Noob Nickel Cadmium Questions

[darryn]

Hi there all.

At what rates should a nickel cadmium battery be charged and discharged?

TIA

Darryn

[WayneBrown]

average setting is 1/10 of the packs rating. So a 1000mAh pack would charge at 100mAh.
discharge differs, You should be able to discharge at 4x the capacity with no problems.

[darryn]

Thanks for the reply Wayne.

So, if my Tx battery is 600Mah, then I should charge at 0.6A and should discharge at 2.4A?
Does the output voltage of the pack not come into the equation at all?
Should these packs be cycled at every charge? If so how many cycles per charge?

TIA

Darryn

[WayneBrown]

You 'could' discharge your TX battery at 2.4A, but the fuse and wiring inside the box probably would not survive..
All the other assumptions are right. You should discharge to 1.1 to 1.2v per cell, however NiCd's are more forgiving. You can take that pack to 8.8v, and recharge it safely.

[darryn]

Thanks again Wayne.

Let's take an example of an RX pack.
It is 4.8V 1100mAh.

I charge the battery at 1.1A ?
I discharge it at 4.4A ? (as it is not going through any other electronics)
What do I discharge to pack to? Not sure what you mean by "to 1.2V per cell". It looks like a 4 cell pack to me so that would be 4.8V? But that is also the rating of the pack? I'm not sure I understand the specs all that well.
If my assumption regarding the Tx battery is incorrect, what would you recommend?

Thanks for your help.

[WayneBrown]

1.1A is correct. 1.1v per cell x4= 4.4v which is the 'safe' discharge voltage.
As you charge your packs, you will find a 4.8v rated pack will charge to 5.4 to 5.6v easily.
The discharge profile of a NiCd pack will reveal the pack voltage will drop to 4.9-4.8V and hold that voltage for awhile, then will quickly drop to 4.7 and lower.
Charging or discharging a TX pack should be limited to 1A or less if left in the case, *Personal experience* The batteries will generate heat during charge or discharge, and if unmonitored *WILL* melt the plastic transmitter case.
FWIW: the higher charge/discharge rate will heat up the packs, increasing the internal resistance and impede the amount of charge accepted by the battery.
Field charging especially should be limited to infrequent, and you need to accept the risks of heat damage.
To truly safely charge your packs for longevity, keep rate of charge to around 150mA, and have a longer charge time.
Over the counter battery cyclers will charge/discharge at 150mA overnight...

[z11355]

actually, the manufacturers use the following numbers (lets use your 1100mAH battery as
an example) so you need to duplicate that (close enough) to get the numbers on the package.

1100mAH = 1.1AH

Discharge 1/5C = 1100/5 =(approx) 200-250mA
Charge 1/10C = 1100/10 = (approx) 100mA

You can charge at any number of values within reason.

[darryn]

So to concur between Wayne and z11355, to get the best life out of my packs, I should discharge at 1/5C down to 1.1V per cell and charge at 1/10C?

To make sure I got this right
A 4.8V 1100mAh pack:
Discharge @ 0.22A down to 4.4V (4 Cell pack)
Charge @ 0.1A

TIA

Darryn