Let's go through a simple example.
This is an 18v Milwaukee NiCD battery.
First, we remove all the parts.
Here, we weld the cells we will use into 'positive, negative' pairs.
Next, we configure the pairs to match the original battery.
Now, we have flipped the packs over and marked where we need the connecting strips.
Following the markings, we weld down the nickel strips.
We reassemble the battery as needed.
Put the battery back into the case.
This battery is all NEW where it counts: