Is that a voltage mismatch

Hi,
I have a rechargeable vacuum cleaner from which I lost the power adapter a long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?
Thanks,
Sam
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On Nov 18, 6:35 pm, snipped-for-privacy@yahoo.com wrote:

yes
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On 11/18/2012 3:35 PM, snipped-for-privacy@yahoo.com wrote:

long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

Yes, but it's worse than that. Even if the voltages on the label match, it can still result in damaged goods or overcharged batteries or melted wall warts. More recent stuff with regulated wall warts is more compatible, but not always. Older stuff is a crap shoot.
There's a reason the manual says, "use only the AC adapter we gave you." YMMV
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long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

GENERALLY the wall wart has a higher voltage than the battery being charged. A 14.4 volt Lithium battery is charged by a 20 volt power pack in a Dell computer. An 11.1 volt lithium battery in an HP laptop is charged by a 16 volt power supply. If the voltage of the pack matches the voltage of the battery it will NEVER be charged as it requires extra "pressure" to force the electrons into the battery. The charge regulation circuitry is built into the computer or vacuum cleaner or whatever,
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wrote:

It is more then just the voltage you need to make sure that polarity is correct and that it is DC voltage and not AC some step-down transformers look identical to DC adapters/chargers and yes all charger may have slight higher voltage then actual battery.
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You forgot to mention, there are three types of dc. Unfiltered, filtered, regulated. I don't think the op said ac or dc. Also, if you use a higher rated current transformer on a unregulated output, the voltage will also be higher with less load current.
Greg
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To all that you can add that the charger must match the type of battery. The older nicads are not that critical, but some of the newer types are are.
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On Sun, 18 Nov 2012 22:19:36 -0500, "Ralph Mowery"

But the charger in this, as in many other, case(s) us built into the device and only a "power supply" is external.
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mike wrote:

long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

Given that a great many power adapters have only OEM labeling and no indication of the brand of product they came with it is a really good habit to mark what the adapter goes with on it in something like a white paint marker.
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<stuff snipped>

Good idea! I always mark each power supply with the item it belongs to, the voltage, AC or DC, regulated or unregulated, amperage and tip polarity. I use a fine point silver Sharpie and make the same notation on the device the wallwart is powering because jacks are typically not marked very well. Once the wallwart gets lost, it's hard to figure out what's needed to replace it without the markings.
If the voltmeter reads the rated voltage without a load, I assume it's a regulated unit. So far, when I've had to replace a wallwart I've had no trouble matching a replacement power supply because I know what each device needs.
-- Bobby G.
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On 11/18/12 6:35 PM, snipped-for-privacy@yahoo.com wrote:

long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

In addition to a Voltage mismatch, a bigger issue is the Amps. The adapter must have a higher amps rating than the vacuum. Other wise the adapter can be overdrawn and melt or burn.
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long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

Actually not necessarily true if it is only used as a charger. The adapter will charge the battery more slowly - and will not run the vacuum - but in MANY cases the vacuum will not run when the charger adapter is plugged in anyway. Neither of the battery operated mini-vacs I had would run with the adapter plugged in.
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On Nov 18, 9:38 pm, snipped-for-privacy@snyder.on.ca wrote:

Why do you say that 12.5V charger will charge a 9.6V device "more slowly"?
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On Mon, 19 Nov 2012 10:14:55 -0800 (PST), DerbyDad03

long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

a bigger issue is the Amps. The adapter must have a higher amps rating than the vacuum. Β Other wise the adapter can be overdrawn and melt or burn.
My reply that a lower amperage charger might charge slower is correct.
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On 11/19/2012 12:30 PM, snipped-for-privacy@snyder.on.ca wrote:

long time ago. Now I found one (I think!) and it fits and everything, but I'm not sure. The vacuum cleaner says "9.6V" but the adapter says "12.5V". Is that an indication that it's the wrong adapter?

You guys are oversimplifying it. I've been out of the compliance business for 20 years. The details have surely changed, but the basic principles should be the same.
When you take home your new gizmo and open the box, everything in the box was designed as a system. It has to all work together AND meet safety and EMC requirements. Power units are particularly troublesome. The numbers marked on the label of your wall wart comply with some safety regulation. the numbers marked on the product, if they exist at all, are likely the same as those marked on the wall wart. For unregulated supplies, the numbers on the wart are only loosely coupled to the the numbers you'd get with a voltmeter.
Getting back to the SYSTEM aspects... If you have a 20 year old dustbuster, it's likely that it contains NiCd batteries. It's likely that the charger is a transformer and a diode. The charging current is determined by the transformer impedance defined by the coupling coefficient and winding resistance. It works mostly because the line voltage is sorta regulated. What happens with this method is that you use the dustbuster until it quits working. That likely reverse voltages one or more cells. Over time, one or more cells short. Now the model is wrong and the other cells are seriously overcharged. That's why the cells vent or the plastic on the case melts, or the wall wart melts.
The current number written on the wall wart is some combination of what it can supply under normal operating conditions with THAT SPECIFIC device and the testing methods imposed by the regulations. An ancient wall wart has zero current limiting capability. The current goes to whatever's allowed by the transformer impedance and stays there until the transformer overheats enough to pop the overtemperature device.
If you lose your wall wart and blithely attach one with the same voltage numbers and a bigger transformer, the charge current for your cells can be WAY bigger than the design value.
Newer devices have some combination of internal regulation and regulation inside the wall-wart. You'd think you could interchange those. Well you can...except when you can't. A 99% statistic is meaningless when YOUR device catches fire.
If you want some fun, take a look at the schematic for a Compaq Aero laptop from the early 90's. The battery is connected directly to the charge connector with a FET disconnect swtich. The charge current is limited exclusively by the current limit in the wall wart. I learned this the hard way when I connected a $2,000 laptop to a stiff power supply. The FET caught fire. This was a seriously flawed design...but the SYSTEM worked as designed.
Bottom line is that, without reverse engineering all parts of the power system, it's dangerous to substitute wall warts on ANY device. Random inputs from a newsgroup are not a reliable indicator.
This will get better as some of the "green" compatibility standards take hold.
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Depends on where on the vacuum cleaner it says 9.6V because it can be one of two things:
It could be the voltage of the batteries inside. 8 Nicds would be 9.6V. It could mean the input voltage of the charger. You should be able to tell which of the above applies.
In the first case, a 12.5V adapter may be the right one. In the second case, the adapter is definitely wrong.
One possible way to be sure is to find a product photo and look at the adapter. Or find a product manual and check the specs.
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Or find the same product in a store, and open the package, but only if you can reseal it so it looks good.
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