Carl Fink wrote:
On Thu, Jul 13, 2006 at 10:51:03PM -0500, Jay C Vollmer wrote:On Thursday 13 July 2006 21:24, Carl Fink wrote:I'm not an electrochemist, but modern Li-ion batteries don't developmemory, they just lose capacity each time they're charged.Isn't what you're describing 'memory?'No. A NiCad battery has true memory. If you discharge it 35% then recharge it, it tends to be only 35% of capacity ever after. With Li-Ion batteries, if you discharge it 35% and recharge it, it might lose (WAG) 1% of its capacity.
Actually a number of tests were done by NASA and Amateurs over the years and proved that NiCD memory effect is often caused by improper (read: cheap) charging systems.
NiCD's are used in almost every satellite flying today, and don't exhibit memory problems when charged and maintained correctly on-orbit. Some of the Amateur-built satellites (groups like http://www.amsat.org) have seen very extended mission profiles from properly maintained, monitored, and charged NiCD systems, and even longer lifespans after the batteries have "died" and won't accept a charge, but still allow current from the solar charging systems to pass through to the satellite radios and equipment.
Too many people don't understand this and "expect" battery problems from NiCD technology so manufacturers spend little money on their charge circuits knowing that consumers will happily buy another battery in 2-3 years. Most consumer charging circuits for NiCD don't monitor properly and charge at far too high a rate for the battery, which overheats the battery, causing them to vent small amounts of gas in the process, which destroys the battery over time. LIon batteries aren't nearly as popular as NiCD in spacecraft/aerospace use, because of NiCd's WELL-KNOWN properties in those circles. But in consumer devices, the myth still exists that they exhibit "memory" when this is almost always a result of improper charging and maintenance.
Nate