I am a master auto technician, and I am seeking the opinion/advice of other master technicians who work in the field.
We've all come to know (and love, in my opinion) battery jump-boxes in the last 10 years or so. The days of jumper-cables are pretty much over.
What would it take to make a jump-box part of an automobile?
Let me explain... a jump box can easily be connected to a battery, and even left there if desired. A basic parallel circuit. It would then take a charge from the alternator right along with the regular car battery. Trouble is, if something were left on such as an interior light, the jump-box would be drained right along with the car's battery. Not the result I am looking for.
What device might be created that would allow a jump-box to be wired into a vehicle were it would be charged during vehicle operation, but not drained when the vehicle was turned off?
Example: vehicle drives from point A to point B. The battery and the jump-box are charged along the way. Owner shuts the car off but accidentally leaves the dome-light on, thus killing the battery.
How might it be possible for the jump-box to receive the alternator's charge but not be drained by the forgotten dome-light?
Some sort of magnetic switch (a solenoid, perhaps) comes to my mind, but how that configuration might be alludes me.
It has occured to me that constant charging of a battery (jump-box) might not be a good thing, but I have also observed that a vehicle can charge a battery for dozens of hours without said battery exploding. I have also seen jump-boxes be left on a plug-in charger for weeks (even a month) with no apparent negative effect.
The final product I seek: An jump-box stored in perhaps the trunk or elsewhere that is kept charged by the alternator during vehicle operation, but would not be drained if a device were accidentally left on after the engine was shut off. Should the vehicle have a dead battery, just take that jump-box out of the trunk and get going.
Is it possible? It must be. It has to just be a matter of power here, switch there, relay here, jump-box there...
Calling on the best of the business, I know you're out there!
Matt