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Old 02-01-2016, 03:14 PM   #21
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Don't want to insult your intelligence...but having a stainless washer or lock washer between the terminal end and the contact in the switch is also a no no.

A lot of stainless I guess has a very low conductivity rating compared to direct contact or brass/tinned stuff.

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Old 02-01-2016, 03:17 PM   #22
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A poor post connection on the switch when your drawing high amps, that resistance will definitely heat it up a lot, enough to melt some plastics.
I have a new blue seas and an old switch made of bakelite which does not melt. That old switch is 45 years old, and still is fine. Done it's job from 1970. The old switch is twice the size of the new one.

A washer ought to be next to the nut. SS does have a higher resistance.

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Old 02-01-2016, 08:18 PM   #23
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I would suspect the cable crimp, the switch lug will pass heat easily.
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Old 02-01-2016, 09:40 PM   #24
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Blue seas
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Old 02-02-2016, 08:28 AM   #25
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low voltage high amperage

After talking to Magnum techs, it's likely the extremely low voltage condition of my battery bank and the high amperage needs of the inverter may have started the melt down of the switch. An interesting thought that I intuitively would not have thought of.
The magnum inverter stops inverting at 10 volts, the amperage draw of the inverter at that voltage would have been over 200 amps. this would be close to the switch's rated capacity. Other factors like resistance in the cable from the switch to the inverter and the switch heating up may have increased the load as well.
After checking my batteries with a hydrometer they check just ok. they are five years old and a couple have cells that are marginal, the other four are in good shape. So I guess I'll get by with these for a while.
As to Thermal protection between the battery banks and the switch's there was none. I'm adding a 400 amp in line fuse as soon as it gets delivered.
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Old 02-02-2016, 12:14 PM   #26
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A lot of stainless I guess has a very low conductivity rating compared to direct contact or brass/tinned stuff.


Ampacity is a portmanteau for ampere capacity defined by National Electrical Safety Codes, in some North American countries. Ampacity is defined as the maximum amount of electric current a conductor or device can carry before sustaining immediate or progressive deterioration.
Ampacity - Wikipedia, the free encyclopedia


Many boat hassles can be found with a digital thermometer .

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