Starter battery charge while on EHU

[heliart]

OK, following on from the problems with my new 2022 Dethleffs and the fact that the dealer removed the starter to HAB fuse. I've been away a few times and the leisure batteries are working as expected. So all good.

I fitted a Victron Smart Shunt to monitor battery state, this is also connected to the starter battery to monitor it's charge.
I was suspicious that the starter battery was not charging while on EHU.
Just been able to confirm today that it's not. Starter battery down to 11.8v after almost 4 weeks on EHU.

The starter battery is definitely connected to the Schaudt Booster, but one thing I am suspicions about is that the Dethleffs control panel always shows over 13v to both the leisure and starter battery when on EHU. I know for sure that this reading is wrong for the starter battery.
Makes me think something is connection incorrectly.

Any thoughts before I contemplate the hassle of going back to the dealer.

 

[heliart]

And let me update my own thread.
From the EBL 402 manual:-

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[Burgo]

Any thoughts before I contemplate the hassle of going back to the dealer.

Don't trust display - unless you calibrated it yourself recently you don't know that's its correct. Use a seperate digital meter to verify the voltage on the battery after leaving it for 30 - 45mins off charge (off mains, off alternator, off solar). Then use the meter to check the voltage when charging. Then you'll start to know what the state of charge actually is and whether there is a problem. The attached may help...

 

[Kannon Fodda]

Without being able to hands on poke around with your system it's hard to confirm what needs to be done.

EHU, and often solar, are often set to charge only leisure batteries, not the engine. But some of the hab and cab may be linked. In my Autotrail when upgrading the habitation the charging link from cab battery was removed, but the display panel, due to loops that had to remain for steps and stuff, still suggests the cab is connected and charging, but it's reading the hab and cab as one.


Solution is to fit the vanbitz battery master which trickles the cab from hab when there is a voltage difference.

 

[heliart]

I will talk to the dealer this week, but to be honest I know more then them in most cases. They would have to go off and talk to Dethleffs anyhow. It's very frustrating that the manufacturer don't give you wiring diagrams and direct support. But I understand why.
In conclusion, the starter battery voltage is now at 12.05v as I ran the engine for a little while. DVM and Victron shunt confirms this. This voltage is also getting to the booster and the EBL, but on EHU it never raises that voltage. Manual states it should be 13v to the starter, and that's what the panel shows. It's like there's a fuse or connection missing within the EBL but looking at the EBL schematics there's is no obvious fuse just for the starter battery.

Maybe a battery master is the way to go. At least I'll know it's been fitted correctly if I do it myself.

Cheers,

Steve

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[autorouter]

Which EBL is it? Most EBLs charge the starter battery via the fridge 12V heater element feed from the starter battery. It is a separate wire, with a 15A or 20A fuse on it near the starter battery. That's usually next to the main starter battery fuse to the EBL, probably 50A or so.

The fridge relay is inside the EBL. There's a pos and neg wire from the starter battery to the EBL, and a pos and neg wire from the EBL to the fridge 12V heater element. It's normally only in use when the engine is running. When the engine is stopped and EHU is plugged in, that wire is used to charge the starter battery. So, does the fridge work on 12V when the engine is running?

 

[heliart]

Thanks for the pointers, this is a great site for technical advice.
It's a Schudt EBL 402.
Schematic of it below, sorry if a bit small to see.
I'm not so clear on the wiring of the starter battery. I asumed it was direct to the Schudt booster.
You're talking about the 25A fuse external to the EBL - pin1, block 2.
I'll try tracing that when I'm back from my next trip.

It might all be related to my original problem where the dealer had removed the main starter to hab battery fuse. Maybe they were chasing some fault, and also removed fridge fuse.

Thank you.

Steve

 

[autorouter]

I'm not so clear on the wiring of the starter battery. I asumed it was direct to the Schudt booster.
You're talking about the 25A fuse external to the EBL - pin1, block 2.
I'll try tracing that when I'm back from my next trip.

