that's again Dave, going to change the props with two bladed props(looks like alot more pitch on them two) move motors and battery back and give it another go

Cheers for the advice again

Tim

HI Tim
Battery and ESC should be fine. You say new 12v - what is the Ahr capacity? Two 550's with big props could be drawing a lot of amps.
I am confused about your motor and ESC wiring.
Each ESC output should be connected to its own motor.
The power to the ESC's should be connected to the 've and -'ve battery connections, duly fused for safety.
The control input is plugged into a receiver channel or a Y lead if both ESC's are run off one channel. if this is the connections soldered together that would be OK.
If your motors and battery were very hot 😓 after your run I would suggest trying smaller props. Also the balance point is Important - is it possible that the single 12 v battery sits well forward - moving further back would help performance.
Finally its is possible that your battery (Being new) may not be up the full spec and could Improve with use. Also its not unknown for new batteries to occasionally be faulty. if you run both motors with a voltmeter over the battery terminals a good fully charged battery should give a reading between 12 and 12.5volts
Hope this helps

thanks Dave for a quick reply,

the battery is just a normal 12 volt lead battery, the esc's are running of one channel and been soldered together (motor are wired up so in both positive wire together0, all the speed controller are max 14 volt and 50amps.

Many thanks

HI Tim
Welcome to the site 😀
A single 12v battery will be exactly the same as two 6v's wired in series, assuming the Ah capacity is the same.
Separate speed controllers for your 550's should not effect the output. How are you controlling your ESC's - are they on separate channels or linked to a single channel by a Y lead? When you say 12 cell do you mean 12 NiMh/NiCad (ie 14.4v)? Some ESC's have a max working voltage so this may be Important.
Please supply a bit more info so we can give relevant help