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post #2 of Old 09-26-2012
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Re: Grounding Batteries to Eng. Block

Well just based on that snippet alone I can't know exactly where they are going with that but there are a few things.

First, a simple example of ground sourcing is when you have negative voltage supplies. Negative voltages are common in all sorts of electronics for various reasons (especially perhaps in measurement devices like your shunt monitor). There is nothing special about them except that if you hooked up a multimeter you'd see a minus sign in front. If you wanted, and I've never heard of it done, you could wire your entire boat upside down with + connected to the engine etc, and - fused and switched to all your loads. In this case "ground" would be "sourcing".

Second you could have short term negative voltages due to electrical noise, static, or inductive devices like motors that can generate voltages especially when they turn on or off. In this case ground can be seen to sourcing current.

However, I think the bottom line that they're getting at is that ground is your reference - it doesn't matter what you do to it, it stays the same. In usual boat applications, 99% of the time this means that ground is sinking current.

Last edited by asdf38; 09-26-2012 at 11:10 PM.
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