Fiat Ducato Posted November 13, 2017 Share Posted November 13, 2017 Evening All Just a quick question, I own a 1997 Fiat Ducato 1.9TD Motorhome coachbuilt by AutoRoller. Now I have made some changes to the original setup. Mainly regarding the leisure battery, obviously when this vehicle was made they fitted the leisure battery right at the front in the engine bay in a tray attached to the front cross member. After plenty of reading and through exploration, discovered that this location wasn't ideal as gets covered in water and mud, dust etc. And is also open to the winter elements e.g frost, ice, drop in temperature. So I relocated it to under my dining seats on the other side of the water boiler, mounted it properly with brackets etc and vented it correctly. Now recently while doing some maintenance work underneath my van I discovered that the main cable (Blue) which is from 12v Vehicle battery to the unit, runs underneath in plastic conduit, a section was damaged and after further investigation discovered that the wire was in fact damaged, right through the sleeving and half way through the copper strands. Repaired it, but looking at the route of this Blue 12v + cable, it is connected directly to the vehicle battery via a large mega fuse. And then this is connected to my main 12v power/charging unit to the vehicle 12+ connector. My question is - Is this the correct way of doing this? this as not been altered or modified as the conduit is held in place my conduit clips that screw into anchors along the route. I was under the impression that the 12v + feed comes from the Alternator D+ not from the vehicle battery. Shall I leave it as it is, or re route it to the Alternator D+ output instead of my vehicle battery, that way there will only be power available when the engine is switched on. Appreciate any advice, comments etc Paul Link to comment Share on other sites More sharing options...
aandncaravan Posted November 13, 2017 Share Posted November 13, 2017 Even though the power for charging, etc, is provided by the Alternator B+ (not D+), the physical wiring is usually connected to the Starter battery as this is obviously connected to the Alternator. We don't know any installer who takes a feed directly from the Alternator, although we think they should now that Alternators are 180amps. Wired direct from the Alternator may reduce some common issues with poor charging, but the Alternator is often hard to access, hence the Starter Battery option usually being taken. If you do wire from the Alternator, also worth taking an Earth point from the Alternator body as well to the habitation battery. Note that the Alternator D+ is not a 'Charging' output/cable. It is only a 2amp 'signal' cable to tell the vehicle to extinguish the 'Battery Warning light' and tell the main Habitation area power controller unit that the Alternator is spinning so it can connect the batteries together. Also connects in the Fridge 12v, lowers down the Sat system Dish, etc. The main Alternator charge output is usually via a fat cable from the B+ Alternator output. D+ is often a thin Yellow cable. You will spot the difference on the back of the Alternator. See the last few section of this webpage for hints and tips on improving charging without the need for a B2B : http://www.aandncaravanservices.co.uk/add-a-second-battery.php Link to comment Share on other sites More sharing options...
Fiat Ducato Posted November 19, 2017 Author Share Posted November 19, 2017 Hi thanks for the reply aandncaravan, appreciate sharing all your knowledge and wisdom. I decided to leave the wiring set up as it is, connected to my vehicle battery. There are 2 smaller black wires that are connected to the alternator socket on the connector to my main Nordeletronnica 12v/240v power and distribution unit. I had another question for you regarding the 12v negative cable. There is only one connected to my main unit, even though there are 2 spaces on the main power connector for 2 Negatives. There is a main 12v (Blue Cable) from the the vehicle + positive battery. A (Red Cable) to habitation + and (Black Cable) from the habitation battery - to the chassis then to the main power connector on the unit - supplying all the negative terminals. Should there not be another negative feed from the vehicle battery via the chassis to the main power unit? or is one negative - feed substantial? Appreciate any help or advice regarding this. Many thanks Paul Link to comment Share on other sites More sharing options...
aandncaravan Posted November 20, 2017 Share Posted November 20, 2017 Because most Motorhome builders connect the Starter Battery and Habitation battery together, they think one decent fat cable might be sufficient. However, large cables tend to need large connectors when many Power Controllers/Fuseboards only have 20amp Spades. Therefore having two paths of reasonable sized cable going through 2 connectors will, effectively, double the capability of the Fuseboard current handling over a single 20a connector. Having two cables, one from each battery also reduces the effect of poor connectivity that one fat cable might suffer. In reality many Motorhome cables of this type are undersized leading to significant voltage drop, but others are a big step up in quality. Hymer for example use two each of Power and Negative cables of a decent size into 50amp connectors to reduce voltage drop and handle the current safely, even in small vehicles. Because of this low voltage drop and high efficiency, a B2B is a waste of money on these vehicles as the units already charge the batteries at the maximum possible commensurate with long life. The wild claims of upto 3 times faster charging of some B2B's are based on assumptions of both poor connections and undersized cable, etc. demonstrating the importance of the cabling. A good example of a burnt unit where single 20a spades are used is the photo below. To be fair the owner added a second Habitation battery when the box isn't designed to support one, but shows you the different approach by Motorhome builder/Electronics manufacturers. You will see the Habitation (White) battery Spade is burnt from being asked to supply too much and the Starter battery (Red) terminal just starting to go from passing too much current to 12v Fridge and Alternator charging. One negative cable is probably sufficient with a single 100Ah Habitation battery where all the connections are perfect, but adding a second battery or additional electrical loads might risk overloading? Link to comment Share on other sites More sharing options...
