-=sT3V3=-

Hello bernd! 
I have been looking at doing a DIY battery too, there are not many on the forum here.
Some guys on here might be able to help with the seplos BMS experience.
I am disappointed you need to use an external balancer.
 
From my research the market in SA is flooded with over the counter batteries which compete with a DIY option. Ordering batteries from alibaba is pretty risky in SA.
I need to build a 24V battery and cannot find any suitable options on the market.

I have recently been looking at this topic lately and have come to find there is no fix standard for vendors to adhere to which leads to wildly different specs. If you need to meet a standard/regulation for your install, use that as the guide line as Justin suggested. If not, let your budget decide the best mm2/meter per rand product.