Just be very cautious with Litium technology. There are instances where this stuff has burned down houses. Do your charging with the cells outside if possible or at least in a fireproof container. When they fail it is sometimes like a road flare! Properly harnessed they are the best technology available. two years on my laptop & going strong... John Ferrell http://DixieNC.US ----- Original Message ----- From: "Russell McMahon" To: "Microcontroller discussion list - Public." Sent: Monday, February 14, 2005 6:45 AM Subject: Re: [EE]: Battery repurposing >>>Now for the million dollar question: How the hell do you >>>charge lithium ion batteries, anyway? Ideally I'd like to >>>avoid converting the battery pack into a charred, smouldering >>>mess in the process, especially seeing as the cells are >>>actually pretty good quality (Sony Fukushima US18650GR type) >>>and seem to be in reasonably good shape. > >> L-ion cells are quite fussy about charging. It's essentialy a constant >> current charge with a very critical termination voltage of 4.2volts. If >> you try to charge the cells much past 4.2 volts you are likely to end up >> with a fire. A typical charge rate for laptop batteries are 0.7C, >> smaller cells can often be charged a little quicker. >> >> One important point, if the cell voltage has fallen below 3.0volts, then >> a trickle charge of 0.1C should be used to bring the cell voltage above >> 3.00volts before attempting to use the full charging voltage. >> >> Do not keep L-Ion cells on a trickle charge, they cannot accept >> overcharging without becoming potnentialy dangerous. > > Here's an excellent short article on the subject which addresses most > points and explains the chemistry behind the process. > > http://www.motorola.com/ies/ESG/pdf/motorola.dec.02.pdf > > The methods behind the electronics are actually SIMPLER than for NiCd and > NimH charging - it's just that they are more critical and there is a > higher chance of REALLY bad things happening if you stray too far from the > fold. > > > RM > > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist