Hi Mike,
Based on the words that you have used, I have offended you...this was not my intention.
But I will go on further based on information that I have read and from those in the industry....without any intention to offend.
1. My agm exide factory battery fitted to my D4 needs a boost voltage of 14.4 and a float voltage of 13.6. Info supplied by exide technologies in the US.
2. My alternator only ever reaches 13.7 and as low as 12.8. Float voltage is only a guide but irrelevant in battery life. Sat NAV only shows surface voltage.....not state of battery condition.
3. Topix confirms how the alternator works, and explains how the alternator, when the surface charge reaches 13.7 from memory, will reduce power input and cut back in at around 12.8. Not a recipe to look after AGM batteries.
4. My uncle is an auto sparky, and as a person in the business, he has told me that the modern alternators never truly charges a battery to the full amount needed to prolong battery life. He has checked my charge output and confirmed its works within factory spec....but it will never full charge my battery.
5. I have a client that works for exide technologies in Perth Western Australia. He constantly sees issues with modern alternators not providing a true deep charge for batteries, and hence premature battery failure.
6. Southern LR (where I purchased my D4) also recommended a battery charger to look after the batteries. I told them that I have always done this and will continue to do so. They see failed batteries regularly due to the function of the alternator.
7. My neice works for Toyota. The Landcruiser also has a "smart" alternator, and they are constantly replacing batteries.
8. And just based on my own personal experience, a smart charger looks after batteries better than any alternator ever will.
I personally don't expect to need to replace my battery in my D4 in 5 years....I have never actually had a battery replaced on any vehicle to this date. Maybe I am doing something right by using a smart charger each month and not relying on factory alternators ?
I am no alternator/battery expert, but always listen to others who are experienced in their chosen field as their advice is invaluable.
Brett.....