Best way of power desktop speaker in car

Question

I want to power up my Sony SRS-D9 multimedia speakers in car. The speaker system powered by an adaptor which having

input : AC 120V-240V~50/60Hz 60W out put : DC 18V 2.6A I am living in India. Here 230V AC plug available in my home.

I have two options to install it in my car.

1) Buy a 12V DC to 230V AC converter and plug the adapter for power the sound system.

2) Buy a 12V to 18V converter and directly power the sound system without adaptor.

Which one is the best solution. Which drains the car battery quickly if the engine is off. What are the pros and cons. What are the practical challenges for this setup?

Answer 1

I would choose the 12V to 230V to 18V pathway. Yep, it has more losses, but that doesn't matter if the speakers are powered only when the engine is on. 18V 2.6A is only 46.8W. Compare this to typical car engine power (100 kW = 100 000 W).

12V to 230V adapter is more versatile than 12V to 18V adapter and likely cheaper as well due to economies of scale. If you ever want to run a laptop from your car, the 12V to 230V adapter will do it, but the 12V to 18V adapter won't (unless your laptop uses exactly 18V).

Your 12V to 230V adapter also has 150W power, whereas the 12V to 18V adapter has only 90W power. More power for less money should make it obvious which one you want.

You aren't going to save the planet by using the more energy-efficient 12V to 18V DC-DC converter, as the losses are so minimal.

If you for some reason cannot use an ignition controlled supply, then 12V to 18V DC-DC converter has smaller quiescent current, which may prove to be useful. But in my opinion the quiescent current of such a converter is still too large for continuous operation with engine off.