[scrubjaysnest]

Here are my test results of the solar panel set up we got. I replaced the 12 awg 30 ft run with 10 awg 22 feet. The Sunsaver 10 is mounted within a foot of the battery(s) and is connected with 8 awg wire. There is 3 ft of 12 awg from each panel to the so called combiner. The combiner has MC4 connectors and has two 1 ft pieces of 12 awg spliced, unknown how it was done, into a 1 ft 12 awg with another MC4 connector. This in turn connects to my 22 feet of 10 awg. For calculating voltage losses you double the number of feet. The current has to pass through both the plus and minus wires. Air temperature was between 69 and 72 degrees and as solar days go during the test it was mostly good to excellent with about 15 minutes of fair thrown in.

The battery was discharged by runing the refer on DC for three hours, this gave about a 50% SOC on the battery, or 12.26VDC measured. I don't have a hydrometer so can't measure specific gravity to get the real SOC.

1 panel 12.89VDC 4.78amps 2 panels 14.05VDC 9.6amps
Vdrop to controller 0.05 VDC 0.79VDC
Batt voltage 12.75VDC 13.05VDC

Remember when you start to charge the panels want to push as much current as the battery can take. This means the voltage won't start at 14.4VDC. As the battery takes on charge the voltage will rise until the controller can switch to absorption mode, 14.4 VDC for mine.

I started the test at noon and the controller was in float mode by about 3:30 pm.

Float voltage was 13.71VDC at 1.3amps

Absorption Voltage was 14.36VDC at 6 amps.

The system total volt drop is greater than the desired 3% or less and although it can be lived with on bright sunny days it will be a killer on cloudy days or in partial shade.

My best guess is to get rid of the MC4 connectors and run 10AWG from the panel terminals all the way to the controller.

My calculated volt drop was 0.5VDC or about 2.7%

Some further testing before we leave in March this year is required.


Went back and relooked at the figures, the panels were only generating about 135 watts on average. Loss from the panels to the controller was 6.6 watts and total watts lost was 9.6watts. So all considered maybe not so bad. The battery did get a full charge.