Nicad charger

"Gingre

** Just get one of these and watch the time.

....... Phil

You must use the proper charger for your battery. If not, you can damage the battery, or have a fire hazard!

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JANA _____

Yes but what constitutes a "proper" charger? It can't be "what the manufacturer recommends or sells" and anyway in this case the manufacturer doesn't sell them any more. It must either be a voltage or current characteristic. So could you be more specific about this?

. . .

Often also cell temperature.

Andy Wood snipped-for-privacy@trap.ozemail.com.au

It depends simply on how fast you want to charge it. If you want a fast charge then you need to control voltage, current, AND cell temperature. If the charge is slow enough, you only have to worry about current. That usually means 24 hours or more though.

MrT.

Yeah and time... But not many chargers for general use have temperature sensing.

Any decent rapid charger does. But you are correct in so far as most cheap "general use" chargers are slow types that will almost certainly not have temperature sensing.

MrT.

You will need to know the recommended charging current and overhead voltage for charging the particular battery type. The charger will have to be properly regulated for both the voltage and current, and have the proper safety design in order to not overcharge the battery.

Many of these batteries have thermo sensing devices that feed some logic circuits in the charger. This is to cause the charger to shut down in the case if the battery overheats.

In working in this industry, I have seen injuries and fires started from improper charging of NiCad and Lithium batteries. Read the warnings on these batteries.

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JANA _____

If it would be an old fashioned standard NiCad and you don't know anything more specific, assume that the charge has to be

14 hrs at 10% of the capacity, when fully discharged. i.e. a 1 Ah Cell will be charged with 0.1A for 14 hrs. 10% current of this again, can be safely applied as trickle charge 24/7 to keep the battery full and ready to go (1% of capacity). Your battery has 8 cells with nominal 1.2V*8 = 9.6V. When fully charged it will have 8*1.4V = 11.2V Measure the current when fully charged with 12V applied. If it is like the trickle charge (about 1% of capacity) you could just switch a light bulb in series that has about the power of 2.4V*[10%of capacity]. It will act as a constant current source over a fair time of the charging process, and also as a current limiter. Make sure that your power supply is rated for your charging current.

Cheers

Tony