Chuck,
Actually most common Li ion batteries are not "rated" to give
particularly high current,
many are only rated 2C. There are some types rated for higher currents
typically using a
different electrode material, but they are not so common except for special
uses radio control
helicopter users and power drills. Most common Li-ion cells have built in
internal curent
limiting electronics, so you cannot draw too high a current, to prevent them
self igniting! The
NiMH are actually frequently rated for higher current and more importantly,
don't have any built
in protection electronics.
In this particular case, of the so called "3V " lithium batteries these are
frequently not
Li-ion, but some other Li chemistry like Li-FePO4 (~3.3) with electronics or a
diode to reduce the
voltage a bit more. They reqiuire a special lower voltage charger too. I would
not be surprised
if their rated current was quite modest, like <2A.
But this is a guess based on not seeing the batteries so, I can't say
definitively, except the
symptoms fit well with them having limited current capability.
Tim Hughes
--- Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> But remember that these are supposedly rechargeable lithium ion
> batteries and not elemental lithium. The thing that makes lithium ion
> batteries potentially dangerous is that they are capable of delivering
> far higher currents than alkaline or even NiMH batteries.
>
> So, I don't think your analysis can be correct if these are truly
> lithium ion batteries. But maybe the problem is that they're not
> lithium ion.
>
> Chuck Norcutt
>
>
> Tim Hughes wrote:
> > John,
> > I am Making some big assumptions here, since I don't have enough info
> > from what you have
> > said, but I think this is what happens:
> >
> > When the flash capacitor is completely discharged at a cold start then
> > initially the current
> draw
> > is greatest. As the capacitor charges up a little the current is somewhat
> > reduced and then
> > eventually drops off rapidly near full charge.
> >
> > It may be the particular Li batteries you have, can't supply the very high
> > initial current of
> a
> > completely discharged flash capacitor and the internal electronics then
> > stops the charging,
> when
> > the battery voltage drops too much at cold start. Once the capacitor is
> > slightly charged
> using
> > the regular batteries, then the Li batteries can supply the lower current
> > to continue charging
> it
> > up. The flash capacitor does not completely discharge even after a full
> > dump, so once you have
> > charged up the capacitor a little, with the regular batteries then it will
> > operate fine
> > thereafter, off the Li, until you switch it off and leave it to discharge
> > completely.
> >
> > Tim Hughes
> >
> >
> >
> >
> > --- om4t@xxxxxxxxxxx wrote:
> >
> >>
> >> I normally use two rechargable 3 volt lithium ion battery packs in an OM
> >> flash gun with my
> E510.
> >> The flash is a dedicated gun for the E series.
> >>
> >> When the flash has not been used for several days the battery packs do not
> >> bring the flash
> gun
> >> to life. If I change over to four Ultra Duracell 1.5 volt batteries the
> >> gun springs to life.
> If
> >> I then change yet again to the LI battery packs the flash springs to life
> >> immediately. It is
> >> almost as if the flash needs to be initially energized with the Duracell
> >> batteries before the
> LI
> >> packs become operative.
> >>
> >> The LI packs are only a matter of a few weeks old, are fully charged and
> >> the connector points
> on
> >> both packs and in the camera are clean.
> >>
> >> When I start off from "cold" with the LI packs installed in the flash gun,
> >> the gun still
> remains
> >> inoperative even if I jiggle the packs slightly or apply a little pressure
> >> to the slide mount
> >> cover on the flash gun casing so as to effect a "better" contact between
> >> the terminals on the
> >> packs and in the camera.
> >>
> >> Does anyone have any idea about what might be ailing my flash gun and / or
> >> LI battery packs?
> >>
> >> John Hudson
> >>
> >>
> >>
> >>
> >>
> >>
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