12 volt sockets - some require ignition

Hello.

We own two veihicles. On one (the family van), the 12 volt sockets work even when the ignition is off. On the other (my truck) The keys have to be in the ignition and turned to expect power at the 12 volt sockets.

On fishing trips in my truck, I like to attach devices like a 12 volt battery jumper box and NiMH battery chargers. With this design, I know that my battery won't get drained or that there won't be short and a fire when I step out of the car overnight. In the van, I have to be real careful, as these devices will continue to drain the battery until nothing is left.

Any logic as to why auto makers design these one way versus another? Any 12 volt devices that stops draining when source is below a certain level? Any way to (simply/inexpensively) convert the van?

Finally, can somebody give me a simple primer on 12 volt current regarding the following test:

What happens if I attatch a very tiny (very low amperage) 12 volt bulb directly in parallel to my car's 12 volt battery. Will it blow up? shine really bright and soon burn out? or work just fine, lighting as bright as it can? How does the wiring in a car regulate the amount of light that this bulb might produce without costing the battery with resistance - say for example that this was a bulb in my dash for instance?

Many thanks for any help or information.

Reply to
jason
Loading thread data ...

Incorporate a SPST relay where the coil is energized by something that is switched with the ignition, like the radio. Wire the relay contacts in series with the accessory outlet. If your not familiar with electronics, suggest you have someone who does do the work.

The bulb will operate just like any other light in your car, lasting probably many hundreds, if not thousands, of hours.

Each circuit presents its own resistance across the terminals of the battery. Multiple lamps in series will reduce the overall current draw from the battery, and the resulting light output of the lamps will be diminished.

Reply to
Mike Behnke

You forgot the fact that some vehicles have both types of 12V socket- switched and un-switched. Switched ones are more "idiot proof," but un-switched ones are very important for things like battery powered coolers and so forth... unless you like food poisoning :-)

Recreational vehicle dealers have battery isolators that can be added to your car's electrical system, and allow you to add multiple deep-cycle batteries that will automatically be charged while the engine is running, but will not discharge the vehicle's starting battery when the engine isn't running.

As for the bulb question, the wiring doesn't regulate anything. How bright the bulb burns when connected to a 12 volt source is entirely a function of the BULB. If you connect a headlamp directly to the battery, it will burn as brightly as a headlamp. If you connect a dashboard lamp the same way, it won't burn like a headlamp but will burn like a dashboard lamp. On the other hand, if you connect a home light bulb to the battery, it won't burn at all (or VERY dimly) because it needs about

120 volts to reach its rated brightness. And finally if you connect bulb from a 2 D-cell flashlight (3 volts) to your car battery, it will burn out immediately.

snipped-for-privacy@cyberp> Hello.

Reply to
Steve

Sears I believe sells a battery that AUTOMATICALLY cuts off with X amount of power left so you are NOT stranded.

Sounds like JUST WHAT YOU ARE LOOKING FOR.

Never read any comments on whether it works well or not.

Reply to
Conase

I have a flashlight which charges from the lighter socket so it's always ready to use. It claims it won't drain the battery even in cars where the socket is powered all the time. I rewired my socket to be always on so that the flashlight would always be charged.

Cheap way to convert is just find any "accessory" power cable that's switched, such as for the stereo, and hook the socket onto it. Downside is it might not be fused at enough current if your load is too high. Could use a relay to solve that like somebody else suggested.

Reply to
nottoooily

Similar to this? Quote, 'PriorityStart is an automatic computerized on/off "switching" system protecting battery voltage and starting power. If battery voltage drains below 11.9 volts when engine is off, it automatically disconnects the load. The battery voltage immediately recovers. TO START: just step on brake pedal, starting power is automatically reconnected. Designed to handle 1000 "starting amps". PriorityStart will not disconnect the battery when the engine is running, even though the battery voltage level drops below the factory-set safe threshold. Circuits within this product recognize an "engine running" condition by sensing electrical "noise" (30 millivolts) created by fuel injectors, fuel pump, fan motors, etc., and will not disconnect the vehicle battery. If a vehicle alternator or alternator belt fails, the "engine running" circuitry recognizes the condition and prevents disconnection at the 11.9-volt threshold, allowing the vehicle to continue on the reserve capacity of the battery. In such a situation you are entirely dependent on the reserve capacity of the battery.`

formatting link

Reply to
Indian Summer

Note that at 11.77vdc most modern TCU, ABS, etc will not operate and may cause harm to a car or to humans. Wouldn't we be better off without the electrical noise sensing circuit...

Reply to
Indian Summer

Depends upon what part of town you're in when your alternator belt decides to commit suicide. Having your car quit at the wrong moment could cost the lives of you and your family. Somehow the life of the battery becomes pale in comparison.

JazzMan

Reply to
JazzMan

It's been my experience that vehicles will continue to run below

11v.. I've even seen idling with under 10 volts. Think about what battery voltage is while cranking.. usually below 11.7 volts.

regards,

Jim

Reply to
Jim

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.