Background: I generally keep a strong spotlight with what I believe is a lead-aid battery (12V, like the car) connected in my cigar lighter to keep it charged. The gauge of the wire is NOT large, basically being similar to wire on most adaptors which plug into house current.

Dumb Question: By keeping that connected when I am starting the car, is the battery in the spotlight helping to supplement the power from the car battery? I realize, in any event, that the wire is one limiting factor, but is there some one-way aspect to the power connection which doesn't let it flow BACK to the car? I was wondering if this was anything like the ads I've seen for "keep your hands clean" batteries to assist starters which you can connect to the cigar lighter.

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Originally Posted by someconcerns

Background: I generally keep a strong spotlight with what I believe is a lead-aid battery (12V, like the car) connected in my cigar lighter to keep it charged. The gauge of the wire is NOT large, basically being similar to wire on most adaptors which plug into house current.

Dumb Question: By keeping that connected when I am starting the car, is the battery in the spotlight helping to supplement the power from the car battery? I realize, in any event, that the wire is one limiting factor, but is there some one-way aspect to the power connection which doesn't let it flow BACK to the car? I was wondering if this was anything like the ads I've seen for "keep your hands clean" batteries to assist starters which you can connect to the cigar lighter.

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You're dealing with very small amps here. Not even enough to raise any concern.
You could say the charging connection is a one way device, though.