12v cabelling advice please

[IainW]

so in an effort to be a bit kinder to our batteries when off shoreline, i'm looking to fit some cigarette lighter sockets throughout the boat for charging laptops and phones (and maybe powering LED TV). We've got the appropriate charger systems for our laptops and phones for use in our car, looking to use these in the boat. The reasoning being not using the inverter for items that can be easily charged via 12v is better.

 

i'm not sure of the size and type of 12v cabelling to run through the boat for this job. I'd be looking at a set of cigarette lighter sockets about 30ft from the battery bank and another about 45ft away. We're looking at charging two mobile phones and two laptops at once as a maximum. I'm not too sure how many amps this would be roughly and thus what size/type cabelling to go for.

 

We've got 440amp/hrs battery capacity, currently run LED lights and only really the 12v fridge sapping much in the way of 12v power. We have 470w of solar. Not sure if this info is helpful?

 

advice one how to do this would be much appreciated!

[by'eck]

I would consider using these superior DIN sockets and matching plugs with higher (12 amp) current rating.

 

3.5mm² or maybe 5mm² cabling for the longer run should be fine to connect to suitable fused feed.

 

[FadeToScarlet]

I've used 4mm^2 cable, run from the distribution panel to the socket and back, for the rear three sockets- about 35' away from the distribution board- and 6mm^2 for the socket at the front, 65' or so from the distribution board.

 

I wired each simply- just a pair of wires for each one from the fuse holder on the board, to the back of the socket, and then back to the board. No voltage drops seen yet ( must confirm that with the multi meter) and the one at the front gets enough power to operate a mini inverter.

[Ex- Member]

I would consider using these superior DIN sockets and matching plugs with higher (12 amp) current rating.

 

3.5mm² or maybe 5mm² cabling for the longer run should be fine to connect to suitable fused feed.

 

 

Yes we've used these also, a far superior 12v plug & Socket. The only thing is, some 12v gadgets have fused and volts adjustable standard cigar lighter male plugs, there is an adaptor you can use to revert back though.

[smileypete]

For a 45ft run I'd have thought 6mm² would be be OK to serve both sets of sockets unless both lappies are really power hungry 'lap toasters'. 4mm² would be OK for small chargers and stuff but cutting it fine if both lappies are charging.

 

6mm red and black cable can be had cheaply (relatively - that is) as 'tri-rated' cable via Ebay or from an electrical distributor:

 

http://www.ebay.co.uk/itm/5-METRES-TRI-RATED-6mm-RED-CABLE-84-0-30-6-0mm-5M-PANEL-SWITCH-WIRE-/251053346659

http://www.ebay.co.uk/itm/TRI-RATED-6mm-CABLE-BLACK-84-0-30-6-0mm-5-METRES-PANEL-SWITCH-WIRE-5M-/250959214693

 

As others say the cigar lighter sockets are only good for about 10A if that, so best have a 10A fuse or breaker next to each socket or group of sockets to protect them, then a 20A fuse or breaker back at the distribution panel to protect the 6mm² cable.

 

cheers, Pete.

~smtp~

Edited January 5, 2014 by smileypete

[IainW]

thanks a lot folks, i'm going with cigarette lighter sockets to stay with equipment i can charge in the car too.

 

smileypete - you seem to know your stuff, would it be possible to pick your brains about the install too?

[trackman]

You are spot on about avoiding running a large inverter for this purpose. Not only will you save power, we think car mobile chargers off 12V charge our phones quicker too.

[furnessvale]

You are spot on about avoiding running a large inverter for this purpose. Not only will you save power, we think car mobile chargers off 12V charge our phones quicker too.

Perhaps it is just my perception, but I feel that a phone charged on the boat using 12v doesn't seem to last quite as long as when charged at home at 240v.

 

This has seemed the case with several different boats and different phones.

 

George ex nb Alton retired

[smileypete]

thanks a lot folks, i'm going with cigarette lighter sockets to stay with equipment i can charge in the car too.

 

smileypete - you seem to know your stuff, would it be possible to pick your brains about the install too?

 

Why not just post away and pick everyone's brains, the more the merrier

 

cheers, Pete.

~smpt~

[FadeToScarlet]

Perhaps it is just my perception, but I feel that a phone charged on the boat using 12v doesn't seem to last quite as long as when charged at home at 240v.

 

This has seemed the case with several different boats and different phones.

 

George ex nb Alton retired

Yes, I think it's something to do with the current, USB from a 12v charger gives 300 mA, whereas you can get 500mA from 240v.

 

Or something like that, I'm sure someone will correct me.

[Keeping Up]

You are spot on about avoiding running a large inverter for this purpose. Not only will you save power, we think car mobile chargers off 12V charge our phones quicker too.

That's not always true. The losses in the cables at 12v can often be greater than the power wasted in the inverter, especially if you are running the inverter anyway. It depends on the situation, although I would agree that with just a USB charger the 12v route is probably more efficient.

[dor]

Make sure your connectors are fitted properly - this can be more important that the cable used.

