powering a external hard drive from a car

[jms1989]

Hi, I've had an idea floating in my head about powering a external 3.5" hard drive from a car. I understand that a car's system can go from 11 to 13.8v without the starter and down to 6v when the starter engages due to the high amperage. A hard drive needs a steady 12v. I would think a simple 12v regulator would work but given the voltage fluctuations, it might not be able to keep it at a proper voltage... it'd have to regulate up and down. a big enough capacitor can smooth out any brief drops. can a zener diode take care of the overvoltage or does it need more sophisticated electronics? normally, I'd just use a small 2.5" lappy drive and power it from the receiver or laptop.

What would be used and how would it be used to accomplish this?

 

[FvM]

If you want to keep the 3.5" drive power supply specification (12V +/- 5%), you'll need a buck/boost converter or equivalent.

 

[tpetar]

Hi, I've had an idea floating in my head about powering a external 3.5" hard drive from a car. I understand that a car's system can go from 11 to 13.8v without the starter and down to 6v when the starter engages due to the high amperage. A hard drive needs a steady 12v. I would think a simple 12v regulator would work but given the voltage fluctuations, it might not be able to keep it at a proper voltage... it'd have to regulate up and down. a big enough capacitor can smooth out any brief drops. can a zener diode take care of the overvoltage or does it need more sophisticated electronics? normally, I'd just use a small 2.5" lappy drive and power it from the receiver or laptop.

What would be used and how would it be used to accomplish this?

Lowest voltage is many cars with good battery and fully functional starter, and ok cables, dont fall down below 9,6V during cranking. Normal is 13,8-14-14,2V when engine running.

Zener is not smart scenario.

Boost voltage to higher voltage lets say 15-18V then regulate to 12V.

Is there possibility to switch 3,5" with 2,5" HD, 2,5" need 5V ?