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Old Aug 2, 2002, 10:19 PM   #1
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Default Repost: NiCad to NiMH Metz battery rack conversion

I posted this in the old forum, repost it now, may be it's useful for someone:

One of my flash Ni-Cad battery pack nearly goes dead , so I decide to put NiMH in it.

Important note : 45 series Metz flashes use different electrical connections for the Ni-cad rack ( 7.2 Volts) and the Alkaline AA rack (9 Volts), so you can't use directly NiMH AA in the Alkaline rack, it will false the metering computation.
Since the NiMH are also 1.2V per cell, it's perfect for Ni-Cad replacement (and improvement)

I use 6 Energizer 1700 mAh AA NiMH cells , to replace the 6 original 500 mAh Ni-Cad cells .
Wow! It's like tripling the gas tank in your car , long way to go
The original charging adaptor is simple AC output. A rectifier bridge and 3 volt bulb are located in the base of the battery pack. The bulb act as ballast resistor and charge monitor as well . Typical charging current is 300 mA at the begining , dropping to around 200 mA steady after.

It really worth because a new Ni-Cad pack price is around 80 $Can ( 50 US)

The pictures speak for them self ...

The last pic shows the electric contacts of the alkaline (9V) and the rechargeable rack (7.2V) , If you like you can convert a alkaline rack to use NiMH AA's , but DON'T PUT ALKALINE AGAIN IN THAT RACK !
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Old Aug 7, 2002, 3:39 PM   #2
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I'm debating which way to go with my Metz. It would be simple if I already had a NiCad rack but at $60 for a new one I'm not sure it's worth it to convert. Still, a spare alkaline rack is $30 and converting it leaves the risk of putting alkalines in and connecting 9v to the 7.2v terminals in the flash. I'll keep shopping around for a used NiCad rack.
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Old Aug 11, 2002, 7:13 PM   #3
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Default Caveat Experimentor

Well, I converted my standard Metz alkaline battery rack to use NiMH batteries. It uses the 7.2v contacts as the factory NiCad rack does. It wasn't a difficult conversion but I won't give instructions as there is too much liability. You have to rearrange the contacts in both the top and bottm of the rack as well as insert the cells in a different arrangement. If you don't arrange the cells right you'll reverse cells and get about 2.4v out. If you mix up the bottom and top of a converted rack with the stock alkaline rack you'll short out a pair of cells - very dangerous.

Performance is good, I get recycle times of about 6-7 seconds on full power which agrees with Metz's data for NiCad. Actually recycle times with NiMH in the alkaline rack are much, much faster. In fact Metz says the reason not to use NiCad is that the high current flow could damage the flash. If you need ultra fast recycle times get a high voltage external pack.

BTW the Metz flash is outstanding. I'm using old fashioned thyristor mode with my Dimage 7 and exposure levels seem to match the camera's built in flash just fine. The bounce mode and secondary flash tube allow a lot of flexibility and make for dramatically better results than the built in flash. I'm debating just how much the dedicated TTL cable will improve things. There are some situations that fool thyristor such as forground objects not in the frame but for the most part it works fine.

[Edited on 8-12-2002 by padeye]
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