Hi Scott and sorry mate, but DiscoMick’s post is spot on the money.
And as to your claim that there is a about how alternators charge, well you are correct about the fallacy, but it is the exact opposite of what you are claiming, as Eevo pointed out.
The problems associated with cranking batteries ( and auxiliary batteries ) not being fully charged by an alternator has nothing to do with some fictitious claim that the alternator is the cause, but is actually because the vehicle is not driven long enough after each start.
Adding a DC/DC device to the limited charging time does not resolve the problem, rather than fix the problem, it can actually exacerbate it, if the auxiliary battery is in a low state of charge in the first place.
In this type of situation, you are correct, eventually, the DC/DC device will, after many short drive, bring the auxiliary battery up to a fully charged state, but a Land Rover alternator will have the auxiliary battery fully charge in the same situation but with much few short drives required to do so.
Next, you posted up that “all AGM battery manufacturers 14.7v is the preferred AGM charge voltage”. This is not correct and is also a misunderstanding of what the manufacturers are stating.
The 14.7v quoted, is not the required voltage needed to be able to fully charge the battery, the 14.7v is the MAXIMUM SAFE voltage that “MANY” not all, AGMs can tolerate, above which the battery can be damaged
Unlike your claim that this is for all AGMs, again, Odyssey and Optima batteries are just two AGMs batteries that can be SAFELY charged will voltages in excess of 15v.
I noticed you quoted info from the Optima battery site, but you only picked the sections that supported to your argument. Had you read all the info you would have seen that Optima specifically states “Alternator 13.65 to 15.0 volts, no amperage limit.”
So even if Land Rover alternators worked at a much lower voltage, they would still be within the required charging range of an Optima, which is one of the most common batteries using as an auxiliary battery in Land Rovers.
You also raised the point about having dissimilar batteries. This is another one of these myths used to make people think there is a problem with charging dissimilar batteries at the same time, with an alternator.
If you believe the crap they spin, saying you need to separate batteries to charge them properly. Well this is only the case if you have Lithium auxiliary/house batteries.
But when all the batteries are lead acid the batteries, be it AGMs, Gel, Wet Cell or the new Lead Crystal batteries, alternators charge each battery at it’s optimum charge voltage and current.
And here is a fact for you that most people are unaware of. When charging with a DC/DC device or a battery charger, if you set the maximum voltage to no more than 14.4v, can charge mixed battery types at the same time as well.
There is a lot more to this subject, and while you may be happy with what you have, you do NOT have the optimum charging setup.
But when it comes to the optimum Land Rover dual battery system, there is nothing better than one of my setups, and they cost a lot less than a DC/DC setup yet give far better performance.


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