There is plenty of proof on youtube about the fast strobe recycling NiZn allows. On average, I've non-scientifically estimated around a 30-40% decrease in recharge time to full power. So if your strobe takes 2 seconds to fully charge up to full power, the NiZn battery can cut it down to 1.2 seconds. The charge life in strobe terms is about the same as the Maha Immedion, where I shoot over 150 full power shots, which is good enough for me. For fast strobe recycling time, NiZn is definitely the battery to have. A nice feature of the high voltage draw is that the performance will keep going about the same way until the battery is drained, whereas there is a distinct curve to NiMH, which means slower recharge times as it drains.
The marketing is a little fuzzy. They use mWh, when most batteries use mAh. To get equivalency, a Maha Imedion 2100mAh battery has 2520mWh, which is virtually identical to the Powergenix 2500mWh at nominal voltage rating. Or it has about 1500mAh @ 1.65V.
There are a few caveats.
OFF GAS: NiZn is known to off gas a bit (like NiMH does). When I used it the Inon Z240, it fired very well but if I leave freshly charged batteries in the Inon overnight, the off-gas builds up pressure, which, at worst, can cause the strobe to leak or at the least, pop the cap off while you open it. My normal workflow is always to put in fresh batteries in the morning and not leave batteries in the strobes. For those who like to set up the strobes the night before, you will need to revise your workflow to use NiZn batteries.
Another thing is the charger is only ok fast, taking about 2.5-3 hrs to fully charge 4 AA batteries. One big bummer is you can't use your old NiMH chargers, but you can use the Maha C9000 to test the charge. It won't tell you how healthy the battery is though. So basically, you have to buy a specific charger for NiZn batteries, which also can't charge NiMH batteries. It is cooler after charging compared to NiMH batteries.
Life Cycle is a bit murky: A dirty little unmentioned fact of this NiZn is the cycle life compared to NiMH/NiCd batteries. I did a bit of Googling but found no evidence of Powergenix stating what the cycle life is for the batteries. With NiCd/NiMH rated up to 1000 deep discharges, Powergenix's claim to meet this specification. However, some people think it is around 200 deep discharge cycles, based on documents found on Powergenix's website. I could not find such a document anymore but found it linked elsewhere. I've had them on 60 cycles or so and they still work well.
High Voltage burn out: The high voltage of the battery (sometimes over 1.8V after charging) can fry unregulated devices like torchlights etc.I tried it on my LED light and it worked fine. Same thing goes for strobes as the bulb may burn out due to thermal overload from rapid firing at full power!
Self-Discharge is average: This battery is about the same as normal NiMH batteries (but not the slow-discharge NiMH like Eneloop and Imedion) on discharge. It does mean they have to be recharged when not used for while.
So why am I raving about these batteries? They've more environmentally friendly and the power draw is fast, making a normal strobe feel like it's on steroids when it comes to recycling. This is very useful for full power shots from my Inon Z240 while shooting wideangle animal behavior, where a few rapid fire shots may be required. It is a pity it is only available in AA cells now.
Do I recommend using it as a replacement to AA NiMH? For strobes, yes. For everything else, I'll have to see in about 8 mths time when it gets older and how long it lasts. It costs about the same as the NiMH batteries. The need to be recharged after storage is a negative but it does last longer than the Eneloops in my tests. However Imedion recently released their 2400mAh slow discharge AA battery, which may even the endurance performance a bit. That said, NiZn is the choice for fast cycling strobes, bar none.
PowerGenix Cell Specification
Nominal Capacity (at c/5 rate) 2.0Ah
Nominal Capacity (15 Amp Discharge) 1.7Ah
Nominal Voltage (1C/15 Amp Discharge) 1.6V
Specific Energy (15 Amp Discharge) 60Wh/kg
Volume Energy Density (15 A Discharge) 169Wh/L
Specific Power at 30 Amp Discharge 900W/kg
Internal Impedance (1,000Hz) <4.5mOhm
Internal Resistance (DC) 7mOhm
Charge Time 2xAA 1.5 hours80% in 1 hour
Charge Life at 15 A Discharge (100%) 200 cycles
Ambient Temperature Range Charge +5°C to +40°C
Ambient Temperature Range Discharge -20°C to +60°C
Ambient Temperature Range Storage -30°C to +50°C