. My pack is ready and fully operational. Real life always turns out different that the tests.... I made the rust test for all my nickel strips again, but this time I only soak them in salt water solution for about 10 minutes and then left them outside during the night. In the morning I got my answers to the weird difference in welding times for 0.15 and 0.20 mm strips. All 0.15 strips that I have turned out to be nickel plated steel! The good news was the 0.5kg 0.2 strip that I bought last didn't have any rust on it, so definitely the good stuff. That explains why I had a very different welding times between the two types of material. Looks like steel strips are much easier to weld than pure nickel. That was a good lesson.
Now to the actual job. The weld times between 0.2 nickel and battery terminals was easier than what I experienced during my tests between two 0.2 nickel strips. The explanation is probably the same a above - weld is easier between nickel and steel. All I needed to weld the whole pack was between 17 and 20 ms secondary pulse and 1.5 initial. I tried making slotted strips and it took forever to make the slots, just to shave about 5-6 ms of the second pulse, so I decided to not do it. Instead, as you can see in the photos below, I used a generous amount of strips. I got sure to use at least two connections per battery (good for at least 14Amps) and at least 4 or 5 connections between the 10cell packs - good for 28-35 Amps.Some of the series strips are doubled and tripled, which is not visible on the photos....
For the positive and negative ends I used a split cable end with multiple solder connections to ensure smooth amp handling.
And now about the welder. All I can say is EXCELLENT! I finish all the welding in about 4 days, working a few hours in the evenings and preparing the strips at work during the day. Every welding session was limited to 150-200 welds by the heat build up on the welding cables/terminals and lasted 10-15 minutes with rest sessions of 5-10 minutes in between. I had 0 misfires and 0 blowouts. Ones a strip was attached with the first weld it was very fast to make the rest 20-30-40 welds. I touched the schottky diode a few times and it was slightly warm at worst. I used 17ms for the strip-battery terminal welds and 20-21 ms for second and third layer between the nickel strips. I tried a few times after the first weld to pry a strip and they were holding well. By the way, I never tried the power board that I bought from Paul, finished all the work with the board I made (photos in the first pages of this thread)
One more fact to share. I was able to charge the battery all the time during welding, no problem with this at all. I used SkyRC B6AC V2 charger and was able to monitor the battery voltage during welding. The whole pack (approximately 5000 welds total) used about 45 Ah to complete (3 nights by 15Ah to fully recharge). Now I have a nice 14S10P 52V battery pack about 33Ah capacity made with Sanyo GA batteries from Tumich.
I hope I did provide some useful information for anyone newbie like myself for their future DIY battery pack projects.