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post #1 of 4 (permalink) Old 18-04-2013, 12:17 Thread Starter
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cable draw?

Hi

i have a question, if have a 2 cables connected to a 12v battery

one cable capable of carrying 10amps connected to cigar socket and one cable capable of carrying 200amps connected to inverter.

when i turn inverter on does and draw 186amps the current flow down both cables or just the 200amp one?

i know it may be a stupid question


but i just trying to understand.

karl
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post #2 of 4 (permalink) Old 18-04-2013, 12:46
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Electric current must flow round a "circuit". If the inverter is connected to the battery by one cable, then that is the cable the current flows through. If the cigar socket is totally independent, then there is no reason for current to flow through that.

Note: if you joined one wire to another wire, eg to run an extra rear light off the original rear light, then the original cable would have to carry extra current eg original lamp 5A, extra lamp 3A there would be 8A flowing in the original cable upto the point where you have placed the join. This is the way that some cables get overloaded.

[ It is far more likely to happen in your home, where you may use a 13A extension lead to power a 10A kettle, a 5A TV and a 1A reading lamp. You could have each appliance on by itself without any problem, or the TV + lamp (5+1 = 6) or the kettle + lamp (10 + 1 = 11) but if you put the kettle AND TV on (10 + 5 = 15) then you would be asking for trouble. Theoretically, the extension lead would have a 13A fuse, and this would "blow", cutting off the current. Theoretically, the extension lead wires could cope with more than 13A "just in case". Worst case scenario: the fuse passes 15A but the wire overheats, melts the insulation, catches on fire and the house burns down, killing you, your family and all your guests ]
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post #3 of 4 (permalink) Old 18-04-2013, 12:57
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Karl.

Not exactly an answer, which has already been given.

But - if your cables are attached directly to the battery ensure that each of the positive ones have a fuse at the battery that is capable of protecting the cables.

ie: 10A in one and 200A in 'tother, assuming that the cables are able to withstand those currents respectively.

There is no such thing as a stupid question.

As my (late departed) father used to remind me (annoyingly often):

The importance of any question lies in the consequences of getting the answer wrong!
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post #4 of 4 (permalink) Old 18-04-2013, 13:02
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Re: cable draw?

Quote:
Originally Posted by kbsserv
Hi

i have a question, if have a 2 cables connected to a 12v battery

one cable capable of carrying 10amps connected to cigar socket and one cable capable of carrying 200amps connected to inverter.

when i turn inverter on does and draw 186amps the current flow down both cables or just the 200amp one?

i know it may be a stupid question


but i just trying to understand.

karl
The short answer is "just the 200 amp one"'.

For current to flow there must be a circuit back to the battery negative through the load i.e the cigar lighter or the inverter.
If you switch the inverter on then current will flow in that circuit. If you push the cigar lighter in then current will flow in that circuit. The amount of current that flows in each circuit will be the the wattage divided by the voltage in each circuit.
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