There is indeed a thick wire from the starter battery to the Schaudt booster input, which originally went straight to the EBL. The wire you highlighted in the top right of your diagram, labelled +SB is now is connected to the booster output.

The mains charger output has a 20A fuse, and there is a path to the relay 'Mains charging SB'. This relay is switched on by the EBL 'PCB EBL 400 ST' when it senses the mains charger is sending power. The output to the starter battery is restricted to a trickle charge by the resistor and diode near the relay, and then proceeds along the path you highlighted to Block 2 Pin1, and so to the starter battery via a 25A fuse, using the fridge power wire.

 

[heliart]

You're very knowledgeable on this, I appreciate it.

What does that 25A starter battery for fridge output actually do? Is it used to tell the fridge to switch to AC mode, and then onto the starter battery for a maintenance charge? I kind of assumed that the fridge would auto detect 240v AC input and switch itself.

Cheers.

 

[autorouter]

There's a bit missing at the bottom of your diagram. That highlighted wire continues through the fridge relay to Block 1 Pin 4, which goes to power the fridge 12V heater element. The relay is triggered by the D+ (engine running) signal.

An Automatic Energy Selection (AES) fridge has a control board that does all the switching between gas, 12V and 240V, and controls the gas ignition and the thermostat too. It runs from 12V, but the power is entirely separate from the 12V heater element power. It is a permanent low-current 12V supply from the leisure battery. Not sure which fuse it's on, but I'd guess it's either Circuit 1 or Circuit 2 (labelled Kreis 1 and Kries 2 on the EBL front panel).

If that 25A fridge 12V heater fuse blows, the control board is still powered from the leisure battery, so the fridge will still work fine on gas and 240V, but not on 12V. So if that is what is happening to you, it may indicate that the 25A fuse is blown. Or missing like the other one.

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[heliart]

Thanks again, so much.
Just back from a few days away.
What I see if that I get 13+ volts on Block2.1 when on EHU - Starter Batt for fridge. This is the charge for the starter battery I assume.
Now, I would expect this to be connected directly to the starter battery through that 25A fuse.
The fridge runs on gas, 240v and 12v just fine, so I assume the relay and the switching is all connected correctly.

Tracing that 25A fuse is the next task. Any idea where that might be? EBL end, or nearer in the starter battery?

Cheers,

Steve

 

[autorouter]

Tracing that 25A fuse is the next task. Any idea where that might be? EBL end, or nearer in the starter battery?

In theory it should be at the starter battery end, within a foot or so of the battery. On mine it is right next to the main 50A starter battery feed to the EBL.

If on EHU you're getting 13+V at Block 2 Pin 1, and the fridge is working on 12V OK, then I don't understand why it's not charging the starter battery when on EHU.

 

[GeoffnDee]

heliart when you say fridge works ok on 12v is this when the engine is running ? Some Motor homes fridges can run on 12v without the engine running but it also needs to be working on 12v engine running circuit.

 

[heliart]

heliart when you say it works ok on 12v is this when the engine is running ? Some Motor homes can run on 12v without the engine running but it also needs to be working on 12v engine running circuit.

OK, just did some measurements.

Engine off, no EHU, fridge switched to 12v : Current drain from HAB battery about 14A (powering the fridge)
Engine on, fridge on 12v : Fridge works as expected. (this was the initial problem that in this mode the HAB battery would drain as the starter was not charging the HAB battery due to missing fuse).
I can hear a relay click behind the fridge when switching from 240v or 12v on the fridge.

Fundamentally, I should expect to see >13v on the starter battery when on EHU? In that the starter battery should be connected to block2.1? I see >13v on block2.1, but not on the starter battery.
I'm suspecting that the connection to the fridge is good, and when the engine is running and the fridge is on 12v the power is coming from the HAB battery (which is also being charged by the starter).

Could it be that the starter battery for fridge connection (block2.1) is connected to the fridge directly, but the fuse is between the fridge and the starter battery? I assume that's what the 25A fuse is protecting?

This is the HAB current drain while on 12v and no EHU and engine NOT running.
I only ever see the starter battery voltage increase when the engine is running, so can confirm it's never charging when only on EHU.

