Date: Wed, 10 Oct 2001 22:28:39 +0800 From: Raymond <[EMAIL PROTECTED]> Subject: Re: [LIBRETTO] Raymond's Solar Reply
>>Would "brownout" occur due to lack of Voltage or lack of >>Amperage. > >Well the solar panel has a reasonably high internal resistance so the answer to your >question is both - an inability by the panel to supply sufficient current (eg. under >clouds, trees, etc.) will result in an increase in internal resistance resulting in a >lack of voltage at the output. Oh ya and before someone picks me up on playing fast-and-loose with terminology I'll better clarify ... the panel can only supply as much power as there is light hitting it, subtract some energy conversion premium. The result is that the voltage you get out of the panel is roughly inversely proportional to the current you draw out - obviously if you draw no current you get the most voltage and if you short the terminals (ie. no voltage) you get the most current. This can be approximated by a line with negative slope - a 'load line' that is quite steep for a solar panel and gets steeper as the amount of light available decreases (the slope being represented by the internal resistance I talked about earlier). The Libby won't like this as its used to a perfectly flat horizontal load line (which is what the libby's transformer provides - up to a good 2 or 3 amps you'd have minimal voltage change). Thats why I said you can't really treat the solar panel like the libby's plugpack for charging purposes - not only is there a slope to the load line on the panel but that slope will move around as lighting conditions change. Solar battery chargers on the other hand would be designed with this in mind and will cut charging as appropriate or perhaps reconfigure the panel or the pack so that the lower voltage can still charge the pack but at a lower charging rate. Such regulators seem pretty easy to come by - flipping through a catalogue now there's a suitable regulator which will work off a 16 to 20 volt panel and charge a 12 volt lead acid cell at a maximum current of 1.5A (I doubt you'll get this much out of your panel but it'll compensate) for about $10.00USD or so. Other regulators which can boost voltage (assuming your panel can supply enough current or if your panels are rigged in parallel, perhaps for redundancy or ease of isolation?) are also available for similar prices. They also do nice things like reverse current blocking (because the solar panel works both ways, you may accidentally turn it into a heater at night if you leave the battery connected!). Hope this helps! :-) - Raymond ************************************************************** http://libretto.basiclink.com - Libretto mailing list http://libretto.basiclink.com/archive - Archives http://www.picante.com/~gtaylor/portable/faq.html - FAQ -------TO UNSUBSCRIBE------- Reply to any of the list messages. The reply mail should be addressed to: [EMAIL PROTECTED] - Then replace any text on the message's subject line: cmd:unsubscribe --------TO UNSUBSCRIBE DIGEST------ Do above but with this on subject line: cmd:unsubscribe digest **************************************************************