 

There are good quality 10 amp cigar lighter sockets available but do try and avoid the cheap ones. Try running something at maximum rating (i.e. 10A) and check that nothing gets hot.

[WotEver]

You could buy a sheet of perspex like this and cut it down to fabricate some neat faceplates with the socket and associated fuse alongside each other.

 

Tony

Edited January 6, 2014 by WotEver

[NMEA]

Why guess or think "that's heavy enough" when the calculation to arrive at the circular mill is so simple and far more accurate than tables? It also puts you in control of exactly the volt drop you will get, that is assuming of course that all terminals and sockets are of good quality and properly executed.

The formulae assumes 12vDC and is: 10.75 (the constant for copper conductor) multiplied by the amps to be drawn multiplied by the cable length (battery + to battery - ) divided by the voltage loss acceptable in volts not percentage.

As an example 10.75 x 10 amps x 120 feet round trip divided by a volt drop of one would be 12900 circ mil or 6.5mm2 in order to get a 1 volt drop when drawing 10 amps. I have it on a spreadsheet in my tablet because I use it every day for transferring to estimates and job specs but it is such a simple formula that just keeping it in a notebook would do just as well.

Edited January 6, 2014 by NMEA

[ditchcrawler]

Was it Starcoaster who had laptop problems with fag lighter sockets?

[trackman]

That's not always true. The losses in the cables at 12v can often be greater than the power wasted in the inverter, especially if you are running the inverter anyway. It depends on the situation, although I would agree that with just a USB charger the 12v route is probably more efficient.

Of course it makes sense to charge off 240V if the inverter is on anyway for a larger load, but the OP and I were considering the situation where an inverter might be used only for the mobile or laptop.

Your comment about cable losses is true if the installation is poor but if the OP uses correctly sized cables, the object of the query made, that won't be an issue.

[Tunneltug]

Cables come in only a few sizes, 2, 4, 6 square mm for example. The previously mentioned formula is a good way of doing it but if it helps my electrician told me that for runs up to 5m simply divide the Max amps by three and that will give you an ides of the cross sectional area of your cable, I.e. 75 amp alternator will need 25mm cable.

 

For the ratings look on the back of the appliance where the power consumption in Watts should be stated. Divide the stated

Watts by the voltage and I think that will give you the amperage. Eg for an old lap top the consumption might be 120W divide this by 12.7 volts gives 9.45 amps divide this by three and round up gives you 4mm cross section cable.

[Ex- Member]

Was it Starcoaster who had laptop problems with fag lighter sockets?

 

When we first were thinking about electrics I was adamant that laptops tv etc would be run on 12v, there's even leads you can buy for charging with regulated voltage.

 

Anyway I then found out that for the majority of the time it's best to use 240v with supplied brick. We now do that, the reason being as it affects battery life using12v DC all the time. The Brick intelligently charges the batteries, (much like boat battery chargers I suppose) so the lap top batteries get a better regular charging regime which promotes battery life. What with the cost of lap top batteries and already suffering inverter losses due to a fridge, we now use 240 and charge when engine or solar is charging.

 

Not sure is Starcoasters' issue in a similar vain.

[IainW]

thanks for this folks, i like the idea of amps divided by 3 - simpler for my brain!!!

 

part of the reason we want to go the 12v route is when we turn the inverter on, it fires up a whole 240v system in the boat and no doubt we will have left something else plugged in or whatever. As we are heavy laptop and phone users, it can be a pain in the booty to check all the 240v sockets every time we want to charge something small. A simple 12v socket doesn't have this issue.

 

i don't suppose anyone has some pictures or links to pictures of the wiring system i.e. connectors, fuses etc going from the battery bank/fuse box to the sockets? I'm thinking DIY on this one but i haven't really done this before. It would be good to refer to something as i work my way through it!!!

[George94]

I have a 12V charger for my laptop and it seems to draw much more current than I expected. I now prefer to charge when the genny is running.

[jonathanA]

thanks for this folks, i like the idea of amps divided by 3 - simpler for my brain!!!

 

part of the reason we want to go the 12v route is when we turn the inverter on, it fires up a whole 240v system in the boat and no doubt we will have left something else plugged in or whatever. As we are heavy laptop and phone users, it can be a pain in the booty to check all the 240v sockets every time we want to charge something small. A simple 12v socket doesn't have this issue.

 

i don't suppose anyone has some pictures or links to pictures of the wiring system i.e. connectors, fuses etc going from the battery bank/fuse box to the sockets? I'm thinking DIY on this one but i haven't really done this before. It would be good to refer to something as i work my way through it!!!

thats a bit of a how long is a piece of string question.

 

slightly depends on how confident you are with 12v wiring systems if your not then ask around for some help/advice.

 

I would start by looking at suppliers of the 'bits' such as Vehicle wiring supplies http://www.vehicle-wiring-products.eu/VWP-onlinestore/home/homepage.php or auto electical supplies http://www.autoelectricsupplies.co.uk/ to see what sort bits are available that you might want to use.

