Campervan draining engine battery when on EHU?

[Taipan]

My Sister has a 2016 Renault Master campervan. It was converted by a man who normally works on narrowboats and well, not so narrow boats. He built this as a off grid type thing with 3 solar panels on the roof and some invertors etc. Recently my Sister was at festival and was on electrical hook up, but after 3 days they went to leave and whilst the leisure batteries were all fully charged the engine battery was dead as a dodo. She said once before they stayed overnight off grid and it only just started, but they thought they hadn't shut the drivers door properly.

I though most vehicles of this age had an eco setting where as you cant leave interior lights and radios on for any length of time as the van would shut them off of its own accord? So if it isn't that, any ideas on how its drawing power from the engines battery? I assume, but don't know, it as a split charge relay system? I know of these but have never seen one. Where would such a relay normally be located? Are they literally just a small relay that I could change for little money, or are they a big hefty expensive type?

Is it possible there isn't a relay and it has to be switched over manually using something inside that lot below? Any other ideas on how it could be drawing from the engines battery?

TIA

[Rockburner]

Errrr - from memory, in my van, there WAS a doodad that ensured that the solar panels charged both the leisure AND the vehicle battery, and IIRC it prevented the leisure circuits pulling power from the vehicle battery..... somehow.. .but it was all taken care of by the black boxes.

My van had a factory built leisure system, so I'm assuming the relevant black box was part of that.

Can't really help with a home-brew.

[iansoady]

A substantial diode between the vehicle battery and leisure battery circuit should prevent that.

[Yorick]

In my camper there were 2 complete 12v systems. No overlap so vehicle battery was always safe.
The split charge relay sent power from vehicle circuit to the leisure batteries. But was definitely only 1 way.

[Mr. Dazzle]

It's just as likely the vehicle battery is just dead for standard vehicle battery reasons, unrelated to the leisure stuff. I'd discount that simply possibility first.

The idea of all the clever black boxes is that you never run leisure off the vehicle battery when the engine's off and hence never get stuck. They also allow you to plug in to site power etc. Generally though they're not set up to charge/power the vehicle from the leisure batteries (indeed the point of a split charging is to separate the two) 'cause the starter motor can fry a leisure battery.

There's a shit load of boxes and wires there though

Hence my statement above, I'd rule out "normal" reasons first. Sis has already said the battery died once before right?

[Taipan]

It's just as likely the vehicle battery is just dead for standard vehicle battery reasons, unrelated to the leisure stuff. I'd discount that simply possibility first.

The idea of all the clever black boxes is that you never run leisure off the vehicle battery when the engine's off and hence never get stuck. They also allow you to plug in to site power etc. Generally though they're not set up to charge/power the vehicle from the leisure batteries (indeed the point of a split charging is to separate the two) 'cause the starter motor can fry a leisure battery.

There's a shit load of boxes and wires there though

Hence my statement above, I'd rule out "normal" reasons first. Sis has already said the battery died once before right?

Yes, she had the battery load tested by a garage. Its sat for 3 weeks since then and started up fine after that time?

[Mr. Dazzle]

yeah fair enough, obvious cause investigated

[Taipan]

A substantial diode between the vehicle battery and leisure battery circuit should prevent that.

Is that not what the split charge relay is? I assumed it would have one to prevent back drain?

[Flux]

Drop test was the first thing I was going to suggest, so you've proved the battery is good. Next check the alternator (12.5v across battery terminals under no load, rising to over 14v with engine running).
I would expect if a split charge relay is fitted it should be charging both engine and leisure batteries as demand requires regardless of power source (hook up solar or alternator), but worth proving alternator first as it's such an easy test.
If the van has a smart alternator then you should also have a b2b so too much current isn't supplied.
You can check for battery drain, easiest with a clamp meter (normal ammeter otherwise), with everything off you should see only a few mA being drawn from the battery. My classic mini kept going flat and it turned out to be the stereo drawing 400mA when off, over time this was enough to depleat the battery...

