NiZn rechargeables – a good battery for QRPers?

niznI first heard about NiZn AA batteries about three years ago via a photography blog I follow (you can read the article here). They were all the rage over there – for a while.

Having a higher per cell voltage than NiMH batteries, they offered a significantly faster recycling time for flashes which is a Good Thing for some types of photography.

Then those who used them started reporting that their flashes were eventually burning up due to the higher voltage (that info is here).

So I forgot about them and settled on Sanyo’s Eneloops.

An email from Howard KO6WL asking if I had any experience with these batteries re-ignited (no pun intended) my interest in them as a possible battery-of-choice for QRP rigs that make use of internal AA batteries.

The very characteristic that causes these batteries to destroy flashes – higher voltage – may make them ideal in QRP rigs that make use of internal AA batteries.

For example, Elecraft’s KX1 has provision for six internal AA batteries and has a maximum operating voltage of 14 volts. A set of NiMH batteries will provide about 7.5 volts key-down while the NiZn batteries would provide 9 volts key-down. Safe in both cases.

While that increased voltage will burn up a flash unit, it will provide more RF out of a QRP rig. How much more depends on the operating characteristics and efficiency of the transmitter stage and will vary from rig to rig.

The bigger question is how that increased output power would manifest itself in the headphones of a distant receiver – but that’s a whole ‘nuther topic…

A few “heads-ups”:

  • The NiZn batteries require a dedicated charger – a NiMH charger won’t work.
  • PowerGenix rates these batteries as having a capacity of 2500 mWH. Yep – that’s milli watt hours. All other AA batteries – alkalines, lithiums, NiMH – are rated in terms of mAH. By rating them in mWH’s, PowerGenix is able to put a larger number on the label in hopes that most consumers don’t understand anything other than “the bigger the number, the better the battery”. As tested (at a 300 mA discharge rate) the PowerGenix NiZn batteries have a capacity of 1300  mAH vs 2500 for the latest (but lower voltage) Sanyo Eneloops.
  • Other reports mention that the failure rate for these batteries is higher than that of NiMH batteries. Also, whereas Eneloops are rated for 500 charge/discharge cycles, the NiZn batteries are only rated for 200. To me, this is a non-issue – 200 cycles is a lot. I do a lot of photography and I doubt I’ll ever reach that many charge/discharge cycles. If I do, I’ll consider myself as having gotten my money’s worth long before then.

Below is a chart of how the NiZn cells compare to Sanyo’s highest capacity (2500 mAH) Eneloop with each cell being discharged at a 300 mAH rate. Note the flat discharge curve for each type – another Good Thing.

To look at the chart in another way, the NiZn cells provided 300 mA for about 4 hours while the Eneloops provided the same current for ~7 hours. Not really an issue if you’re going to the park for just a few hours of operating since most KX1, Norcal 40 type of rigs draw far less average current then 300 mA.

NiZn_vs_NiMh

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  3 comments for “NiZn rechargeables – a good battery for QRPers?

  1. Larry W2LJ
    January 16, 2013 at 10:53 am

    Hey John,

    Not a comment on this post, but I see “The Strobist” blog mentions Greg Heisler. That name’s a blast from the past. I used to repair Greg’s equipment back when I worked for Sinar Bron.

    Small world.

    73 de Larry W2LJ

  2. Tony
    February 20, 2013 at 1:09 pm

    John a FWIW. I have some AA NiMH batteries that won’t fit in my Mag Lite flashlight. The diameter is slightly too big. I think these were rated 2500 mah.

    73 Tony

  3. Howard KO6WL
    February 24, 2013 at 7:40 pm

    I am enjoying using 6 of these batteries with my KX1. I am very pleased with their performance and their light weight. My original charger was faulty, Gail from Powergenix returned my call and in 3 days I had a new charger. That’s excellent customer service!

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