Engine battery draining while traveling, technical help please

[John52]

On 06/09/2023 at 13:23, Goneoff said:

Hi Onecal

Just to clarify the engine/cranking battery is the factory fit AGM battery, I think it’s AGM due to the stop start function. The lithium set up is on the habitation side not fitted to start the engine. 

No its not AGM - some of the start stop batteries are lead acid as yours is

If you peel the top labels back you will find plugs in the top you can unscrew to check the electrolyte level

Shouldn't be necessary though as they are supposed to be sealed for life.

[Goneoff]

We left Italy heading to the Côte d’Azure a distance of circa 290 miles with one stopover planned we left with a full engine battery (12.8v) after being on hookup our new plugin dash voltmeter was allover the place throughout the entire 138 miles with highs of 13.5v and lows of 9.0v averaging circa 11.0v when we arrived at out stopover the engine battery had fallen to 12.3v when the evening cooled down it measured 12.1v. All a little disappointing. After the two night stopover we set off to cover the remaining 155 miles with the battery at 12.1v the engine fired up immediately. However there was a significant change in the plugin dash voltmeter reading it was extremely steady at 13.7v - 13.8v when I backed off the accelerator down hill it rose to 14.4v. Overall extremely steady volt meter readings like night and day compared to the first half of the journey. As for the battery when we arrived it was with everything turned off it was showing 12.9v. A great result and a big relief. It looks at this stage you guys have resolved the issue with the battery wiring you suggested. So a very grateful thank you to all of you who were involved. Thank you. 

Why it didn’t work on the first half of the journey is a bit of a mystery maybe it was something to do with the battery setting off fully charged and the system needing a reset which it got when we turned off the engine with the battery run down to 12.3v. Perhaps one of you guys may have an explanation. 

Thanks again 

[onecal]

Hi

I think you have answered your own question  with your reply, Starting with a full battery of 12.8?(it may even be higher) looks like this maybe the issue and as previously stated masking your problem Also your plug in dash meter may not be very accurate and giving you inaccurate  readings .  You really need to have a good overall diagnostic check including your "hookup" charging system checked out by a good electric tech' on your return Best of luck have a lovely holiday If it's starting up on a low reading  every time now ,then just enjoy ,Smart alternators really aren't that smart lol 

Regards

[John52]

3 hours ago, Goneoff said:

we turned off the engine with the battery run down to 12.3v. Perhaps one of you guys may have an explanation. 

To measure the state of charge you need to check the battery with no load on it. (ideally after 24 hours standing)

Which you can't do with your plug in voltmeter because you have to switch the ignition on to switch the cigar lighter socket on. Which means the battery voltage will be reduced by the connected load which may be substantial (eg computer, sidelights, glowplugs etc) - so the battery will be more charged up than the (12.3v) voltage suggests.  Thats why I fitted another cigar lighter socket direct to the battery.  Which Fiat don't do in case you leave something plugged in that drains the battery so you can't start, 

These cheap  cigar lighter plug in voltmeters are also not very accurate, especially with the poor connection of a cigar lighter plug and socket. Because they give a digital numerical display  people expect the number to be correct - But in my experience they actually tend to be less accurate than the old dial meters. 

But they are essential to check whether a smart alternator is working because you can see them when you are driving.  When you take your foot off the throttle going downhill and see the voltage rise to 14.8v or so,  you know the alternator is working.  Doesn't matter if the indicated voltage is a bit inaccurate.   It still tells you what you need too know.

The usual method of measuring the voltage when stationary to see if the alternator is working properly is no good with a smart alternator.

[Robinhood]

...as I said earlier up-thread, you need to give the re-wired situation an extended test and let the current sensor settle.

There are a number of other things that could still be suspect if you don't experience a continued improvement, but at least prima-facie the battery negative wiring was in error, and that could be the sole/main cause of your woes.

As regards the rest of the kit, I'd be wary of casting aspersions until/unless I knew what was fitted and how it was wired. The initial photos indicate that a dc-dc converter is probably fitted, and the neatness of the labelling and wiring give the possibility that this has been done competently (though that is mere surmise).

It does lead one to conjecture that the towbar fitting was done later by someone less understanding of stop/start and smart alternators, and the wiring was repositioned then.

Whatever, if you experience further problems it's worth a check by a competent electrician, if you don't I'd be wary of going to the expense of a Sterling b to b, as you may be replacing a perfectly competent existing b to b.

(The initial photos have wiring labeled DC-DC, it would be interesting to see what that feeds - possibly/probably a workable b to b charger?)

