Keeping NiCd battery pack charged - Page 1
Forum section: electronics / projects

author: soldar
author_rank: Super Contributor
timestamp: April 30, 2024, 06:48:56 pm
content: 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?

author: jpanhalt
author_rank: Super Contributor
timestamp: April 30, 2024, 07:38:03 pm
content: "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?

author: Gyro
author_rank: Super Contributor
timestamp: April 30, 2024, 07:45:57 pm
content: 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.

author: soldar
author_rank: Super Contributor
timestamp: April 30, 2024, 08:39:17 pm
content: Quote from: jpanhalt on April 30, 2024, 07:38:03 pmI 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.

author: soldar
author_rank: Super Contributor
timestamp: April 30, 2024, 08:48:56 pm
content: Quote from: Gyro on April 30, 2024, 07:45:57 pmCharging 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.

author: jpanhalt
author_rank: Super Contributor
timestamp: April 30, 2024, 08:50:51 pm
content: @soldarI agree completely. I actually have an old Craftsman NiCd battery powered drill. It does have its uses. I have replaced the battery packs thrice since 1998. Finding real NiCd replacement packs in the USA is getting more and more difficult. For anything heavy duty (e.g., hammer drill, angle grinders, small planer, router, etc. ), I am still mains powered.As for trickle charge, I stand corrected. I never did it, but apparently it is OK, if the current is low enough (https://batteryuniversity.com/article/bu-706-summary-of-dos-and-donts)

author: helius
author_rank: Super Contributor
timestamp: May 01, 2024, 06:28:51 pm
content: I doubt that "memory effect" was ever observed with common cylindrical NiCd cells in power tools or RC toys. The satellite batteries were sintered-electrode prismatic cells, almost totally unlike the former.In discussions of NiCd "memory effect", it's notable that no mechanism is ever proposed that would account for a "memory" in a non-sintered-electrode cell.That's not to say they don't suffer the same problems as all rechargeable batteries, where shallow cycling can cause charge point depression by building passivation on the electrodes. It affects some chemistries more than others, but they all experience it to some degree. NiMH battery chargers have "refresh" charge-discharge-charge cycles to deal with it, although NiMH cells do not have "memory".

author: soldar
author_rank: Super Contributor
timestamp: May 02, 2024, 08:24:34 am
content: I have decided to trickle about 40 mA permanently and see how that goes. When the packs fail I will just replace the NiCd cells with NiMh.This particular drill has two batteries and only one charger.I always install a cable out of the back of the drill connected to the battery terminals. That way I can1- Run the drill with external PSU, of which I have several.2- Recharge the battery while it is in the drill and3- Use the drill battery to power other things. Comes in handy when the mains power fails.

author: nctnico
author_rank: Super Contributor
timestamp: May 02, 2024, 10:36:24 am
content: Quote from: soldar on April 30, 2024, 06:48:56 pmI have replaced such drills with corded ones from Makita. Plug in and go. And these are not very expensive either.

author: soldar
author_rank: Super Contributor
timestamp: May 02, 2024, 02:59:50 pm
content: All my cordless drills are "corded" by me.I always install a cable out of the back of the drill connected to the battery terminals. That way I can1- Run the drill with external PSU, of which I have several.2- Recharge the battery while it is in the drill and3- Use the drill battery to power other things. Comes in handy when the mains power fails.Low voltage drills have their uses. I also have regular corded drill machines but for other heavy duty tasks.