Alt-BEAM Archive
Message #01066
To: Bob Shannon bshannon@tiac.net
From: Steven Bolt sbolt@xs4all.nl
Date: Sun, 28 Feb 1999 08:49:56 +0100 (CET)
Subject: [alt-beam] Re: Li-ion cell charger
On Sat, 27 Feb 1999, Bob Shannon wrote:
> Actually you need to check the specs for your cell. Hard carbon cells
> have different demands than graphite based Li-Ion cells. Some may be
> trickle charged.
Thank you for the information; according to my files, no li-ion
cells are able to deal with overcharging. My main concern is that
tinkering with li-ion is a bad idea. Not all li-ion cells can be
treated equally, they can be quite dangerous, and the tinkerers may
not have the pertinent specs.
> Li-Ion is far safer than the hydrogen cells needed to feed a fuel cell.
It looks like we may expect small alcohol/air fuel cells in the
near future, targeted at portable telephones. They would offer a
much higher energy density than li-ion, and be much safer as well.
> If you want to use a Li-ion battery, simply use the whole pack from a
> small cell phone like the Motorolla Star-Tac. These often have all
> the charger control circuits internal to the pack.
If the `bot is the right size and you know what you're doing, have
a go. The packs are too large for my Spider :)
And we shouldn't overestimate the `bot value of a 100% gain in
energy density. I'm looking at a couple of hours walking on four
70mAH NiMH or nicad cells, weighing a total of 14 grams. In an
hour the Spider can `eat' a good charge using a delta-v algorithm
running on a shared uC; almost no extra hardware required. The cost
is also very modest. The four cells together cost about $8 (nicad).
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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