Fitting 12 VOLT BATTERY SPLIT CHARGING RELAY

[by'eck]

That would be fine if there weren't the downsides of using them - the bank damage, the noise, the difficulty in sorting the electrics (as demonstrated by big col), the cost and maintenance issues - and the ridicule from pompous non-BTers like me!

 

Says he with an Empiribus installation

[nicknorman]

Says he with an Empiribus installation

Yea but no but yea but Empirbus is COOOOL!

[bigcol]

Long ago boating in Poole no BT,gps, chart ploter,was Deca then?

Never dreamed of having BTs then. Went on courses re navigation Radio licence, yes still had a few toys

Next twin engine boats, easy to put anywhere, then able to buy boats with BTs, if there their,use them.

Very handy for tight mooring in marinas, but could berth a boat with out, but yes it's so easy with a BT.

Eight years break from boating.

 

Diagnosed with testicular and secondary cancer 2008/9, chemo,operations on going treatment, last year Prostrate out, bladder op etc still 2 operations to go,, Peripheral neuropathy the main problem Very unsteady! enjoy falling down a lot,and testorone level of a 80 year old,But game on!

Joined forum same time,a life line,giving us a goal.Now living on a boat, living our dream!

Wouldn't concider not having a bow thruster, it's a must, I don't move the boat much, One day being more confident and maybe won't push the silly button so much. But till then the BT gives me some confidence! need to make sure I can get close in to the bank.

 

A bow thruster is a luxury, but for some people it enables folks to get on the water.

I get frustrated, and want to do so much, unfornatley last time I went out it,was to the winding hole and back,And fuck it,I did bow thruster nearly all the way there and back,but boy did It felt great.

Any way it makes a nice noise lol, I do agree with going back to basics

Remember the time it was all chart work, then decca, then gps, chart plotters,

do you still need to have a charts on board by law?

 

Having friends on the Thames, when the hospitals out the way, We would love to join them

And If I Need to use the BT, I will, one day,maybe I go a day without,and yes the forum will hear about it.!!!

Some days the forum is all I need, pain,bed bla bla,bla bla,I be on the iiPad, and not a paper in sight.!!!

 

Enjoying life with my amazing strong wife, soon be proper boating,5 years been out just 7 times,!!

And as members may recall, one of those was 3 continues days of tests at MK hospital,so motored to MK marina to stay whilst being at the hospitalThere and back, rubbish around the prop, no weed hatch!!, that's a recent thing isn't it, years ago was unheard off

 

That's me having a prescription drugged induced rant lol

A lucky happy man,with a flare for electrics! with BOW THUSTER!

Honk your horn if you got one!

Edited February 11, 2014 by bigcol

[Paul's Nulife4-2]

THRUSTER USERS UNITE !.

 

As with most things, Each to there own.

Edited February 11, 2014 by Paul's Nulife4-2

[Phil Ambrose]

Nothing wrong with a bit of Thrusting.

Phil

[WotEver]

I suspect the size of cable would effectively limit the maximum current that could be drawn anyway even if the fusing wasn't right.

 

Only by glowing red.

 

What's a fuse? It's a thin bit of wire. It doesn't 'limit' current, it glows white hot and burns through when its maximum current is exceeded.

 

A length of 7mm cable with 300A going through it would drop a huge voltage across it, but the current flow would have it glowing like a bar fire.

 

Tony

[Paul C]

Long ago boating in Poole no BT,gps, chart ploter,was Deca then?

Never dreamed of having BTs then. Went on courses re navigation Radio licence, yes still had a few toys

Next twin engine boats, easy to put anywhere, then able to buy boats with BTs, if there their,use them.

Very handy for tight mooring in marinas, but could berth a boat with out, but yes it's so easy with a BT.

Eight years break from boating.

 

Diagnosed with testicular and secondary cancer 2008/9, chemo,operations on going treatment, last year Prostrate out, bladder op etc still 2 operations to go,, Peripheral neuropathy the main problem Very unsteady! enjoy falling down a lot,and testorone level of a 80 year old,But game on!

Joined forum same time,a life line,giving us a goal.Now living on a boat, living our dream!

