I’ve made some atempts at using recycled laptop batteries. One of the issues with 18650 batteries is that the chargers usually charge them in pairs. As the projects where I use are very current intensive, usually the batteries are used eight or twelve at a time and that means lots of chargers.
One of the solutions that I’ve tried is making a batch battery charger using very low current charging (Lithium batteries are very dangerous and this should never be attempted unless you know what you are doing) and a cutoff voltage of 4.19 Volts.
One of the best combinations that I’ve found throughout the years is the use of metal spring tabs (I’ve bought theses at Farnell) with PLA holders. This way I can charge up to twelve batteries at a time. One dangerous side of this solution is the possibility of sorting the cables that go on to the power supply, didn’t happened yet (fingers crossed).
I’ve used similar approaches for storage and for the fabrication of ad-hoc batteries, in series and in parallel, but the experience tells me that a mean of balancing the batteries must be in place for it to be a permanent solution.
So there is usually some good cells in every broken laptop battery, and this is a good way of using them, if you know what you’re doing.
Hope you enjoyed it!!