>-----Original Message----- >From: piclist-bounces@MIT.EDU [mailto:piclist-bounces@MIT.EDU] >On Behalf Of SME >Sent: 06 November 2007 13:05 >To: PIC List >Subject: [EE]:: Thoughts on extra cheap and nasty Li Ion charger > > > >QUESTIONS: > >Is a 10 cent charger viable? I'm not (yet) convinced if this is for a commercial product to be used by people expecting it to work like any other rechargeable product. > >What wouldn't work that I have described? The Zener may well work out ok to prevent Vordinance being reached. But more data needed: What is maximum charging current? Zener dissipation could be an issue? Consequences of Zener failure modes? (usually s/c IME). The simple transistor switch can prevent the cell voltage falling too low under normal use, but what prevents the cell being charged if it has fallen below Vdo_not_recharge just through self discharge? This is typically the failure mode of laptop batteries that haven't been used in a long while, you plug them in only to find they won't take any charge at all, as the cell voltage has fallen so low during storage that the internal fuse has blown. > >Why not use 4 x NimH? Why not indeed? Cells are cheap, though will 4 cells be cheaper than a single Lithium Ion? Can be trickle charged indefinitely by ultra simple charger with some life trade-off. No special precautions needed for low voltage discharge. Ordinance style fail modes very rare. Available in pleasingly high energy densities (for a price). I think NiMh is inherently a better fit for a 10c charger design, if the extra weight and size is a non-issue. I'm hoping to be proved wrong. Mike ======================================================================= This e-mail is intended for the person it is addressed to only. The information contained in it may be confidential and/or protected by law. If you are not the intended recipient of this message, you must not make any use of this information, or copy or show it to any person. Please contact us immediately to tell us that you have received this e-mail, and return the original to us. Any use, forwarding, printing or copying of this message is strictly prohibited. No part of this message can be considered a request for goods or services. ======================================================================= -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist