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Old December 22nd 06, 05:15 PM posted to rec.bicycles.tech
peter
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Posts: 296
Default Rechargable Cells/batteries for Lights

Keiron Kinninmont wrote:
"Ron Hardin" wrote in message
...
Supposedly, Lithium cells thrive in cold. I don't know about the

rechargeables.

If anyone knows anything further about rechargeable litium cells i'd be
greatly interested. Truth is i dismissed them because i could only find
1000mAh (limited search i grant you) but will these 1000mAh lithium cells
out perform 1000mAh cells of the other varieties in any respect?


Which kind of lithium cells are you looking at? Li+ (lithium ion)
cells are rechargeable and produce 3.6 V, compared to about 1.2 V for
NiMH and NiCd cells. Since you're really interested in the energy
output, you'd be looking at the product of the voltage and the mA-hr
capacity. Therefore a Li+ cell with 1000 mA-hr capacity would be
equivalent to a NiMH cell with 3000 mA-hr capacity. Of course you'd
need to adjust the number of cells you use in series to be compatible
with your light.

There are also Eveready lithium/iron-disulfide AA cells which produce
about 1.6V and a capacity of 2900 mA-hr, but these are not
rechargeable. Both these and the Li+ cells do perform very well at low
temperatures - much better than either NiMH or NiCd. I haven't noticed
much difference in low temperature performance between NiMH and NiCd -
the latter have so much less capacity and also have disposal problems
so I no longer use any.

If the light unclips, carry a second one in your pocket and swap them, to
double the runtime. Maybe the second one will then heat back up, and you
can continue the process.


A fair idea but the commute isn't really long enough that the cells would
warm back up, it's only a 25min max commute, long enough for the negative
effect but not long enough to warm anything back up. Even if i start with a
spare in my pocket it's generally quite cold when i comes to changing it.


That would presumably depend on where the pocket is located. An inside
pocket should stay warm from your body temperature, so the spare pack
would be warm when you start using it.

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