back to solar power

combiners:




My portable solar setup consists of several strings of 100w flexible solar panels, which are connected in
series using a panel combiner. Four panels will produce an open circuit voltage (Voc) of just over 90 vdc.
At full load the voltage (Vmpp) on the string will drop to 58 VDC and current (Impp) will reach about 5.1 amps.
The panel combiner incudes four small voltmeters so I can spot any irregularities with individual panels.

If more than one string is available, they will be then connected in parallel (using a string combiner box)
before going to the controller. This does not affect the voltage, but will add together the current from all
strings. The string combiner box has a single large meter that displays volts, amps, watts, and also counts
up watt-hours.

My usual delivery wire is 10ga of high strand count CCA, with a length that varies depending on site options.
Typical length is 50 to 100 feet. As long as I keep the current low, the loss is negligible. Heavier wire is
available if panel current is producing unacceptable power loss.

The above strategy brings the voltage up near the safe limit of the controller, which is 100v for the panels,
while minimizing current on the delivery line, which minimizes power loss. If instead I had connected all
16 panels in parallel, Vmpp would be 14.6 volts, but Impp could theoretically hit 80 amps. The controller can
handle 40 amps, but that would lead to significant power loss on the delivery wire.

Originally I had a total of 8 panels (two strings of four) and my combiners were thrown together on the evening
of a Field Day, so they were built in a way that was quick and got the job done, but wasn't pretty, sturdy, or
safe. (due to exposed high panel voltages) The panel combiners were also exposed to rain. I'll call these
prototype designs my Mark 1 Combiners.

Since then I have obtained more strings to increase production on overcast days. This isn't going to really
affect my maximum power production because my controller is already at its power limit with two strings, but I
needed to create a new string combiner that could handle 4 strings instead of just 2, and it was also high time
I made proper panel combiners, so now I have Mark 2 Combiners. These will allow me to collect my maximum
(or at least, more) power during poor solar conditions such as morning, evening, and overcast.


importance of panel combiners


LiFePO4 combiner


mark 1 combiners


mark 2 combiners



last updated 02/16/2025 at 16:26:40 by make_www_index.command version 2025.02.14.A