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[OM] Strobist: New NiZn Batteries Offer Lightning Fast Recycle--paging D

Subject: [OM] Strobist: New NiZn Batteries Offer Lightning Fast Recycle--paging Dr. Battery
From: usher99@xxxxxxx
Date: Tue, 05 Jan 2010 18:57:33 -0500
They do look pretty cool but can fry some flashes if not careful, no?  
Seems they mislead a bit on total energy content.  I don't think the 
eneloops work well in the older Vivitars, IIRC due to the voltage?
Here are some comments from an Amazon--likely an engineering type but 
would prefer to hear from our own Dr.Battery.
Perhaps they are better for high current items as long as they are not 
fried.  Pretty cool find though.  Thanks Dr. Flash.

Mike

>From a review:

"The product description of PowerGenix Nickel-Zinc Rechargeable AA cell 
promises many advantages over other rechargeable batteries: higher 
voltage, higher energy density, lighter weight, longer cycle life, and 
so on. But how does it stack up against the current gold-standard of 
low-self-discharge NiMH cell, the Sanyo Eneloop? Let's examine the 
following aspects:

[Operating Voltage]
The NiZn cell has a nominal voltage of 1.65V, which is 30% higher than 
that of a NiMH cell (1.25V nominal). When freshly charged, its terminal 
voltage is even higher at 1.85V!

[Power Density]
Since 'Power' is defined as 'Voltage * Current', most people may assume 
that "30% higher Voltage" translates to "30% higher Power". But it 
depends on the application:

- Most electronic gadgets (digital camera, MP3 player, etc) contain 
internal DC/DC regulators which operate in constant-power mode. If the 
battery voltage is higher, then input current will drop to maintain the 
same output power. That's why higher voltage alone does not make your 
digital camera shoot any faster.
(One exception is photo flash unit, which operates in constant-current 
mode. So in this case, 30% higher voltage does translate to 30% higher 
power and shorter cycle time)

- For an unregulated appliance such as a flashlight or power tool, its 
current increases with voltage (although not linearly). A typical 2-AA 
flashlight bulb is rated for 2.3V * 0.5A = 1.15W. When you apply 3.6V 
to it, the current may increase to 0.65A, so the power consumption is 
now 3.6V * 0.65A = 2.3W. Twice the power means twice the heat. That's 
why the bulb may burn out in seconds.

[Energy Density]
The PowerGenix AA cells are marketed as "2500 milli-WATT-hour" (energy 
capacity). Most people may confuse this with "2500 milli-Ampere-hour" 
(charge capacity). But the data sheet for NiZn AA cell shows that its 
current capacity is only 1500mAh (this is verified by my own testing). 
It turns out that an 1500mAh NiZn cell actually contains the same 
amount of energy as a 2000mAh SANYO eneloop AA cell:

- Energy in eneloop AA cell: 1.25V * 2000mAh = 2500mWh
- Energy in PowerGenix AA cell: 1.65V * 1500mAh = 2475mWh

[Weight]
The weight of each NiZn AA cell (25g) is essentially the same as that 
for eneloop AA cell (27g). For certain applications, it is possible to 
use three NiZn cells (3*1.65=5V) to replace four NiMH cells 
(4*1.25V=5V). Doing so reduces battery weight by 25%, but it also 
shortens run time by 25%.

[Cycle Life]
Technical data found on PowerGenix web site says NiZn cells are rated 
for 200 cycles (at 100% deep-discharge). This is much shorter than the 
1000 cycles cited for eneloop cells.

I have tested a set of 4 PowerGenix AA cells. After subjecting them 
through 12-16 deep discharge cycles, the average charge capacity 
already dropped 5% from original value. In comparison, I have a set of 
4 eneloop AAA cells that have went through about 100 cycles in the past 
2.5 years, and they still exhibit over 95% of original capacity.

[Self-Discharge Rate]
In my long-term storage test after two months, a set of four NiZn cells 
retained 74% original charge capacity on average. This translates to 
about 13% loss per month, which is much better than that of ordinary 
high-capacity NiMH batteries (with capacity > 2500mAh). But it cannot 
compare to low-self-discharge NiMH cells.

Previously, I have conducted storage test for several brands of LSD 
cells, including Sanyo eneloop, Rayovac Hybrid, and Kodak Pre-Charged. 
All those cells can retain 85-90% of original capacity after FIVE 
months in storage.

[Recharging Time]
The PowerGenix NiZn cells must be recharged using a specially designed 
PowerGenix NiZn Charger. The charger is called '1-hour', but it 
actually takes 2.5 hours to fully recharge a set of four 1500mAh cells.

Eneloop (and all other brands of LSD cells) can be recharged using any 
good quality 'smart' NiMH charger. Depending on which charger you use, 
the charge time can be as short as 15 minutes, or as long as 8 hours.

[BOTTOM LINE]
The only verifiable benefit for PowerGenix NiZn cell is its higher 
operation voltage. However, even this may turn out to be a curse rather 
than a blessing, as higher voltage can cause unregulated appliances to 
burn out.

If you have a digital camera that works well with eneloop, stay with 
it. Switching to NiZn will not offer more power nor longer run time. 
Only if your camera does not work well with eneloop, then it is 
worthwhile to try NiZn cells as a last resort. But you better contact 
PowerGenix, and ask whether they will assume warranty liability for the 
use in your camera. Otherwise, try it at your own risk! "






<http://strobist.blogspot.com/2010/01/new-nizn-batteries-offer-lightning-
fast.html>


This is pretty cool. These NiZn batteries are recycling a Nikon SB-900 
in approximately 2 seconds. That's almost as fast as a Quantum Turbo. I 
don't know yet where you get them or what they cost but I think I'm 
gonna get some. A lot less weight and cost than a Turbo.

Dr. Flash

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