[fb_penpho]

After being continually disappointed with batteries. I tried the Ni - Zn batteries. They have a voltage of 1.8v of full charge, compared to Alkaline 1.65v when new. As 4 batteries are the norm, I did not expect the 0.6v extra on 6.6v would cause a problem. I have tried them in my Metz and Yongno flashes with good results.

The problem with the other batteries Ni MH is that their low voltage indicates to the electronics that the batteries are low on charge, even when they have barely been used. The batteries are just showing their normal low voltage, it does not indicate that they are low on charge. The Ni-ZN have worked for me.

[photoptimist]

For sporadic use and in some well-designed devices, those higher-voltage batteries probably do work quite well.

But they do put extra thermal stress on the circuits which increases the risk of failure and may shorten overall device lifespan.

[UncleVanya]

This may be worth reading:

Battery Guide -- Battery types, pros & cons, comparisons, tips & tricks

Ni-zn have a short shelf life, lower capacity in milliamps, and very poor recycle tolerance (capacity drops, self discharge ). Lastly they are semi discontinued according to the site below:

Rechargeable Batteries explained in detail (NiMH, NiZn, NiCd, RAM) (more detailed)