[John52]

15 hours ago, Goneoff said:

Why it didn’t work on the first half of the journey is a bit of a mystery

Because the wiring was on the other side of the sensor, the habitation battery would have been taking current the computer thought was going into the main battery (hence the main battery wasn't getting enough)

We don't know how much current the habitation battery was taking because we don't know what you were using, or how much was being put in through hook up.

It could be OK now

I second everything Robinhood says in the post above, especially "I'd be wary of going to the expense of a Sterling b to b, as you may be replacing a perfectly competent existing b to b.  give the re-wired situation an extended test and let the current sensor settle."

If moving the wires hasn't fixed it, you still have plan B - unplugging the battery sensor, or more easily just pulling the fuse that supplies it.  Its in the fuse box in front of the driver's right knee, centre row furthest to the left 7.5A - That fuse doesn't supply anything else so its OK  But don't do it if you don't have to because its likely to bring on the engine management light (MOT fail) because the start stop won't work.

 

Edited September 12, 2023 by John52

[Alanb]

I would like to echo the sentiment of not replacing what is probably a perfectly adequate B2B.  Phil will probably now realise this is quite different to a basic split charge relay.

What should be considered, as I have previuosly suggested, is moving the relocated wires from the earth side of the current sensor to a true earth point.  I appreciate that the wires may need extending, but it would ensure that the battery negative disconnector was fully functional.

Alan

Edited September 12, 2023 by Alanb

[John52]

22 minutes ago, Alanb said:

What should be considered, as I have previuosly suggested, is moving the relocated wires from the earth side of the current sensor to a true earth point.  I appreciate that the wires may need extending, but it would ensure that the battery negative disconnector was fully functional.

Alan

Yes I agree that would be better

The habitation battery circuits would still be live though, whichever way you do it?

[John52]

If there was anything wrong with the existing B2B charger itself I'm pretty sure it would be the habitation battery that suffers, not the main battery which is where your problem was.

(It could have been wired wrongly I suppose?They are supposed to be turned on by the D+ current from the alternator.  But that is difficult to find on a Ducato.  So sometimes they get wired to the ignition circuit instead.  Which means it starts pulling current from the main battery when its trying to start the engine, instead of waiting till the engine starts and the alternator kicks in.But that doesn't sound like whats happened here.  Especially since it failed to start after 2 hours driving and a brief stop to fill with diesel.  Motorhome too, so it will have the converters socket in the base of the door pillar with a D+ connection there)

Edited September 12, 2023 by John52

[Alanb]

2 hours ago, John52 said:

Yes I agree that would be better

The habitation battery circuits would still be live though, whichever way you do it?

Yes, I should have said starter battery negative.  The habitation battery would require separate isolation when required.

Alan

[Goneoff]

I should clarify all my engine battery readings have been taken from the Phantom app invariably within an hour of stopping then again a few hours later with everything turned off except the Phantom of course which is always a slow parasitic drain. As for the plug-in volt meter I am more than confident that on the first half of our journey it was recording accurate voltages can’t say it’s precise, it maybe + - 1.5v who knows but certainly it wasn’t a poor contact in the socket, it was recording low and erratic voltages these were borne out with the batteries condition at the end of the journey, measuring 12.3v/12.1v. In contrast to the second half of the journey when the same voltage device  delivered a very steady 13.7v - 13.8v +. Delivering a full engine battery at the end of the journey. 

I should add I don’t desperately want to invest in a new b2b Sterling charger but we spend a minimum of five months in our motorhome and having invested in a new to us van I would like to extract the benefit of the lithium system it has onboard. My understanding is that the onboard Burstner b2b factory fit unit (a Schaudt) that sits directly behind the Schaudt ELB 119 only trickle charges which I have to say I find hard to believe. 

Everything is new to me on the van so I can’t talk from experience. If I can get away without buying a high amp output Sterling I will be delighted but for sure I will invest in a Battery Master to keep the engine battery topped up whilst the van is in storage for six months. 

Thanks again for your support. 

[Robinhood]

If the b to b is a Schaudt WA121525* it will charge your lithium battery(ies) at 25A maximum. Only you can decide if this is an adequate rate, but it's more than enough for me. * there is a higher rated unit which I think is 45A, but I suspect this wouldn't be a factory fit, and uprating might challenge the standard wiring.

On the road,the vehicle battery receives a substantial charge from the alternator at the same time (dependent on alternator rating).

Under normal circumstances the EBL will ensure a trickle-charge of the vehicle battery (the max amps varies by EBL model) from the mains charger, and any solar, if appropriately wired (via the EBL or separately) may well do the same. This (trickle-charging) isn't relevant for charging whilst driving.

