Electrical System Testers

This product sounds like a great idea. Test your battery, starter and charging system and reset European computers when you change out the 12v battery. As a mobile mechanic I need the equipment I use to be accurate. When I got this and tested my own vehicle batteries they all tested good. This could be the case, but when checking my charging system the charging voltage was registering as low as well. I had to pull out my multimeter and find out what was going on. The battery tester was reading .6 volts lower than actual voltage. My first impression is maybe I needed to update the tester. So I plugged it into my computer and started up the process to reprogram it. You have to register the unit first, but they need a 16 digit serial number. The battery tester only has a 12 digit serial number. Contacting the company they had not had any issues with other testers being off and were unable to help me get a 16 digit serial number so I could get it registered and try an update. Long story short, I decided to contact the sellers I bough this from to see if I could just get it exchanged. after over a week of them checking with their warehouse and my business being without an accurate battery detector I opted to return the tester.