 

[GeoffnDee]

I think you should find that with the engine running the block 2 pin 1 allows power INTO the EBL from the starter battery to power the fridge 12v heater element (via the EBL) but when the engine is not running and on EHU the same connection allows a trickle charge OUT of the EBL into the starter battery. (unless the EBL402 is not the same as others ?)

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[heliart]

I just did some more measurments on the EBL.
What this tells me is that Block2.1 is not connected to the starter battery. I only see a voltage on that connection when on EHU, otherwise nothing. The smart alternator D+ signalling is all correct.
I can't explain the fridge connectivity, but it does appear to be working correctly.

I'm tempted to just buy a battery master to get through the winter and have the dealer look at this when it goes back for it's first hab service.
But,
1. I would like to understand it myself.
2. I don't trust the dealer - currently been totally useless.

Thanks.

 

[GeoffnDee]

It seems as if the 25 amp fuse has been removed (or wire disconnected from starter battery) and the fridge is getting its power for its 12v heater element from another source, but I do not know why this would done ,possibly to use the leisure battery even when the engine is running, but if this is the case you still need the circuit between Block2-1 and the starter battery for mains charging when on EHU.

 

[heliart]

It seems as if the 25 amp fuse has been removed (or wire disconnected from starter battery) and the fridge is getting its power for its 12v heater element from another source, but I do not know why this would done ,possibly to use the leisure battery even when the engine is running, but if this is the case you still need the circuit between Block2-1 and the starter battery for mains charging when on EHU.

And this does make complete sense. The dealer had removed the main starter to HAB fuse for some reason. Assuming they were trying to fault find some issue. With this fuse out, the HAB battery never charged with the engine running, which meant the fridge was running on HAB battery while driving, which then went flat.
Refitting that fuse fixed this issue, in that, the alternator now charges the HAB battery also, but as per this thread, the starter battery is now never getting charged on EHU.

I need to trace this starter frred through thr 25A fuse.

Cheers.

 

[autorouter]

The power for the fridge heater element is quite high, and is near the limit for those pins. I've had one develop a bit of resistance, and heat up, partly melting the plastic shell. If that has happened to the previous owner, they might have decided to run a completely separate wire through an extra relay for the fridge 12V heater.

Then the question would be, as GeoffnDee says, is anything still connected to Block1 Pins 3 and 4, which would normally send power to the fridge? If not, you could just put the 25A fuse back, or maybe use a smaller 5A or 7.5A fuse, and this will be OK for the EHU trickle charge.

Chances are the wire has been disconnected and taped up at the fridge end. This can be tested by remove the Block 1 connector, and testing the wires on pins 3 & 4 when the engine is running. If there's no sign of life, the wires are isolated. In that case you can reconnect Block 1 and put a fuse in the 25A slot. That will carry EHU trickle charge power to the starter battery.

You can't do the obvious thing and just disconnect Block 1 permanently, because it also powers the fridge control board and sends the D+ (engine running) signal to the fridge (Pins 1 & 2).

 

[GeoffnDee]

heliart as you have said you can hear a relay operating behind the fridge , the dealer may have done as autorouter has suggested and fitted a remote relay and used the connection from the starter battery that should be going to the EBL , as the relay 12v heater element supply side.

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[heliart]

heliart as you have said you can hear a relay operating behind the fridge , the dealer may have done as autorouter has suggested and fitted a remote relay and used the connection from the starter battery that should be going to the EBL , as the relay 12v heater element supply side.

I'll reiterate - this is a new van. Brand new in June. These problems have been there since delivery.

I've just traced the feed from block2, and the pins 1,4 & 5 go through a connector and off into the loom down the centre of the van. It's very hard to see where it goes after that, and getting behind the fridge seems like too much work at this stage.
So, with what I now know I've just contacted the dealer and will articulate a detailed email on what I've found, and asking the question on where these three wires are routed.
Questions will be:-
1. Does EBL Block2.Pin1 actually charge the starter battery?
2. If EBL Block2.Pin1 should connect to the starter battery, then does it go through a 25A fuse as per the EBL manual?
3. Where is the fuse for that connection?

