I've got loads of them. I'm sure I'm not alone. The thing is I no longer know which adaptor came with what tool.
My questions:
If the adaptor fits the battery unit is it ok?
What if I use an adaptor which has a higher voltage than the battery rating ie., adaptor has a 24v output and battery is 12v and conversely?
I don't want a fire or a ruined battery.
mark b
On Sat, 29 Jan 2005 23:27:48 -0000, "mark b" strung together this:
No.
It won't instantly explode but it won't do them any good if they're left connected for any period of time. Easy way to find ou, (usually), is to match the voltages on the cells and chargers.
I don't mean to be unkind, but this has to be a troll, right? Are you really expecting the answer to be "yes, no problem, all chargers will work fine with all batteries"?
Google groups by author is usually a laugh on suspect posters and yup
9/10 posts really are genuine . . . . , v scary.
Actually there's a product around using a wind-up thing, presumably based on the Bayliss clockwork radio, which claims to charge most things. How it handles voltage and polarity I don't know - presumably some sort of sensing electronics.
No, there would be no way to accurately determine how a battery pack should be charged electronically.
With NiCds and NiMHs you need to charge them at a constant current, the value of which is dependant on a) how fast you want to charge them and b) their capacity. Furthermore, you need to control the length of time for which you charge them.
I can provide more info if required, but this is textbook stuff which can readily be looked up.
Think you can, by measuring the rate of current change, etc.
Well I wasn't intentionally trolling. Anticipated answers more useful than this one might have suggested that a
12v charger won't charge a 24v battery or will take 10 days, or maybe an over rated charger might do it more quickly but if you forget about it something goes bang. Obviously matching battery to original charger would be ideal but in reality I have found the chargers not to be branded as per the tool. I don't know how battery chargers interact with differing batteries so I asked the question. Isn't that the reason for being of this Newsgroup, people ask what they don't know and those who do know answer and vice versa.When I get to know everything about everything as you clearly do I will be able to advise accordingly and not delight in smug and arrogant answers.
Thank you
mark b
Hey - no need to get so offended. Like many people on this group, I've been caught out answering silly questions posted by trolls in the past. Kind of makes you cautious.
A 12V charger won't charge a 24V battery, ever. A charger intended to charge 24V batteries will destroy a 12V battery pretty quickly. A 14.4V charger could be used for charging 12V batteries, but whether it will damage them depends on how good a charger it is.
If you look at my posting history it will become quite clear to you that I certainly don't know everything about everything, nor do I think I do.
Ok, let's explore that further. Imagine you have a black box, containing a NiCd battery. You know the following:
- it could contain 2-20 cells in series
- they could have capacity between 1.2-3.6 AH
What voltage would you apply initially, and what would you do after you've measured the initial current?
That is actually straight forward, and would be handled by a decent constant current delta peek charger.
The voltage is not actually relevant since a constant current supply will modulate this so as to achieve the selected current (i.e. charge rate). Monitoring the applied voltage should show a slight rise with time, with a peek and then a decline as the pack reaches full charge. The delta peek detector will sense this and turn off (or reduce) the charge current at that time.
(I built a charger years ago from some spare bits I had. It is basically a linear PSU with 40V DC output, and it uses a thick film hybrid IC constant current/voltage regulator (a "L200" IIRC) configured in constant current mode. A rotary switch selects one of a number of presets that control the required current, the current regulator drops the required voltage to match pack attached. No delta peak on my one though, perhaps I will save that for an enhancement ;-))
It is unlikely to charge it at all... but see anon.
No guarantee that the original charger will be "best" for the tool either!
One area where there is a huge variation in quality between different tools, is in their batteries and also their chargers. It is possible to build very good universal chargers that will fast charge an arbitrary number of cells (i.e. different pack voltages) without any apriory knowledge of the pack voltage, and also stop charging it at the right point. (Makita usually ship a charger that will do just this - it is quite happy to charge a 9V or a 18V pack without damaging either).
It is also possible to build a "charger" that is nothing more than a transformer, single power diode, and a limit resistor! This will stick half wave rectified DC through cells at a varying current. If limited to low charge rates, this will actually work OK even though it is not the "right" way to charge a NiCd at all. Scale up the power however, and it will toast a cell in no time.
The poor ones don't, better ones use delta peak detection, and/or thermal detection.
yup... don't get too bent out of shape one flippant remark though, most of the input you get from these parts is pretty good (and Grunff is one of the good guys!)
Not read much IMM yet then ;-)
That easy, eh? ;-)
But it would need to be able to apply a voltage high enough to drive the necessary current, right? So if a charger is built with the intention of charging say 12V packs max, it may not be capable of applying a high enough voltage to push any current through a 24V pack, no?
As a theoretical point, you could make a charger to cope with the majority of common power tool batteries, yes. But of course cost is a factor, so this isn't likely with commercial designs from B&Q.
IMHO ;-) I charge all these at the 14 hour rate - and they thank me for it. ;-)
A good one from markb, "Brass is metal, I suspect you mean steel"
So why has my "decent" Ansmann delta V charger got a NiMH/NiCd switch?
It does detect dead batteries (NiMH and NiCd) and those inserted with incorrect polarity ...
AFAIR, because (a) the delta-V is much more pronounced for NiCd than NiMH, so telling the charger what you've got avoids oversensitive premature switching to trickle-mode for NiCd; (b) because trickle/top-up charging for NiMH wants to be at a notably lower current (C/50?) than for NiCd (C/15?), so telling the charger what you've got avoids overcooking the NiMH cells.
The 'nicest' chargers supplement delta-V detection with temperature-rise detection; but that's hard to do reliably without a dedicated thermistor deep in the heart of the pack - common enough on higher-end batteries, but no standard contact arrangement means 'universal' chargers don't do it, and it's awkward to arrange for a thermistor to be in good enough contact with generic single cells to be much use.
At least, that's what my long-ago reading of Maxim charge-control-IC datasheets has left in my brain ;-)
Stefek
Indeed, using a bit of delta-T as well (but that would be difficult on mine as it has a fan to cool the batteries down) sorry it was a rhetorical question.
Just wondering how John's mythical universal charger would know!
The newer ones also have a non-volatile memory and a built in ammeter to integrate the total charge ...
You can get the clever stuff all bundled into single ICs these days... so no need to be more complex than a PSU (if you ignore the minor point of the black magic that goes on inside some SMPS!)
Yup spot on. For any given design of charger there will be a maximum number of cells that it can cope with. Oddly more is not difficult (just use a higher voltage output transformer, but then doing fewer cells becomes harder since you have more volts to drop across your regulator.
If you think about it there is a market opportunity here. Stick a "standard" socket on all battery packs in addition to the normal connector used by the tool to allow connection of a third party charger. Then offer a "cheaper still" range of tools that come without a charger for those who have already bought a "one size fits all" charger.
The flaw in that suggestion however is that most of these sophisticated charging schemes work so much better on packs where the cells are reasonably matched, which rules out your average shed special (or at least condemns the pack to a short life irrespective of the care of the charger)
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