lw395
Well-Known Member
Sorry most of that is just plain wrong.
A classic 1B2 system can switch off and isolate either battery leaving everything running on the other.
If your starter is 1 and it goes bad, you can switch to 2 and isolate it.
Another one bites the dust
- Thread starter PaulRainbow
- Start date
Sorry most of that is just plain wrong.
A classic 1B2 system can switch off and isolate either battery leaving everything running on the other.
If your starter is 1 and it goes bad, you can switch to 2 and isolate it.
GHA
Well-Known Member
Are they?
This came up in another thread and ISTR there was no real evidence for this, other than the cheapo nasty ones.
lw395
Well-Known Member
In my experience, cheap battery isolators are far mroe unreliable, but then to be fair, most of the failures I've seen have been on RIBs.
Always carry a spanner to move both cables to one terminal.
Always carry a spanner to move both cables to one terminal.
Bru
Well-Known Member
Older ones are better quality
Nobody I know of, at least not to each individual battery. But I have split large banks into two with separate isolators (there were reasons)
I wouldn'ty panic anybody into changing them. If it ain't broke, don't fix it! But when they fail that's when I recommend changing over to seperate isolators
That rather depends on how the charging side is wired. It varies but often the charging to the batteries is NOT wired to the switched side of the 1-2-both switch (and strictly speaking it should not be because the switch is a battery selector not a battery isolator.
It is common to find that the shore power charger is wired directly to the batteries, ditto solar panels and sometimes even the output from the alternator (less common but I've seen it often enough)
So although I grant, and to correct what I said, you can indeed select which battery (bank) to run on, all too often you cannot isolate the other bank from some of the charging inputs (I'll add that this isn't of itself a fault of 1-2-both switches, it's how they are often installed)
Well I see regular failures and not always the cheapo nasty ones either.
I think it's telling that every marine sparky who owns a boat replaces the damn things asap.
Look, if you've got one and you're happy with it, happy days. Like I say, I would never suggest replacing one just because unless there were other good reasons for doing so. And I have and will install direct replacements for failures if that's what the customer wants.
[70521]
Well-Known Member
If it is such a bad system why are the coasts of the oceans not littered with burnt out hulls?
I've seen some pretty dodgy wiring in my time and suspect that this causes more problems than the switch.
Tranona
Well-Known Member
"Bad" does not mean that the boat burns. Thought both Paul and Bru have explained the "bad" features clearly so why do you exaggerate?
You are right. Many, particularly older boats have rubbish electrical systems, not necessarily because they were bad when new, but because they are modified by owners over the years as they add equipment to the boat, much of which never existed when the boat was built.
When I refitted my 1963 built boat in the early 1990s I wired it according to best practice at the time and when seeking advice from professionals, not one suggested using a 1,2,both switch. So this aversion to the device is not new. I agree it is perhaps not necessary to replace it if the system is otherwise sound and the owner has learned to use it properly. However is one is replacing the system or refining to remove faults or increase capacity for example, it makes sense to go down the separate circuits split charge route.
JumbleDuck
Well-Known Member
[citation needed]
lw395
Well-Known Member
When it started to go wrong is when people stopped using 1B2 switches as battery isolators.
Basically when additional forms of charging became prevalent.
It seems usual now that battery switches only isolate the loads.
There is often as Bru says, 'permanent' wiring for chargers.
Which seems to me less safe than being able to isolate the batteries.
If I'm faced with the smell of hot battery charger, I want to disconnect it from the mains and the batteries. The same with a solar regulator.
On some boats, it's not a ten second job to get access to the battery terminals, to actually isolate the battery.
Basically when additional forms of charging became prevalent.
It seems usual now that battery switches only isolate the loads.
There is often as Bru says, 'permanent' wiring for chargers.
Which seems to me less safe than being able to isolate the batteries.
If I'm faced with the smell of hot battery charger, I want to disconnect it from the mains and the batteries. The same with a solar regulator.
On some boats, it's not a ten second job to get access to the battery terminals, to actually isolate the battery.
pmagowan
Well-Known Member
They made it with a lot of blood and tears. We learn from their mistakes. Progress
GHA
Well-Known Member
More prone to failure than isolators?
Genuine question, LX refit underway & if there is evidence that 12B are prone to failure significantly more than one/off switches then they will get binned.
