Its a simple question but I can't seem to find any info on it. I have two Ni-Cd batteries (listed bellow) so i want to know how to charge them? And how to know if they are completely dead or are still alive. Each battery has 3 cells with the same type of package style as shown in the images.
The normal charge rate for Nickel Cadmium (NiCd) cells is 1/10th of the capacity for 14 hours.
For the ones you have there the first would require a constant 30mA with the second needed 60mA.
You could use a resistor from 12v to provide the constant current but keep monitoring the voltage and current to determine if anything unusual occurs.
The voltage should not go over ~1.5V per cell.
NiCd are not legal in new equipment so those are old (The data code on the second is 0904 probably meaning 9th week of 2004). They have probably degraded to the point where they do not function well.
When the batteries get old not only do they have reduced capacity but they also tend to have high self-discharge so even if they do charge up they may discharge by themselves in only a few days.
As the other poster indicates cadmium is toxic so they should be disposed of in an approved manner.
You can learn more at Battery University.
The NiCd is one of the most rugged and forgiving batteries.
You need a charger. A NiCd charger will charge them fastest, 1-2 hours. A NiMH charger will take 2-4 hours.
To achieve a reliable voltage signature, the charge rate must be 0.5C and higher. Slower charging produces a less defined voltage drop, especially if the cells are mismatched in which case each cell reaches full charge at a different time point. To assure reliable full-charge detection, most NDV chargers also use a voltage plateau detector that terminates the charge when the voltage remains in a steady state for a given time. These chargers also include delta temperature, absolute temperature and a time-out timer.
Fast charging improves the charge efficiency. At 1C charge rate, the efficiency of a standard NiCd is 91 percent and the charge time is about an hour (66 minutes at 91 percent). On a slow charger, the efficiency drops to 71 percent, prolonging the charge time to about 14 hours at 0.1C.
During the first 70 percent of charge, the efficiency of a NiCd is close to 100 percent. The battery absorbs almost all energy and the pack remains cool. NiCd batteries designed for fast charging can be charged with currents that are several times the C-rating without extensive heat buildup. In fact, NiCd is the only battery that can be ultra-fast charged with minimal stress. Cells made for ultra-fast charging can be charged to 70 percent in minutes.