Anyone tried rejuvenating nicads by putting them in a freezer for a couple of hours to remove the memory effect? Some webpages also recommend tapping the frozen cells for a minute or two to break up any crystals.
I've got an ancient Dustbuster which uses 8 Sub-C nicads and it dies after a couple of minutes. I'm not going to spend money on new nicads, but wondered if I could get some more life out of the present ones with little effort.
No. BTDTGTTS
I'm not sure 'the memory effect' is generally a thing, unless you are talking about the nicads used in satellites? What you might be seeing is more like 'hibernation'. ;-)
Pass.
That's exactly what I did the other day for a mate and an old nicad powered drill pack (with little effort). It did however involve a fairly expensive charger / discharger.
The symptoms was that when put on charge it showed it was charged very quickly but only ran the drill for a few seconds.
I set the charger to the right chemistry, the right max / min voltage for that number of cells and chemistry, the max charge and discharge rates and delay between stages ... and the number of cycles ... and pressed start.
When finished it tested at around 1Ah (only 1.3Ah from new) and would hold a 3A load for the appropriate amount of time.
I gave it back to him with the instruction of giving it some use and doing so reasonably regularly, if he wanted to keep it 'alive'.
I'm awaiting feedback.
Cheers, T i m
p.s. As it happens I'm going though my collection of rechargeable and have done the same sort of thing with my 'hibernating' AAA and AA's (mostly NiMh) in my little YC4000 charger / discharger.
The 4 AA's that are in there now initially said they were charged but lasted only a matter of seconds when you discharged them. I set the slots to 'Refresh' and again they showed 'Full' very quickly (a matter of a couple of minutes). *Now* they are cycling much longer and are still going from last night. It will continue charging and discharging them till they stop showing an increase in capacity, then they show 'Full' and the final capacity.
Not tried freezing or impact maintenance. Zapping with a PP3 or 12 V SLA to blow "fuse" the wiskers. Improves them initialy, maybe up to
50% of orginal performance but the effect doesn't last long.The problem is that you can often get all bar 1 to revive a bit. The failure is more to do with the reverse charging of the weakest in a series charge discharge system. That kills them pretty effectively. Why not use nickel metal hydrides in it instead? They look like normal round type batteries with tags to me, unless yours was different. Having said that however, the dustbuster was possibly the most inefficient cleaner on the planet. It should have been sold by K-Tel!
Brian
I'm with TNP, it is just not worth the faff. If you want to recover an othewise useful bit of hardware, re-cell it with tagged NiMH which will perform better, last longer, and be happy on the original charger.
Even then it may be a bit of effort, the old cells tend to be squeezed into place really tight. I just threw away an otherwise good angle drill even though I have some NiMH in stock.
But what if that is part of the point?
That is the spirit of the OP's question, but with some caveats ...
But I don't think the issue was 'Nicads' or Ni-Mh', but having to buy
*anything* if the process of reviving this Dustbuster.And that's fine if you don't need the drill or were interested in seeing if you could get some life out of it?
Like I said, I took an otherwise 'dead' drill and with little effort at all (setting up my charger and pressing start), made it a useable drill again (to varying levels of 'useable' given the DustBusters I've used weren't very good even when new) and the same could be the case for Jeff.
Is it going to as easy for him (without £150 pounds worth of charger) as it was me? No, I doubt it, but it wouldn't take much to
*effectively* do what the charger does using the existing Dustbuster and it's charger.If he just keeps charging it up and running it down, it *might* start to pick up and if he fancies giving that the time, it isn't going to cost anything else to at least try?
