NICAD Battery charger/reconditioner HELP

[moltra]

I am trying to make a NICAD battery charger / reconditioner. The battery specs are 6 1.2 volt cells 600 milliamp hour capacity. I am looking for a design that will discharge the battery module to 6.6 volts and then recharge the battery. I would like it do this cycle for a adjustable amount of cycles. I would love to have an milliamp hour meter to tell me what the actual discharge was to compare it with the battery specs. These battery modules are used in a atmosphere monitor which most people in the plant leave on charge contantly or they use it for a short period of time and then place it back on charge. The battery modules that I am trying to recondition are $90.00 each. I would like to be able to save as many of the modules as possible. If anyone has any ideas or advice please let me know.

[audioguru]

Moltra,
I think that you are being ripped-off for expensive battery modules that contain only 6 common AA cells.
If you simply discharge the seriesed battery cells down to 6,6V, then you run a risk that the weakest cell will discharge completely, and then be charged in reverse by the stronger cells, causing damage. If the cells in the module are well-matched, then that problem will not occur.
Discharge into a 600mA constant current sink, monitored by a counter/timer and stopped by a voltage comparator, which also initiates charging.

[ante]

Moltra,

To cycle the cells as

[moltra]

The battery module is in an atmosphere monitor, if I open the battery module it voids the explosion proof requirements of the unit. I have not taken one of the modules a part yes, but I have been told that there is resistors and other components in the module to make it safe in an explosive inviroment

[ante]

moltra,

I see, it

[moltra]

I have about 30 of these batteries. I was hoping to take the design and make duplicates of it.

[hotwaterwizard]

How about This?

Nicad Charger
http://electronicprojects.org/content/view/9/

[moltra]

Looks good, but would this work on a battery module with 6 1.2volt cells? Do you have anything on a battery reconditioner.

[hotwaterwizard]

No but, These will! :o




http://www.lennard.net.nz/electronics/fc.html#cct





http://homepages.paradise.net.nz/bhabbott/charger.html





http://www.angelfire.com/electronic/hayles/charge1.html

[Ldanielrosa]

Moltra, I'm going to have to rain on your parade. Reconditioning NiCads is temporary, and some say of debatable value. Two failure methods come to mind (I'm no expert)- 1: the electrolyte was cooked dry, 2: the electrodes grew dendrites. The second one can be fixed, but it won't last.

The price per launch is probably much higher that the battery. If you can't open the explosion-proof casing without damaging it, you can still do a failure analysis- 30 samples will give a (barely) valid statistical profile.

If you have weight to spare (unlikely) and run out of power before all the data collecting ability is used up (entirely possible), you might consider sending up a reconditioned battery as well (with a diode in series, this will protect the main battery from secondary failure but will only start using secondary power when main power is down 0.7V).