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Old 16 April 2012, 08:42   #1
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Isolator Switches -Good or Bad?

I always swore these were an essential item - mainly to ensure batteries don't get drained with something like fishfinder or radio left on but also to ensure no accidents with hydraulic Trim and Tilt.

However, given that the usual red keyed one used on boats can be a source of poor contact and frequently not difficult to knock off, I'm sort of having second thoughts. If the battery disconnnects while the engine is running it'll blow something in the charging circuit - most likely the Rectifier/Regulator or the Stator itself and I've seen it wipe both out. I've also just heard of the "Grand Slam" taking out the CDI unit as well for good measure. Stators (alternator in a car) are pretty high output these days to drive fuel injection etc, so if all that power has no battery to go to, it tends to short things.

BTW, the common or garden isolator switch is also IMHO a long way short of waterproof and if you open one you'll see why you never want to mount one in a "catch-water orientation"
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Old 16 April 2012, 08:49   #2
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Yeah, I;ve had to replace two so far in 2 boats..... Current boat has it fitted in a "hatch bucket" - if you go onto a laser sailing website you'll see it in full effect - basically take a standard 3" (or bogger) access hatch for dinghy bouyancy tanks etc.

While buying the hatch, also buy the "bucket" designed to to hold your mars bars etc. Glue / epoxy the bucket in place (the more exopensive ones will latch in). Mount the isolator on the bototm of the bucket, and site the hatch on a vertical surface. The hatches are designed to be watertight, and if vertical, any water that gets in will not puddle i nthe switch. When finished, put the (watertight) hatch cover on. So far so good......

Or buy a really expensive IP68 rated one!
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Old 16 April 2012, 10:20   #3
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Quote:
Originally Posted by 9D280 View Post
Yeah, I;ve had to replace two so far in 2 boats..... Current boat has it fitted in a "hatch bucket" - if you go onto a laser sailing website you'll see it in full effect - basically take a standard 3" (or bogger) access hatch for dinghy bouyancy tanks etc.

While buying the hatch, also buy the "bucket" designed to to hold your mars bars etc. Glue / epoxy the bucket in place (the more exopensive ones will latch in). Mount the isolator on the bototm of the bucket, and site the hatch on a vertical surface. The hatches are designed to be watertight, and if vertical, any water that gets in will not puddle i nthe switch. When finished, put the (watertight) hatch cover on. So far so good......

Or buy a really expensive IP68 rated one!
Fit a good quality unit like this Power Store and you cant go wrong.
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Old 16 April 2012, 11:07   #4
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Agreed, those 'red key' types are notorious for failure. But then, they are a pretty cheap and basic design so it's no wonder. I've always used BEP or BlueSea components and never had a problem. They may still not be waterproof, but at least they are properly designed and are meant to be vapour-proof to prevent explosion risk from accumulated fuel or battery gases.
I would never contemplate a set-up without an isolator switch. If nothing else it means there is no circuit for electrolysis.
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Old 16 April 2012, 11:20   #5
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I've had a Perko (non-keyed) selector switch for 6 years. Like this guy .

No problems aside from a possible cable to switch connection problem (loosen, clean, tighten, might have fixed, if it was a problem to begin with.)
It is in a fairly protected location (well, the back is protected; the switch side is exposed.)

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Old 19 April 2012, 08:10   #6
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Looks like we're all still keen on isolators and there are some good ideas there to improve on the standard red key version.
Those Perko ones metnioned by jyasaki are good as they protect against accidental switching off of the battery circuit - presumably with a big fat diode across the switch temrinals. I wonder......
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Old 19 April 2012, 11:20   #7
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There are some that have (I think it's called) a field disconnect circuit that protects the alternator and related bits should it be switched to off with the motor running. Mine doesn't have this.

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Old 19 April 2012, 11:58   #8
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Had the red key isolator, lasted about 2 weekends. it's rubbish if your out in the rough would often turn off my gps due to it losing connection for a split second.

Don't have a isolator now and I've never had a problem, just remember to turn everything off!
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Old 19 April 2012, 12:03   #9
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I have used a Lucas cut off switch with a fixed knob on my RIB for the last 2 years. I have mounted it facing downwards on my consol with the electrical parts inside the consol and the switch poking out of a downwards facing ledge. I have packed it with silicone grease and had no problems. It is not clearly visible and isolates everything but the radio and GPS's.
See link for picture:
LUCAS BATTERY ISOLATOR SWITCH - SSB106
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Old 19 April 2012, 12:11   #10
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I have one of these fitted which does the job.
Liverpool Power Boats
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