USB 5v to 12V step up for cooling fans required. please help!

[jpoopdog]

hello,

i own a toshiba qosmio x500, and as many owners of this laptop, or computer guru's will know, is this is the most stupidly designed gaming computer ever built by toshiba. the laptop has a 2mm clearance from the surface it rests upon, and the air intakes are all located beneath the laptop, meaning that anything which uses more than 20% cpu and ram, will overheat the laptop causing a restart (in which case the thermal overload trips again and again until you get a blue screen of death), or a blue screen of death.

Anyway, i have decided to build a cooled stand, very simple design, its some folded aluminium sheet metal, about 3mm thick, and i plan on cutting holes for the air intakes.

now, another downside to the design of this computer is that even if it has air access, at over 70% capacity of cpu and ram (or 100% cpu and over 20% ram and vice versa), it cant get enough air in, also, 3 of the 4 air intakes dont really suck in any air at all. for normal gaming over a few hours, it needs a cooling pad with extra air flow.

now, i need a 12v supply, to power my PC fans. i plan on getting a battery pack, likely a flat SLA, and need a 12v charger from the USB port of my laptop, the SLA in turn will power my fans, and also a peltier cooler, but thats only when its plugged in.

I need a circuit which can provide sufficient current to power the fans without the battery, around 800-1000mA will suffice ill take whatever the usb ports can give, i have a usb 3.0 port to use as well, im not sure how much power it deliveres, but im sure it is more than a normal USB port.

i just need a circuit for converting 5v to 12v whithin the limits the usb port(s) can withstand.
also, if anyone has some pointers, i would very much like them on how to add an SLA to this , but if its simpler to use a pack of rechargable AA's , ill use them instead.

any help is greatly appreciated.

 

[konradIC13]

USB 2.0 can provide up to 500mA current per USB
USB 3.0 can provide up to 900mA current per USB

Shorting together Dada+ and Data- can give you up to 1.8A

Remember that drawing so much current from your laptop battery will lower its battery run time. If you plan to use it only when laptop is plugged its more convenient to power your cooling pad from DC adapter. Also you dont need 12v, sure 12v fans are most common but you can also use 5v fans. Most of fans i saw have current not greater than 250mA so with just two of them you can power them directly from USB.

 

[Reloadron]

You may want to rethink this a little. You mention using a 12 volt SLA (Sealed Lead Acid) battery. IN reality a 12 volt SLA battery when charged outputs about 2.15 volts/cell or about 12.9 volts (give or take). Therefore the charging voltage must exceed that level. Give this link a read. I would consider using 5 volt off the shelf fans. Standard 40mm fans like the ones shown in this data sheet are inexpensive.

A DC/DC converter can be bought or built For example a unit like this one runs about $30 with focus on the ZUS60512 in the link and provides about 500 mA. Again, that will not charge a 12 volt SLA battery.

You also mention a peltier cooler. Granted only when on mains power but the price of cold with these units is considerable current draw.

My thinking is that all things considered you may want to rethink this project.

Ron

 

[jpoopdog]

i have come to realize it might only be practical to run the fans off a 10-12v battery, and then use the usb port to slowly charge the battery, rather than the fans off the usb directly.

At least that way i wont need to worry about making a super efficient system, i just need to make a 12v battery charger circuit. my gaming sessions wont really last THAT long, so it wont matter if the fans can only run for a few hours before the battery goes dead.

what would i need to do, in order to charge a 12v NiMH battery(made from 10xAA 1.2v batteries) from that 12v 500ma that converter can output?