Voltage questions

[Frijolito1988]

Hey guys been playing around with this multimeter gauge .

I have a known good battery that looses all its juice.

I charged the battery up to about 12.5 volts and the truck barely started.

Once started the volts dropped to 11.6 and im sure if i left the truck on longer it will drop and drop.

Now. I am working out some problems with the internal alternator conversion and my alt is reading 16.1 volts at idle ?? Whats wrong here ?


To recap .

Battery looses juice really fast, and alt is reading 16.1 volts at idle.

Hope you guys can leed me in the right direction.