Unsavoury language and voltage drop
Submitted: Monday, Apr 25, 2011 at 13:35
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Member - Corrugate75
G'day,
Having spent the best part of
Easter Weekend installing a better upgraded 12v system through the camper trailer I also installed an isolation switch recommended by my local autoelect man.
Upon testing the system I seem to have 0.7volts drop across the isolation switch - 12.9v across the battery, then 125mm (5inches) of 6B&S cable to the isolation switch and only 12.2volts out the other side!
Needless to say there was some bad language used. I've done everything possible to avoid voltage drop and yet, induced a problem I think?!
Have I used the wrong isolation switch, or is this to be expected?
Thank you in advance for advice...
Cheers
Corrugate
Reply By: Member - John and Val - Monday, Apr 25, 2011 at 21:08
Monday, Apr 25, 2011 at 21:08
And the answer to Notso's key question? How much current was flowing through the switch when you took your measurements?
A better way to measure the voltage drop across the switch is to connect the meter directly across the switch, not measure two voltages to earth. The voltage directly across the switch will depend on the current going through it, hence Notso's question. With a few amps running through it and by measuring right at the switch then moving progressively outward you should be able to narrow it down to the switch itself, or the crimped (?) terminals, the connecting wire, battery terminals..... I'd
check for any voltage between the battery terminal post and the terminal that's clamped onto it - might look like a good tight metal to metal bond, but can corrode in there and cause losses. With a few amps flowing you shouldn't see more than a few millivolts drop anywhere. (Of course with no amps flowing you should see no voltage drops at all.)
Cheers
John | J and V
"Not everything that can be counted counts, and not everything that counts can be counted."
- Albert Einstein
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