Is my alternator working properly?

[Epic-Rob]

Ok my question has a few parts to it and there seems to be many threads covering bits and pieces of what i want to know but not everything so here goes.

2016 bluemotion DSG

OK so i have a 100ah AGM battery under the driver seat fed by a 105w solar panel on the roof running through a 20a MPPT controler (i am in NZ so we do see slightly more sun than you guys ;-) )
I have a few led lights and the tap pump - the biggest draw being the Crx50 fridge. which when i 1st put the system in ran the fridge 24/7 with out any dramas.
so on my last trip away the solar didnt seem to be able to keep up and after about 2 days fridge died when leisure battery got to low 11V .

ok so home battery recharged and fridge test again - cant keep up.

so i refits the split charge relay - powered from a rather chunky wire that goes to the fuses under drivers seat and is fed through a 50amp fuse under battery (this only seemed to become live when engine running). ok so i run fridge again and it seemed to top up leisure batt as i was driving but never got to 100% (high 12v on solar disply) always seemed to struggle to get to 13v. battery was tested and changed to eliminate that - but no improvement.
i also changed the solar controler to eliminate that.

so i just thought i would check what was going into the battery when engine running and split charge relay doing its thing so putting a multi meter on it was about 12.5v so i checked the starter battery as i know it doesnt kick in till starter battery at a good charge - this was also at about 12.5v so i left it ticking over for 30 mins and then went for a 30min drive no diff - still sat about 12.5v. but here comes the alternator question - if the starter battery is 12.5v wouldnt the alternator but pumping amps in? so i would have expected to be seeing 14ish V on the battery terminals.

AND to make it worse the leisure battery had lost some power with nothing drawing on it despite solar working away - is this a possible feedback from leisure to starter battery i have read???

Any suggestions as to what to try next?

 

[Epic-Rob]

And on a note to the above found an excellent article by Mr Dellmasive saying basically a SCR wont work on the stop/start engine like i have so it seems thats out the window and a DC-DC charger required, also covered why alternator not showing a charge - only works when you put the brakes on .....
so maybe a DC-DC charger will sort it and maybe a bigger panel.

A question though - can i use the power supply i found under drivers which the SCR is powered from or does it need to go into BCM ?

 

[Niknak]

If the cables under the seat are factory fit that currently go to your scr then yes you should be ok to use these and I’m sure others have on here
Best off asking @Dellmassive or @Deaky
They will point you in the right direction,

 

[Loz]

Read the start if this it will explain what the alternator is doing.

https://www.t6forum.com/threads/how-to-fit-a-travelvolts-dc-dc-battery-to-battery-charger-kit.6263/

 

[Pete C]

The behaviour of the alternator, that you have described, sounds exactly how a smart alternator should work.
Definitely get a DC-DC charger.

Pete

 

[Pauly]

AND to make it worse the leisure battery had lost some power with nothing drawing on it despite solar working away - is this a possible feedback from leisure to starter battery i have read???

This is quite feasible, as im sure you now know the starter battery is only ever charged to around 80% by the engine/alternator, if you use solar to take your leisure batt above 80% then when the split charge relay engages and joins the batteries together they will equalise and engine batt could go up slightly and make the leisure batt go down slightly

If you have decent solar setup that used to run the fridge indefinitely but now wont i think that would be the focus of my attention ?
Perhaps something to monitor leisure battery current flow/charge would give you a better idea of whats going on as you would be able to see exactly what was going in and out of the battery and know what state of charge it is at

 

[Dellmassive]

Some great advice above..

To add to that I'd ask for a few pics of your starter and leisure battery setup. And the solar... to get an idea of the cables and setup.

You need to swap the SCR for dc-dc charger to work in conjunction with your solar. And yes you can use the feeds from the SCR, but be cautious of the Amp rate ... you said above you had a 50A fuse feeding the SCR?..... so maybe look at a 25A DC-DC or fit a better cable set then you can fit a high Amp DC-DC. (Well see more with the pics)

Also what spec is the solar controller?

And as Paul said..... monitoring is the key....if you had a voltage logger you could visually see the whats going on and the effects of your solar and fridge business. (A cheap BM2 will do it)

What spec is the leisure battery?. How old? Has it been tested.? Possibly knackered?

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Have a quick look here :

Dellmassive’s "How I Done It" blogs.

