High Efficiency USB Car Charger

[Jacob Sheldon]

I am looking to find a high efficiency USB car charger with two ports. I need one that is really efficient because I made a small solar panel with a battery pack and I need to get the most out of the batteries. The charge controller I have running the whole thing puts out 12v and I have a cigarette lighter port coming out of the charge controller. Does anyone know of a USB car charger with over 75% efficiency? Thanks.

 

[Harald Kapp]

Welcome to electronicspoint.

No I'm not aware of such a device (although you can find tons of them at the usual sources).

As you've built this contraption yourself, may I ask why you first regulate to 12V and then down to 5V? Having two regulators in series is never as efficient as having a single regulator spit out the 5V in the first place.

 

[KJ6EAD]

Practically all of them use an MC34063A switching circuit so they're at least 83% efficient as long as the inductor is of a high enough value and low resistance. You can improve the performance of these cheap, off-the-shelf chargers by replacing underspecified components such as the inductor, schottky diode and capacitors or you can design your own using a better controller chip. If your current draw requirement can be held to a narrow range, you should be able to achieve efficiency >90%.

 

[AnalogKid]

The 34063 is the darling of the car charger universe and is in every one I've taken apart, one port, two ports, whatever. If you don't need the packaging, most car chargers open up by unscrewing the collar around the sprint-tip.

ak