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I have an off grid powered house powered by 6 x 12v batteries all hooked up in parallel. I also have 4 x 150w 12v solar panels all hooked up in parallel too. Things were good however I decided to move up to 24v. I rewired the batteries so that they were now in three pairs so they were 24v. I did the same with the solar panels, putting them into two pairs so they were also 24v.

My mppt can switch between 12 and 24v with auto detection.

Hooked it all up and everything worked.

Happy days.

HOWEVER

I recently bought a new 290w 24v solar panel and added it to my array. The others being functionally 24v and this one being 24v I thought there would be no issues. So I hooked it up and was surprised to see no increase in power. Checked all of the connections and they were fine. I even removed the other panels to just have this one running and still no amps would flow (confirmed this with fluke clamp metre). Checked the volts and it was as expected approximately 30v. I connected just the original panels up and everything was fine, around 15 amps. However as soon as I attached the new panel it dropped down to about 9 amps as if the panel was drawing amps instead of adding them. I contacted the supplier and they sent out a replacement panel. However after hook it up today I am having the same issues. The amount of amps going to my mppt DROPS when ever I add the new panel to the array.

Any help would be much appreciated as I am very confused at this stage.

Thanks!

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  • 1
    Could you please clarify the following: You hooked up the new 290W panel to your MPPT and then a load of some sort, and NO current flowed?
    – Tim
    Commented Feb 1, 2020 at 8:38
  • Can you provide a wiring diagram? Sounds like the wiring of the new panel may be suspect. Have you tried connecting the new panel to the existing wiring that worked for the existing panels?
    – LShaver ♦
    Commented Feb 1, 2020 at 17:12
  • Maybe you need some diodes in there to stop the panels from interfering with each other. The panels are likely to have significant design differences (as your question implies there was a significant interval between purchase of the first panels and the new one), so the voltage from one may be able to force a reverse current through the other. Possible wiring diagram here: instructables.com/community/…
    – M Juckes
    Commented Feb 5, 2020 at 21:25
  • 1
    Check panel is not installed backwards!
    – Polypipe Wrangler
    Commented Feb 14, 2020 at 6:17

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