She got a letter on Friday, informing her that she had won.
Mrs Powdrell said her victory was more about principle than about getting her money back - in fact after going through the tribunal, there wasn't much change from her $150.
"I just thought it wasn't right, not in a democratic country like New Zealand," she said.
"I don't like dishonest people ... and you just feel really stunned when it happens to you. You think we live in this nice little country where things like that don't happen."
Mrs Powdrell was illegally clamped by NZ Wheel Clamping two weeks before Christmas after parking in the Glenmall carpark for a dental appointment.
The carpark had prominent signs which said: "Private Property. Customer Parking Only. P120."
NZ Wheel Clamping tried to argue that Mrs Powdrell had been parked for more than 120 minutes and so was rightfully clamped. She did not agree.
The 36-year-old mother of two told the tribunal that she parked about 10.25am and went straight into the dentist, where records show she arrived a few minutes later.
After buying some bread and milk at a dairy that she passed on her return walk to the carpark, she got back to her car about 12.15pm but it was already clamped and she had to pay a $150 release fee.
However, NZ Wheel Clamping claimed one of its employees marked every vehicle in the carpark with pink chalk and informed the call centre which noted the time on the computer as being 10.13am. The firm said her car was clamped at 12.24pm.
But a disputes tribunal at the Auckland District Court last week found that the clamping firm's evidence that Mrs Powdrell's car was chalked at 10.13am was unreliable.
It was not proved that Mrs Powdrell exceeded the 120-minute time limit.
The tribunal also did not accept that she had breached a condition of parking because she was not a customer because the signs were ambiguous about what a "customer" was.
NZ Wheel Clamping group manager, Sean Hika, said the company accepted the ruling because "there is no value to either of us pursuing it further".
