3.5" USB HDD enclosure ran off of ni-cd rechargable bat

[elmezie]

I have a usb 3.5" hdd enclosure , currently it uses an external 40watt ac adaptor to power the hard drive. Is there anyway i could replace this wihth a rechargable battery?

 

[mechie]

More Info

Give us a clue ... what voltage is required ?
If I guess at 12v then 40W is about 3.5 Amps (P = V*I)
If I guess at 18v this comes down to 2.25 Amps.
This will only be required when the HDD is running so a battery pack could cope but its life will be short unless you have power-saving options on your computer to stop the HDD when not required.

Maybe a sealed rechargeable, Yuasa make a 2.8Ah 12v battery, #if the voltage is correct# it would give just under an hour of operation per charge. A 7Ah one would give 2 hours.

Disposables such as a pair of PP9's in series would give 18v and last for a couple of hours (at a cost of 6 pounds (UK) a time - that's £3 per hour !)

Does the size and weight matter?
A 30Ah car battery would last for 10 hours?

 

[elmezie]

The power supply that comes with the usb hdd enclsorue has an
AC input: 100 - 240V DC output: +5V/+12V

I only want to be able to use the drive for like 30 minutes at a time. In between use i wanted to recharge the batteries using a charging station or something.

 

[mechie]

HDD Power

I guess the 5v line will be around half the total power (20W = 4A).
It now gets messy ...
A 12v battery and a 5v regulator capable of 4A.

If my guess is right - the regulator (simple series type) will waste 4A*7v = 28W as heat in addition to the HDD power requirements.
40W just went up to 68W !

Can you tell us the currents for each power line ? maybe only a few mA are required for the 5v line ...