[Demannu]

Did the problem go away when off ehu?
It looks like there is a selector for solar/ehu, which might isolate the 12v system, so any cab usage, radio, lights etc would flatten the vehicle battery. I dont see a 12v charger unless that is part of the Sterling unit.
Neat set up though.

[Taipan]

Did the problem go away when off ehu?
It looks like there is a selector for solar/ehu, which might isolate the 12v system, so any cab usage, radio, lights etc would flatten the vehicle battery. I dont see a 12v charger unless that is part of the Sterling unit.
Neat set up though.

Yes, it only happens on EHU. The Stirling unit is a B2B/DCtoDC device thing. I'm waiting on a better photo to fond put which model...

[Mr. Dazzle]

Did the problem go away when off ehu?
It looks like there is a selector for solar/ehu, which might isolate the 12v system, so any cab usage, radio, lights etc would flatten the vehicle battery. I dont see a 12v charger unless that is part of the Sterling unit.
Neat set up though.

Yeah good shout, it might isolate the vehicle battery when you plug in to EHU to avoid the possibility of firing high voltage into the 12V system At which point the vehicle battery is potentially running light etc as you say.

[Taipan]

Its kinda weird as its a developed fault since shes had it. She hasn't changed any settings or anything, just one time when she was away, everything seemed fine until she went to leave and had a dead engine battery?

This is the B2B unit.


picture upload

[Demannu]

Like I said, there is no 12v charger fitted in that system, so the solar is isolated on ehu setting. There should be a second feed from the mppt which she can send direct to the vehicle battery to keep it topped up on ehu. The b2b unit doesnt have a SCR function back to the vehicle battery iirc.
In future maybe stay off the ehu. Unless she's using an oven to cook with!

[Demannu]

Possibly, because the converter is a boat person, his system doesnt take into account that the engine battery also powers some of the internal stuff, so needs to be included in the solar circuit. Just a thought!

[Taipan]

Yes, its very weird, because this is a developed fault. It never used to be like this.

We turn the inverter off when we use the hook up so we use the electric not solar power. If there was dismal weather like we have lately and used the TV, charged our phones and had the lights on the solar power would drain after a couple of days . But we used to be able to use electric for couple of days before, like when we have been on site at Mersea and didn't have any problems when we started the van up, so I'm not sure what has changed and affected it?

[Demannu]

As an aside, your sis has 330ah of leisure battery there!
If they are draining that in 3 days off grid, they need to re-evaluate their usage patterns or possibly their hardware.
I have 6 x 3w led bulbs for interior lighting, never need more than 3 on at a time. Entertainment is by a 10" tablet connected via usb mifi router. We could go for a cello 16/19 TV, but we dont go away to watch telly! Phones charged directly from solar controller (got a cheap one).
We get @4ah charge from our single solar panel and as yet, apart from when she uses the hairdryer, dont struggle for power needs.
As for your sister's issue, the simple solution is to wire up the V battery to the secondary solar outlet, or fit a SCR to it.
Or take it to an auto sparky, and let him have a poke around and guess a bit!

[Yorick]

Yes, its very weird, because this is a developed fault. It never used to be like this.

We turn the inverter off when we use the hook up so we use the electric not solar power. If there was dismal weather like we have lately and used the TV, charged our phones and had the lights on the solar power would drain after a couple of days . But we used to be able to use electric for couple of days before, like when we have been on site at Mersea and didn't have any problems when we started the van up, so I'm not sure what has changed and affected it?

I think there's some confusing understanding here. Just trying to work it out.

The inverter just changes 12v to 240v.

Again, in our camper the inverter was attached to the leisure batteries directly. Never saw the vehicle battery.

[Cousin Jack]

What you have is a gremlin. No known cure except to destroy it by fire.

[Yorick]

What you have is a gremlin. No known cure except to destroy it by fire.

We can burn @gremlin ?

Cool