Technical Ducato Accessories and Starting problem

[Choady]

G'day all,

Thought I would post an update as we have found a solution to the problem. After the car had been towed to the auto electrician, that night I was sitting looking at some wiring diagrams which I had downloaded from the Victron website. I had used these as the basis of designing the setup in the rear of the Fiat.

There are several components not installed, like the lithium batteries, associated battery monitors, remote protect, inverter etc, but the solar, dc to dc (Orion) solar panels, -ve and =ve buses and the shunt are all fitted.

(edit) the site wouldn't let me post a link to the diagram so I made another post to hit '5' and the link is now two posts below. refer to that link and what I said in last sentence might make sense !

It dawned on me that although I had a cable running from starter -ve through the DC to DC charger to the battery negative (via the neg bus and shunt), and even though the neg bus was grounded to the chassis, there was no direct cable from the front battery -ve to the rear -ve bus - just the chassis earth. I noticed in the diagram that there was a dedicated cable going from front battery to -ve shunt in the rear.

So the next morning first thing I went out there and the same problem still existed, 7.5v between starter -ve terminal and the chassis.

I disconnected the -ve cables at the DC to DC charger and connected them together, thus bypassing it and making a clean path for the electrons to follow.

Low and behold the voltage disappeared between chassis and earth, the BMV began reading correct starter battery voltage and all the problems disappeared. Accessories on, car started fine.

So it was certainly an earthing issue, but nothing to do with the factory wiring. Luckily for us the mechanics had not started work and cost us nothing. tow was under roadside assistance.

I have since added a new cable linking front and rear -ve terminals for direct path for elecetrons to flow and have re-connected the DC to DC charger and all is good.

I still can't work out why though, when I physically disconnected everything from the rear to the front, that the gremlins remained. They too should have disappeared at that time !

Thanks for everyone's assistance on this. You all helped greatly.

 

[Choady]

Post to get 5 posts so I can put link in

 

[Choady]

Link here to the wiring diagram I refer to in the above post. It wouldn't let me put it in until I had made 5 posts.

www.victronenergy.com/upload/docume...-Batt-mini-BMS-MPPT-100-30-Orion-Tr-smart.pdf

 

[Communicator]

Choady,

To summarise the original problem, the starter motor functioned OK, but the engine either did not start, or failed when headlamps etc., were switched on.

I suspect that the two negative connections to the Orion B2B unit may not be linked, and perhaps only used to monitor the respective battery voltages.

You have removed the symptoms, by running a new negative cable between the starter battery -ve post, and the recently installed -ve busbar, from which there is a connection to the vehicle chassis.

I fear that you have only bypassed the original fault, and that it still exists. The symptoms descibed in previous posts, still point to the main chassis earth point under the battery. I appreciate that you have already examined the chassis area under the lug, but as Anthony489 has suggested, what about the lug itself? (I have a 2006, x244, 2.8JTD, and I am not aware of potential problems in this area, but there is always a first time.)

Would it be possible to make a short heavy temporary lead with 8mm and 6mm lugs to connect between the chassis point, and the battery negative clamp? Perhaps just a jump lead to a temporary lug at the chassis point, with your new -ve lead disconnected?

 

[Anthony489]

Hi Choady

I have looked at the amazingly comprehensive Victron diagram, which looks more like an advert for "how much stuff can Victron sell you" !

Interestingly, this doesn't show a starter battery connection to chassis as per the original vehicle, but instead shows a dedicated cable going back to the rear negative busbar, which in turn is connected to chassis. So, as Communicator points out, by effectively adding this cable in parallel to the original chassis connection (which we strongly suspect has an intermittent fault ) you have solved the symptoms.

As long as the cable you fitted is thick enough (given its length) this may well work fine from now on. However I can't help feeling it would still be a good idea to solve the original fault in the factory wiring. If you don't, then you will sometimes have one earth path and sometimes two, as the connection comes and goes.


Incidentally, there is nothing wrong with using the body/chassis for an electrical path. Even though steel has about 4 times more electrical resistance than copper for the same sized conductor, the chassis normally has such a huge effective cross sectional area that a good low-resistance connection is still made. That's why vehicle makers have been sucesssfully using chassis returns for nearly 100 years !

 

[Choady]

I suspect that the two negative connections to the Orion B2B unit may not be linked, and perhaps only used to monitor the respective battery voltages.

Communicator - Definitely. I checked the two negative connections to the Orion DC to DC charger and there is no continuity between them which makes sense. The DC to DC charger needs to be able to monitor both the starter and the rear battery separately to determine (a) when then engine is running which is the trigger to connect the two batteries, and (b) what the SOC of the rear battery is in at the start of the charging cycle.

Would it be possible to make a short heavy temporary lead with 8mm and 6mm lugs to connect between the chassis point, and the battery negative clamp? Perhaps just a jump lead to a temporary lug at the chassis point, with your new -ve lead disconnected?

We tried this already using a jumper cable (neg starter batt terminal to the lug connection at C002) early on in the troubleshooting. At the time the problem did not go away when we tried this.

It is worth highlighting that these problems only started when we originally wired in the Orion DC to DC charger which was actually the wrong model - so we sent it back.

While we waited for a replacement I had 'hotwired' the two respective positive and neg cables together (the input and output of the orion) using heavy duty cable connectors so that the 240V to 12V DC charger (which is only active when connected to shore power) could charge the front battery from the rear of the car as I originally thought it was just the starter battery on its way out.

Ironically, the accessories all worked and car started fine the next morning and each day thereafter, reinforcing my belief it was a flat battery that the overnight charging rectified. At that stage my friend had made her original post (at my request) but I hadn't made a post yet as I thought we had it was sorted.

