Date: Sat, 29 Sep 2001 16:47:04 +0800 From: Raymond <[EMAIL PROTECTED]> Subject: Re: Homebrew battery packs
Gee I really like this mailing list already! Some mailing lists I'm on, no-one knows or says anything ... at least here I can really learn things! >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. Hmm ... I dunno about boosting to 15 volts but to cut the power so the libretto knows its on internal battery, couldn't you use those cheap $5 battery monitor kits with 3 LEDs that you could buy from the local electronics store (the ones you'd normally use in your automobile to warn of low battery voltage)? Instead of the 'power good' LED, one could hook up a relay (perhaps through an optoisolator if the coil has a chance of confusing the circuit) so that when the power good LED goes off (signifying insufficient voltage) it totally disconnects the pack. Of course, you'd need a switch to temporarily bypass that circuit to get the relay to turn ON in the first place. It occurs to me that you could probably also use that same switch to temporarily connect the extra cell to give the Libretto the 15 volts it needs to start ... anyone see any potential issues with such a setup? Also regarding charging NiMH packs, I've had a look at the MAX712 data sheet ... seems like an awful lot of mucking around to get some use out of a battery pack (besides which actually GETTING one of those is annoyingly difficult around here anyway) ... would there be much danger in using a simple semi-constant current source (or even just hooking the 15 volt supply straight to the battery through a few diodes) to charge the battery and just make sure I cut the power after 1.5 hours or however long the charge period should be? - Raymond P.S. I'm still having trouble seeing how that light bulb icon can be described as being 'hairy'... ************************************************************** 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 **************************************************************