Seems reasonable to me.

Otherwise it's going to be a trip back to the dealer - which is painful for me, plus I have zero faith that they know the vehicle this well and will have to ask these questions back the Dethleffs anyhow.

Cheers,

Steve

 

[GeoffnDee]

Is there a fridge vent on the outside that you can remove and have a look through to see if a Extra (To the EBL one) relay has been fitted ?
I do not expect that the fridge was removed for whatever modification has been done to its wiring/relay set up and that is where the fridge connections normally can be found and it may be useful to know that the dealer may have added things when trying to sort out your original problems.

 

[heliart]

Is there a fridge vent on the outside that you can remove and have a look through to see if a Extra (To the EBL one) relay has been fitted ?
I do not expect that the fridge was removed for whatever modification has been done to its wiring/relay set up and that is where the fridge connections normally can be found and it may be useful to know that the dealer may have added things when trying to sort out your original problems.

I did'nt know those panels came off so easilly. Thanks for the pointer on that.
So, there is a correct connection to a relay in there behind the fridge. It's one of these fused relays (20A in this case)
This relay is switched via the D+ alternator signal to indicate the engine is running.
The connection from the EBL to this point is correct. (13.7v on the EBL block2.1, and 13.7v on the relay).

I've just written a detailed email to the dealer technical manager - but not holding my breath. Their default position is that the customer is always wrong and most often bloody stupid.

Cheers and thanks all - learning a lot.

Steve

 

[GeoffnDee]

The relay that has been used may be the one that some fridges are factory fitted with, is it a Dometic RM10 series Fridge/Freezer ?

 

[heliart]

The relay that has been used may be the one that some fridges are factory fitted with, is it a Dometic RM10 series Fridge/Freezer ?

It's an RM10, yes.

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[GeoffnDee]

I think the fridges own relay has been used in this case as it is part of the fridges own smart electrical system (not a problem ) but the starter battery to EBL extra fridge connection has not been made because it was thought to be not needed , but as you have found , it is needed to remain connected for mains power starter battery charging. (maybe connection just forgotten ?)
Not sure if the EBL is still used for leisure battery heater element power supply control when the starter battery is not the power source .

 

[autorouter]

Not sure if the EBL is still used for leisure battery heater element power supply control when the starter battery is not the power source .

In other MHs, including mine, the EBL can power the 12V heater element from the leisure battery. To do that, a fuse has to be inserted on the front of the EBL. Then if the fridge is switched (probably manually) to 12V the supply will go through Block1 pins 3 & 4, just like it does when the engine is running.

However in this case, if those pins are not connected to the fridge heater element, then it won't work.

Actually, that's another test you could try. If you insert a 20A fuse into the slot marked 'Sicherung nur fur AES Kuhlschrank' (= Fuse only for AES Fridge), then in my MH the fridge runs on 12V from the leisure battery when the engine is not running, if switched manually from the fridge control panel. If it works, that would tell you whether the Block 1 Pin 3 wire is reaching the fridge heater element. Or maybe that relay.

By the way, it's not a very popular option, because the fridge will run an average leisure battery flat in less than a day, even overnight. But it's useful on a short ferry crossing where you can't leave it on gas.

 

[heliart]

OK, thanks everyone for your inputs. I learnt a lot about how my van, and motorhomes in general are wired.
I think I'm going to draw a line under it now. I still have an open question with the dealer - so we'll see, and I'll post an update accordingly.
As for a solution, I'm just going to fit a battery master - at least it will also keep the starter battery topped up even if I'm not on EHU.

Steve

 

[heliart]

Let me update this thread.
Nothing back from the dealer's technical manager (no surprise there).
I've since fitted a Ablemail AMT12-2. I like that you can program exactly what you get.
All appears to be working well. For those familiar with this device, I opted for program 1 to keep the starter battery at 12.8v.

Cheers,

Steve