Is it safe to connect Li-Ion batteries in series and then in parallel?

I plan to use packs of 18650 Li-Ion batteries as power source for my hobby project. I would like to combine two 4-packs connected in parallel. Each 4-pack connects four batteries in series. So there is total 8 batteries. Assuming nominal voltage of 3.6V per battery each 4-pack will give 14.4V. Connecting two 4-packs in parallel will maintain 14.4V but double the capacity, at least that's what I expect.

I'm going to draw 1-2A from above setup. I will use identical 18650 batteries and will charge them individually with smart charger, outside of above setup.

My questions are:

1. Is it a valid circuit for Li-Ion batteries (are there any caveats)?
2. Can I expect the combined batteries to have the capacity equal to the sum of individual capacities? My reasoning is: If one 18650 battery has 3000mAh at 3.6V then series of four should have 3000mAh at 14.4V. Times two gives 6000mAh at 14.4V from combined 8 batteries.
• I will use identical 18650 batteries and will charge them individually with smart charger, outside of above setup That is asking for trouble. If there is a slight voltage difference between battery packs, one will charge the other, large currents could flow causing damage/fire/explosion. So don't. You will need to balance the cells individually so they all have the same voltage, then connect then and leave them connected. Apr 3, 2017 at 19:00
• The basic questions you have about using LiIon cells makes me MOST STRONGLY advise you to not make your own battery pack but instead buy a ready-made pack of the required voltage and capacity. Apr 3, 2017 at 19:03
• @FakeMoustache If I balance the batteries and leave them connected permanently - What would be the best way to charge them? Apr 3, 2017 at 19:03
• With the proper LiIon charger, one where you can set the voltage/number of cells and maximum charging current. Yes those are expensive. Again, the fact that you have to ask this means you're not experienced enough for using these LiIon cells in this way. Treat them wrong and they can and will explode. You MUST know what you're doing. Apr 3, 2017 at 19:06
• @FakeMoustache Thanks for your response (put a proper response so I could accept it). As I suspected this couldn't be that easy :) I think I'll use ready-made battery pack. Apr 3, 2017 at 19:13