I have been given a damaged Panasonic 240W 12V/24V panel. The glass has had a stone dropped on it, the panel still works, but I will need to seal the small damaged area. The rest of the glass is crazed, but I'm hoping moisture won't get in, if it does I'll have to replace the glass I suppose. The specification says 72 cells in series. I think the maximum voltage output of this type of cell is ~0.7V and 72 x .7 = ~50V which is near the VMPP in the specification. That confirms the cells are all in series and that the cell(s) underneath the damaged glass must still work or there would be an open circuit. I want to use the panel to charge a 12V battery for use in a garage without a mains connection. To provide lighting and possibly some power through an 800W inverter.
I have a few questions about it:
I have a few questions about it:
- The model description is "Panasonic 240W 12V/24V" , but the specifications say "Voltage VMPP: 43.6V and Voltage Voc: 52.4V" I assume that 43.6V is the voltage at which maximum power is developed and the 52.4V is the open circuit voltage. So what is the meaning of the "12V, 24V"? Does it mean that it is suited to charging a 12V or 24V battery bank with the right regulator? Since a 24V battery needs a charging voltage of 2x14V (28V) and the regulator needs a voltage difference between input and output (say 5v), that gets us to 33V. So that sounds about right.
- There is a small junction box at one end, which appears to have several strips running to it. I don't really understand the need for this arrangement if the cells are all in series.
- I think the top of the junction box can be taken off, would it be practical to reconnect it inside to give me 1/2 the voltage at twice the current? It would save risking damage by taking it apart if someone told me that rewiring would be completely impractical.
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