Wouldn't concider not having a bow thruster, it's a must, I don't move the boat much, One day being more confident and maybe won't push the silly button so much. But till then the BT gives me some confidence! need to make sure I can get close in to the bank.

 

A bow thruster is a luxury, but for some people it enables folks to get on the water.

I get frustrated, and want to do so much, unfornatley last time I went out it,was to the winding hole and back,And fuck it,I did bow thruster nearly all the way there and back,but boy did It felt great.

Any way it makes a nice noise lol, I do agree with going back to basics

Remember the time it was all chart work, then decca, then gps, chart plotters,

do you still need to have a charts on board by law?

 

Having friends on the Thames, when the hospitals out the way, We would love to join them

And If I Need to use the BT, I will, one day,maybe I go a day without,and yes the forum will hear about it.!!!

Some days the forum is all I need, pain,bed bla bla,bla bla,I be on the iiPad, and not a paper in sight.!!!

 

Enjoying life with my amazing strong wife, soon be proper boating,5 years been out just 7 times,!!

And as members may recall, one of those was 3 continues days of tests at MK hospital,so motored to MK marina to stay whilst being at the hospitalThere and back, rubbish around the prop, no weed hatch!!, that's a recent thing isn't it, years ago was unheard off

 

That's me having a prescription drugged induced rant lol

A lucky happy man,with a flare for electrics! with BOW THUSTER!

Honk your horn if you got one!

 

The fact remains though, is that using a bow thruster 100% of the time can't be done with an electric one, because the bow thruster typically needs many hundreds of watts power, more so than any kind of cable can supply over that distance. If you really need a bow thruster which can be used for long periods of time, possibly a hydraulic one would do the job?

Also, the bow thruster will burn out, its not designed for continuous use. For example check out the specifications here:

 

http://www.vetus-shop.com/vetus-bow-thrusters-c-22_30.html?osCsid=fc91ff6a17181d786b6835ec4a319f51

 

Electric bow thrusters are typically rated for 4 mins/hour. Hydraulic bow thruster can be used for "virtually unlimited" amount of time, so long as the oil can be cooled.

[bigcol]

just want to clarify a couple of things

 

As far as I know, Ive never mentioned or expected 300 amps to go through a 7mm wire?

it was the charging cables only 7mm rated at 50 amps,

On 240v 30 amps max through 30 amp charger,

when under way max 40 amps through alternator.

 

I Have exaggerated, tongue in cheek, how I've used my Bow Thruster,

I understand 10 second blasts, but used it when departing berth,

clearing other moored boats,getting use to the steering over again

correcting a approach to bridge.

 

But on return to berth, I've noticed a change in tone, still working,

And when sitting down having a think, couldn't understand why this is the case

 

Through the powers of this forum

I now know I've installed inappropriate size charging 7MM 50 amp cables

The cables linking battery's, fuse and BT are the correct 400 amp cable

 

as forum members have advised, 70mm thick cables will be installed,

The battery's will also be checked as it maybe they are knackered.

 

Helming a boat, like any thing else,Its all about practice, and as yet haven't had much practice

but I will,

 

Col

 

edited fat fingers

Edited February 11, 2014 by bigcol

[Alan de Enfield]

Have a 'greenie'

 

We all know nothing to start with, as we go through life we learn everything we know, via parents, teachers, books, peer groups and even this forum.

 

The 'trick' is to learn, correctly apply, remember the new knowledge and 'pass it on' when the time comes.

[bottle]

 

As far as I know, Ive never mentioned or expected 300 amps to go through a 7mm wire?

 

True but you wanted to connect your domestics and bow thruster batteries together (split charge relay).

 

If the bow thruster batteries were unable to supply the load (flat or just down on charge) of the bow thruster it would have asked for power from the domestics that is when the 300 amps ++ would be trying to get down the 7mm.

[bigcol]

A update

 

Went to collect the cable, all changed,ordered wrong confusion over core dia

Cable size now 12.6 mm,

35 nominal overall diameter 12.6 mm! 300 amp

30 mtrs weighing 14 killo

 

Guess its going to be a job and a half

The 70m cable was 17 mm thick

 

Thanks all

[bigcol]

True but you wanted to connect your domestics and bow thruster batteries together (split charge relay).