The problem only came back AFTER the point the replacement Orion DC to DC charger arrived and we wired it in. That is when we saw 6 V on the starter battery through the BMV monitor again.

The BMV is connected in parallel to the +ve cable coming in from the starter battery (connection at the Orion DC to DC input). The -ve connection for the starter voltage cable was being made through the chassis earth. This connection comes from starter battery -ve, through chassis to the 'green cable' at rear of vehicle, to -ve bus bar, shunt and then -ve rear battery terminal.

The car previously had a rear battery system with a voltage sensitive relay controlling the connection of the two batteries and a separate shore power connection with 240V fuse box connected to 240V outlets throughout the vehicle.

At the start I had used the original existing DC wiring to connect the Orion DC to DC charger and as mentioned that is when the problems first manifested. As part of the elimination process, while we were waiting for the replacement DC to DC charger - I stripped out the old wiring and replaced it (it was only 30A cable and we needed 60) plus they had it fitted through a 100A CB which was clearly not a suitable combination. All new cabling was fitted and new 60A fuses IAW the Orion user manual.

Just for clarity, the original wiring went like this:

Starter -ve direct to rear battery -ve.

The 'green cable' went from rear chassis earth point in parallel to -ve terminal of rear battery.

Starter +ve to 100A CB, then to input of VSR. Then output of VSR to rear 100A CB, then to rear +ve terminal.

All 12V devices from rear battery were birds nest wired to +ve and -ve battery terminals - very poorly I might ad.

So I am struggling to believe there ever was a problem with the factory wiring as surely it would have manifested itself before ?

Maybe if I had of 'shorted' the 7v we saw in the chassis when I disconnected the newly added front and rear battery connections totally - perhaps that would have allowed accessories to come on - but I never tried that.

 

[Crossingkeeper]

I've followed this thread with some interest as I've always *enjoyed* (in the Chinese curse sense!) electrical problems and am pleased that there has been a solution found.

I have a basic B2B (a CSB2) which has followed me from van to van which only requires 3 connections: starter battery +ve, leisure battery +ve, & chassis -ve.

As the problem seems to have been resolved by connecting the two -ve terminals at the Orion B2B together, and indeed on the wiring diagram there is continuity, I'm now wondering why two separate -ve inputs were specified for this unit?

 

[Communicator]

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Just for clarity, the original wiring went like this:

Starter -ve direct to rear battery -ve.

The 'green cable' went from rear chassis earth point in parallel to -ve terminal of rear battery.

Starter +ve to 100A CB, then to input of VSR. Then output of VSR to rear 100A CB, then to rear +ve terminal.

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So I am struggling to believe there ever was a problem with the factory wiring as surely it would have manifested itself before ?
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Choady,

I hope that I have absorbed your last post.

The section about the wiring that I have quoted above describes, as does a lot of the the post, what I suspected to be the case. Particularly that there was a connection to chassis via the additional wiring.

I am almost certain that the operation of the vehicle is now dependant on the new negative connection to the rear, and the connection to chassis from the negative busbar. (It believe that it was like this, before you started tidying up the mess.)

This reliance on the rear chassis connection, could be illustrated by temporarily disconnecting it at the busbar.

At the risk of repetition, all the symptoms point to a long standing problem with the main chassis earth below the battery. It could be, as Anthony489 has suggested, corrosion between the crimp terminal and the battery negative cable. The cable itself may be OK, as you have not reported any problems with the starter motor.

I hope that you can now see, that a fault on the factory wiring could have existed for some time, and been masked by the additional chassis connection. The fault only came to light, when you installed the Orion B2B module, and broke the through negative connection.

 

[Choady]

all the symptoms point to a long standing problem with the main chassis earth below the battery.

It could be, as Anthony489 has suggested, corrosion between the crimp terminal and the battery negative cable. The cable itself may be OK, as you have not reported any problems with the starter motor.

Thanks everyone for your continued inputs. The car is back with its owner and out and about at the moment, but when I get it back next I will do the following to confirm Communicator's concerns.

1. Disconnect 'new' -ve connection I recently installed to fix the problem.

At that point, assuming there is a problem with the chassis earth at C002, the problem should return. (ie no accessories and unable to start). Previously the problems were independent of whether or not the 'green' chassis earth was actually connected or not to the -ve bus bar at rear of car.

If for some reason the problem does not return, I will disconnect the 'green chassis earth cable' from the -ve bus bar. That should definitely re-introduce the problem.

2. I will then disconnect the connection at C002.
3. I will connect a temporary earth strap to C002. (I have ~1m length of 2AWG with battery lug terminals)
4. I will connect the other end of this strap to the -ve terminal.

If there is a problem at the crimp terminal this should bypass that and the problem should disappear (ie accessories on and car starts), thus confirming the conclusion there is a poor connection between the crimp terminal and the cable.

I still struggle with the concept that a single poor connection at C002 could cause so much trouble as C003 is also earthed to chassis via a cable that is connected to the -ve terminal of the battery.

If C002 and C003 connections were no good, then nothing would ever work as wouldn't that be like removing the negative terminal from the battery ? Very confusing for me but I am certainly no expert.

 

[Communicator]

I still struggle with the concept that a single poor connection at C002 could cause so much trouble as C003 is also earthed to chassis via a cable that is connected to the -ve terminal of the battery.

Choady,

Perhaps you have not read my correction of the naming of C002 and C003. Sorry for any confusion.

I reply to your question, please consider the connection between the engine/transmission and the chassis to which the ECU, headlamps, and heater fan are grounded.
Engine/transmission are on rubber mountings, as is exhaust pipe. Engine connected by rubber/plastic hoses, which leaves driveshafts and supension/steering which abound in rubber bushes. Possibly some route through them, but it would probably involve current flowing through bearings, which is not a good idea. Such a current would reduce bearing life, by spark erosion.