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Say I have 2 solar panels with slightly different ratings with ~36 VDC 8 A. I assume there is a voltage regulator with 18 VDC output, so I connect two 18 VDC voltage regulators and later try to bring it up back to 36 VDC by connecting the voltage regulators in series like batteries do. Is that possible? I'm trying to provide a steady input voltage to a single inverter.

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    \$\begingroup\$ Welcome! Please draw a block diagram of what you have and how you intend to connect them. \$\endgroup\$
    – winny
    Jun 2, 2022 at 9:48

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This is possible if you use isolated DC/DC converters. If you use a LDO or something similar, the negative output is typically assumed to be at the same voltage as the negative input (and the two often share a pin on the regulator).

Since you want the negative output of your "upper" regulator to be connected to the positive output of your "lower" regulator, it needs to be isolated from the negative input.

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  • \$\begingroup\$ ..mybe I should string the panels in series and buck it up to the inverter max limits..but I can't find a DC DC converter ranging from 30-100dcv input with variable output ranging from 10 - 60dcv max 20A.. \$\endgroup\$
    – Suren Bono
    Jun 3, 2022 at 11:39
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If the panels match coarsely on current rating but not voltage, wire them in series. They will work at the spec of the smaller panel, which is no big deal if the difference is small.

If the panels match fairly precisely on voltage but not current, wire them in parallel. Use a charge controller appropriate for the resulting voltage.

Otherwise you'll need 2 charge controllers if you want reasonable performance.

Your trick with voltage regulators is not going to work. Controlling solar panels is complicated. The charge controller needs to interact with the solar panel's unique voltage/current behavior, or it's not going to get good power from the panel. The charge controller knows how to do that. So it needs to be given access to the solar panel directly without hardware in the way.

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  • \$\begingroup\$ ...i can only try it on parellel since the grid tied inverter can only accept upto 60 dcv..but the terminal melted under heat due to out off tune/loss..so mybe I could use a DC DC converter just to bring both volt& amperage to tune..but I can't find any of those size..the grid tied inverter help to reduce consuming from the grid when the sun is up..my latitude 2°N \$\endgroup\$
    – Suren Bono
    Jun 3, 2022 at 8:33
  • \$\begingroup\$ ...if a grid tied inverter could track and push voltage across the AC grid can't there be a device that can regulate DC voltage in between panels and the inverter for mixed panels?..so far we got string DC optimisers but it's limited to a specific manufacturer..we need one to fit any inverter \$\endgroup\$
    – Suren Bono
    Jun 3, 2022 at 9:02
  • \$\begingroup\$ @Suren The #1 cause of terminal meltdown is incorrect torque - loose connection arcs. Again a DC/DC won't work because you can't have anything between the panels and charge controller. Anything. Since you're buying hardware either way, buy the right charge controller. Yes, there is such a device, it is the charge controller lol. It has one job, get best power out of the panels and turn it into correct output voltage. \$\endgroup\$ Jun 3, 2022 at 18:02
  • \$\begingroup\$ ...I got no problem with the charge controller or the Grid tied inverter..I mixed panels and tried parallel on the inverter...so I think it's probably better the get a separate low power inverter each...I plan to cut 2 kWh/ day out off daily 15kwh consumption using it.. \$\endgroup\$
    – Suren Bono
    Jun 4, 2022 at 20:41
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I wouldn't advise it.

If one of the solar panels is covered and doesn't produces power, you might have current externally "forced" through the second converter (which might suffer from it).

In an ideal world, even if you regulators survive and regulate, if they produce different current, you will be limited by the smaller of both.

So I would rather advise you to put either your solar panels in parallel, or the converters in parallel, rather than putting the converters in series

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  • \$\begingroup\$ ..what about DC DC converter..can it do it? \$\endgroup\$
    – Suren Bono
    Jun 3, 2022 at 8:36

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