Thursday, April 24, 2008

batteries for your flash units....

Last night at Bossier Parish Community College
during one of the classes that I teach
I started a discussion on batteries

Did you know that Ni cad batteries are 3 tenths of a volt less that regular alkaline
1.2 volt per cell for Ni Cad versus 1.5 volt per cell for alkaline
if the flash you use takes 4 cells then you are short 1.2 volts even with brand new freshly charged Ni Cads !

One of my students (Victor Green) did some research and shared this with me...............

Power source options for external flash units :

Most Canon external flash units run off four standard AA (LR6) alkaline cells, though one - the tiny and discontinued Canon 160E - used instead a small 2CR5 lithium battery of the type used by many EOS cameras. Here are some power source options for the AA type of flash.

Remember that all batteries can leak. If they do you?ll find your beloved flash unit full of a corrosive liquid that will damage or even destroy it. It?s wise to remove any cells from your flash if you aren?t planning on using it for some length of time - a few weeks or whatever.

Note also that some flash units can behave erratically when battery power is low. Normally weak batteries just result in long recycle times, but on the 430EZ at least low batteries can result in strange behaviour - the flash triggering randomly, the zoom motor buzzing at odd intervals, etc. So if your flash unit suddenly starts acting strangely try changing the batteries. This can also happen if the flash unit isn?t firmly seated in the hotshoe or if the contacts are dirty or corroded.

Standard AA non-alkaline (zinc carbon) cells.

- Pros: Available for next to nothing.

- Cons: Don?t last very long at all and can?t be recharged. They also have fairly high internal resistance and so it takes a few extra seconds for the flash unit to recharge between shots.

Standard AA alkaline cells.

- Pros: Alkalines are cheaply and readily available anywhere. They store a fair bit of power and let you go a reasonably long time between replacements.

- Cons: Last much longer than carbon zinc cells but otherwise have the same disadvantages. Recycle time to full power can range from 6-20 seconds, depending on how new the cells are.

Rechargeable nickel-cadmium (NiCad) cells.

- Pros: Relatively inexpensive, rechargeable hundreds of times. They have a fairly low internal resistance and so decrease the recycle time the flash unit will take to recharge to full power to 4-6 seconds. NiCads also have better cold-weather performance than alkalines - their performance suffers when the temperature drops below freezing, but not as badly.

- Cons: Don?t store as much juice as alkalines, so you have to switch batteries much more often. NiCad cells are also hazardous household waste (heavy metals) and should not be thrown into the regular garbage system. NiCad cells drain flat (?self-discharge?) within a few weeks after charging.

Lithium AA (FR6) cells.

- Pros: A fairly new development, these are lithium cells built to an AA shape. They store a lot of power, have long shelf lives, and recharge the flash at roughly the same rate as alkalines.

- Cons: Really expensive and not rechargeable. Steep death curves - they?ll work fine and then suddenly run out of power unexpectedly. Most importantly, only the latest Canon Speedlites can use them. Older models are not compatible with lithium AA cells owing to power issues, and might be damaged by them. The 540EZ and all EX series flash units can safely use lithium cells; all other flash units cannot.

Rechargeable nickel metal hydride (NiMH) cells.

-Pros: Affordable and rechargeable hundreds of times. Higher capacity (1600 mAH and up) cells have similar capacities to alkaline cells. Not as hazardous to the environment as NiCads. Have a similar recycle time to full charge as NiCads - around 4-6 seconds. Personally I think NiMHs are the best AA battery technology around when you factor in cost and performance issues.

- Cons: Require different chargers from commonly available NiCad chargers. Supposedly can self-discharge in a couple of weeks, but I?ve never had a problem with this.

External battery pack.

- Pros: High-power packs can decrease recycle time to a second or two, letting you shoot flash photos more rapidly. Store a lot of power and so mean you don?t have to change batteries as often.

- Cons: Large, bulky packs linked to the flash via coiled cords. High-power battery packs work only with a handful of high-end flash units with the necessary power socket. Third-party battery packs are required for use with other Canon flash units, but don?t have as rapid recycle times.

Some also use NiMH cells

Give your battery choice more than a glancing thought !


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