Discharge NiCad battery?

[caseydugan]

Does anyone have a suggestion for how to discharge the NiCad battery for the UK C8 without keeping the light on and thus reducing the life of the bulb? Leaving it on without the bulb in it doesn't complete the circuit and thus doesn't draw on the battery. I'd like to reduce the memory effect, but the battery isn't always down after 2-3 dives.

Thanks
CD

 

[H2Andy]

i have no clue, but this guy seems to know a lot about NiCd batteries:

http://www.repairfaq.org/ELE/F_NiCd_Battery.html#NICDBATTERY_029


also, i have heard that the memory effect is not really an issue with newer
NiCd batteries:

http://www.repairfaq.org/ELE/F_NiCd_Memory.html

 

[misfit]

There are several models of the chargers on the market with the discharge function that U needed.

And there are 2 defects while U discharge Ur batteries with Ur lite directly :

1. Shorten the life of the bulb.
2. Over-discharge the batteries.

misfit

 

[Charlie99]

Fully discharging a NiCd or NiMH battery stack might possibly eliminate a small amount of memory effect. It will probably reverse charge and damage the weakest cell.

The memory effect is virtually non-existant and not worth the effort to avoid unless you are repeatedly doing exactly the same charge/discharge curve (as in a satellite,where the memory effect was noted many years ago with early NiCds. Even then, the "memory effect" was just a small depression in voltage of about 0.1V).

In addition, if you discharge the cells in series (as they are in a light) you risk the very real possibility of reverse charging the weakest cell. It's voltage will go to zero, and then be reversed as the stronger cells continue to discharge. Just like sticking cells into a charger backwards, this isn't a good thing. Reverse discharge will damage cells. A good rule of thumb for end-of-cycle voltage is to never discharge a NiCd battery to less than 1.1x(N-1), where N is the number of cells.

If still insist on discharge cycling a battery, it is best to do it on an individual cell basis.

 

[cool_hardware52]

Does anyone have a suggestion for how to discharge the NiCad battery for the UK C8 without keeping the light on and thus reducing the life of the bulb? Leaving it on without the bulb in it doesn't complete the circuit and thus doesn't draw on the battery. I'd like to reduce the memory effect, but the battery isn't always down after 2-3 dives.

Thanks
CD

"Memory" in spirol wound consumer cells is a myth. It's a very pervasive myth, but still a myth.

You don't have to believe me, but I've sold over 100,000 rechargeable bike lights using Ni-Cads in the last ~20 years.

Check the cell manufacturers, i.e. Sanyo, etc. See what their applications and charging guides say.

Needlessly deepcycling a battery to avoid the "mythical memory effect" is a sure way to shorten it's cycle life.

Depth of discharge is the surest predictor of cycle life, and the effects are nonlinear. By that I mean 50 cycles to a 100 percent of capacity does far far more damage to a battery, than 100 cycles to 50 percent of capacity.

My advice is to forget about memory, and recharge at every opportunity.


Regards,


Tobin

 

[hdtran]

A red LED in series with a resistor to prevent too quick a discharge; do it one cell at a time. What you really want is a forward diode drop of about 1.1 V, so you might use two silicon diodes in series.

Choose the resistor to get a nominal full discharge in 2 hrs or longer (e.g. if you have a 1000 mA-hr NiCad, design for a 500 mA or less discharge current).