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Electrical problem-need some advice


SoJo

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My neighbour is having electrical problems and some advice is required.His boat is fitted with a 3KW pure sine inverter connected to the batteries with cable rated 300amps through a battery master switch rated at 350amps continuous.To date the battery master switch has been changed twice due to the supply terminal melting.He runs his washing machine through the inverter which pulls 180amps at its peak,he is careful not to run any other electrical equipment to minimise inverter load.

Nobody seems to be able to tell him why the battery master switch keeps failing on the output side,any advice would be gratefully received.

The battery bank is 4 X 110amp leisure batteries in case that is relavent.

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My neighbour is having electrical problems and some advice is required.His boat is fitted with a 3KW pure sine inverter connected to the batteries with cable rated 300amps through a battery master switch rated at 350amps continuous.To date the battery master switch has been changed twice due to the supply terminal melting.He runs his washing machine through the inverter which pulls 180amps at its peak,he is careful not to run any other electrical equipment to minimise inverter load.

Nobody seems to be able to tell him why the battery master switch keeps failing on the output side,any advice would be gratefully received.

The battery bank is 4 X 110amp leisure batteries in case that is relavent.

 

 

Hi There

Have a look at these -

 

http://www.gscontrols.com/battery-isolators-22-c.asp

 

The standard switch will only handle 100A he may well need 250A to be safe

The conections must always be very tight.

 

Alex

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Yes, it sounds like your man might need to fit some decent battery switches instead of those cheapo ones often seen on boats.

 

Some more options:

 

http://www.power-store.com/?id=191

 

There are some smaller ones in the BEP range if those are too big.

 

http://www.power-store.com/?id=188

Edited by blackrose
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My neighbour is having electrical problems and some advice is required.His boat is fitted with a 3KW pure sine inverter connected to the batteries with cable rated 300amps through a battery master switch rated at 350amps continuous.To date the battery master switch has been changed twice due to the supply terminal melting.He runs his washing machine through the inverter which pulls 180amps at its peak,he is careful not to run any other electrical equipment to minimise inverter load.

Nobody seems to be able to tell him why the battery master switch keeps failing on the output side,any advice would be gratefully received.

The battery bank is 4 X 110amp leisure batteries in case that is relavent.

Is the cable 95mm2 or greater, a lot of people use welding cable which is only 35mm2 but marked as 300 amps, but this is only a two minute rating. You require continious 300amp rating for an Inverter.

david

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When it comes to switch ratings there seem to be two types of "Amps"

 

There are European/American "Amps"

 

Then then are Far Eastern "Amps".

 

The former seem to be about 5 times bigger than the latter :lol:

 

Also, the word "continuous" seems to have completely different meanings between the two areas.

 

This sounds facetious but the reality is that European/American switches rated at 250 Amps seem to handle 250 Amps all day long. Far Easter switches rated at 250 Amps melt at 75 Amps after a few hours.

 

The Blue Sea switches are good, the Lucas 219SA is a good one, and Durite also make a clone of that switch which isn't quite as good as the Lucas but its still better than lots of the other rubbish kicking around.

 

If your mate has the very common black plastic one with a red pull out key marketed by Hella (amongst many others) then they melt at about 30 Amps after a few hours.

 

The problem that the switches work initially, but after a while the contacts get dirty, they then introduce a tiny bit of resistance, this then causes a bit of heat to be generated in the switch, which causes a carbon build up, which introduces more resistance, which then generates more heat. The cycle continues until the switch generates so much heat it fails.

 

The good quality switches can be dismantled to clean the contacts. The cheap ones are rivetted together.

 

Gibbo

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My neighbour is having electrical problems and some advice is required.His boat is fitted with a 3KW pure sine inverter connected to the batteries with cable rated 300amps through a battery master switch rated at 350amps continuous.To date the battery master switch has been changed twice due to the supply terminal melting.He runs his washing machine through the inverter which pulls 180amps at its peak,he is careful not to run any other electrical equipment to minimise inverter load.

Nobody seems to be able to tell him why the battery master switch keeps failing on the output side,any advice would be gratefully received.

The battery bank is 4 X 110amp leisure batteries in case that is relavent.

 

If only one terminal is getting melted, I wouldn't rule out a poor/high resistance crimp connection between the cable end and ring terminal that connects to the isolator.

 

cheers,

Pete.

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One problem with battery isolators is that people often use them as switches rather than isolators! If you switch a load you will get momentary arching between the contacts proportionate to the current being drawn. This arcing causes pitting and oxidation of the contact surface which increases the resistance of the contact. As the resistance increases so does the heat generated leading to melting or even a fire. The stud type contacts are prone to this more than a wiping contact. As with battery contacts they should be clean and free of any grease, do not try to clean the contact with a squirt of WD40 as this will burn and further damage the contact.

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