24V mistake I made

wxh3

I made the switch from 12V to 24V this past summer with my small 2x135W ground mounted system. All seemed fine until recently when shading from a nearby building/fence has become more and more of an issue. There is quite a bit of time during the day when the top panel is in full sun yet the bottom panel is partially shaded. Thus, my output drops to almost nothing since the panels are in series. Anyway, this paritial shading is something I should have considered more closely when making the switch.

Unfortunately, relocating my panels to a sunnier location isn't really an available option for me.

I went from having too much power in the summer to not enough now. I didn't really need the (24V vs 12V) power savings in the summer and now the 24V series setup is costing me a lot of output.

BTW, does anyone make small (< 100W) 24V panels? It seems like all small panels I see are 12V. I was thinking about maybe having a temporary, seasonal small 24V panel in parallel with my main panels that I could try to put in a sunnier location.

Or maybe I should just go back to 12V...

n3qik

Re: 24V mistake I made

I would go back to 12V. Better to get 100 Watts than nothing during shading.

I hope you kept all of the 12V stuff.

niel

Re: 24V mistake I made

i agree stay with the 12v if shading is problematic for you. if the <100w 24v pvs exist they would somewhat rare now. i do recall that some pvs in the past had the option of 12v or 24v depending on how they were wired, but i don't remember who made them, if they are still being made, or their wattages. it's best just to reverse your wiring for 12v with the setup you have assuming that is a downconverting mppt controller that you have. if you're worried about the voltage drops then upgrade your wires.

icarus

Re: 24V mistake I made

I have a memory that Solarex panels could be wire 12 or 24 vdc, some of them anyway.

Niel is right, if all you are doing is charging 12vdc from a mppt, then just rewire. If on the other hand you are charging 24vdc, and inverting from 24vdc and you don't have the old hardware, changing back could prove expensive. Can you replace a section of the fence with a glass panel? Shine a mirror on the bottom panel for a few weeks?

Remember, we are about 3 weeks from the solstice so the process will reverse itself. How many weeks will you be without full production?

Good luck.

Tony

crewzer

Re: 24V mistake I made

whx3,

Check your PV modules for bypass diodes. Assuming your system is a 24//12 configuration and the modules have bypass diodes, the array voltage output should drop by ~ 1/2 when just one module is shaded. The remaining array voltage should be enough to continue operation, especially in the winter.

HTH,
Jim / crewzer

wxh3

Re: 24V mistake I made

The panels are Kyocera KD 135GX-LP panels. I am currently charging a 24V battery bank (2 110AH 12V AGMs in series) with a Sunsaver MPPT. The MPPT has a 200W limitation at 12V which is one of the reasons I went to 24V. (In full sun at 24V I have read over 250W coming from the panels but it is true that most of the time I would be getting under 200W anyway.)

Of course I still have several weeks to go before I see the shading at its worst. It has been an issue for about a month now I think.

crewzer

Re: 24V mistake I made

Bypass diodes won't help with a 24 V / 24 V configuration... sorry.

Regards,
Jim / crewzer