[split] How to design a batt pack

I am working on a project to replace an aging Lead Acid battery pack that is 2 24v 10Ah in series with Lithium Ions. My primary goal in everything I do is to reduce stuff going to be melted down/recycled/trashed if I can help it.

So to accomplish this I am using re-claimed 18650 cells from old laptops and other sources that are not uniform. To get to the 48v the current lead acid is coming up with I need 13 cells in series. To get to the power needed burst of 20A and 5A sustained I need to go at least 5 cells wide. I have way more batteries than needed to accomplish these requirements, so my question is this:

Do I build packs of cells in parallel that are uniform and mix higher capacity cells with lower capacity cells or do I keep similar capacity cells together and vary the size of the packs? Is there any real difference and/or reason why I shouldn't do one or the other?

1) Create your own thread and not start off on your own in someone else's thread, please.
2) Please read the FAQ located on the homepage
3) You don't want 13s. You want at least 14s, and possibly even 15s depending on the hardware you'll get/have (charger & inverter)
4) NO laptop cell will be able to do 1A repeatedly and live very long. 1A load is far heavier than even in a laptop. You'll want at least 10p for 5A load, and a 15p would be better. If using powertool cells, then this is possible, but you still run into the issue of capacity, so you'd still need larger parallel to keep the capacity
5) Please read through other threads of similar titles. There are pros/cons to every type of build design, layout, cell types, cell connections, etc. It's something that "you" need to weigh out to come to an educated decision on your build.