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Forum Index : Solar : Solar panel without diode
| Author | Message | ||||
| Georgen Guru  Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Hi, I've got few Watt 12V solar panel without diode. What diode should I put to prevent battery leaking power back to solar panel at night? I know the simplest is to disconnect it, but when I am not there? George |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Georgen Pick a diode with a amp and voltage rating double the panels rated output, just to be safe. If its a 12V 20 watt panel, for example, then a diode rated at 24 volts or more, 3.2 amps ( 20W / 12V * 2 ) or more will do the job. It doesn't hurt to go bigger, diodes are cheap. For a 12v panel, a diode with a low forward drop voltage would be better too, means a little extra power in low ligh conditions, but not critical. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Funny thing about those recommended diodes in solar panels. I once tried to measure the reverse current with a smallish panel that was placed upside down on a table to block all light out. The reverse current was very small, so small that I wonder if its worth to bother about it with fitting diodes. Maybe some solar panels are different, mine was a polycrystalline type. Has anybody else tried to measure the reverse current. Klaus |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hi Tinker I think it depends on the type, some leak, some dont, but other than that I dont know. I also remember something about diodes across each cell in case some cells are shaded, they can overheat if reverse biased. But again, old brain cells at work here, and this was for a solar car where each cell was wired individually. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
Thank you very much for help. Just was told that local Dick Smith doesn't keep any components, only selected shops do now. Looks not many people do things themselves, and shelf space now carries some games. Will have a look at JayCar. George |
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| Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462 |
[quote] depends on the type, some leak, some dont [/quote] Measured couple of nights current back to panel and looks it is negligible. (did not pick up on 0.06 mA scale on my Multimeter) So as you said, some don't leak All good then, thanks again for help. George |
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