Hi, first post, so be kind :wink:

I am the administrator for a resource site for an old camera -- don't ask -- http://www.9000.org/.

This camera has as an option a special external motor pack, powered by a removable Ni-Cd pack containing thirteen "N" size batteries. I get many questions about the charger for this pack, which is often missing or broken. The data for this charger can be seen at
http://www.9000.org/index.php?page=motor_winder

Now, finding a charger with these exact specs (22v/23mA) has proven pretty hard. On the other hand, some chargers are close to that, or have significantly higher charging current. I don't know much about charging technology, but shouldn't higher current just translate into shorter charging times (provided the batteries can handle it)? Any other tips? i'd like to post some kind of solution on my site, to be able to answer these questions :?

 

Hi magnus ,
22/13 = 1.69 V for each battery.even though this is a little high for rechargeable batteries , i suppose its ok..
if i understand correctly the charger is seperate from the motor winder and plugs into the wall ??..
if so you could use an LM317 from National semiconductor.. and set it up to output a constant current of 23 mA ..
to answer your question , you dont want to pump excessive amounts of current into your batteries..

 

Come on you newbies, earn your keep :lol:

A power supply 240 or 120 vac input
(depending where in the world you are)

output 22v DC , current limited to 23 milli amps


[Minolta 9000...old? qwipes ...I still use my Zenit olympic!]

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It may seem like a good idea at the time but.. never stir your cold coffee with a soldering iron.

 

You might take a few minutes to research what would amount to the proper care and feeding of nicad batteries. As with just about every rechargeable battery there are some simple ways to do it - but those simple ways may not be optimal for the battery itself in terms of life. An extreme example might be in applying excessive amounts of current - that might rapidly charge the battery but might also shorten life or be dangerous. There may be a way to charge the battery in a way that yeilds a longer battery life - less in terms of the charge and more in terms of the number of charge/discharge cycles. I don't want to make it harder than it is but if the battery packs themselves are hard to come by and simple charger that is hard on the battery pack might not be what you want. I have seen some slightly more complex chargers that give due consideration to battery life, charging time, etc - and found the schematics posted on the internet. Sorry I don't have the URLs handy. Many of them use specialty ICs by National Semiconductor, Maxim and others. The manufacturers usually provide applications info that includes schematic diagrams.

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stevez

 

Yeah a higher voltage or higher current capacity power source could be compensated with a simple resistor.

This isn't a great way to charge NiCds though. Normal charge procedure would be at least 10x that current, and then stop the charge when the peak charge is detected. Charge detection is a trick- the battery voltage actually drops, but not very far and not for very long. Or stop the charge when the battery begins to warm up (indicating the power being delivered is turning into heat rather than storing as chemical energy).

Trickle chargers like this are slow to charge the battery, and never stop slowly overcharging when full, which reduces the overall life of the battery. But it's still quite common.