Early 2015, I started a new project: Re-use cells from discarded laptop battery packs
I got a lot of them from the battery trash at work and some on eBay after looking at Jehu Garcia's work to try build cheap battery packs, first to replace the aging NiMH one in my Electric Go Motorboard 2000X, and maybe for another Energy Storage System at Home .... A 3rd one, yes ;)
I am very excited about this new cell format and discovering how to work with it along the way;
Also you probably know that this is the cell Tesla uses to build its Roadster and Model S packs, with 7,000 Panasonic cells in a Model S ....
Opening the laptop battery case is more or less difficult, and I have to be carefull no to short circuit anything during the process; Inside the cells are mostly made by Panasonic and Samsung SDI, with various external insulation colors (different generations of cells probably)
Every pack has 3, 6 or 9 cells, in 1P, 2P, or 3P and always 3S configuration to have a common 3 x 3.7V = 11.1V nominal
This 18650 cell is to be charged at 4.2V maximum using a ususal Constant Current & Contant Voltage Charger
Guess what's inside ? an "over-engineered" - Jack Rickard's language - PCB / BMS with leads to every group of cells in parallel, and as usual I don't think it is very usefull - apart from the thermal sensor(s) - and in many cases it damaged cells trying to bablance them on top while charging ... the same old story => there are going to trash / recycle because I won't need these at all
An example this morning: out of 6 cells, 2P 3S, a set of 2P is at 0.05V and all the rest is at 3.7V .... where does this come from ? (answer the BMS, which in this case can be called a Battery Murdering System !)
As usual, I am using my good old Low Cost Bottom Balancer, used on all my others battery chemistry projects: Mottcell 39Ah, CALB CA180FI, LEAF Battery Modules, and now 18650; The 2 first the bottom balance voltage was set to 2.75V, and the 2 last to 3.0V (but could be 2.75V too as Jack Rickard did bottom balance his LEAF Modules from the Renault Fluenze Better Place to 2.75V per half module)
Like Jehu, I find out that some cells are close to 0V, some around 4V, and all over the place in between of course ...
When the cell is showing a lower voltage than 3.0V, I charge it to go beyond this value and then proceed to the bottom balancing phase, and all cells are then stored at 3.0V in a box, filling up slowly
Most of the cells originally had between 2 to 2.4Ah of capacity, but they are used, so the real / remaining capacity is the question here ...
I started charging using a eSmoke charger - charges to 4.2V - but it is way to slow for me,
so I siwtched a to 12V lead-acid 2.7A battery charger (Mascott from Norway, a pretty good charger BTW)
To see the current drawned and pushed in the 18650 cells, I wired an analog Ampmeter, and I am discharging at 4A, which is 2C, and charging at 2A, which is 1C
With this setup, I can quickly see in few seconds if a cell has a lot or not so much, or not any more capacity left, as it will show "resistance" on the charging and/or discharging side
I got a lot of them from the battery trash at work and some on eBay after looking at Jehu Garcia's work to try build cheap battery packs, first to replace the aging NiMH one in my Electric Go Motorboard 2000X, and maybe for another Energy Storage System at Home .... A 3rd one, yes ;)
I am very excited about this new cell format and discovering how to work with it along the way;
Also you probably know that this is the cell Tesla uses to build its Roadster and Model S packs, with 7,000 Panasonic cells in a Model S ....
Opening the laptop battery case is more or less difficult, and I have to be carefull no to short circuit anything during the process; Inside the cells are mostly made by Panasonic and Samsung SDI, with various external insulation colors (different generations of cells probably)
Every pack has 3, 6 or 9 cells, in 1P, 2P, or 3P and always 3S configuration to have a common 3 x 3.7V = 11.1V nominal
This 18650 cell is to be charged at 4.2V maximum using a ususal Constant Current & Contant Voltage Charger
Guess what's inside ? an "over-engineered" - Jack Rickard's language - PCB / BMS with leads to every group of cells in parallel, and as usual I don't think it is very usefull - apart from the thermal sensor(s) - and in many cases it damaged cells trying to bablance them on top while charging ... the same old story => there are going to trash / recycle because I won't need these at all
An example this morning: out of 6 cells, 2P 3S, a set of 2P is at 0.05V and all the rest is at 3.7V .... where does this come from ? (answer the BMS, which in this case can be called a Battery Murdering System !)
As usual, I am using my good old Low Cost Bottom Balancer, used on all my others battery chemistry projects: Mottcell 39Ah, CALB CA180FI, LEAF Battery Modules, and now 18650; The 2 first the bottom balance voltage was set to 2.75V, and the 2 last to 3.0V (but could be 2.75V too as Jack Rickard did bottom balance his LEAF Modules from the Renault Fluenze Better Place to 2.75V per half module)
Like Jehu, I find out that some cells are close to 0V, some around 4V, and all over the place in between of course ...
When the cell is showing a lower voltage than 3.0V, I charge it to go beyond this value and then proceed to the bottom balancing phase, and all cells are then stored at 3.0V in a box, filling up slowly
Most of the cells originally had between 2 to 2.4Ah of capacity, but they are used, so the real / remaining capacity is the question here ...
I started charging using a eSmoke charger - charges to 4.2V - but it is way to slow for me,
so I siwtched a to 12V lead-acid 2.7A battery charger (Mascott from Norway, a pretty good charger BTW)
To see the current drawned and pushed in the 18650 cells, I wired an analog Ampmeter, and I am discharging at 4A, which is 2C, and charging at 2A, which is 1C
With this setup, I can quickly see in few seconds if a cell has a lot or not so much, or not any more capacity left, as it will show "resistance" on the charging and/or discharging side
A little bit is done at night when I am back home, a liitle bit in the morning before leaving to work, and most of it during the week end; It is taking time but I like it - picture taken yesterday -
Stay tuned for more in Episode 2 ....
