Date: Sat, 29 Sep 2001 00:05:04 -0500 From: David VanHorn <[EMAIL PROTECTED]> Subject: Re: Homebrew battery packs
> >Hmm ... could you recommend a webpage or book which would have a suitable >circuit or a suitable discussion on how to build a simple circuit that >would allow me to charge the pack using a 15 volt supply like the >Libretto's power supply? I wanted to use NiMH because I've got a new 3.5AH >12 volt NiMH battery pack which is a good size (its about 2/3 the area of >the Libretto's base so if I were to make it into a slice there would be >plenty of space for a charging circuit) - it WAS for a laptop I used to >have which died about a month after I got the new pack :-/ How many cells are you running? I wouldn't put much more into it than the 10.8V of a full charged Li-Ion pack, at least not in through the battery terminals. If you've got say a 9 cell pack, then you could do a simple slow charger. You'll get into charge depression if you leave it on slow rate too long though. The MAX712 is a decent charge controller, but it's a bit of a project. Lead acid cells really are the simplest to charge. Just feed them a constant voltage, limit the current, and you're done. >What sort of battery life do you people with 50CTs get with new battery >packs? I know the pack is rated at 1.2AH but my Libretto 50CT is second >hand - the battery pack is already shot so it only runs for half an hour >on a full charge. An hour or so on the standard pack IIRC. Mine's hardly new. I haven't timed them out recently. >For that matter, does anyone have any opinions or experience regarding how >you can trick the regulator on the Libretto by first applying 15 volts (to >get it to turn on) then dropping back to 12 volts to run? (Xin does it on >that page I posted earlier.) I'm just a little hesitant to try that out as >the manual does state (page 2-3 in my manual) that 'Inadequate voltage ... >could damage the computer'. For that matter, given the inbuilt pack is >10.8 volts, is it likely to charge if the input was dropped to 12 volts? >(I have no idea what sorta voltage drop your average charge circuit would >have). 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. -- Dave's Engineering Page: http://www.dvanhorn.org Got a need to read Bar codes? http://www.barcodechip.com Bi-directional read of UPC-A, UPC-E, EAN-8, EAN-13, JAN, and Bookland, with two or five digit supplemental codes, in an 8 pin chip, with NO external parts. ************************************************************** 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 **************************************************************
