I am wondering if you guys can help me a little.

I have 5x 100w panels (VoC 22.5V), the EPEVER Tracer A 4210, the wifi tracker and 8 car batteries ranging from 50AH up to 80AH (the majority being around 75AH), 560AH ish total.

I have hooked my panels up in parallel and similarly with my batteries, do you think this is the best way to go forward or do you feel i should go in series? I am quite worried about going in series as the manual for the controller says the maximum open voltage is 100v. At the moment the tracking graph doesn't show the controller performing MPPT too well, and I am wondering if that is because I have wired the panels in in parallel.

Of course you should go higher voltage on the panels. That lets MPPT work better, it even says that in their manual. Wire loss will be less too.

I don't see what you are worried about at 44V or 88V VOC but having a odd number of panels won't help, what are you going to do with the last one?

I wouldn't go with 5 in series if that is what you are thinking.

Sounds like 12V panels. They are cheap now, get some 24V panels and big ones like 300W and put together a good system so you can enjoy it.

I run 2 "24V" panels in series on the 4210 CC all the time but with 24V batteries, which is the way to go.

A little info on the panels, they are Plaza Solar 100W panels;

Pmax - 100 Watts
Voc - 22.5 Volts
Isc 5.83 Amps
Vmp - 18 Volts
Imp - 5.56 Amps
36 Cells

I was almost tempted to run them all in parallel but even in the UK (where I am) i figured that might end in fire and disaster lol.

Yeah if I had a 6th panel I might run 3 lot of 2x100, but I have 5, there is a reason for that, which is mainly to do with their free availability lol. Even the controller etc has come second hand and the batteries cost less than a case of beer  :)