Nickel zinc (NiZn) batteries for Speedlites

Discussion in 'Canon EOS' started by michael_young|3, Nov 11, 2010.

  1. This is probably not Canon specific, and I hesitate to say anything before this gets fixed under warranty. Disclaimer: I'm posting this for an associate, and nothing I write here necessarily reflects my own experience with my own equipment.
    With one EX-430ii already in VA for warranty repairs, its newly purchased replacement likewise suffered a quick, identical death after shooting 56 shots at 1:1 power in 130 seconds. The flash just stopped working. The LCD panel was blank, even after changing to known good, charged batteries. The batteries were warm to the touch when they were taken out to be replaced. There was a slight but noticeable "electronic" type smell when the battery door was opened. The batteries are PowerGen NiZn AA. The other flash died in an identical manner, under very similar use and conditions. (Indoors, nothing at all strenuous except perhaps the cycle rate.)
    Consider this a strong warning about using the PowerGen NiZn batteries in Canon SpeedLites.
  2. From the 430EX II manual:
    "To avoid overheating and degrading the flash head, do not fire more than 20 continuous flashes. After 20 continuous flashes, allow a rest time of at least 10 minutes."

    "Using size-AA batteries other than the alkaline type may cause improper battery contact due to the irregular shape of the battery contacts...Size AA Ni-MH or lithium batteries can also be used."
  3. There was another post not long ago with someone describing this exact scenario. It seems the NiZn batteries ouput too much juice? Don't know for sure, but your stories are identical. Was that your post as well?
  4. Abusing a shoe mount flash will kill it very quickly. There is a reason why they put cooling fans in studio units that can recharge that quickly. :)
  5. Nickel Zinc batteries have an output voltage of 1.6 volts. The batteries in the flash are wired in series so you were supplying 6.4 volts to the flash instead of the designed voltage of 6 volts. While the extra 0.4 volts wouldn't have any significant effect on onld incandecent flashlights and lamp and electric motors. They will cause semconductor electronics to run hot and hard and that would qickly cause permenant damage.
    Never run any electronics device above its rated voltage. Running a device at less than rated voltage generally doesn't cause damge although the device may not work as well. Conventional nicad and NiMH batteries run at 1.2 volts so those are safe to use. regular alkalin run at 1.5 volts. You damaged 2 flashes and Canon might not honnor the warrenty if they determine the batteries were the cause.
  6. Yeah, it sounds like you seriously overdrove the limits of that flash model. And the flash wasn't designed to handle anything more than 1.5 volts per cell. When it was released I don't think viable NiZn consumer AA cells were even on the market, were they?
    This is why the 580EX II has a potentially annoying cutout mechanism to prevent inadvertent flash unit burnout - Canon doesn't like to do warranty repairs on units run over their duty cycle.
  7. My guess is that it's most likely due to flagrantly exceeding the manual's instructions on repetitive firing, and probably not due to battery voltage.
    Voltage figures cited for batteries should be taken with a grain of salt, if for no other reason than that a battery's voltage can vary significantly with load. Alkaline batteries, for instance, are usually said to be 1.5V, but it can be over 1.6V under low load while even a fresh alkaline will drop significantly under 1.5V when under heavy load (like when charging a flash unit). Lithium AAs, also nominally 1.5V, have a higher voltage than alkalines under low load (as high as 1.7-1.8V). If the 1.6V figure cited for NiZn is at low load, that's not a problem; it's well within the range that Li batteries provide under low load, and even my old 420EX (two generations older than the flash mentioned in this thread) can use Li batteries according to its manual. If the 1.6V figure is the voltage the NiZn cell puts out even under high load, then it could be an issue; that's slightly higher than Li and a fair bit higher than alkaline, NiCd, or NiMH.
  8. Here's a discharge graph I found on Amazon. Resting voltage is above 1.6 V over most of its discharge life. Cycling it in presumably a P&S with its small flash, voltage under load is about on par with resting voltage for fresh alkalines.
    The problem actually seems to be the 430EXii lacks thermal protection. The batteries do seem to do what I bought them for. They cycle the flash faster, possibly longer. Averaging about 2 seconds between full power shots for 2 minutes straight is really cranking juice through the flash. Knowing this now, I would revise my earlier warning to be less strong. The NiZn batteries apparently can push the 430EXii's duty cycle beyond its ability to cope with the heat. The photographer's prudence is the only real protection for the flash, regardless of battery type used. If the 430EXii has a thermal safety, I didn't see mention of it in the manual. Does anyone know if the 580EXii has one?
    Anyway, I replaced my batteries with Eneloops after the last incident. They cost only minimally more than the NiZn's. That leaves only the problem of what to do with 20 of these (over-achieving) batteries. They're too good to throw out, and I can't think of anything but the flash that can make good use of its characteristics. Even my flashlights are all LED now, and don't benefit from higher voltage.
  9. I'm of the school of thought that it was the 56 full power shots in 130 seconds that killed it, not the voltage. I'm pretty sure that 1.6v vs. 1.5v isn't going to be a big deal. You just fried the flash by working it too hard.
    I suspect the NiZn batteries would be just fine in a Speedlite flash if the flash was used in more normal operation. Hot shoe flashes just aren't meant for heavy duty cycles.
    I would have thought Canon would have thermal protection built into the flash, but maybe not. As pointed out above, in the manual they warn against firing multiple flashes at the maximum recycling rate (and that's the maximum recycling rate with NiMH or alkaline cells).
  10. Speedlites have a non-resettable thermal fuse inside. When this sees overheating it goes open circuit and stops the unit working. The replacement component costs pence but much more to have it fitted. Why Canon don't use a self resetting thermal switch I can only speculate about. They probably consider it a fire prevention device, and not a revenue generating device.
    The 1.6V batteries were not directly responsible for the Speedlite's demise. They may have enabled the unit to recharge faster and so overheat quicker owing to the excessive number of continuous flashes.
  11. >>> My guess is that it's most likely due to flagrantly exceeding the manual's instructions on repetitive
    firing, and probably not due to battery voltage.

    Absolutely. Nothing to do with the 7% increase in voltage.
  12. NiZn batteries have a number of advantages such as using non-toxic elements so they are easy to dispose of but one of their main features is for high power applications. NiZn batteries have low internal impedance which means they can provide more power in the form of "current". (Power is voltage x current = watts). Current is the flow of electrons, like the flow of water, which charges up your flash. Voltage is the pressure behind that current. Most electronics devices are designed to just take the current they need (they have high internal impedance) without ill-effects but not a flash unit – it opens the floodgates so to speak and the flash gets charged quickly. The problem is that your flash was never designed for the rate of flow coming from NiZn batteries and so this extra current flow is stressing the flashes electronic components. Your flash will charge faster but it will be squealing, you should be able to hear it, it should charge faster than with regular batteries too but in this case these are not good things, especially if you do it too many times in succession

    Incidentally, it’s the lower internal impedance that yields the extra power. Lead acid batteries such as those used in your car have even lower internal impedance which is why if you short them out they will melt even your jumper cables. If you car battery was an alkaline battery then shorting it out would not cause any problems because the batteries internal impedance would limit the current flow.

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