What on earth is has the possessive apostrophe got to do with batteries in parallel? You truly are the king of the red herring.
A little light humour to start the Year!
Sorry if that doesn't doesn't appeal to your sense of fun.
Pleased to note that your adherence has gone from zero to 33%.
The resistance of two items connected is parallel is calculated by summing the reciprocals of individual resistances (1/R_total = 1/R1 + 1/R2 + ...) a
WRONG.
You first need to sum the reciprocals of the individual resistances and then find the reciprocal of the total.
Which is exactly what “1/R_total = 1/R1 + 1/R2 + ...) “ does.
and Ohm's law is not involved.
And Ohms law is fundamental in that calculation and is therefore DEEPLY involved.
Ohm's law is the relationship between voltage, current & resistance.
The parallel resistance formula holds true whatever voltage is applied , Ohm’s Law is NOT involved
Summary
We agree on the way to calculate the resistance of two or more objects connected in parallel.
You express it in words “You first need to sum the reciprocals of the individual resistances
and then find the reciprocal of the total. “.
I prefer a formula ““1/R_total = 1/R1 + 1/R2 + ...) “
Others probably are not interested.
We agree that two leisure batteries connected in parallel should be the same type.
I believe they should also be the same make/ capacity / age.
You disagree and state this to be scientific fact supported by [sic] Ohms law.
Conclusion
I think neither of us will convince the other to change their opinion,
Others are, no doubt, getting bored with our discussion and will make their own decision about what batteries to fit.
I respect your right to add further comments, but as far as I am concerned the matter is finished and we must agree to differ.
All the best for 2026.