Date: Sun, 30 Sep 2001 08:45:12 From: "neil barnes" <[EMAIL PROTECTED]> Subject: Re: Homebrew battery packs
I just woke up ... you reserve the right to abuse me in the list ;-) HOkay, consider yourself abused :) >1: Use an external pack of 10 NiMH 3.5AH cells (13 if I can get my hands on >more 3.5AH cells but I very much doubt it) connected in series and plugged >into the external DC-IN port on the L50CT WITHOUT any buck or boost >circuit. The existing 10.8V LiIon pack is retained and left inside the >Libretto as backup. If I'm stuck with a 10 cell NiMH pack then I'll add a >couple of AA NiCad cells and hook them up in series using Xin's diode >circuit in order to start the Libretto (I'll check the diode direction >again but it looks right to me ...). I'll add a resistor and diode and wire >it up so that I can get those cells to trickle charge when I apply the >charging voltage for the main pack so they don't die on me. Don't bother with the extra cells (there, I've just saved you money!). Right at the end of Xin's fixup battery page, there's a cheater circuit which works very well from 12v - but note that the LED (not the diode) is the wrong way round. When you use it, you should see a short flash on the LED. >2: Use some voltage monitoring circuit (I just realized I've got a basic >bargraph voltmeter automotive battery warning kit lying around, I might use >that instead) so that the NiMH pack is disconnected (on the battery side of >the circuit so that it won't oscillate when it gets close to 11 volts) if >it falls below 11 volts (1.1 volts per cell), safely above the 10.8 volts >of the internal pack so that the Libretto knows when to switch to internal >power. That ought to do the trick but I don't know the trigger voltage - it may be down a lot lower than that...there's a *very* clever switchmode between the input socket and the internal circuitry/battery pack. Unfortunately I can't think of a way to test the trigger voltage, except: o charge internal cell to 100% o run lib for an hour or so from a bench supply at (say) 11.5v o check internal battery level o if still 100%, try running at a lower input voltage o repeat until you see some changes, set your voltage trigger a bit higher... _________________________________________________________________ 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 **************************************************************