Fiat Ducato Posted November 20, 2017 Author Share Posted November 20, 2017 aandncaravan - 2017-11-20 9:01 AM Because most Motorhome builders connect the Starter Battery and Habitation battery together, they think one decent fat cable might be sufficient. However, large cables tend to need large connectors when many Power Controllers/Fuseboards only have 20amp Spades. Therefore having two paths of reasonable sized cable going through 2 connectors will, effectively, double the capability of the Fuseboard current handling over a single 20a connector. Having two cables, one from each battery also reduces the effect of poor connectivity that one fat cable might suffer. In reality many Motorhome cables of this type are undersized leading to significant voltage drop, but others are a big step up in quality. Hymer for example use two each of Power and Negative cables of a decent size into 50amp connectors to reduce voltage drop and handle the current safely, even in small vehicles. Because of this low voltage drop and high efficiency, a B2B is a waste of money on these vehicles as the units already charge the batteries at the maximum possible commensurate with long life. The wild claims of upto 3 times faster charging of some B2B's are based on assumptions of both poor connections and undersized cable, etc. demonstrating the importance of the cabling. A good example of a burnt unit where single 20a spades are used is the photo below. To be fair the owner added a second Habitation battery when the box isn't designed to support one, but shows you the different approach by Motorhome builder/Electronics manufacturers. You will see the Habitation (White) battery Spade is burnt from being asked to supply too much and the Starter battery (Red) terminal just starting to go from passing too much current to 12v Fridge and Alternator charging. One negative cable is probably sufficient with a single 100Ah Habitation battery where all the connections are perfect, but adding a second battery or additional electrical loads might risk overloading? Hi thank you once again, that was my line of thinking too. And to be honest the one Negative cable is not that big, looks like 4 or 6mm2 tri rated cable. Think I will run another length alongside the 12v = Cable to vehicle negative or chassis (although obviously the vehicle negative battery stump is connected to the chassis. What size cable would you recommend, cant be too big as it won't fit into the negative connector mount securely. Link to comment Share on other sites More sharing options...
aandncaravan Posted November 20, 2017 Share Posted November 20, 2017 Use whatever cable works with the Spade terminals you are using. Because you already have a cable in place, just copying the existing size will effectively get you more than double the rating you have now in terms of the connectors. Remember it is the connectors that are the weak link, but a second cable will also reduce voltage drop. Link to comment Share on other sites More sharing options...
Fiat Ducato Posted November 20, 2017 Author Share Posted November 20, 2017 aandncaravan - 2017-11-20 1:22 PM Use whatever cable works with the Spade terminals you are using. Because you already have a cable in place, just copying the existing size will effectively get you more than double the rating you have now in terms of the connectors. Remember it is the connectors that are the weak link, but a second cable will also reduce voltage drop. Thank you once again. You are truly a valued member of this forum, I know you have been getting some negative views regarding your other post about driving with fridge on gas. Those people like you said obviously don't repair damaged pcb boards from all different manufacturers every day for a living. I'm afraid my Nordelettronica NE13GT_CI power supply unit, as basically had it, spent loads of money and time on it, repairing broken tracks on the pcb board, replacing burnt out connectors. Finally got everything working as it should apart from the charger on 240v, every time I connect it, it trips the 10Amp fuse on the unit. Fed up with it now, want to replace it, but finding the right one for my old van and not spending a fortune is proving hard. I own a 1997 Fiat Ducato Auto Roller. Which in the past 2 years have spent well over £2000 on it lol. Shame your business is not closer to where I live, but I'm afraid I am right down in Dover. Regards Paul Link to comment Share on other sites More sharing options...
Alanb Posted November 20, 2017 Share Posted November 20, 2017 Fiat Ducato - 2017-11-20 1:04 PM Hi thank you once again, that was my line of thinking too. And to be honest the one Negative cable is not that big, looks like 4 or 6mm2 tri rated cable. Think I will run another length alongside the 12v = Cable to vehicle negative or chassis (although obviously the vehicle negative battery stump is connected to the chassis. What size cable would you recommend, cant be too big as it won't fit into the negative connector mount securely. A larger cable say 6 sq mm will help to conduct heat away from the connectors, which as Allan has pointed out are the weak link. Alan Link to comment Share on other sites More sharing options...
Fiat Ducato Posted November 20, 2017 Author Share Posted November 20, 2017 Alanb - 2017-11-20 1:50 PM Fiat Ducato - 2017-11-20 1:04 PM Hi thank you once again, that was my line of thinking too. And to be honest the one Negative cable is not that big, looks like 4 or 6mm2 tri rated cable. Think I will run another length alongside the 12v = Cable to vehicle negative or chassis (although obviously the vehicle negative battery stump is connected to the chassis. What size cable would you recommend, cant be too big as it won't fit into the negative connector mount securely. A larger cable say 6 sq mm will help to conduct heat away from the connectors, which as Allan has pointed out are the weak link. Alan Hi Alan Yes that is the cable size that I have 6mm sq tri rated black cable 53Amps rated. Link to comment Share on other sites More sharing options...
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