'Myth' until, you know, tests and amperage readings are actually observed. http://www.smartgauge.co.uk/batt_con.html
I didn't want to continue this argument but, come on, you guys are taking your opinion a bit far; you're misinforming people. The industry disagrees with you.
While I don't disagree with the numbers quoted in your linked article, there is a "practical" realization to live with. For our purpose, using multiple batteries to provide more amp/hours in our RVs. The examples given in the article are splitting hairs....to the extreme. The analogy that I would make is that if your car/truck battery was reading 12.6 volts, as measured with a perfectly calibrated volt meter and you engaged the starter to start the car/truck.....neither you or anyone else could tell the difference between that 12.6 volt battery starting the car and one that reads 12.5 volts. It's no different that you common household voltage variations. I can take a meter out to the breaker panel at my house and read one side of the 240VAC coming into the house and get 124.7volts to the neutral, then read the other hot line to neutral and get 124.2volts......can you tell the difference between the brightness of one light bulb being fed off of one side of the incoming power vs. another light bulb being fed off of the other phase coming in......with a .5 volt difference?
I work as a High Voltage Journeyman Electrician and some of the testing that we do on high voltage breakers and contactors for motor control, involve testing them for contact resistance, phase to ground resistance, and leakage current to ground which tests the amount of current flow to ground with specialized, highly calibrated test instruments. I see readings that are so small that most people would simply ignore them or not even know what it meant. An example of this....while applying 10,000 volts to a high voltage breaker, we measure the amount of leakage current to ground for that particular conductor of the breaker and sometime see as little as 1/10 of one micro-amp...that's .0000001 amp of current. Many times the resistance reading for that part of the breaker might be as high as 8 or 9 teraohms.....and one teraohm is equal to 1,000,000 megaohm....so suffice to say....a very high resistive value.
So, I've said all of that ^^^^^ to say this. For all intents and purpose of hooking up a charger to the battery bank of parallel batteries, it really doesn't matter where you hook it up for our practical use of the batteries in our RVs. Are you really going to see that .0001 voltage drop? Are you really going to see any performance degradation from it? And furthmore, I quit reading the article when I rechecked their math and found some of his published numbers to be wrong. .00012 (cable resistance for 20cm of cable) AND the additional .0002 (connector resistance) plus another .0002 connector reistance does NOT add up to what he said... .0015 ohms. The actual total resistance for what he is talking about...two connections and one length of cable is.... .00012 + .0002 + .0002 = .00052 not .0015. And again, these are very, very, small resistance numbers that in real life, what we are using our batteries in the RV for, have no noticeable effect on our battery charging/usage.
In my world of high voltage breakers and contactors when dealing with 2300V, 4160V, and 13.8KV, those small numbers in the micro amp and teraohm range have significant meaning and will determine whether or not a breaker will safely operate according to IEEE testing standards......in the real world of 12 volt batteries in an RV...........not so much
And then, to top it all off, the O.P. gave us the wrong information in the original post and stated that he had a parallel hookup for his batteries. Turns out, he has two 6 volt batteries that are hooked up in series to provide 12 volts.....and we all know that Ohms law states that the current flow in a series circuit is the same throughout the entire circuit, and that amount of current flow is based on the applied voltage and the total circuit resistance.
Sorry for the very long-winded post, but I felt that some "practical" light should be shed on the subject and information given that will work for our purpose.
And a quick PS......I don't consider this discussion an "argument". To me it is simply a discussion with the hope of coming to some conclusion for our practical use of batteries in our RV's.....a common sense approach if you will.