I hope you are not charging more than 1 cell with a TP4056, there have been a lot of fires due to that.
At the moment i'm charging 2 cell's parallel.
I have heard more warnings about this but also claims that it should be no problem, so i'm a bit confused now.
As far as i know. In commercial battery packs like a 10S2P pack, the parallel batteries are just connectet together. They use a better BMS of course, but the parallel batteries are not checked individualy.
I'm not trying to be a smartass or stubborn, i'm trying to understand the difference.
Is this a problem when using the TP4056?
I do have the small 1S BMS pcb's on stock, if i add one on each cell would that be a safer option with the TP4056?
And if not, is there another safe way to charge 2 cell's parallel?
Thank you
If batteries are well matched in battery capacity (mAh or Ah), it should be no problem to connect and charge them in parallel.
The trouble you are very likely to run into with batteries salvaged from a used pack is that one or more of the batteries is damaged or dead, and thus not well matched with the others.
It is easy to measure LiPo battery capacity. Simply connect the battery to a load resistor and monitor the discharge voltage curve with a multimeter or Arduino. Be sure to stop the experiment before the battery voltage drops below around 3.0V, otherwise it will be permanently damaged.
Thank you for explaining, i understand.
The batteries i'm using now came from the same pack and both had 3,741V about a month ago, i measured them before joining and they were both at 3,740V. Same brand, capacity and they have no physical damage.
For the moment i'm pretty convinced they won't blow up in the next couple of days.
I will see if i can set up a capacity tester, i should have most parts available.
Better safe then sorry.
And "internal series resistance" (ISR or IR) - How to Test Lithium-Ion 18650 Cells and Battery Health Checking - Cell Saviors