I'd counsel caution in fitting a battery master when the EBL has the trickle-charge facility, unless you're very careful with the wiring. It wouldn't be sensible to have both in place at the same time. An ability to disable the battery master circuit when not in storage would probably work (I'm assuming hook-up and/or solar are not available in storage, otherwise the EBL trickle-charge would probably suffice)

[John52]

2 hours ago, Goneoff said:

As for the plug-in volt meter I am more than confident that on the first half of our journey it was recording accurate voltages can’t say it’s precise, it maybe + - 1.5v who knows

But 1.5v is huge when you are trying to measure the state of charge of a battery

You shouldn't drain them below about 50% capacity or it will seriously shorten their life

So the effective difference between fully charged and flat is only about 0.5 volt 

[John52]

1 hour ago, Robinhood said:

On the road,the vehicle battery receives a substantial charge from the alternator at the same time (dependent on alternator rating).

The standard Ducato Smart Alternator is a Bosch 180 Amp so its got serious power.

Takes my 510ah battery bank up to 15 volts on regenerative braking with a simple split charge relay Generating free electricity instead of brake lining dust / air pollution.

Which is why I'm reluctant to splash out on a B2B

Edited September 12, 2023 by John52

[Goneoff]

We are finally home and for good order here is my final report about the engine battery charging issue. Since I moved the neutral wires on the battery as advised by you good folk I have had no problem with starting whatsoever. The strange thing is after I moved the wires to behind the shunt (for want of a better term) it was a gradual build up of charging by the smart alternator over several trips during the holiday (watching the cigarette voltage monitor plug). However now it all appears to be working fine although the battery never gets to a full charge even after a very long journey usually around 12.3v but certainly is a world apart from what I was experiencing prior to starting this massive thread. 

I thank each and everyone of you who have contributed to the resolution of my battery charging problem. 

Thank you 

[Robinhood]

Glad it seems to have been sorted, let's hope it stays OK.

The voltage will of course depend on how/where it is being measured (with a decent meter across the terminals is  the only reliable method), but, as I posted somewhere above, I've certainly seen reports of a lower-than-expected standing voltage with smart alternators - something I've never seen explained despite researching.

See this quote from another forum:

"Often with smart alternators, a "full" starter battery is not regarded as being around the 12.7V mark, but at the 12.4V reading (it is not really full, but leaves space for regenerative braking and charge 'dumps')."

[John52]

Thanks for the update to let us know - some people don't bother.

I have since discovered that adding secondary batteries with a smart alternator is unlikely to bring on the engine management light.

I had 2 code readers that failed to recognise a faulty Particulate Matter Sensor fault that was bringing on the engine management light

With no fault codes showing I could only guess it was due to the extra batteries I had fitted, because the Varta website says a different type of batteries can bring on the engine management light

But then I got a new chromebook that does google apps, downloaded the free car scanner app and used it with a streetwise wifi plug from Euro Car Parts.  It identified P24AE Particulate Matter sensor fault, which I got replaced under warranty.  The Fiat technician didn't even comment on the 4x100ah batteries I have added.  Now the engine management light stays off whatever batteries I have connected.

[Alanb]

7 hours ago, Goneoff said:

...Since I moved the neutral wires on the battery as advised by you good folk I have had no problem with starting whatsoever.

A minor correction. Negative, would be appropriate when referring to a direct current (DC) circuit when the positive is the live conductor. ( In some applications, negative can be the live conductor, One example being older automotive systems, where positive was connected to chassis/earth.

Neutral is the name applied to the return conductor of an alternating current (AC) system, where the live conductor voltage oscillates between positive and negative with respect to the neutral.

Thanks for posting the outcome.  This is too often neglected, despite promises to do so.

Alan

[Goneoff]

14 hours ago, John52 said:

Thanks for the update to let us know - some people don't bother.

I have since discovered that adding secondary batteries with a smart alternator is unlikely to bring on the engine management light.

I had 2 code readers that failed to recognise a faulty Particulate Matter Sensor fault that was bringing on the engine management light

With no fault codes showing I could only guess it was due to the extra batteries I had fitted, because the Varta website says a different type of batteries can bring on the engine management light

But then I got a new chromebook that does google apps, downloaded the free car scanner app and used it with a streetwise wifi plug from Euro Car Parts.  It identified P24AE Particulate Matter sensor fault, which I got replaced under warranty.  The Fiat technician didn't even comment on the 4x100ah batteries I have added.  Now the engine management light stays off whatever batteries I have connected.

👍🏼