http://elecraft.85.s1.nabble.com/K3-Why-fuse-the-negative-lead-from-a-battery-tp6233377p6233898.html
> Where will the current will flow if there is a fault? That is the
> question.
>
> There are two things involved here - wiring the radio negative directly
> to the battery or wiring it to the vehicle chassis. It does make a
> difference because of the way most vehicle batteries are tied on the
> negative terminal.
>
> If one wires both positive and negative directly to the battery, the
> negative should be fused to protect the RADIO in case of a fault between
> the battery and the engine block. It is not a safety issue.
>
> Note carefully that the battery negative is wired both to the engine
> block and to the chassis by direct wires from the battery negative. If
> the battery were tied only to the engine block and then the chassis were
> also tied to the engine block (as was pointed out in the case of the
> boat), the failure mode would not exist.
> And it is all because the radio is grounded to the chassis through the
> antenna connection in addition to the negative lead. If both these
> grounds go to the chassis instead of the battery negative, the problem
> solved by the fuse in the negative lead would not exist.
>
> If the radio negative is connected to the vehicle chassis, the problem
> does not exist and the negative lead should NOT be fused.
>
> 73,
> Don W3FPR
>
> On 4/2/2011 9:40 AM, David Ferrington, M0XDF wrote:
>> I'm not positive (forgive the pun), but I think ideas have changed on that in the UK and you again don't fuse the -ve lead, but I'll need to check.
>> 73 de M0XDF, K3 #174, P3 #108
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