Charging MZ-NH900 through USB?

[803cd]

When I connect my MZ-NH900 to my PC by USB does the battery get charged?

[Haybrd]

When I connect my MZ-NH900 to my PC by USB does the battery get charged?

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My understanding is that is does not get charged. The MD player becomes USB powered i.e. does not take charge from the battery but from the PC, but no charge goes into the battery.

Edited August 24, 2005 by Haybrd

[Sparky191]

My understanding is that is does not get charged. The MD player becomes USB powered i.e. does not take charge from the battery but from the PC, but no charge goes into the battery.

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Thats my understanding too.

However this might be an alternative.

http://forums.minidisc.org/index.php?showtopic=5121

[KrazyIvan]

That method is risky. A usb bus is not designed to deliver the amperage needed to recharge a unit. You are risking burning out the USB port or motherboard and possible damage to your unit.

[Christopher]

MDX-400's response at the end of that thread pretty much nullifies any concerns, in my opinion. I've quoted it below:

I know this is an old thread but since it is stickied...

Why was everyone so concerned about the 5V that the original cable was outputting?  Because newer MD units, including pretty much all the NetMD models have a degree of protection on their DC inputs.  Since the original cable worked I would say that there wouldn't really be any problems with using it that way.  At your own risk of course...  But the truth is if you apply about 6 or 7V to the DC in on a newer unit, it won't fry it.  Instead you'll get a message on the MD unit saying "Hi DC In" and the unit activates its protection circuitry.  Certainly, given enough voltage you will likely fry the unit but 5V DC, even constant, isn't going to harm anything. 

Unless you have some sort of power surge through your PCs power supply you'll be okay, plus motherboards usually have some kind of regulation for the USB ports too--if you did get enough voltage through the USB to fry an MD unit your motherboard would probably be fried as well.

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[803cd]

Thanks all

[MDX-400]

MDX-400's response at the end of that thread pretty much nullifies any concerns, in my opinion. I've quoted it below:

Hmm I think KrazyIvan's concern, above, was more about the current capacity of the USB on the computer motherboard rather than the voltage requirements/tolerances of the MD unit.

I don't know what the NH900s AC adapter is rated at but most of the non-Hi-MD NetMD units were rated at 500mA with the higher models getting 800mA or 1000mA (@ 3VDC) AC adapters. I think the USB bus on most computers these days has to be at least capable of 500mA, per port @ 5VDC. Some motherboards will also have current-limiting protection built-in, but from what I've read the overcurrent protection employed is often not per port but globally for all ports (meaning if you have 8 ports you wouldn't get any protection kicking in until the total draw was at the very least 4A.)

Also you should consider that the current draw of the MD unit at 5VDC would be less than the current draw if it were getting only 3VDC. (Both under load I mean, since the AC adapter's float voltage will be high and under load it will come down, whereas the USB voltage will hold fairly constant under load as it is designed to.)

How long does it take an NH900 to charge a NH-14WM gumstick? (I'm trying to get an idea of how much current it would use during charging.) Older units like the non-Hi-MD NetMD units provided perhaps 300-600mA of charge current @ ~1.5V to charge the battery in the unit. Even considering efficiency losses, if the NH900 is anything like the MD units of recent past, then it won't be a lot of current required from the 5V USB. Even considering that the charge controller in the unit would increase its charge current with a higher supply voltage (which may well be the case), I don't think you'd end up damaging the USB port(s) on the motherboard.

I think, on a modern PC, provided your USB ports aren't all taken up by current-using USB-powered scanners, HDDs and other USB-powered devices, charging an MD unit from the USB shouldn't really be a concern. I think even if it took upwards of 1A @ 5V on one USB port to charge the battery you'd still be okay (and I seriously doubt any MD unit would require that much current, at that voltage, to charge a battery--MD units are relatively slow battery chargers).

Roland M.