Converter breaker tripping sometimes

I had one that tripped the breaker sometimes but not all the time. I contacted the manufacturer and they decided there was a problem with the convertor when it cut in to charge the batteries. It was just out of warranty but they sent me a rebuilt one anyway free. I bought a new Progressive Dynamics with Charge Wizard while the troubleshooting was going on and I am happy with it. I keep the rebuilt as a spare.
Brian