 

Then as with any job a good coat of planning is needed basic things to think about as a start are:

 

• does the existing fuse board/distributuon panel have any spare capacity or can it be expanded/replaced with a bigger one.
• how will you physically run the wiring,
• does it need conduit or trunking ?
• how many wires or cables do you need to run to supply the number of sockets end points
• what are the end points and how will you physically fix them in your boat and where ?

this is by no means exhaustive or comprehensive but if you start by trying to draw out how you will get from the battery to the lap top charger that should throw up any more questions / concerns and ultimately you will get to a shopping list of what you need !

[smileypete]

For making decent connections with the yellow/blue/red crimps for spade connectors do invest in a 'ratchet crimper'.

 

Only about £10ish off Ebay and is a very worthwhile step up from using the cheap and nasty 'plier' type tool, here's an example of a ratchet crimper:

 

http://www.ebay.co.uk/itm/9-RATCHET-CRIMPER-PLIER-CRIMPING-TOOL-CABLE-WIRE-ELECTRICAL-TERMINALS-/111108606593

 

Also try to get decent quality terminals from trade type suppliers, red ones are best used for cable from 0.25 to 1.5mm, blues from more than 1.5 up to 2.5mm, yellows from more than 2.5mm up to 6mm.

 

The better spade/blade connectors have an extra 'anti vibration' sleeve that helps support the cable and make a tighter crimp:

 

http://www.ebay.co.uk/itm/20-x-Yellow-6-3mm-Female-Fully-Insulated-Spade-Connector-Push-On-Crimp-Terminal-/200929561111

http://www.ebay.co.uk/itm/20-x-Yellow-6-3mm-Piggy-Back-Spade-Electrical-Connector-Crimp-Terminal-/190849073198

http://www.ebay.co.uk/itm/25-pack-of-yellow-3mm-hook-blade-terminal-crimp-connectors-/190877248946

 

The last ones can be handy for getting 1 or even 2 wires neatly into a terminal block.

 

cheers, Pete.

~smpt~

Edited January 10, 2014 by smileypete

[NMEA]

I really would try to avoid pre insulated red, yellow & blue terminals, I spend quite a lot of time changing them during fault diagnosis, it is not possible to inspect the crimp quality either when made or during fault diagnosis, OK you can do a standard pull test but that's it. Open barrel uninsulated terminals are not only better and inspectable (is that a real word?)before putting into service but also cheaper even including the separate covers, the crimp form is what the Americans call "ass cheek" and is much more secure and the positioning of the insulation crimp for strain relief is also much better, The pre insulated types simply squash the terminal onto the conductor and insulation rather than a proper "roll formed" crimp. The crimp tools for these are now available in DIY quality and price wheres until fairly recently there were only pro tools available at a price that few amateurs were prepared to pay so worth thinking about for anybody doing much cabling work. The tool also allows the use of multi block connection terminals including water resistant AMP types.

[smileypete]

I really would try to avoid pre insulated red, yellow & blue terminals, I spend quite a lot of time changing them during fault diagnosis, it is not possible to inspect the crimp quality either when made or during fault diagnosis, OK you can do a standard pull test but that's it.

 

That's because they're poorly made!

 

Without using a half decent ratchet crimper and/or good quality terminals, which is why I posted the advice to the OP in the first place. I don't think there's anything wrong with the method itself.

 

Here's a few pics of blue insulated crimps done with a ratchet crimper and the sleeves then removed, the two on the lower right have the preferred 'anti vibration' rings that support the wire insulation better and make for a tighter crimp.

 

 

Note the way the crimp rolls in on itself in the centre 'ass cheek', the one on the lower right is pretty close to what you would get on a non insulated crimp.

 

Open barrel uninsulated terminals are not only better and inspectable (is that a real word?)before putting into service but also cheaper even including the separate covers, the crimp form is what the Americans call "ass cheek" and is much more secure and the positioning of the insulation crimp for strain relief is also much better, The pre insulated types simply squash the terminal onto the conductor and insulation rather than a proper "roll formed" crimp. The crimp tools for these are now available in DIY quality and price wheres until fairly recently there were only pro tools available at a price that few amateurs were prepared to pay so worth thinking about for anybody doing much cabling work. The tool also allows the use of multi block connection terminals including water resistant AMP types.

 

OK, so could you pick out a suitable non insulated crimp tool on Ebay that the OP or anyone interested can use?

 

In a professional capacity I'd be perfectly happy to use either method, but when when making my earlier post I'm also thinking of the very wide range of insulated crimp terminals readily available including blades, lipped blades, and pins, (even the decent quality ones are quite economical) which makes a ratcheting crimp tool quite versatile.

 

cheers, Pete.

~smpt~

Edited January 11, 2014 by smileypete

[NMEA]

My post was not about what is or is not a good crimp, simply about the fact that it is not possible to inspect whether or not the crimp is a good one or not, both before putting into service and during future inspection. I really wouldn't feel comfortable recommending unbranded stuff from eBay though some of the mid £20 stuff may or may not be suitable for light DIY if used carefully, never seen them so can't in all conscience condemn them either but Paladin make a sub £50 one that will give years of service to the amateur user.

Edited January 11, 2014 by NMEA