Disconnecting batteries...... Live or neutral cable first??

[jenevers]

I'm thinking better to disconnect neutral cable before live. Am I right?

Edited February 23, 2016 by jenevers

[Guest]

I'm thinking better to disconnect neutral cable before live. Am I right?

 

Yes.

 

Ground first, ground last.

[Alan de Enfield]

Irrespective of any 'electrical' reasons I do negative before positive.

 

Reason :

If the negative is still connected and I loosen the positive and my spanner happens to touch something metal, I don't end up with sparks and a 'welded on' spanner

Edited February 23, 2016 by Alan de Enfield

[jenevers]

Yes.

 

Ground first, ground last.

Thanks thought so.

Irrespective of any 'electrical' reasons I do negative before positive.

 

Reason :

If the negative is still connected and I loosen the positive and my spanner happens to touch something metal, I don't end up with sparks and a 'welded on' spanner

Not nice. Edited February 23, 2016 by jenevers

[MtB]

I'm thinking better to disconnect neutral cable before live. Am I right?

 

 

Point of order M'lud,

 

Batteries being DC have positive and negative terminals, not live and neutral. L & N is the convention used with AC.

[Paul C]

If you're competent enough to not spark the spanner between terminal and boat's metalwork, then positive first is best. There is a technical reason relating to certain devices retaining a negative connection and its being substituted as a return path during disconnection and damaging them. But its a general rule. If you don't have any devices like this, then negative first is best.

[BruceinSanity]

If you're competent enough to not spark the spanner between terminal and boat's metalwork, then positive first is best. There is a technical reason relating to certain devices retaining a negative connection and its being substituted as a return path during disconnection and damaging them. But its a general rule. If you don't have any devices like this, then negative first is best.

ISTR this one of the things Gibbo used to get very excited about. Thing is, how do you know if you've got one of these separately earthed bits of kit. Is there a list? I've a feeling that inverters may figure here because of the AC neutral/earth bond.

[by'eck]

Switch off the battery isolator first which should be in the positive feed then disconnect battery negative followed by positive. Reverse to re-connect.

[Tony Brooks]

On a metal boat Turn all electrical items and circuits off and then disconnect the negative first (despite what Gibbo said). Having had King Dick branded across my hand there is no way I will risk shorting a spammer between positive and metal, especially with the access afforded on so many narrowboats with their batteries on the uxter plate. Ensuring all the equipment is turned off tends to protect against the problems Gibbo and Paul alluded to.

 

Now we no longer have exposed cell interlinks (apart form those with 2V cells) on no metal boats I would do whichever is easier.

[Keeping Up]

It's actually one of the safety things in favour of having the isolator in the negative lead. Once it has been switched off you could touch either positive or negative to the hull (not both at once of course) without getting any sparks.

[bizzard]

On a metal boat Turn all electrical items and circuits off and then disconnect the negative first (despite what Gibbo said). Having had King Dick branded across my hand there is no way I will risk shorting a spammer between positive and metal, especially with the access afforded on so many narrowboats with their batteries on the uxter plate. Ensuring all the equipment is turned off tends to protect against the problems Gibbo and Paul alluded to.

 

Now we no longer have exposed cell interlinks (apart form those with 2V cells) on no metal boats I would do whichever is easier.

Batteries with exposed interlinks are still made to order. I was at Shield batteries last week and there were three freshly built ones on the counter, no doubt for an older vehicle enthusiast or something.

[by'eck]

It's actually one of the safety things in favour of having the isolator in the negative lead. Once it has been switched off you could touch either positive or negative to the hull (not both at once of course) without getting any sparks.

 

Not a good idea due to possibly unforseen secondary earth paths through thin wires or sensitive components. As alluded to by PaulC in post #6.

[WotEver]

Seeing as the ONLY justification for disconnecting the neg first appears to be that if you're being ham-fisted you can short the spanner to the hull when disconnecting the pos first, and seeing as real damage can occur on many boats if the neg is disconnected first then I would advocate not being ham-fisted as the best approach.

 

And disconnect the Positive first.

 

Tony

[NMEA]

If you are doing any regular work on batteries then use an insulated spanner, I have Bahco dynamic drive ones that I have had many years, I usually disconnect the live first and then the return so they are doubly important.

Edited February 23, 2016 by NMEA

[bizzard]

Woolworths used to sell Melba chocolate tool sets. The box had many useful tools inside including hammer, pliers, saw and spanners of which one no doubt would have been ideal for seeing to the nuts on battery lugs, ''smartly though before you ate it'', being non conductive, well almost, In cool weather though in case they melt.

