I have one of the older NSb g-3100 marine batteries and I used a mid-tronics pbt-200 tester today and volts were at 12.83 but cca was right around and over the 500 mark, It should be almost 3 times that. My question to the battery guru's is how can a battery still read 12.83 volts but only have a 3rd of it's cranking ability.????? Thanks
