Originally Posted by Ian G.
It is actually exactly the opposite, as a battery discharges the acidic content of the electrolyte decreases (the electrolyte become closer to water). A fully charged battery has a higher acidic concentration. This is why a fully charged battery will not freeze where as a discharged battery will.
Thanks Ian, I stand corrected.
AFAICT the discussion of damage from maintaining even a partially discharged state still stands.
Sulfation and How to Prevent it - Battery University
This web site is a fascinating read and I am working my way through it. Much of it is about other technologies which have little relevance for us RVers.
My problem is that I live in my caravan, connected to AC, so the batteries are charged however much they are charged and then sit at that charge for long periods. Given that, I would prefer that my batteries are fully charged. It isn't clear whether I need to periodically use them some amount, and if so what that amount might be.
What is clear is that the built-in charger in my converter does not use a remote sense, does not use a remote temperature sense, and according to the converter manufacturer simply times the bulk charge phase. And according to the manufacturer, the voltages that they use seem to be selected based on a "do less harm" algorithm, i.e. avoid overcharge at all costs. Given that they do not use any type of remote sensing it becomes clear why they follow this strategy. Given that they are not programmable at all, i.e. battery type or environmental temperature, the fact that I have a pair of 6v batteries pretty much guarantees that their "do less harm" algorithm is badly maladjusted for my needs.
Thus I choose to spend extra money to go third party.
Since I don't drink, and thus haven't a benchmark such as "a good bottle of wine a year", I tend to simply equate the cost of a third party charger to the cost of a pair of batteries.
I only need to avoid one battery replacement cycle to recoup my costs.