Date: Thu, 28 Feb 2002 12:24:17 -0500 From: "Lawrence Young" <[EMAIL PROTECTED]> Subject: Re: [LIB] Power use in standby
Actually all Li-ion batteries come with some electronics (you can find it inside the Lib battery pack) to monitor the exact amount of juice left in battery cells. The electronics serves two purposes: (1) during charging, monitor the charge process and cut off at the right moment to prevent over charge. (2) during discharge (use), monitor the amount of juice left in the cells and cut off the battery around 20% of juice left to prevent cells from over drawn. Li-ion battery is the only type of rechargeable battery that let you know exactly how much juice is left. Of course, how long it will last depends on the usage of the machine (i.e. how much mA the machine requested). There is a company that is developing a technology that allows li-ion cells to be drowned down to around 10%(?) instead of 20% so effectively increased the battery capacity. ----- Original Message ----- From: "Pres Waterman" <[EMAIL PROTECTED]> To: "Libretto" <[EMAIL PROTECTED]> Sent: Thursday, February 28, 2002 10:25 AM Subject: Re: [LIB] Power use in standby > Date: Thu, 28 Feb 2002 10:20:21 -0500 > From: Pres Waterman <[EMAIL PROTECTED]> > Subject: Re: [LIB] Power use in standby > > > Umm ... I fully charged until the battery indicator showed green then left > it for 9.5 hours, booted it to quickly check the charge state then suspended > again, plugged in the power adapter then timed how long it was before the > battery indicator went from orange to green (about 20 minutes) ... I assumed > the charge/discharge ratio (eg. N where you can run the libby for X minutes > then charge for X*N minutes and end up at the same state of charge) stays > the same throughout the charge cycle of the battery ... is this a valid > assumption? > > > No, not at all. > > Nickel and Lithium technology batteries, as opposed to lead, have very flat > voltage output over much of their life. The discharge curve looks slightly > like this: > > end of charge, beginning of use: > -- > \___________________________________ > \ > > | > > The percentage indicator Windows shows is a farce. Because unless you have a > very sophisticated processor in the battery, knowing exactly: > > how many mA are, > were, > and will be drawn out, > exactly where on the above "curve" you are, > how much self-discharge has taken place ( how do you know THAT? ), \ > temperature, > age of the battery, > the exact mAH capacity of the battery TODAY.... > > well, everything is a guess. > > The only use of the battery gauge, is to have one session after charge right > through discharge, know how long your battery typically lasts, and put in a > wild fudge factor as to how may disk accesses you have, modem calls you will > make... you get the point... you have a guess as to how long you can keep > typing. But when it's discharged, it's dead. Often unexpectedly. Always > inconveniently. > > Battery chargers these days pay attention to the minute voltage change that > occurs after a full charge ( it actually peaks and drops ) plus temperature > plus a timeout safety factor. When you plug in a Libretto it starts to > charge and when that peak-drop happens it shuts off. > > Under no circumstances should you look at "8%" and think it is any more > meaningful than "a bit" vs. "a lot". > > Look at the curve again and consider where you are on the life of the > battery. Pretty hard to tell. Always carry a spare battery. > > Thanks > > Pres Waterman W2PW > c/o Patchogue Motors, Inc. > Long Island Ford and Kia dealer > > GO BILLS! > > > > > ************************************************************** > 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 > ************************************************************** > ************************************************************** 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 **************************************************************
