Planning to build a 72V 18650 battery pack with used laptop batteries. I have a few questions to what happens when you have different batteries.
What happens to batteries in parallel with different voltages? Say, five batteries are rated at 4V and one is rated at 3V. What will be the overall voltage of the group?
What happens if batteries are in parallel with different capacities? Say, five batteries have 4000 mAh and one has 3000 mAh?
What happens to batteries in series with different capacities? If one group has 10 Ah and one has 20?
Overall, if I have batteries with different internal resistances, capacities and voltages, which are the most important? Should I group based on internal resistance, capacity or votltage?
OP here 2 years later haha. I ended up making this battery. I got a bunch of used laptop batteries for free and connected the ones with similar capacities, voltages and resistances into a large 48 V pack. It worked perfectly for 1.5 years and then it failed (didn't catch fire). Overall a risky but fun project!