[Murflynn]

 

 

Point of order M'lud,

 

Batteries being DC have positive and negative terminals, not live and neutral. L & N is the convention used with AC.

we really need to start a separate thread for us pedants to discuss the differences and the correct terminology when referring to battery negative, boat's earth and 'neutral' (which in most folks' minds suggests earth). Of course in AC circuits, neutral is connected to earth by the electricity company, but your RCDs wouldn't behave very well if you connected blue to a big copper rod stuck in the garden lawn.

[cuthound]

If you are doing any regular work on batteries then use an insulated spanner, I have Bahco dynamic drive ones that I have had many years, I usually disconnect the live first and then the return so they are doubly important.

In the early days of my career I was holding the ladder for a colleague who was undoing a coonection stud on a bus-bar extension to connect a load bank. He was using a tubular box spanner which was insulated with an outer sheath of PVC.

 

Suddenly I got caught in a shower of sparks, which set my hair (I had plenty on those days) on fire. My colleague jumped off the ladder whilst I beat my smouldering hair out.

 

It transpires that the box spanner was just long enough to reach the stud on the other busbar, allowing the uninsulated inside of the insulated box spanner to short out the bus-bars when it touched both studs.

 

When working on batteries it is always best to use insulated tools, even if they are DIY insu!ated by wrapping them in insulating tape.

[Theo]

 

 

Point of order M'lud,

 

Batteries being DC have positive and negative terminals, not live and neutral. L & N is the convention used with AC.

 

Could you not say that, because the negative is grounded it is also neutral? In a positive earth boat (are there any?) the positive would be the neutral.

 

N

[Keeping Up]

A mate of mine in a telephone exchange, back in the days of the GPO, was cleaning the inside of the windows. He climbed the ladder, then placed his metal bucket down on a couple of handily-placed metal rails. The resultant bang, and the cloud of steam which ensued, was quite spectacular. He was "promoted" to cleaning the toilets next.

 

 

Not a good idea due to possibly unforseen secondary earth paths through thin wires or sensitive components. As alluded to by PaulC in post #6.

 

Except that in my book there should NEVER be any connection on the battery side of an isolator switch, be it positive or negative, unless it is itself suitably fused.

[cuthound]

Could you not say that, because the negative is grounded it is also neutral? In a positive earth boat (are there any?) the positive would be the neutral.

 

N

No, only AC supplies have a neutral. The correct terminology is live and neutral,came only the neutral is ever intentionally earthed.

 

DC supplies are always referred to as positive and negative, either of which may be rather (although in recent times it is normal to earth the negative).

[swift1894]

Point of order M'lud,

 

Batteries being DC have positive and negative terminals, not live and neutral. L & N is the convention used with AC.

I stand corrected.

I never stop learning.

[Theo]

No, only AC supplies have a neutral. The correct terminology is live and neutral,came only the neutral is ever intentionally earthed.

 

DC supplies are always referred to as positive and negative, either of which may be rather (although in recent times it is normal to earth the negative).

I have to bow to your greater knowledge.

 

I have seen the terms "line" and "neutral". Was "line" a typo?

I stand corrected.

I never stop learning.

 

In the educational jargon which was current when I left teaching you are a "life-long learner". As am I.

 

N

[WotEver]

I have seen the terms "line" and "neutral". Was "line" a typo?

Nope, line is correct.

 

I don't know the history of the terms (and can't be bothered to look it up) but I'd take a guess that 'live' has a derivation from the fact that it certainly feels live if you grab hold of it. The other side, neutral, is the centre of the star generator - it sits in the middle of the three phases and is therefore a neutral connection.

 

That last paragraph is simply conjecture as to the etymology, but "Line" is definitely correct in the UK.

 

Tony

 

Okay, I did a quick Google. Line is the current (sorry) term, live is the old term, now deprecated.

 

Tony

[MtB]

Okay, I did a quick Google. Line is the current (sorry) term, live is the old term, now deprecated.

 

Tony

 

 

I've noticed the term "phase" being used more and more instead of 'live and 'line'.

 

This strikes me as a backwards step as people unfamiliar with electrical terminology probably won't have a clue what it means, unlike 'live'.

[WotEver]

I've seen folk use phase too. As far as I'm aware it's not an 'official' word for line.