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If I have 500v of solar power can I run 10 mppt charge controllers in series? So each mppt would only see 50v because I'd be using 10 cheap mppt controllers in series. From there it'd be charging a 24v system.

I don't think pwm would work well in this, but mppt might.

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  • \$\begingroup\$ I suspect their control laws would fight each other, generally you'd only want one controller one source. \$\endgroup\$
    – Neil_UK
    Commented Dec 3, 2020 at 6:09
  • \$\begingroup\$ No. I have never seen an MPPT charge controller that was designed to operate in series with other controllers on a high voltage string. If it was designed to operate that way the manual would explain how to wire it and configure it. There are micro-inverters designed to operate one per panel. But that isn't exactly what you are talking about. \$\endgroup\$
    – user57037
    Commented Dec 3, 2020 at 6:32
  • \$\begingroup\$ There are MPPT converters for series connection, each panel (or some of them) has its own MPPT converter. In a series connection it would create HV DC bus. But I don't understand you question about using 10 converters in series to charge 24V battery? \$\endgroup\$ Commented Dec 3, 2020 at 7:56
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    \$\begingroup\$ No. For one thing they don't isolate input from output so connecting them to the same LV system makes one massive short circuit.Split that string into smaller strings 50 to 100V each and you can use separate charge controllers on each string. \$\endgroup\$
    – user16324
    Commented Dec 3, 2020 at 11:49

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If the controllers were put in series, it would create issues for the MPPT algorithm because the algorithm calculates how much power it is drawing from the solar panel and the current from each MPPT controller would be the same (because they are in series) so each controller would calculate an incorrect power from the load.

In addition not each controller is created equal, so placing them in series will cause each one to draw a little more or little less power.

Another problem is the controllers probably don't have isolated grounds on the inputs and this could create problems for the electronics as they would not be referenced to ground.

Probably not a good idea.

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  • \$\begingroup\$ That's not an issue, there are MPPT controller for series connection. The current is the same, but voltage varies. They are floating, the max DC bus voltage must not be exceeded. \$\endgroup\$ Commented Dec 3, 2020 at 8:02
  • \$\begingroup\$ @MarkoBuršič they are not really in series, though, are they? Because there is one per panel (or one for every few panels). Otherwise, if all panels have the same current, then you would only need one MPPT instead of many. \$\endgroup\$
    – user57037
    Commented Dec 4, 2020 at 4:30
  • \$\begingroup\$ @mkeith Each panel has an arbitrary MPPT working point, determined by MPPT converter (panel optimizer) then these optimizers share the same current with different voltages when connected in series. If somehow one is shaded or dead, it still forwards the current by use of bypass diode. \$\endgroup\$ Commented Dec 4, 2020 at 8:56

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