Isolator Switches -Good or Bad?

Daibheid · 16 April 2012, 12:42

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"

9D280 · 16 April 2012, 12:49

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!

Chris · 16 April 2012, 14:20

Quote:

Originally Posted by 9D280

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.

Erin · 16 April 2012, 15:07

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.

jyasaki · 16 April 2012, 15:20

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.)

jky

Daibheid · 19 April 2012, 12:10

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......

jyasaki · 19 April 2012, 15:20

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.

jky

Nathan k · 19 April 2012, 15:58

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!

Rokraider · 19 April 2012, 16:03

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

kerny · 19 April 2012, 16:11

I have one of these fitted which does the job.
Liverpool Power Boats

nugent · 19 April 2012, 16:27

DURITE MARINE BATTERY ISOLATOR SWITCH 300 AMP ROTARY OF/1/2/BOTH 0-605-09 | eBay

just purchased one of these my self

dougcrock · 20 April 2012, 08:04

Ive used these for many years no probs
Absolutely sure your battery is disconnected
Prior to that the isolators were crap

martini · 20 April 2012, 08:56

I don't think having no isolator at all is a good idea on a boat, for fire safety reasons.

For example, I once lost an outboard off the back of a boat at speed which left me with a bunch of cables and live wires inc battery cables and fuel hoses hanging in the breeze. The first thing I did was isolate the power at the battery switch, I would've hated to not be able to do that.

Oscarguitar · 20 April 2012, 10:32

Used the BEP unit for 3 years now with no problems. Had to red key ones on a Sunseeker for 7 years and changes them twice, and they were in a really dry well protected position compared to the rib!

PeterM · 20 April 2012, 11:19

Risky moment here ....

I've not got one on my Avon ( despite being 'professionally' rigged from new) . I had one on the old boat that was painful due to corrosion when it wasn't looked after before I got it.

My car doesn't have one and it doesn't burst into flames , but of course when you crash a car one of the first things the fire & rescue ( can I call them brigade any more ? ) service do it cut the battery wires under the bonnet ( assuming its located there).

I think they can cause more hassle than is really worth it, but of course in the situations like Martini describes well worth it.

I wonder how many fires start due to dodgy switches etc .....

I'll get my coat .....

Rokraider · 20 April 2012, 16:27

Quote:

Originally Posted by PeterM

Risky moment here ....

I've not got one on my Avon ( despite being 'professionally' rigged from new) . I had one on the old boat that was painful due to corrosion when it wasn't looked after before I got it.

My car doesn't have one and it doesn't burst into flames , but of course when you crash a car one of the first things the fire & rescue ( can I call them brigade any more ? ) service do it cut the battery wires under the bonnet ( assuming its located there).

I think they can cause more hassle than is really worth it, but of course in the situations like Martini describes well worth it.

I wonder how many fires start due to dodgy switches etc .....

I'll get my coat .....

Stating the obvious..
The problem with heavy electrical cables coming direct from the motor to the battery, means that in the event of any fire whether it is caused by petrol or oil, once the flames get to grips with electrical stuff and a short occurs, the cables themselves short and spread the problem along the length of the vessel to wherever the battery is situated. With the electrics isolated at least it should hopefully be limited to the source of the problem. With a car you can stop, get out and walk to a safe distance and there are likely to be other people about to give assistance.

Daibheid · 20 April 2012, 16:36

Quote:

Originally Posted by dougcrock

Ive used these for many years no probs
Absolutely sure your battery is disconnected
Prior to that the isolators were crap

I had these on a rib a few years back and quite liked them. For those who haven't seen them they use a quick lever action to clamp the wires on/off the battery terminals. So you can isolate but not so easily by accident and battery location can make a big difference to their practicality.
The only thing I didn't like about them is they didn't appear well protected against corrosion.

spartacus · 20 April 2012, 19:59

I fitted a Blue Sea M-series switch. Feels solid, seems waterproof, and worth every penny.