6 Volt to 12 Volt conversion

[Flylo]

I am new to the Cart world, I bought a used cart (92 marathon) that has a mixed set
of batteries (different ages) the time it holds a charge is quite short.
First can anyone tell me how to check the batteries.
Second can anyone explain why it would not be a good idea to convert to 3 12 volt bateries

 

[dougmcp]

Start with a digital voltmeter and post up all the individual battery voltages. A fully charged 6v battery should be 6.37v or better.
You can use 3x12v batteries but your run time will be severely reduced and your battery life will be about 1/2 or less.