Tuesday, August 17, 2010


The cryptic title for this post will be very readable to a few die-hards (pun intended) and perhaps become increasingly recognizable in the future. This post is about the rechargeable nickel-zinc size AA batteries that I just could not resist.

The great thing about NiZn batteries is that each battery has a nominal voltage of 1.6V. In comparison, the old zinc-carbon and alkaline batteries are 1.5V; nickel-cadmium (NiCd) and nickel-metal hydride (NiMh) are 1.2V. Although there is a lot more to batteries than voltage, higher voltage can mean better (usually meaning faster or longer) performance in some devices.

The bad thing about NiZn batteries is that each battery has a nominal voltage of 1.V. This higher voltage can damage some devices.

Cowardly Disclaimer: These NiZn batteries can damage your equipment. Don't blame me! 

My interest in NiZn was initialized months ago by a now-forgotten discussion thread somewhere on the Internet claiming that recycle time on battery powered external flashes could be halved or better by using NiZn batteries. The unfortunate side effect – quickly pointed out – was that NiZn batteries recharged the flash so quickly that there was no time to cool and the flash “burned out” or went into a thermal overload lockout. The possibility of losing a flash for the sake of a few seconds kept me from buying NiZn at the time but the temptation did not go away. Finally, I conceded and placed my order.

I just received a set of four PowerGenix NiZn AA batteries with their own special quick charger. It is not recommended to charge NiZn batteries in NiCd or NiMh chargers or to charge other battery types in the NiZn charger. Each battery is marked 1.6V; 2500mWh. Note that 2500mWh is not exactly the same thing as the more standard 2500mAh listed on some NiMh batteries because the NiZn voltage is higher. The NiZn batteries are green in color because (I suppose) they are 100% recyclable and also non-toxic (according to the packaging).

As the batteries came inserted in the charger and I was anxious to get them charged, I immediately plugged it in. To my dismay, the LED lights blinked and then went off. Nothing. Tried again, again nothing. Then I noticed and removed the small strip of plastic preventing the batteries from making contact. The red LED came on. After about an hour the green LED came on to indicate that the batteries were 80% charged. This is the “quick” portion of the charging cycle. The charger, said to be “intelligent”, then changes to a slower “trickle” charge. Charging is complete after four hours. The batteries did not feel hot during charging (but I did not keep my hand on them).

According to my handy little multimeter, the freshly charged NiZn batteries were all 1.87V whereas my usual PowerEx NiMh batteries are 1.36V (open circuit voltage). But would the NiZn flash and destroy?

Taking a deep breath, I picked up my Canon 580EX II flash – no, wait a minute; how about that old Nikon SB-24?  I set the SB-24 on manual and full power. With one finger on the SB-24 trigger and another on a stop watch, I got 3 flashes in about 10 seconds with PowerEx NiMh batteries. The NiZn batteries could trigger 3 flashes in about 5 seconds – noticeably faster. They work!  No smoke!

For more information, check out the Wikipedia article on NiZn batteries.  Meanwhile, I'll do a few more tests without attempting to set the world record for flashes per minute.

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