2nd battery killing main

[XDrkmanX 10+ year member]

If my 2nd battery was at a voltage of lets say 5v and my main battery at 12v. When I had my vehicle turned off would my 2nd battery be drawing current from my main battery due to the difference in voltage?

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[king ranch 5,000+ posts]

yep

 

[hoss 5,000+ posts]

yes it would, unless there is a battery isolator system involved.

and the difference doesnt have to be that drastic. you can get parasitic drain over multiple batteries with only a few tenths of a volts difference.

 

[XDrkmanX 10+ year member]

Thanks