Pete Biggs wrote:
> I wonder two things about the Lumicycle Li-Ion charger:
>
> 1. It first tests the battery to decide whether it needs a blast of fast
> charging (red mode) before the main, more gentle charge which takes some
> hours (amber mode), before trickle charging (green mode). Would it get a
> valid reading at the start when the battery is freezing cold?
My gut feeling is that it should do, but I wouldn't like to be sure. I
have a feeling that the P.D. will remain the same, but the efficiency
of conversion from chemical energy to electrical energy will be
weakened. I have however drunk a couple of bottles of strong Belgian
beer so this is liable to nothing more than cobblers.
> 2. If it starts on amber mode (maybe red as well), the battery doesn't
> become warm for some time if it's very cold to begin with, so I think the
> charging may be more efficient or "fuller" (?) if the battery was allowed
> to warm up naturally before charging.
As I mentioned earlier (and others have said the same) charging only
becomes an issue at high temperatures, although it might potentially
take more energy (i.e. longer) when cold. At high temperatures, the
rate of conversion to chemical energy is lower than the energy input
and more heat is produced. In NiMH or NiCad batteries this causes them
to expel hydrogen which reduces the battery's capacity and adds the
exciting risk of a small bang. With Li-ion batteriers this is more of
an issue that can result in a very large bang (see for example: some
Nokia phones). Thankfully your Li-ion batteries will contain circuitry
to prevent this from occuring.
> I might take that suggestion quite seriously! My spare DIY NiMH battery
> has no insulation at all so maybe I should wrap it in something warm. I
> aint doing no knitting though!
Despite the humour it is genuine. Discharge rates are far more
obviously affected by low temperatures, so keeping your batteries warm
on cold nights will allow you to take the long route home. My home made
battery packs (Which closely resemble sticks of dynamite) are made from
plastic plumbing tube, PVC tape and heatshrink which means that the
contents do probably hold temperature for a while.
Jon