Folding Solar Panels - check the <span class="highlight">wiring</span>

Hi RMD

You may well be right and in practice it may not matter much depending on what device the solar panels are connected to. And I will not profess to be expert in solar panel theory, nor have I done any tests to check all the possibilities.

The Diode only has to be large enough to carry the maximum continuous current of the one panel it is being supplied from, and the loss of 0.6V would be irrelevant in most situations.

Having an electronics engineering background, let's say it is "technically wrong" (even though it does work) if you look at any information relating to connection of solar panel arrays - a search for "diodes on solar panels" will provide many links and images to the theory. However, with the blocking diodes in circuit, my logic also tells me that an MPPT controller would be vital to getting the most out of each panel such that both panels are supplying current.

I appreciate there are many varying scenarios for the use of solar panels (directly connected to batteries or on various controllers or regulators) and in most cases it may not matter. But the theory as I see it is generally not to allow batteries or other solar panels to push reverse current through panels that are not generating enough output for whatever reason as that is wasted energy.

I would be more concerned about solar panel discharging start battery if it was left attached without a diode to prevent back flow, than the solar panel supplying too much or being partially shaded

I had this occur using a 80w fold out from a australian electronics component supplier, took awhile to figure out what was going on.

Battery fully charged by middle of day left attached early evening looked at led battery status one step away from deep discharge -managed to start engine (just) following morning.

with few days of testing I figured out was due to lack of blocking diodes, contacted manufacturer of solar panel/regulator for their input -sure enough we don't fit them.

ended up replacing with a GSL MPPT unit and on advice of the manufacturer installed a blocking diode inline between regulator and power leads -so far no more issues.

An MPPT controller can't reverse switch to allow any current to flow back into the solar panel. That is like saying a laptop supply will supply the computer battery to the 240v grid.

I have installed the extra diodes on mine - thet are 15A Schottky diodes so forward voltage drop is only 0.3V which is irrelevant to the solar panel voltage.