re: "
Both of these statements demonstrate very well that what I say about the general consensus being wrong." -- I think you need to back off a bit and get your facts straight, both about the consensus and what I am saying about batteries. I much prefer not just labeling something wrong but rather explaining why I think it is so and what is more correct and why that is the case.
re: "
First, the voltage is a very rough indicator of charge level and is very difficult to interpret" -- voltage is the outcome of the same electrochemical process and is directly correlated to specific gravities, which is why you often find charts with both listed versus state of charge. Both voltage and specific gravity need 'interpretation' in light of battery temperature, recent usage (e.g. electrolyte stratification), and other matters. Both need care to assure a proper measure. The use of voltage as a primary battery state of charge indicator can also be seen in its use in battery gauges and in the automatic cutoff mechanisms on many heavy low voltage loads.
re: "
Of course you need to be careful with acid, but how difficult is that?" -- as a matter of fact, quite difficult because it does need attention to detail. Things have changed over the years as people are now a bit more concerned these days about acid burns and eyesight loss and such things. I have my share of acid burned pants and shirts and I have indeed chased mercury globs around the floor and work surface (some say that's the source for my debate points, but I digress ... ;-). I am also acquainted with the fact that many folks don't pay much attention to risk reduction even when they have been carefully trained. That is why I think the best safety is to avoid putting yourself in a spot where special precautions are highly recommended.
re: "
You will find that Ralph, the inventor of the meter" -- appeals to authority do not matter as much to me as the validity of what is offered and being able to understand its reasons, rationale, and context. (And don't get me started on the problems with electron counters! -- especially in regards to proper measurement technique, interpretation of measures, and such things as accuracy versus precision.)
What you cite from Ralph about recommended voltages has several important caveats that need to be understood before being taken as is. One is the difference between applied charging voltage and battery voltage during charging. Another is the role of the current capabilities of the charging sources. Battery charging voltage can be an interesting topic because it has a lot of depth.
re: "
The correct charge voltage varies with temperature, but their chart shows that 14.8V is correct at 77 degrees F." -- this depends upon the battery and what you are trying to do. There are good reasons why RV converter chargers tend to run 14.4v as their bulk phase voltage maximum and absorption switch point (as described above). Float voltages usually run in the range of 13.2 to 13.8. Resting fully charged battery voltage after the surface charge has been removed runs around 12.6 to 12.8v
re: "
I add water to my batteries every three months" -- loss of electrolyte usually indicates overcharging. This might be related to the 14.7v bulk charge voltages or perhaps too high a float voltage. Less common, it might be due to excessive charge or discharge currents (mismatch between bank size and use profile) or heat. Either way, it is something that should be fixed if possible.
re: "
if by the "typical RV enthusiast", you mean the the folks parked elbow to elbow in RV parks, then you may be correct. However, this thread was started by somebody who wants to dry camp. The correct answers are different for him." -- I think that context is indeed extremely important and agree with you on this. But the creation of categorizations to dispute what I offer is way off base - a constructed fallacy as it were. That sort of thing doesn't help IMHO.
The context, the use profile, is a very interesting and important topic in its own right as it has significant influence on battery life, battery warranties, and other matters. I find it especially pertinent when folks get into 'deep cycle' myths or the need for equalization charging.
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The biggest reason that you don't see me on these forums very much is because I get very tired of trying to fight the general consensus that is such a hindrance to those of us who want to successfully go off grid. It took me years to figure it out because everywhere I went I found bad advice.
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I can certainly agree with you here (but I don't think the hubris is appropriate as we can all learn). It is why I try to make sure anything I offer has a reason, a 'because', a careful explanation with appropriate context, reference and citation if needed, and good empirical support.
IMHO, we have a responsibility to clarify the errors and misperceptions that exist and are promulgated in these forums, to provide education as we can, and to help folks understand those technologies upon which they depend.
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