Cheap rechargable batteries

Tim Dunne wrote:
"MartinM" wrote in message
oups.com
I see Maplin do a Li-Ion rechargable pack (meant for camcorders but
prolly adaptable) which is 2Ah, seems a good trade off between weight
and capacity.

Not a good idea - LiIon batteries have a tendency to explode if not
handled and treated in accordance with guidelines - one thing they
don't like is deep current draw and vibration.

The capacity to weight ratio makes Li-Ion batteries good indeed for
high-power cycle lights as long as some protection is built in or added
for over-charge and over-discharge. See www.lumicycle.co.uk for example.

~PB

"Tim Dunne" writes:

"MartinM" wrote in message
oups.com
I see Maplin do a Li-Ion rechargable pack (meant for camcorders but
prolly adaptable) which is 2Ah, seems a good trade off between weight
and capacity.

Not a good idea - LiIon batteries have a tendency to explode if not
handled and treated in accordance with guidelines - one thing they
don't like is deep current draw and vibration.

Lithium polymer are fine under those circumstances though.

Chris
--
Chris Eilbeck
MARS Flight Crew http://www.mars.org.uk/
UKRA #1108 Level 2 UYB
Tripoli UK Member #9527 LSMR

"Chris Eilbeck" wrote in message


Lithium polymer are fine under those circumstances though.

Highly debatable. I was looking into the technologies and did a little
research, the horror stories are remarkable.

Tim

--
Sent from Birmingham, UK timdunne at blueyonder.co.uk
'God's electrician sparked up the heavens once again, heading northbound
on the 7:10. And the lord said let there be commuters...' - Thea Gilmore
Look, mum, an anorak on a bike! Check out www.nervouscyclist.org

"Jim Ley" wrote in message


So the cycle mounts for mobile phones have something to deal with
this, or do they all come with, your phone may explode warnings?

Why should they? The people who make cycle mounts wouldn't care - do you
think it's a good idea to subject a mobile to that kind of vibration anyway?
I've dropped a medical Li-ion pack at work and very nearly been badly burned
in the resultant flare-up.

Do a google, this isn't trivial.

Tim


--
Sent from Birmingham, UK timdunne at blueyonder.co.uk
'God's electrician sparked up the heavens once again, heading northbound
on the 7:10. And the lord said let there be commuters...' - Thea Gilmore
Look, mum, an anorak on a bike! Check out www.nervouscyclist.org

On Fri, 27 Jan, Zog The Undeniable wrote:
Mark Thompson wrote:

- 2 x D, 4,000mAh

That's not a bad capacity for AA and it's an amazing capacity for D (if
it's true).

Not really - Ansmann do a 8Ah D cell (but I don't know how reliable
the capacity is, though I've seen good reviews of their AA cells).
I've seen D cells with slightly higher than that claimed.

GP do a 7Ah D cell (7Ah min, and I trust GPs figures) -
http://www.farnell.com/datasheets/21819.pdf (recommended discharge
currents to 35A, so that'd be a nice bright light).

Admittedly, farnell want 12.42 quid plus VAT for a single GP cell

regards, Ian SMith
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On 28 Jan 2006 03:18:46 -0800, MartinM wrote:

OK thanks. Out of interest does anyone know what the actaul capacity of
the various alkaline D cells on the market is? (the are very secretive
on their packaging).

Not so much secretive, as the answer can't be usefully quantified in
most cases. The useful (or apparent) capacity is strongly dependant
on the drain current, and somewhat dependant on service conditions and
duty cycle. They could quote a value, but it may or may not actually
resemble what you actually get.

Your best bet is to peruse information intended for commercial users.
I find Farnell to be a good source for data sheets. For example, at
http://www.farnell.com/datasheets/31104.pdf you can find families of
curves for Duracell Ultra M3 D cells.

Typically, upper-end alkaline D cells are in teh 15-18 Ah range.

regards, Ian SMith
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MartinM wrote:
Tim Dunne wrote:

"MartinM" wrote in message
groups.com

I see Maplin do a Li-Ion rechargable pack (meant for camcorders but
prolly adaptable) which is 2Ah, seems a good trade off between weight
and capacity.

Not a good idea - LiIon batteries have a tendency to explode if not handled
and treated in accordance with guidelines - one thing they don't like is
deep current draw and vibration.


OK thanks. Out of interest does anyone know what the actaul capacity of
the various alkaline D cells on the market is? (the are very secretive
on their packaging).

In my experience, AA Duracells used in an incandescent bike light or a
digital camera are only about 1200mAH. Basic NiMH cells can equal their
performance. The D cells should be much better, and most big name NiMH
D cells don't take advantage of the larger size to increase capacity.
There are AA and D cells in 2500mAH, for example. I suspect the D cell
has the same innards as the AA - its only advantage being that it will
fit things that require that size.

"Tim Dunne" writes:

"Chris Eilbeck" wrote in message


Lithium polymer are fine under those circumstances though.

Highly debatable. I was looking into the technologies and did a
little research, the horror stories are remarkable.

LiPo batteries from Kokam, Thunderpower etc. are designed for very
high discharge rates, 15-20C, and for use in model aircraft. This
situation far exceeds the duty expected of a battery driving a
lighting system on a bike. True, there can be dangerous problems
associated with lithium batteries but from what I can tell these are
brought about by either impact damage or excessive charging and
discharging. I've been using lithium batteries for almost the last 15
years, from coin cells to 300Ah packs, and I've never had a problem
despite what sometimes appears to be deliberate abuse by some of my
users.

Chris
--
Chris Eilbeck

Chris Eilbeck wrote:

"Tim Dunne" writes:

"Chris Eilbeck" wrote in message


Lithium polymer are fine under those circumstances though.

Highly debatable. I was looking into the technologies and did a
little research, the horror stories are remarkable.

LiPo batteries from Kokam, Thunderpower etc. are designed for very
high discharge rates, 15-20C, and for use in model aircraft. This
situation far exceeds the duty expected of a battery driving a
lighting system on a bike. True, there can be dangerous problems
associated with lithium batteries but from what I can tell these are
brought about by either impact damage or excessive charging and
discharging. I've been using lithium batteries for almost the last 15
years, from coin cells to 300Ah packs, and I've never had a problem
despite what sometimes appears to be deliberate abuse by some of my
users.

Chris

Aren't lithium-polonium batteries a little, err, dangerous?
--
Chris

"Inform all the troops that communications have completely broken down."

Chris Slade writes:

Chris Eilbeck wrote:

"Tim Dunne" writes:

"Chris Eilbeck" wrote in message


Lithium polymer are fine under those circumstances though.

Highly debatable. I was looking into the technologies and did a
little research, the horror stories are remarkable.

LiPo batteries from Kokam, Thunderpower etc. are designed for very
high discharge rates, 15-20C, and for use in model aircraft. This
situation far exceeds the duty expected of a battery driving a
lighting system on a bike. True, there can be dangerous problems
associated with lithium batteries but from what I can tell these
are brought about by either impact damage or excessive charging and
discharging. I've been using lithium batteries for almost the last
15 years, from coin cells to 300Ah packs, and I've never had a
problem despite what sometimes appears to be deliberate abuse by
some of my users.

Aren't lithium-polonium batteries a little, err, dangerous?

Like I say, only if you pierce them, over charge them, or allow them
to discharge at too high a rate or discharge too far. Everything can
be dangerous if you misuse it.

Chris
--
Chris Eilbeck
MARS Flight Crew http://www.mars.org.uk/
UKRA #1108 Level 2 UYB
Tripoli UK Member #9527 LSMR