12 v to 12 v trickle charger

landyacht318 wrote:
Your 2.0 volt differential claim, is simply absurd, and shows you have Zero experience with such a product. Perhaps long ago with older less efficient transistors a 2 volt drop could be expected, but certainly nothing like offered in Mr wizard's link.

I'm a retired electronic tech and have worked with many types of power supplies. Granted, my experience may be a bit dated, but the simple fact is you will not be able to charge a 12 volt battery using a 12 volt source. The charge voltage has to be higher than the battery voltage. Even if the voltage differential was zero volts you will never get more than 12 volts out of the buck converter. The specs for the buck converter that MrWizard mentioned are:

Input Voltage: 6V to 40V DC(10V to 40V is suggested)
Output Voltage: 1.2V to 36V DC

The output voltage will never be higher than the input. At the high end the voltage differential is 4 volts. At the low end it's 4.8 volts. At mid range the differential probably is much less but will always be greater than zero. The simplest solution is to use a boost converter.