Sensor suggestions for measuring DC amps, from +100A to -10A

dc42:
... the reading you get from analogRead tells you the input voltage rounded down to the next step. ... This means there is a case for adding 0.5 to the reading you get before doing the maths on it.

thanks dc42, great info. That makes better sense, I stand corrected.
So the ideal formula becomes:

Current = ((Vcc/1024*(analogRead**+0.5**))-2.5)/0.02

I will work on my shielding and grounding too, thanks for the clues

Roy, OK thanks. Given my scooter will rarely be over 50A, and even then peaking around 60-65 A for perhaps 15 or 30seconds max, I think I'll try out the CS50 for it's greater sensitivity

Can you explain why stainless steel is bad for heat at the connection points?