Date: Sat, 29 Sep 2001 08:12:56 From: "neil barnes" <[EMAIL PROTECTED]> Subject: Re: Homebrew battery packs
>Date: Sat, 29 Sep 2001 00:05:04 -0500 >From: David VanHorn <[EMAIL PROTECTED]> >Subject: Re: Homebrew battery packs > >I don't believe inadequate voltage will hurt anything. >The power pack is a switcher, and will run from DC, I checked it on my >bench DC supply. >The lib behaves nicely at low voltages, but it dosen't start up till you >exceed 13.8V. >Xin's info is good. > A problem. If you use an external supply (i.e. through the socket on the side) then as pointed out, it needs to see around 15v for a short while to tell the lib it's there. Xin's circuit is good for that (though IIRC the diode may be drawn the wrong way round). Once it's seen the 15v it will happily work on the external power till it gets to some terminal voltage which I never got round to measuring, but I'm guessing around 11v. At that point, the lib will silently switch to using the internal battery - but it will tell you that external power is still present. It will also tell itself that :( An hour or so later, the internal battery is dead, but the machine doesn't know it's running from it - so there is no warning, no critical voltage save to disc etc and your work has just vanished. I haven't looked into things recently, but I'd be tempted to use a DC-DC converter which will throw out either 12 or 15v as long as there's power in the external supply (this will cost some efficiency, though less at 12v than 15v) and will then shut down when the input voltage drops too low. At least this way, you'll see when it shifts to internal battery, and you'll have the protection, auto save, hairy lightbulb etc. Design of this power supply is not a trivial task. I have a 12-15v converter for the car which I should probably investigate with an external 12v sealed lead-acid cell, but at the moment I have three battery sticks, which is as long as I can stay awake on a plane anyway! (Though one of them is definitely on the way out :( ) Neil _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp ************************************************************** 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 **************************************************************
