Jump to content

Re: what size cable and run new cable or use existing.


Fiat Ducato

Recommended Posts

Hi I've installed a 12v socket with twin USB outputs under the seats in the dining area and want to connect these to the vehicle battery so my passengers in the back can plug in their phones, laptops etc whilst we are travelling,

 

I also plan on installing a similar design 12v socket with twin USB ports and a digital volt meter to show battery level next to the existing control panel in the rear of my van. As we have no 12v sockets in the rear of the van. And plan to connect these to the leisure battery to use when we are parked up for 12v TV, charge phone and laptops etc.

 

My question is which is the best way to do it and what cable, I already have a pretty good idea but just wanted to double check with other users before going ahead. I was intending to use tri rated 4mm 41A rated cable with an inline fuse. Run the cable for the 12v sockets connected to vehicle battery directly to battery installing the inline fuse as close to the battery as possible.

 

Do the same for the leisure battery. Thought it best just to run a separate new cable straight to the leisure battery but this seems like a shame to run another long length of cable along side the existing main 12v leisure battery cables.

 

I wondered whether it is possible to just connect into the existing cable going to the main 12v/240v power distribution unit. And just add a inline fuse. And if I could do the same for the vehicle battery cable that runs to the main unit. And would this put extra burden on the existing cable.

 

http://www.ebay.co.uk/itm/152302988382_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

 

Link to comment
Share on other sites

Paul,

 

I'm not going to comment on wire sizes but would advise you wire all your new sockets from the leisure battery and not the vehicle battery. The reason being if any item is left plugged in it may flatten your starter battery, not exactly what you want to find after a few days camping. Also, your leisure battery will be directly connected to the starter battery when the engine is running so will make very little difference where you draw the power from.

 

Finally I personally would not recommend tapping into your existing main wiring, extra joints ultimately spell bad news for corrosion and power loss. Connect straight from your leisure battery with a suitable fuse as you have suggested.

 

Keith.

Link to comment
Share on other sites

Keithl - 2017-03-21 7:38 PM

 

Paul,

 

I'm not going to comment on wire sizes but would advise you wire all your new sockets from the leisure battery and not the vehicle battery. The reason being if any item is left plugged in it may flatten your starter battery, not exactly what you want to find after a few days camping. Also, your leisure battery will be directly connected to the starter battery when the engine is running so will make very little difference where you draw the power from.

 

Finally I personally would not recommend tapping into your existing main wiring, extra joints ultimately spell bad news for corrosion and power loss. Connect straight from your leisure battery with a suitable fuse as you have suggested.

 

Keith.

 

Oh yes that never crossed by mind, silly me. Yes you are spot on, that is definitely the way to go. Thank you very much for that Keith

Link to comment
Share on other sites

4mm Tri-rated cable is probably an overkill but if you have the space and you don't mind the extra cost, then play safe and go for 4mm. 2.5mm will be adequate in most cases unless where it is run could get a bit warm (>50degC) or if it will be in a big bundle with little air flow around it.

2.5mm tri-rated will take 30Amp for a single conductor in air but needs derating if bundled or at high ambient temperatures.

I would use multistranded something like 56/0.3mm (or 50x0.25 for 2.5mm) rather than the 7 stranded stuff you can get as these are much more flexible and easier to work with.

I would also crimp the connections rather than soldering them if they can be subjected to vibration.

 

Phil

Link to comment
Share on other sites

This probably doesn't apply in the OP's case but these threads are often read by others who then do the same to their vehicle, but may we advise caution when connecting devices directly to Habitation batteries?

 

The Sargent EC325 has a mains charger which can 'supercharge' the battery at up to 18volts. It isolates the battery from the rest of the van and then powers the van habitation electrics directly from a power supply while the battery is fed the 18v.

Obviously anything connected directly to the battery will then get a lot more than it bargained for.

Hence the importance of using the EC325/328 built in Solar regulator and not charging the battery direct.

 

More and more Power distribution/Chargers include features that mean you may cause issues if you either put power directly into a battery or draw it out.

For example the Schaudt EBL 220 is designed to handle all power into or out of the habitation Battery.

By doing so it can calculate how long the battery will last at any particular usage.

If you turn on a light the EBL knows it is supplying 0.25 amps at a known voltage it can calculate not only the size of the battery bank by the voltage drop, but how long the battery will last, dynamically updating the Display.

 

If a Solar regulator is connected to the battery that the Elektroblock Power unit knows nothing about the voltage may rise from the charge, when the Elektroblock is expecting the voltage to slowly fall due to the 0.25 amp draw. This will make a nonsense of the calculations and in some circumstances may cause the EBL to fault and shut down.

 

Similar results likely if power is drawn from the battery that the Elektroblock knows nothing about, as it will 'see' the voltage drop faster than expected, sometimes incorrectly recalculating the battery bank size, etc.

 

We would recommended, as per the Electronics manufacturers, that all power feeds are taken from the Sargent or whatever power unit, never from the battery. Unless you understand the implications.

 

Adopting this approach also means that when you turn off the Display/controller above the door, all relevant consumers are isolated.

Likewise warn an Alarm Installer, etc not to connect to the battery, they generally don't understand a Motorhomes electrical setup .

 

 

 

 

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...