1) There is already a Batteries thread- no need or reason to make a new, duplicate one
2) If you wire in series, you are in series - and having the problems you describe, if you wire parallel, you're parallel; no probs, end of story. Run wires from your battery to each component needing power.
3) Surely you have one electrical using thing following another, not one, then another on top of it, and then another - going at one time??
4) What is a "european style power bar"??? Actually what is a "power bar"
Fort Collins, CO