March 19th 2020
Ok be warned this is an update on our solar system. If you have been following the progress of our latest solar upgrade you may remember that I have been having issues with a voltage drop at the solar controllers, and it was large enough that it would keep moving the controllers from bulk charge to a float charge and it would do this because the controller was seeing a voltage in excess of 14.4 volt which is the same voltage as our battery’s when fully charged. But actually the true battery voltage was only 13.4 volts, the difference was the 1.0 volt drop that I have been chasing.
This was the style of circuit breaker that I was running between the controller and the batteries, it was a 50 amp unit that clamped down on the 6 gauge wire by means of a set screw. I have tightened them multiple times but they always seemed to be loose. This problem is maybe magnified because it is a multi strand welding cable, so less rigid.
What I was able to trace was that because now we are running the controllers at near capacity, 550 watts each the breaker was causing too much resistance when the panels were were in full sun. I even disassembled the connections and tried soldering the cable ends to get a much more solid surface for the set screw to tighten against, but the breaker would heat up and the resistance would increase causing the larger voltage drop, sending the controller into float charge mode, reducing the output until the controller sensed the correct battery voltage again throwing it into a continuous cycle switching cycle from bulk to float and back again. So the better the solar harvest available the worse this condition would be and the poorer our actual solar harvest would be.
This is what I replaced the circuit breaker with, with it I was able to crimp copper lugs onto the 6 gauge wire, and then tighten them with a wrench reducing any chance of resistance and have corrected the voltage drop so the controller picks up true battery voltage. I had to upgrade to 60 amp fuses but they are to protect from a catastrophic failure so the extra 10 amps won’t be a concern.
It is amazing how one of the most inexpensive pieces in our solar system has caused me the largest amount of grief. I just today finished changing the fuse blocks and even with a rainy morning and a cloudy sky we have harvested more than 250 amp / hours of solar power. We are still seeing a voltage drop but less than one half a volt, and it stays consistent at all amperage, over the summer I will replace the 6 gauge wire with 2 gauge with proper crimps and will shorten the length of the cables by running them more directly to the batteries … my target will be less than one tenth of a volt drop between batteries and controller.
That’s all for the solar updates most likely till we are back into Ontario.
Please be careful and stay safe!