aware of your batteries and use them accordingly .
Now there is a lot more to this stuff and so many experts its just not funny !
I am not an expert , but I do experiment and monitor my batteries and try and have some idea of what is going on .
I have been playing with Li-ion for about a decade now , so I think I have some understanding of the why and where and when .
And understanding why lipo packs flame is some what important .