Well ' the question was relevant but the answer was not good enough as while most cars are 12V and most Trucks are 24v it is good to specify what is the Amper required to get a smooth ignitions' as my 4x4 cars for examples with engines like 2800-3000 require 100 A while private - saloon car require only 55-65 Amper and in the above case the picture show that the Jump-Starter is very big and up to 300 Amper which means he was lucky and took a strong enough jump-starter ' else could get stuck again with no car ignition ;; so in general simple answer of Yes or No us not good enough in such cases and need to ensure supplies all required questioins and answers - good luck - leor Nevo = Jeepon-Naim By Nevo
To add to the confusion... Many engineers are clueless that a "12V" battery isn't 12.0 volts.
I have seen electronics designed for "12V" operation, with a maximum voltage specification of 12.5V. That is, 12.0 +/- 0.5V. Seriously. I surely hope their specs were wrong.
Take a normal American auto and measure the battery voltage when it's running, and it'll probably be something like 13.5 to 14.5V, with spikes going above that.
People who use lead-acid batteries in static operation (I've got one in my den) usually talk about 13.8V (not 12.6) as the nominal steady-state voltage when connected to the charger that is there just to maintain the battery in a charged state. Look up most amateur radio transceivers, and that's what they were designed for (e.g. 13.8V +/- 15%). So even calling it 12.6V is too low and would mean the battery might not be at full charge.
The inability to measure what you build, is one of the reasons for the popularity of SPICE. If you can't get a waveform on a scope, the only way to play with your circuit and see what it does, might be on your computer's screen.
I think much of the "efficiency" has more to do with IR drop through conductors than with energy transfer or conversion.
And anything powered from "the power supply from hell" is suspect! That socket is usually made to the lowest possible standard, very current limited, and certainly subject to all the noise possible. Any sensitive electronic devices wanting to use that thing (or anything directly tied to an automotive electrical system) better have extensive filtering and surge suppression on the input.
Look at all the tech bulletins from Motorola and the auto manufacturers regarding radio installation. That is one messy environment.
Actually not replying but commenting; the Comment function isn't working for me. I just wanted to point out that Linear Technology had an app note about designing electronics to connect to the car battery via the cigarette lighter. I don't have a link, but they referred to it as "the power supply from hell"! Two batteries in series may be experienced for a quicker charge, on the order of 100 V spikes, etc. make it very challenging to keep stuff connected to the cigarette lighter working properly.
Also, a few years ago there was some momentum to change to a higher voltage such as 42 V, but I've not heard anything lately. Something about greater efficiencies in alternators and starter motors. Maybe somebody else with greater knowledge can fill in here?
My own personal vehicle uses a 24 volt battery plant. Actually, it uses a pair of fairly standard 12 volt batteries in series. Most military vehicles (which is what I happen to drive on a regular basis) use 24 volt primary systems. It may have been selected for economy of production when copper for wire was in short supply - or maybe it was selected because many military vehicles are "lorry sized" machines.
Regardless of the initial reason, "we've always done it that way" prevails and now we much design to the standard. Lighting, fuses, breakers, relays, automotive HVAC, and any accessories - including radios - for military vehicle use are the 24 volt variety. And, yes, I have a couple of those radios, too!
With seemingly only heavy equipment and military vehicles using the 24 volt systems, getting the usual 12 volt accessories to operate has necessitated my creation of a subsystem using a switching supply to take 24 to 12 volts. And I use different and non-mating connectors so that never the twain shall meet.
But at least I know when I am looking for parts or accessories that I must look at the specs carefully to make sure it won't let all of the magic smoke out when I connect it to my Pinzgauer vehicle.
I am a 54 YO E.E. graduated in Brazil (I'm a native Brazilian) and I teach for 20 years now. I confess I feel like you were talking to one of my students... I face this daily-basis, kinda 'reality disconnection' since I started teaching, but lately it's getting worse. When dealing with computer science students, I suspect that their so needed 'level of abstraction' to understand what programs do without the need to understand how they do it leads to reasoning emptiness. I am terribly worried about the consequences they are going to face in the future... "Idiocracy" is, perhaps, the movie with the best worst scenario.