Honda civic 2012 charging battery issue without lights

Honda civic 2012 LX 1.8L won't charge under certain load conditions. Had the
reg/alternator and battery check OK. When the battery is not fully charged and it reads
around 12.3 vdc using a voltmeter across the battery terminals. Leaving the voltmeter
across the battery terminals and the car is started the voltmeter reads around 14.3 vdc
for about 10 seconds. Then the voltage starts to drop down to around 12.3 vdc with the
car running. If the head lights are turned on the voltmeter will then go up to around 14.3   
vdc. If driving with the lights on the battery will start to fully charge up. If the car is
driven with the lights off the battery will slowly go dead after several days of starting.
Is this problem a software issue, control module issue, etc.