 

If the bow thruster batteries were unable to supply the load (flat or just down on charge) of the bow thruster it would have asked for power from the domestics that is when the 300 amps ++ would be trying to get down the 7mm.

Thanks for that, I realise and accept,if I hadn't put the post on asking for fitting advice,

and forum members questioning me why and what, i was doing, I potentially would have had a problem.

 

I have to substantiate, I would have asked advice (which I did) before fitting!

 

Col

Edited February 11, 2014 by bigcol

[by'eck]

A update

 

Went to collect the cable, all changed,ordered wrong confusion over core dia

Cable size now 12.6 mm,

35 nominal overall diameter 12.6 mm! 300 amp

30 mtrs weighing 14 killo

 

Guess its going to be a job and a half

The 70m cable was 17 mm thick

 

Thanks all

 

Best to stick with cross sectional area of cable conductor in square millimetres (mm²) Colin. Yes I know its difficult to type, but this is the parameter that determines its safe current carrying capabilities, referred to by safety bodies and how its sold. Its often printed on the cable insulation in the case of the thicker battery cables.

 

Quoting cable diameters or thickness just makes for confusion.

[Paul's Nulife4-2]

As I said Col, I've used 17mm cross section (?? Square mm) cable for - My Bow Thruster that has got 32 ft Black,,32 ft Red.via a 450 amp mega fuse, My Stern thruster that has got 3ft Black,,3ft Red via a 450 amp mega fuse, My Mastervolt Dakar 2500w Inverter that has got 3 ft Black,,3 ft Red via a 300 amp mega fuse.

They are all ultimately fed from my one & only battery bank that are Basic no frills Lead acid Heavy Duty Cranking type ( 4 X 210a hr ) & has been like that and well used for 6 years & it's been a completely reliable trouble free installation for me & my livaboard CCing lifestyle anyway. As you can imagine my batteries take a hammering,but lasted 4 years, & got replaced 2 years ago,

That's my basic low tech simple installation,,Some members may disagree,but if it ain't broke,don't fix it !.

Edited February 11, 2014 by Paul's Nulife4-2

[Phil Ambrose]

As I said Col, I've used 17mm cross section (?? Square mm) cable for - My Bow Thruster that has got 32 ft Black,,32 ft Red.via a 450 amp mega fuse, My Stern thruster that has got 3ft Black,,3ft Red via a 450 amp mega fuse, My Mastervolt Dakar 2500w Inverter that has got 3 ft Black,,3 ft Red via a 300 amp mega fuse.

They are all ultimately fed from my one & only battery bank that are Basic no frills Lead acid Heavy Duty Cranking type ( 4 X 210a hr ) & has been like that and well used for 6 years & it's been a completely reliable trouble free installation for me & my livaboard CCing lifestyle anyway. As you can imagine my batteries take a hammering,but lasted 4 years, & got replaced 2 years ago,

That's my basic low tech simple installation,,Some members may disagree,but if it ain't broke,don't fix it !.

KISS

Phil

[Paul's Nulife4-2]

KISS

Phil

I didn't know you cared Phil,,

 

(Yep,I do know what it means,& yep I agree it's the best way)

[jonathanA]

As I said Col, I've used 17mm cross section (?? Square mm) cable for - My Bow Thruster that has got 32 ft Black,,32 ft Red.via a 450 amp mega fuse, My Stern thruster that has got 3ft Black,,3ft Red via a 450 amp mega fuse, My Mastervolt Dakar 2500w Inverter that has got 3 ft Black,,3 ft Red via a 300 amp mega fuse.

They are all ultimately fed from my one & only battery bank that are Basic no frills Lead acid Heavy Duty Cranking type ( 4 X 210a hr ) & has been like that and well used for 6 years & it's been a completely reliable trouble free installation for me & my livaboard CCing lifestyle anyway. As you can imagine my batteries take a hammering,but lasted 4 years, & got replaced 2 years ago,

That's my basic low tech simple installation,,Some members may disagree,but if it ain't broke,don't fix it !.

interesting assuming you really do mean 17mm² cable (which is an odd size 16mm would be more normal) then you have fused your circuit at nearly four times the 110A rating of 16mm cable.

