USB Charging

[jägermonsta]

So we've picked up about 20+ MINI Barcode Scanners


Each scanner runs on a 150 mAh lithium-ion battery that is charged via a USB interface.

So in order to charge all these devices, we're throwing together some ideas... while a powered USB Hub sounds like the best solution, I've read more and more that these Hubs start to lose their integrity to power devices for the more devices that get plugged in (7 port HUB). This creates a risk for the device itself...

So I'm thinking this, not sure if it would work...

Build a system with ONLY a PSU & Motherboard (No CPU, RAM, HD, etc...). A Mobo with plenty of PCI Slots and a case with a good amount of drive bays.

This would allow me to put in a bunch of 4 port drive bays and a bunch of a 6 port PCI USB cards... Allowing me to possibly charge all these devices at once.

Think that will work?

[Whirlingdervish]

I don't think it will handle them without the CPU, but I could be wrong. Onboard RAM might carry it, but a cheap stick of ddr is easy to come by.

As long as the mobo has USB support, you may not really need an internal boot drive.

[jägermonsta]

Ahh yes. I suppose it would need to post. Or as we spoke in IRC... a bunch of power adapters would work too! I guess it will come down to if they actually want a central system to pull the data off as well.

[QwazyWabbit]

0.150 A x 20 devices is 3.0 Amps, USB only supports 0.75 Amps per port. A 7 port, self-powered hub probably doesn't need a mobo connected to it just to charge devices. I believe the hubs are smart enough to do the power regulation themselves. USB devices are required to power up in low-power mode and negotiate for more current once they have established communication with the hub/node. A 0.15 amp device doesn't need to negotiate up. Three 7-port hubs with their own power adapters would be sufficient. (USB-charged phones use simple wall-wart adapters for their rechargers.)

[jägermonsta]

Yeah suppose they don't require much power.

But still... reviews out there of people attempting to do something similar to what I am trying, explain that 7 port hubs either charge very slowly when all 7 ports are used, or heat up so greatly, the hub or device gets damaged.

[QwazyWabbit]

Reading more closely, I see it's 150mAH, not 150mA charging current. You'll need to know how much they demand from the USB power before you can know how many you can charge at once. Not sure about your application but it seems to me they would be more likely to be used in rotation so you won't actually be charging all of them at once anyway. I'd be looking into available wall-wart chargers like Blackberry and Motorola supply with their devices.