I have a dictation machine which charges an internal AA NiMH cell by being plugged into a PC's USB port.
If I charged from a 2 Amp USB mains charger, would I damage the recorder or battery?
This is USB 2.0 and the PC provides no more than 0.5 Amp current. I'm not sure if the recorder would somehow regulate the incoming current from a non-PC source.
Any views?
It won't be a problem. The device will only take the current needed.
Chris
Well it would be a very silly design that relied on the current limiting in a pc usb to regulate its charge. So no it won't make any difference in the slightest. Brian
Just to comment that the charger doesn't mandate the current. It mandates the voltage, and the current that flows depends on what you connect to it.
The 2 Amp rating means that the charger is capable of giving, at most, 2 amps. You demand more and it limits. Or burns, on bad/old designs.
In general it would be silly however this recorder is specifically designed to plug into a PC USB port for charging and audio file transfer.
It has it's own pop out USB-A plug to go into a PC port.
What happens if you plug it into a USB 3 port that can supply 1A? Mine can supply 1A.
It uses a single AAA nimh battery which will have a capacity of about
700mAHr so it must be current limiting on ordinary USB as it takes about 3 Hrs to charge. It has temperature protection so will stop charging if the battery is too hot.
"Can I use your Dictaphone?" "No, use your finger to dial like a normal person.."
I understand this is how it should work but my concern is that the recorder may not adhere to this standard as I explain below.
The recorder uses a removable AAA size NIMH cell. Normally you would remove it to charge it in a standard NIMH charger. However the recorder uses its USB lead (for PC file transfer) to also charge this cell without removing it and I wasn't certain that the using this same lead with a high current USB charger would necessarily be safe for the recorder.
I've damaged an earlier generation recorder which no longer retains enough charge between battery swaps to keep its internal time and date clock. The manufacturer's service department thinks that the PC may have blown some components (capacitor?) in the recorder when it was attached to the PC for file transfer as there is no on-board clock battery inside. This previous device didn't charge from the PC.
As others have said: The current rating of the charger is just the maximum that the charger can supply. What it does supply in any given case depends on the thing that's being charged and how much current it can draw. You can't damage the chargee by having a charger with a larger than necessary current rating ... the charger does not "push" more current that the chargee wants, electric current doesn't work like that.
Note that the same is NOT true of voltage. That shouldn't be an issue here as all USB ports provide 5V (recent ports can negotiate to supply more, but without a successful negotiation to do so they'll just give
5V).
it's fine.
it's highly unlikely that you damaged anything. something failed and the company didn't want to accept responsibility so they blamed you.
as for the clock, you can easily reset it.
usb-a is always 5v, although shitty chargers are typically poorly regulated and can cause problems.
usb-c can be higher but the device in question is not usb-c.
The problem I had in mind is that the recorder may not have been designed to inform the charger of its current requirement because the recorder is designed to assume a PC USB 2.0 port is always used and that woul dhave a max supply current of 0.5 A.
The photo I posted earlier shows how the recorder is designed for the PC. Also my previous experience of device problems, possibly from the USB connection, has made me extra cautious!
The recorder cannot be designed to use the limiting capabilities of the PC USB port. This is because most PC USB ports will shut down if the 500mA is exceeded, not limit. The recorder has to limit the current to 500mA or less, or it simply couldn't work on a basic port.
if it's not designed to request 500ma, all it will get is 100ma. it'll still work but it will charge really, really slowly, if at all.
of course it can, and any properly designed usb device will do exactly that.
these days, usb ports source at least 900ma, usually more because of all the hard drives and phones people connect.
no it doesn't. what it has to do is request 500ma (or more), which is normally granted but not always.
yes it can.
Interesting. Seems like my worries are ill founded.
I'm sure most people would just plug the recorder in anyway without going through all my angst. I was being extra cautious because I recently bought a couple of new not-so-cheap recorders and didn't want to see them get fried.
they are
no harm in being cautious but unless the device is junk, it won't get fried
Then it would fail to work on most PCs. As I said before, the USB ports are fitted with electronic fuse, not a current limiter.
Maybe so. But what does the recorder expect? If it assumes the USB port will limit at 500mA, then the 900mA one would break it.
500mA is the default if no request is made. I can charge a battery simply by connecting it to the 5V and 0V rails on a USB port. As long as I don't exceed 500mA, it will work fine.No, because the battery when empty might draw more than 500mA, and this would shut the port off until the PC was restarted.
Please don't spout nonsense unless you know a bit about the electronics inside your PC.
I doubt it. No sane electronics use "electronic fuse" that needs replacement. That's obsolete.
if it doesn't work, then the pc is non-compliant. unfortunately, there are junky non-compliant pcs out there. simple solution: don't buy junk.
usb ports limit the current they source. there may also be a fuse, but not always. cheap crap usually doesn't and sometimes not so cheap stuff.
no it wont.
a device requests what it wants and must deal with whatever it gets.
some devices will cause an alert on the host:
if a device gets only 500ma instead of 900ma, the charge time will be almost twice as long. no harm done, other than it will take longer to charge than it otherwise would have. if you leave it charging overnight, it won't matter if it takes an extra couple of hours.
nope. 100ma is the default if no request is made. anything above that
*requires* a request, which can be declined.The host first recognizes the peripheral as low-power, allowing it to draw less than 100 mA of current. The peripheral can ask the host to recognize it as a high-power device in a process called ³enumeration.² Once enumeration is completed and permission is granted, the allowed peripheral current is increased to 500 mA
then your usb port is noncompliant. simple as that.
it won't. the charger circuitry will draw whatever it's designed to draw regardless of the battery charge level. it will be *less* once the battery is close to full (for a top-off charge).
read the usb spec before you start assuming anything.
start here:
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