You're right (as always) as I had forgotten about the current limiting
devices... at least on those that are made as they're supposed to be :-)
I hadn't thought about it before but I guess a battery that it expected
to be driving a camera or other similar device might not be built to
handle the current for a flash. Still I'm very surprised that the
current limit is less than alkalines let alone NiMH.
Chuck Norcut
Tim Hughes wrote:
> 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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> ==============================================
>>>> List usage info: http://www.zuikoholic.com
>>>> List nannies: olympusadmin@xxxxxxxxxx
>>>> ==============================================
>>>>
>>>
>>>
>>>
>>> ==============================================
>>> List usage info: http://www.zuikoholic.com
>>> List nannies: olympusadmin@xxxxxxxxxx
>>> ==============================================
>>>
>>>
>>>
>> ==============================================
>> List usage info: http://www.zuikoholic.com
>> List nannies: olympusadmin@xxxxxxxxxx
>> ==============================================
>>
>
>
>
>
> ==============================================
> List usage info: http://www.zuikoholic.com
> List nannies: olympusadmin@xxxxxxxxxx
> ==============================================
>
>
>
==============================================
List usage info: http://www.zuikoholic.com
List nannies: olympusadmin@xxxxxxxxxx
==============================================
|