 

Presumably you mean 17mm 'diameter' which would be more like 70mm²

 

either way it would appear your electical knowledge is very limited, which makes your post #28 all the more surprising and completely unjustifed.

 

I'm glad bigcol got there in the end

[WotEver]

... it would appear your electical knowledge is very limited...

 

This from the man who said "...the size of cable would effectively limit the maximum current that could be drawn..."

[nicknorman]

 

This from the man who said "...the size of cable would effectively limit the maximum current that could be drawn..."

 

But that's true isn't it? - as the current gets high, the wiring becomes incandescent, so its resistance increases. Anyway, the resulting fire is likely to limit the maximum current. Although perhaps I would change "effectively" to "ineffectively"!

[WotEver]

Ahh, good point, well made

 

ETA Perhaps an even more appropriate adjective would be 'spectactularly'

Edited February 12, 2014 by WotEver

[Paul's Nulife4-2]

interesting assuming you really do mean 17mm² cable (which is an odd size 16mm would be more normal) then you have fused your circuit at nearly four times the 110A rating of 16mm cable.

 

Presumably you mean 17mm 'diameter' which would be more like 70mm²

 

either way it would appear your electical knowledge is very limited, which makes your post #28 all the more surprising and completely unjustifed.

 

I'm glad bigcol got there in the end

Yep, I thought cross section was the same as Diameter !. Do you mean 16 mm squared, OR 16 mm Diameter cable would be more normal ?, its not very clear from what you put in your post above, and unlike you, i woudnt want to assume anything. I would simply ask for clarification. Yep, my Electrical Knowledge may be very limited, compared to yours, but have only ever said how I have done things on my boats & that it has worked for me, Yep, the fuse rating i have installed is correct as per accompanying hand books of devices (I've checked). Nope, I don't think shuddering over what can happen in a worst case sinaro is unjustified as I said in my post 28.

 

It's interesting that you feel the need to post, when you 'assume' something, Change data, Then proceed to base your resulting post on your own alterations & assumptions !. its like arguing with yourself, How Very odd. Which makes your post 92 all the more surprising & completely unjustified.

 

It's also interesting that you neglected to mention the (?? Square mm) bit i put in the very same post suggesting (or you could have assumed if you're good at that) I didn't know the square section measurement of the 17mm cross section cable (i think it was AWG 4/0 i used, but not sure now)

 

And just for clarity, can anyone tell me the amp/current rating of what i im now reliably informed is 70mm squared cable, Although I was rather hoping my 17mm cross section / Diameter cable AWG 4/0 (i think) would infact give a better squared mm maybe somwhere along the lines of 110 mm squared, rather than the 70 mm suggested by our friend as stated in his post above, But what do I know, i bow to his superior knowledge on the subject, (& don't forget I only need 10.5 volts at the end of the cable run)

Please,,please can someone put my mind at rest,so i can sleep tonight,and reasure me that after 6 years of use, my instalation isnt going to burst into flames due to me not being able to type a little 2 !.

 

just found a web site, Bulk wire .com...!.

Edited February 12, 2014 by Paul's Nulife4-2

[Paul's Nulife4-2]

I found a web site that had a little calculation thingy that you input your data, (I know there are several of these sites available,I just clicked on this one,as it also sells the cable.)

The Cross section/diameter mm square, is copper only,ie no insulation covering as I understand it.

So AWG 4/0 over 32ft with 400 amp draw (fused at 450amp) still gives over 11volts at the other end.I need a minimum of 10.5 so all seams ok..I think !.

[nicknorman]

I found a web site that had a little calculation thingy that you input your data, (I know there are several of these sites available,I just clicked on this one,as it also sells the cable.)

The Cross section/diameter mm square, is copper only,ie no insulation covering as I understand it.

So AWG 4/0 over 32ft with 400 amp draw (fused at 450amp) still gives over 11volts at the other end.I need a minimum of 10.5 so all seams ok..I think !.

