You have to look at history a bit.
CRV3 battery originally appeared as TWO AA 1.25V NiMH
rechargeable cells in series. Thus delivering about
2.5V - 2.4V voltage while being discharged in the camera.
Two standard AAs will deliver about 3.1V - 2.5V while being
discharged, so most cameras will be designed to operate
100% fine from about 3.5V down to about 2.4V input.
When Li batteries appeared having a definite advantage of
1) no memory effect which all Ni-based batteries have
(inspite of desceiving advertising with no-mem words)
and 2) virtualy no self discharge - which Ni-MH batteries
have at almost 5% capacity per day - it was a definitely
good idea to make Li based CRV3's.
However, most rchargeable Li-based technology delivers
4.2V per cell when fully charged. Thus a Li-based CRV3
battery has a completely different design than a Ni-MH
CRV3. It has two cells in parallel. But to deliver the
voltage to the camera it uses a circuit to drop the voltage.
Depending on the price/quality of the circuit board inside
the Li-based CVR3 battery - it will either be two diodes
paralleled in reverse, or a more complex voltage regulator
chip and a Mosfet transistor.
In either case, to charge these CRV3's you need a current
controlled voltage source with auto-shutff just as with any
other Li-Ion batteries. And that's exactly why Li-Ion CRV3s
have special chargers. Power101's CRV3 description actually
states that:
http://www.power101.com/item.htm?id=60095
"NOTE: This battery is designed for Li-Ion CRV3 chargers.
It will be damaged if you use a charger designed for Ni-MH
CRV3 batteries."
The problem here lies in the method with which Ni-MH are
charged or "reconditioned". The cheap chargers will just
have the transformer output through diodes and a resistor
directly to the battery terminals. Thus providing what
Ni-MH chemistry requires - more or less constant current
charging. The more expensive reconditioning chargers will
also apply discharging pulses - necessary to "decrease"
the memory effect by shaking the crystalllized chemistry.
The first method will just accumulate "memory effect", i.e.
crystallisation and the original Ni-MH battery will be at
about 50% of its capacity within 2 years. The second
method abuses the battery, but charges it better. The
net result is the same 2-year 50% life expectancy, however
the battery can be safely charged just before use.
Usually, both of these charging methods will still be somewhat
voltage controlled, and should not damage Li-Ion CRV3. They
will not charge them either. However, some cheap chargers
that will not have a voltage control over about 4.4V for charge
or cut off at about 2.2V for discharge pulse - will seriously
damage Li-Ion batteries resulting in total capacity loss.
However, inspite of all these, if you use a camera that requires
2 AA batteries or a CRV3 battery - because of the 5% per day
capacity loss in Ni-MH you probably ran through a lot of times
when you take these batteries charged just 1-2 weeks ago
and not being able to even take 20 shots with it. So a Li-Ion
CRV3 with overnight charging and laying freely for months
without self-discharge is a very valuable alternative.
These Li-based batteries don't have to be cycled or charged
just before use and are much more convinient. The charger
is just a small cost compared to the inconvinience of Ni-MH.
You can actually read:
http://www.power101.com/FAQ.htm
in particular on "How to extend/prolong Li-Ion battery life"
and "What is memory effect".
I have to disclose that I am affiliated with Power101.com.
Batteries for Z740. CRV3
CRV3 follow-up
Linear Mode
