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Just wondering if there is any real-world practical difference between a power switch that disconnects both terminals of a battery vs a switch that just disconnects one terminal.

Are there any possible consequences for leaving the negative terminal of a battery always connected to earth, it terms of battery lifetime or self discharge?

Will a battery that's fully disconnected at both terminals maintain its charge for longer?

Which approach is taken in real world consumer devices?

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  • \$\begingroup\$ An important aspect CAN BE safety. If only one lead is disconnected there may be other paths which MIGHT be made, dependent very much on what the overall circuit looks like. \$\endgroup\$
    – Russell McMahon
    Jun 6, 2019 at 8:11

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If your single switch truly completely disconnects one battery terminal, then there is no difference in self-discharge of the battery.

However, this is one of these cases where there might be a difference between ideal circuit theory, and messy reality. In messy reality, there might be other conductors appear across your single switch that you hadn't intended. Condensation perhaps, a rat or spider making a nest, or a dropped spanner from a careless mechanic. Then, having both terminals disconnected might improve things.

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  • \$\begingroup\$ Messy reality is exactly what I was wondering about \$\endgroup\$ Jun 6, 2019 at 5:51
  • \$\begingroup\$ Only you know how messy your reality is going to get. Is there access for rats or spiders to get in? Will it be operated with condensing moisture? \$\endgroup\$
    – Neil_UK
    Jun 6, 2019 at 6:14

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