-- Dellmassive`s -- "How I Done It" -- thread -- ************************************************** Dellmassive`s -- "how I Done It" -- Thread ************************************************** Kit List And Stuff -- How I Done It & What I Use --...

www.t6forum.com

.

 

[Epic-Rob]

After a bit more playing around today i think the problem may be a bit beyond my spanner and hammer approach i can build the campers (done 3 now) but when it comes to the dark science of electrical fault finding.....

so i came out this morn and the LED roof lights had switched themself on (has done it before) and the battery was showing low (nothing else on) when i switched them off the battery went up - Ah ha i thought ... so i pulled the fuse to see if that might be the prob. Leisure battery was up at 13v so i put fridge on to see how it want, later on i heard the fridge clicking, when the fridge turned on the shown battery voltage immediately dropped from 12.9v to 11.1v fridge sensing low power switched off and the volts went back to 12.9 ish - this repeated.

so i switched fridge off and tried with diesel heater - this had a pretty similar effect, i put the meter on the battery just to check it wasnt some weird reading but multi meter confirmed same. (I have swoped batteries so don't think that's the fault)

so it would seem Covid has got into my electrics! and i am not really sure what to check next.
I have removed the SCR
Solar controller is a 20a Tracer MPPT
I dont know if my van has the REGEN thing on (is bluemotion)

 

[Dellmassive]

2016 bluemotion DSG - has it got stop start?

is it a T6?

can you post a picv of the starter battery NEG terminal . .


going from this pics we can assume it is T6, stop/start EU6 van.



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So i think the way forwards is to fit a battery monitor to the starter and aux battery.

swap out the SCR for a DC-DC charger.

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from this pic we cant see where they have taken the feed for the SCR? its not direct from the battery?

maybe from a link under the seat from the main fuse box under the battery?



**

either way it needs sorting out. . . . If your not confident on fitting the DC-DC then take the van to a local auto electrician or car audio shop and ask them to help.

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i would suggest 2x BM2 battery monitors (one on each battery) - you get an APP on your smartphone that you can use to monitor your battery voltage.

like these : https://amzn.to/3kxDRrF






more on battery monitoring here : https://www.t6forum.com/threads/battery-monitoring-how-i-done-it.15346/

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and swap out the SCR for a DC-DC charger . . . .

more on those here : https://www.t6forum.com/threads/guide-dc-dc-charger-for-leisure-battery-how-i-done-it.15066/

The Redarc is very popular in AUZ, but also look at Renogy and CTEK etc.

you can get a plain DC-DC charger on keep your existing Tracer solar MPPT, or you can get a 2way DC-DC that has a built in "DC-DC + Solar MPPT" , . . . then do away with the tracer.

either way will work..


have a look at these guys.

DC to DC Chargers – 12V DC DC Charger for Your Dual Battery Setup

Our DC DC charger features an inbuilt MPPT & automatic battery isolation, allowing you to get maximum current into your battery. Click here to learn more!

www.australiandirect.com.au

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and an example on the YouTube chanel . .

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also look at upgrading that battery to a decent AGM battery.

the one you have is a standard SLA battery and is possibly knackered after being drained to low a few times. . . .



SLA batteries drop in voltage very quickly and die fast . . . an AGM will cost a bit more . . . but is much better at keeping voltage up.






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https://www.vision-batt.com/site/product_files/6FM100-X.pdf

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[Epic-Rob]

Yes it is a T6 with stop start

the battery i have in is an AGM

the small red wire off the posotive terminal feeds the relay on the aftermarket driving lights (i just put a separate on/off switch in dash)
the power lead i used on the SCR was picked up under the passenger seat its 6mm cable.

i will try a new lead acid battery on 1st see if that has any effect.

Thanks for the help and tipps Mr Dellmassive - i will post what problem was once i sort it.

 

[Epic-Rob]

Ok so moving on with the solution to my problem i am just about to fit a DcDc charger, looking at the supplied wiring diagram it connects directly to the vehicle battery - well thats fine BUT i have what is i am pretty sure the supply wire in-place for a Factory Aux battery which is just under passenger seat.
Can i tap into this for the +feed to the DcDc charger, and do i just need a ground for the earth or does it need to go back to the battery???
(The blue wire to term 5 is not required)
charger is a NDS plus 25 - i wont be connecting the solar side of it.