Have you used 32' as the distance, or 32 + 32 = 64'? Dont forget that there are two wires (+ and -) each of which will drop voltage, so you need to use 64'.

[bottle]

 

So AWG 4/0 over 32ft with 400 amp draw (fused at 450amp) still gives over 11volts at the other end.I need a minimum of 10.5 so all seams ok..I think !.

 

but have you also taken in to consideration that the connections may also cause a volt drop, agreed probably not when new but time may cause them to become loose or corroded.

[Paul C]

Yep, I thought cross section was the same as Diameter !. Do you mean 16 mm squared, OR 16 mm Diameter cable would be more normal ?, its not very clear from what you put in your post above, and unlike you, i woudnt want to assume anything. I would simply ask for clarification. Yep, my Electrical Knowledge may be very limited, compared to yours, but have only ever said how I have done things on my boats & that it has worked for me, Yep, the fuse rating i have installed is correct as per accompanying hand books of devices (I've checked). Nope, I don't think shuddering over what can happen in a worst case sinaro is unjustified as I said in my post 28.

 

It's interesting that you feel the need to post, when you 'assume' something, Change data, Then proceed to base your resulting post on your own alterations & assumptions !. its like arguing with yourself, How Very odd. Which makes your post 92 all the more surprising & completely unjustified.

 

It's also interesting that you neglected to mention the (?? Square mm) bit i put in the very same post suggesting (or you could have assumed if you're good at that) I didn't know the square section measurement of the 17mm cross section cable (i think it was AWG 4/0 i used, but not sure now)

 

And just for clarity, can anyone tell me the amp/current rating of what i im now reliably informed is 70mm squared cable, Although I was rather hoping my 17mm cross section / Diameter cable AWG 4/0 (i think) would infact give a better squared mm maybe somwhere along the lines of 110 mm squared, rather than the 70 mm suggested by our friend as stated in his post above, But what do I know, i bow to his superior knowledge on the subject, (& don't forget I only need 10.5 volts at the end of the cable runy"

Please,,please can someone put my mind at rest,so i can sleep tonight,and reasure me that after 6 years of use, my instalation isnt going to burst into flames due to me not being able to type a little 2 !.

 

just found a web site, Bulk wire .com...!.

 

Its not unfortunately, such a simple thing as just saying "a wire of thickness x can carry current y". Yes, there's a physical relationship between cross sectional area, current and length of wire which gives a voltage drop end-to-end, but ask yourself what happens to that 'lost' voltage? It basically, heats up the cable. So you need to take into account where the cable is installed (is it in free air or buried in a cable loom, in a conduit or snuggled up with some flammable insulation?) and the length of time the current will be flowing along the wire.

 

For example, starter motor cables are often underrated for their job, so their cables heat up and up during use, but because a starter motor typically only needs to run for 10-15 sec at the most, its okay. (A bow thruster is vaguely similar in that in normal use, they aren't used continuously but in short bursts).

 

This heating up of the cable is the issue. And, when a cable gets hotter, its resistance increases, this leads to a snowball effect and its greater and greater resistance causes more and more voltage drop, leading to more and more heating etc. Thermal runaway. This is how fuses work. Its also why you can pass say 40A through a 30A fuse for 0.1 second and it won't blow. But 40A for an hour, and the fuse will have blown by then.

 

To properly specify cable to prevent this, you need to ensure there's no danger of thermal runaway, typically by using an appropriately rated fuse. Because fuses don't blow instantaneously, you need to be well below the point of thermal runaway in the cable, otherwise you'll potentially melt the insulation, then will have issues such as (lets assume the insulation is kept clear) melting a neighbouring cable's insulation too, causing a short circuit with another wire; or grounding to the hull and causing a large spark and current to flow, etc

 

A similar phenomenon to the thermal runaway issue occurs in every electrical component, because they have current flowing through them at some point, eg the windings in a motor or the components and tracks on a circuit board; or the contacts on a switch, etc etc. Notice in the previous link that Vetus's bow thruster isn't continuously rated - its only rated for 4 mins per hour running.