I used this lot and they were hopeless. It was only after I ordered that I looked up some reviews that all said they were slow and had to be chased and, lo-and-behold, they were slow and I had to chase them.
The batteries were crap too. Re-did two Makita sub-C battery packs and they were worse than the dying packs I'd stripped. May as well have bought randomly from eBay at half the price.
Can you recommend a supplier of good quality Sub-C sizes?
Screwdrivers are quite low current draw compared to cordless drills.
FWIW the memory effect of NiCds was grossly exaggerated
NT
Whisker growth is the main problem in my experience, where one cell gets shorted out internally. I have Nicad packs for my Paslode nail gun, one of which does this quite regularly. Easily sorted by a quite zap across a car battery - the pack is 9.6 volts iirc and the quick pulse of high current (12v battery and lowish internal cell resistance) pops the grown strand very effectively.
Andrew
Don't think so. They can be stalled if trying to turn a large enough screw.
And screwdrivers generally have smaller batteries.
both of those mean less current, as does lower top speed
NT
drills.
enough
Er no a stalled DC motor is pretty much a dead short on the battery. When a DC motor is whizzing round the back EMF reduces the current draw.
Everything being equal, the size of the battery determines maximum current. The speed the spindle runs at is largely dependant on gearing.
stall current is immaterial. The fact that its liable to stall means its taking less current when rotating.
NT
current times voltage = power, which is proportional to torque times speed. Half the spindle speed, if torque is the same, means half the battery curent.
NT
"a bit more energy dense" ?
How about "Three times the energy density." ?
You can get AA NiMH cells with capacities up to (and possibly over) the
3AH mark these days. At this extreme, they won't be the Low Self Discharge (LSD) type.The highest capacity AA NiMH LSD cells that I've actually been able to acquire recently (some time during the past 18/24 months) were rated at
2.3AH and marked as Tronic "Eco ready to use" where the expression "ready to use" is simply marketing speak for the LSD type which, unlike the ordinary NiMH cells, don't require being recharged before being placed into service.This effectively allows them to be just as usable as a primary cell equivalent but with the benefit of being rechargeable after they've been exhausted rather than ending up in the "Spent Batteries Box" in Aldididdle (hence the legitimate use of the 'word' "Eco" in its description).
When I first bought a set of 6 AA NiCds for a (still functioning!) electronic calculator back in the late 70s, they were only 0.45AH capacity. Over the years, I saw the capacity of AA NiCds go to 0.5AH, then 0.6AH and finally, ime, a monster capacity of 0.7AH. They may have peaked at 0.8AH but I can't recall with any certainty whether such high capacity AA NiCds were marketed before NiMH developments had rendered such 'high capacity' NiCd cells just a little bit pointless.
The lowest capacity NiMH AA cells I ever used were a two cell set supplied with a little 3MPxl Nikon CoolPix I bought ten years ago and these were rated at 2AH. I think the lowest capacity NiMH AA cells I ever saw had a 1.8AH rating. With that in mind, I think it *is* fair to say that NiMH cells have, at a conservative estimate, three times the capacity of the NiCd equivalent.
Portable electronic kit (radios and digital cameras) *properly* designed to be powered from AA and AAA cells are designed for an end point voltage of, typically, 1 volt per cell with primary cells (Zinc/Carbon or alkaline). The rechargable cells, both NiCd and NiMH, can be considered to be exhausted as soon as they drop to 1.2v, well above the endpoint voltage for primary cells.
Bearing this in mind, it may be somewhat disconcerting to discover that a set of rechargeables used in a P&S digital camera swiftly start to show 'Low Battery' after only a few charge/discharge cycles. The problem isn't due to defficiencies in the battery chemistry but down to high contact resistance due to tarnishing of the battery contacts. This combined with the low initial voltage (1.35v versus 1.6v of a typical primary cell) leads to spurious early 'Low Battery' warnings which can be 'cleared' by cleaning the contacts and re-inserting the cells back into the battery compartment.
The problem is absent when using primary cells simply because of their 'one shot' nature. They're never recycled once their pitifully short life has expired so their contacts remain in pristine condition when used in a camera. Also, any contact resistance is swamped by the higher internal resistance with the higher cell voltage effectively compensating for such volt drops.
If the manufacturers of such AA cell powered cameras were to redesign the battery compartments to use much stronger contact pressures and permit a sliding contact action on insertion of the cells, there'd be a lot less trouble from such spurious low battery voltage warnings. Unfortunately, there's only so much strength in a plastic battery holder and too much pressure to keep the design nice and compact which limits the scope for such niceties as a 'self cleaning' wiping contact battery holder.
I used to be rather prejudiced against digital cameras that eschewed the use of cheap commodity AA cell power for proprietary Li-Ion battery packs but after my experience with AA powered cameras, I've rather changed my mind.
Although the camera makers own replacement Li-ion battery packs are eye- wateringly expensive, you can actualy get hold of decent third party equivalents for not much more than the cost of the watt hour equivilent in NiMH power.
The relatively expensive Li-ion battery (even when using a 'cheaper substitute') does have the merit of being able to employ gold plated contacts (nicely matching the gold plated battery contacts in the camera) which eliminates, at a stroke, the main deficiency inherent in using rechargeable AA cells.
Now when I see the low battery warning in my super zoom bridge camera (Canon SX40HS)'s viewfinder, I can be pretty certain it has everything to do with the state of the battery rather than a battery contact problem.
Had exactly that problem, just as you describe it!...
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