View Full Version : Batteries for Z740. CRV3

04-23-2005, 11:15 AM
I found a place on line that sells reasonably-priced high-powered (1600) rechargeable CRV3 batteries for the Z740. With shipping they come out to about $8.00 each for 2. Their site is http://www.power101.com/home.htm If they don't have the batteries at their website, they also have them listed on eBay. I recommend buying a charger at the same time as the batteries, as the dedicated CRV3 charger seems to be the only way to recharge the rechargeable CRV3 batteries. Plus you save on shipping by buying both at the same time. Also see note below.

05-07-2005, 09:32 PM
The rechargeable CRV3 batteries do not recharge in my Kodak printer/camera dock. A dedicated charger is needed. Also, I have found a RCRV3 battery that is promoted as a replacement for the CRV3. I purchased one of these along with charger and found out that the RCRV3 charger will not recharge regular rechargeable CRV3 batteries. Live and learn. :(

11-06-2005, 05:33 PM
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.