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Keeping NiCd battery pack charged

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soldar:
I have a drill which has two NiCd battery packs and when I go to use them they are always discharged and I am fed up. I end up using other drills which have NiMh or Lion batteries and hold their charge.

Is there any way of keeping them charged?

Float? Trickle?

In the worst case I suppose I could put it on a timer and have it charge x minutes every day. Or something.

I am fed up with this issue. It's not like I use the drill very often and could keep it charged for the next day. it's more like I try to use it after four weeks and it's dead.

I suppose one solution would be to replace the NiCd cells with NiMh but that would cost about $50 per battery pack and is more than I am willing to spend right now. I guess I will do it eventually when these packs fail but I would like to use the NiCd battery packs.

What is the best policy? Any ideas?

jpanhalt:
"Memory effect" in NiCd's was discovered by partially discharging and recharging multiple times (e.g., in satellites).  Do not trickle/float charge.  When they were used in model airplanes (e.g., weekly), I charged the night before I went flying.  We also charged after a flight.

Welcome to battery-power.  They have some conveniences and some serious inconveniences.  My 3/8" Milwaukee electric drill (circa 1980) is still running strong on its original power source.  Can any owner of a battery powered drill say the same?

Gyro:
Trickle charging them at a current of around C/30 will keep them nicely topped up long term. The standard 'safe' C/10 14 hour trickle charge rate is too aggressive for long term use. Constant current charging also encourages the state of charge of the individual cells to equalize (important to prevent cell reversal under heavy load).

If you changed them to NiMH, you would probably get lower self discharge, but higher internal resistance than NiCd (less torque). NiMH also don't tolerate trickle charging the way NiCd do.


P.S. As jpanhalt says, memory effect is a thing with NiCd. Periodically fully discharging them will prevent this, it is difficult to fully discharge them without causing the weakest cell to get reversed charged by the other cells though, particularly in a higher voltage stack. Reverse charging a cell really damages it, so it is best to do it with a very light, cutoff voltage limited load.

P.P.S. Dendrite growth (a side effect of using Cadmium) is another thing that ultimately kills NiCds. It causes intermittent internal leakage, which can again unbalance cells in the pack.

soldar:

--- Quote from: jpanhalt on April 30, 2024, 07:38:03 pm ---"Memory effect" in NiCd's was discovered by partially discharging and recharging multiple times (e.g., in satellites).  Do not trickle/float charge.  When they were used in model airplanes (e.g., weekly), I charged the night before I went flying.  We also charged after a flight.

Welcome to battery-power.  They have some conveniences and some serious inconveniences.  My 3/8" Milwaukee electric drill (circa 1980) is still running strong on its original power source.  Can any owner of a battery powered drill say the same?
--- End quote ---
I agree that mains power is better in many ways. Batteries have never worked well for me. In laptops I could never get anywhere close to the run time they advertised. And batteries are expensive.

Yes, I have drills that are very old and still work fine. Mains powered drills can last forever if not abused. Most of the ones that fail are because they were driven too hard. You cannot abuse them and expect them to survive.

But battery powered drills/screwdrivers are a different tool. They turn slower and more controllable. If I want to drill a hole in the brick or concrete wall I use a mains powered, powerful hammer drill. But that tool is not good for driving screws or slow drilling in metal; for this I prefer a battery type.

But I do have a couple of the battery ones which I can connect to external DC power. If I am assembling something big in the garage and moving around a lot then battery is good, but if I am working on the workbench without moving around too much, then I can use a DC PSU to supply the drill and the cable is not really in the way. In my experience these drills have high tolerance for voltage and I have supplied them from different contraptions and they always work well. They do not require stable voltage at all.

When I am working on some project it is convenient to have several drills, one with a drill bit, another with a screwdriver, etc. and it frustrates me to always find this particular one is flat. It is like I don't have it.

soldar:

--- Quote from: Gyro on April 30, 2024, 07:45:57 pm ---Trickle charging them at a current of around C/30 will keep them nicely topped up long term. The standard 'safe' C/10 14 hour trickle charge rate is too aggressive for long term use. Constant current charging also encourages the state of charge of the individual cells to equalize (important to prevent cell reversal under heavy load).

If you changed them to NiMH, you would probably get lower self discharge, but higher internal resistance than NiCd (less torque). NiMH also don't tolerate trickle charging the way NiCd do.


P.S. As jpanhalt says, memory effect is a thing with NiCd. Periodically fully discharging them will prevent this, it is difficult to fully discharge them without causing the weakest cell to get reversed charged by the other cells though, particularly in a higher voltage stack. Reverse charging a cell really damages it, so it is best to do it with a very light, cutoff voltage limited load.

P.P.S. Dendrite growth (a side effect of using Cadmium) is another thing that ultimately kills NiCds. It causes intermittent internal leakage, which can again unbalance cells in the pack.
--- End quote ---
Charging it hours or the day before is out of the question. I never know when I will be needing it. 

I think I am going to try a, very small, permanent trickle charge. Right now it is like I don't have the battery at all because it is always flat so it's not like I have much to lose.

I think it will be as easy as just inserting a resistor in series with the charger. I am going to give this a try and see how it goes. Maybe even as low as  C/50.

Come to think about it I am b\not even sure of the capacity of the pack . I will just start with a trickle of, say, 50 mA and see how it goes.

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