Originally Posted by mrpeter105
I'm curious about using the box while the engine is running. Is it really necessary to add those 2 diodes? In other words do you think it'll toast the box if you used it without those diodes, with the engine running?
To paraphrase holl_ands
: Just because a piece of equipment has an input jack that is marked 12VDC, doesn't mean that it is a good idea to connect it to the 12V system of a vehicle.
The problem is the tolerance limits on the voltage. I have an 8" TV that has a regulated switchmode AC adapter that very closly regulates the 12V. I asked Audiovox what the tolerance on the 12volts was, but never got an answer. So, to be conservative, I decided to either use the AC adapter with an inverter, or make a battery pack that has a voltage regulator to duplicate the performance of the AC adapter.
I also asked the manufactuer of a CECB that needs 5VDC (not Zinwell) about the voltage tolerance limits if I run it DIRECTLY on batteries. The answer that I got was that I should use an inverter; not too helpful. The sales people in the US would have to ask an engineer overseas that question, which is not likely.
Even if the engineer was asked, he might not know because he had assumed that the box would always be used with the voltage regulated adapter.
One of the excellent links that you listed, talks about using a box on a lower voltage and it still behaves. But, what about using it on a higher voltage? How much is too much for a 12 volt box:---14 volts---15 volts---when will it fry? Which one of us is willing to keep increasing the voltage until our box goes up in smoke? The two diodes in series provide about a 0.6 volt drop for each, a total of 1.2 volts when the vehicle is running. The voltage in my car is about 12 volts when not running, and about 14.5 volts when recharging the battery after starting.
Last night I measured the input voltage and current of my Artec T3A Pro:
OFF: 12.04 volts @ 5.8 mA
ON: 11.96 volts @ 0.31 A
The current when off is lower than many other boxes. There still has to be a little current in order for the remote control to turn it ON. I measured the input voltage and current of my Zinwell ZAT-970A:
OFF: 5.08 volts @ 0.16 A
ON: 4.99 volts @ 0.69 A
Notice how much current it draws even when "OFF," almost 25 % of the ON current.