Originally Posted by
drivesafe
Hi Scoota, for what your planning to use the cable for, 6B&S or 16mm2 twin cable would be the minimum size but you will still get a voltage drop and you might be surprised at how much voltage drop you will get with this thick cable.
Just to give you an idea of what to expect, just last Thursday I was carrying out some operating experiments on a new isolator.
I needed to do this in a real world situation, so the day before, I discharged two 105 Ah flooded wet cell deep cycle batteries down to 12.04v. Thats a fraction under 50% SoC.
I had these two batteries strapped down in the back of my wife’s D4 and had them connected via 6m of 6B&S twin from the cranking battery, via the isolator and through two sets of 50 amp Anderson plugs ( that 2 x 2 plugs ).
I was not interested in the current draw just the ability for the set up to be able to charge batteries without having problems with the isolator, so I only took voltage readings and didn’t bother with current readings.
Just after starting the motor, the cranking battery voltage was 13.78v and the auxiliary batteries were 12.71v
After 20 minutes of driving, the cranking battery voltage was 13.80v and the auxiliary batteries were 12.90v
After 3 hours and 6 minutes of driving, the voltage at the auxiliary batteries were at 13.28 and was 13.66v at the cranking battery.
The two auxiliary batteries have been sitting for a week now so if I get a chance this afternoon, I’ll load test them and see what they were charged to.
