The best charging voltage for AGM batteries depends on what the manufacturer recommends. For our batteries made by Odyssey, the best recommended bulk charging voltage is 14.7 volts. They did a cycle test of some batteries and found that 14.7 volts provided many more charging cycles compared to 14.2 volts. Up to more than twice as many cycles. Their comment is
"The message to be taken from this graph is clear – in deep cycling applications it is important to have the charge
voltage set at 14.4 – 15.0V. A nominal setting of 14.7V is a good choice, as shown by the test results.".
Our bulk charge voltage is 14.4V so we are in the preferred range. After bulk charging the voltage drops to 13.6, then 13.2 for float.
You can read this in their technical manual
here, top of page 14.
