Excuse my ignorance, but what does "cross tie your batteries" mean? If it makes the batteries last so much longer I would like to do it!
This guy says NO.
I would say "NO" to cross tying a battery bank.
If all is working well, then cross ties do nothing (as you have confirmed with your current measurements).
The only time cross tying would "help" is when there is an open cell or electrical connection--And that comes with lots of issues:
If the cross tie "works", then the bypassed failed cell means that other series cell(s) will be in danger of being over discharged (i.e., if you have two parallel strings, that would mean a 50% discharge of the "whole" string would be a 100% discharge of the cell carrying the bypassed current).
And, the whole issue of fusing/breakers... Normally, with paralleled battery strings, you only need one breaker/fuse per string for over current protection. With cross tied batteries, in theory each cross tie would need fusing/breakers too (nobody is going to do that).
Lastly, it makes checking the battery bank for faults (open/shorted cells, bad cabling, etc.) that much more difficult. You have to measure cross tie current to make sure it is zero, and if it is not, then you have to figure out why it is not zero (probably disconnecting the cross tie for debugging). Makes voltage measurements across cells/battery meaningless--If you measure 12.x volts across a cross tied battery, which battery is supplying that voltage (are other batteries low/failed?).
I cannot think of a reason for cross tying that would give any real advantages--And lots of real disadvantages.
And, like Marc/Cariboocoot finds when he makes a black/white answer, I will be awaiting somebody telling me I am wrong and there is/are real advantages for doing this (just none that I can think of).
-Bill "been there, done that" B.