Anything Worth Owning?
If you were hoping to find at least one adapter that did everything right, you'll need to keep looking. None of them offered input voltage surge protection, and many are clearly not designed for 24 V systems despite their ratings claiming otherwise, making it difficult to seriously recommend any of these for anything other than 12 V-based vehicles (and only if you are confident that you have a healthy battery, solid ground connections from the battery to chassis and engine block, along with equally solid connections from the battery positive to the alternator and fuse boxes). That’s a lot of ‘ifs’ just to be sure your vehicle’s electrical environment is safe enough to use one of these unprotected adapters without perpetually worrying about load dumps sending your expensive gadgets to the dumpster.
If we ignore concerns about vulnerability to automotive voltage surges, the runner-ups would be LDNIO for its exceptional efficiency, exceptionally low noise, and high current capability (assuming that my unit was from a bad run with the wrong resistor installed); Wagan for its unique design that meets the company's specifications, user-replaceable fuse, second-best efficiency, and proper current limiting closely matching its specification; and Supnova for its funky input voltmeter and decent efficiency at reasonably high output.
What is someone who is tempted to use the LDNIO adapter but worried about massive over-current to do if he cannot change that resistor? Perhaps there is a simple work-around that can be cobbled together from off-the-shelf parts.
One of these temporary off-the-shelf solutions could involve plugging the LDNIO into the Wagan’s pass-through socket and downgrading the Wagan’s user-replaceable fuse from 8 A to something that more closely matches their combined power draw. Between the LDNIO's 5 A output and Wagan's 3 A at 5.2 V and 90% average efficiency, we’re talking about 50 W of input power or just under 4 A for a typical 13 V running system voltage. Shove a fuse anywhere from 3 A to 5 A in there, depending on how much load you actually intend to put on the adapters and how much margin you want to set aside to avoid having the fuse spontaneously pop under normal load, and that will hopefully be enough to prevent USB cable and port melt-downs even with a LDNIO that has an 8000 A current limit. Had the LDNIO had a 4.28 MΩ resistor instead, I would have been able to make a certain memetic joke about how ridiculous its power level (or current limit in this case) is.
If I had to pick one of the units covered here to leave in my car’s glove box, my first pick would be the LDNIO for its compact size and great (albeit scary) performance.
In a semiconductor market flooded with a growing selection of fully integrated high-current, high-efficiency switching regulators featuring built-in synchronous rectifiers, I am both surprised and disappointed that only one unit from my random selection happened to use one such chip. Given the many substantial benefits and small complexity cost of integrating both high-side and low-side FETs inside a switching regulator, it is startling to see how prevalent old, low-efficiency designs still are. I wonder if the results would be any different if I repeated this little experiment a year or two from now. Considering how tenacious many cheap Chinese manufacturers are with re-skinning their old designs, my money would be on not much.
Did you already own or plan to buy a 12 V adapter for your device before reading this little round-up? How do you feel about the adapter you bought or planned to buy now? Glad that you bought or planned to buy an official adapter? Having second thoughts about the generic adapters you bought or planned to buy? Shocked at cut corners or did I simply confirm what you already suspected? Let me know in comments!