Just an update on the pass through in question, as i got a volt meter 
First off, when i plugged in the pass through for charging (and using) even though i did not press the battery button i was registering 0.30V and when i pressed the battery button i got 3.75V. When it was fully charged and still plugged in and not pressing the button i got 0.08V. Fully charged unplugged and testing it out i got 4.19V
have to admit it was fun learning and testing it and the carts and atties out 
First off, when i plugged in the pass through for charging (and using) even though i did not press the battery button i was registering 0.30V and when i pressed the battery button i got 3.75V. When it was fully charged and still plugged in and not pressing the button i got 0.08V. Fully charged unplugged and testing it out i got 4.19V