If it doesn't work, nothing is lost? ;-)
Cheers, T i m
p.s. Going though my old rechargeable collection, it's obvious that some of the cells (both nicad and NiMh) are shot, simply from the corrosion round them. Others show 0V across them and so the chances are they wouldn't recover either (but I give them a zap first with my bench PSU in any case). But many others are obviously not leaking and are showing a reasonable terminal voltage and so worth giving a cycle
*anyway* to see how they work out. Some are already to go to the battery recycling thing in Salisbury's whilst others are already in torches or awaiting partners of the same make / model / capacity, as / when I find and test them.Do I need to do all that? No, I've just bought a batch of brand new AAA and AA's from Amazon, but I am *interested* to see how the old ones pan out, rather than just throwing them all away. ;-)
Reduce, reuse, recycle. ;-)
No. Be extremely careful. The delta peak drop in voltage that signals a nickel cell has reached full charge is much much less on NiMh than NiCd.
NiMh chargers will charge NiCd all right, but the reverse is not necessarily true...
Here is your puppy. Black & Decker BDH9600CHV.
Paul
Good point (I was forgetting that all my NiCad chargers are explicitly stated as being suitable for NiMH).
What's your time worth?
Correct - I thought I'd made it clear in my OP. The clue was in the use of "ancient". This Dustbuster must be at least a dozen years old. It's been on trickle charge for most of that time, and with very intermittent use. Frankly, I'm surprised the Nicaea are working at all. I've also no idea if the motor has years left or will fail next week. I haven't measured the current it draws, but I found a web page where someone measured the current used in a 14.4V Dustbuster, and found it was 10A! I've read that Nicads are somewhat better than NiMH cells in standing up to heavy current draw, but 10A is really pushing a sub-C cell.
The cells are in 2 x 4 banks, and they are in tight. I'm not going to faff around soldering new sub-Cs and find they just won't fit. Replacing with Li ion is not an option either. By the time I've replaced the charger as well, it would be simpler - and cheaper - to just get a new handheld cordless vacuum cleaner. The only other possibility I've thought about is to simply dump the rechargeable cells and use it with a lead off the lighter socket in the car (99% of its use is a quick clean-up in the car). Some high-power diodes will drop the voltage to somewhat approaching the original 9.6V, but I doubt I've got any in my junk box.
Just a little bit of time, and hardly any effort. I'll try it today.
As a final point, I don't find the suction of Dustbusters and their ilk disappointing. They do what they do with much less power available than any corded vaccy. I find it amusing when they are given one star in reviews and the only reason is failure to pick up pet hairs from carpets. That's often beyond the power of even the most expensive mains-powered devices!
I look upon that sort of exercise as one of intellectual use only! Sort of "Can it be done? Let's try!", and hang the time, effort, and expense. Actually, it's obvious that it cost so much the designer of the webpages chose to save on the price of white pixels... ;-)
longer,
That's assuming the charging system is anything more than a capacity/10 current limited supply at vaugely the right voltage that just dumbly sits there. Most NiCd/NiMH "charge systems" as supplied with kit fall into this grouping.
Again, that's not the point?
Jeff fancied giving it a go so that should be enough eh? ;-)
Have you never had a 'I wonder if I could ...' moment, even though the chances of a positive outcome might be very low?
Cheers, T i m
He did say "with little effort". Whenever I have done this sort of cell replacement I have usually thought "was that worth it?" Batteries in DECT phones are normally easy to replace.
Many early NiCad chargers weren't really suitable for NiCads either. Leave them on too long and they'd fry them.
He did, so that could include say 'putting them in the freezer' or trying to cycle them?
But I think he's pretty well discounted doing that because it would probably be 'loads of effort'. ;-)
Oh sure, and something we have just done in ours, even though we can't dial out on them now for some reason (nothing to do with the battery change). Not sure if it's the DECT base, some setting or our PBX (but given we rarely use the ll to call anyone ... and still have wired phones that do work, it's just another thing on the rountuit list). ;-)
Cheers, T i m
Not power tools. You need faster charging than ten hours...
supplied
An ancient Black and Decker Dustbuster is hardly a "power tool". I have one, it was pretty crap when new. The charger is just a wallwart PSU, I think there is a current limiting resistor in thing, doesn't even have "power/charge" LED! It was barely used even before the NiCds gave up.
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