PaulRainbow
Well-Known Member
You'll like the switches i used then, all keys are removable when in the off position :encouragement:
lw395
Well-Known Member
I'm not sure it's valid to compare experience of 20-40 year old switches with modern.
Bru
Well-Known Member
I'm a marine sparky. Paul is a marine sparky. I could mention several others by name who hold the same opinion but I would feel obliged to ask their permission first.
In my experience, yes. Much, of course, depends on the quality of the components. At the cheap end of the market it's probably even stevens. At the costly "quality" end of the market, I've had problems with 1-2-both switches costing three figures. Rarely, in contrast, have I had issues with good quality individual isolators.
GHA
Well-Known Member
Indeed - the modern osilator switches down the chandlery certainly look a bit flimsy compared to the big tracks of copper inside the vetus 12b I just whipped the back off, no idea what's inside the isolators though.
Seems more opinion than data on here regarding reliability so maybe it's not possible to know if they are nasty unreliable devices prone to failure.
PaulRainbow
Well-Known Member
What's complex about turning a switch on or off ? Arrive at boat, turn domestics on. Time for the engine, turn it on. Time to lock up and go home, turn switches off. Complex ?
Circuits consist of some cabling, little more than with a 12B, with the addition of a £40 VSR. If the VSR fails the engine battery still get charged by default and you can charge the domestics by temporarily using the "Emergency" switch.
The whole system is visible in pic 2, which also includes the shunt for the battery monitor, a 4 way blade fuse holder (which replaced some inline fuses fitted behind screwed in panels) and the midi fuses for the domestic and charging circuits. Even with the extra bits in there, it doesn't look complex to me.
Simple, failsafe, almost foolproof.
Last edited:
pvb
Well-Known Member
I hate 1-2-Both switches. Not because they are necessarily unreliable, but simply because they introduce an element of risk that the switch will be set wrongly and result in a flat engine battery. With a properly designed system with simple on/off switches, there's no risk of getting it wrong, it's utterly foolproof. Now there are lots of people who say they know how to use a 1-2-Both switch properly, and I'm sure they do, until they or a well-meaning crew member forgets and sets it wrongly. The number of RNLI "rescues" of boats which can't start the engine would reduce dramatically if everyone changed to a foolproof system.
PaulRainbow
Well-Known Member
That's silly, what i fitted is nothing like a 12B switch and requires no manual intervention, other than turning the switches on when you arrive and off when you leave.
PaulRainbow
Well-Known Member
Why the change ?
That's unfounded and an unnecessary comment.
I don't think i've ever removed a 12B because i panicked the owner. I do much more than removing 12B switches, that's usually done because other changes or upgrades are being done. In this particular instance my remit was to design and install a complete new battery/charging system, add an extra battery, check everything on the boat worked and sort the wiring out in general. I had a free hand to fit whatever battery and charging system i felt best suited to the boat and it's intended use.
The system i chose would not necessarily suit all boats and all intended patterns of use, it dos fit here though and would equally fit most small/medium cruisers used by typical leisure sailors. I could have fitted a 12B switch and left the VSR out, which would have saved the owner about £60 in total and would have not made any difference to my earnings. But i am genuinely interested in what i do and will always fit what i think is the best system for the job in hand. It's certainly not all about money, for me.
PaulRainbow
Well-Known Member
I clearly don't have a database of international failures, but my experience is the same as Brus, i've seen more 12B switches fail. There are more contacts in a 12B switch, so technically more to go wrong. Plus, they are often switched under load.
Failure rates aside, on the typical cruiser with the setup in my OP, the 12B switch is a single point of failure. If it breaks, no power anywhere. With separate switches, if, say, the engine isolator failed you just turn the "Emergency" switch on and you can start the engine, handy if you need it in a hurry.
It's best to try and think of everything that could possibly go wrong and design a system that prevents as possible, whilst building in as many failsafes and backups as possible. We do it in many areas of sailing, we passage plan and plan alternate destinations, ports of refuse etc. We fit plotters, laptops and tablets, put nav' app's on our phones, carry handheld GPS and VHS and still carry paper charts. I use that same thought process when i'm working.
GHA
Well-Known Member
What's the mode of failure please?