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 develop
memory, 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
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