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Running a GTI on batteries...

Discussion in 'Renewable Energy' started by Jules_Theone, Jul 27, 2012.

  1. Jules_Theone

    Jules_Theone Member

    Joined:
    Jan 22, 2009
    Messages:
    167
    Likes:
    3
    Location:
    Exeter, England
    I have a 4kWp and 500Wp grid-tied solar systems installed and can read that during the day they are feeding into the grid more than the 50% export payment is (not that I think the elec company is ripping me off). Because I don't have an immersion heater to dump power into something useful I thought of using the excess electricity to charge batteries and then power a smaller GTI off of them later in the day to offset my consumption even more. I have two GP-350 14-28V 350W GTIs from China and tested one connected to two 12V 14Ah batteries in series. Firstly it doesn't seem to draw the maximum it should (350Watts). Is that because the GTI is trying to track MPP and not just trying to draw maximum current. It seems to draw around 260W at 24V, with decreasing voltage as the batteries run down it draws more current, as expected. But I don't understand why it doesn't try to max out. I've tested a similar 250W inverter before on 24V lead acid batteries and a series resistor and that seemed to behave more appropriately - around 235W with minimal series resistance. Is it possible that the 350W GTI is just a relabeled 250W and the Chinese are lying?

    The other issue was that i can hear the fan come on and then the current it draws from the batteries (or solar panels) drops to near zero then ramps back up after waiting for a minute. Does that sound over-heating related?


    Thanks,

    Jules
     

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