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Another EBL/Fridge Problem
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userplwsm2000
Posted: 11 December 2020 3:54 PM
Subject: RE: Another EBL/Fridge Problem
 
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747Heavy - 2020-12-10 11:21 PM
...
However: Just to clarify, as it stands the 12 volt fridge heater supply is most definitely direct from the habitation battery terminals, through a 20 amp fuse.
I have an idea of how that affects the situation but how would that fact change your analysis of it?

Will

Will,
Obviously the main purpose of the fridge heater element is to keep the fridge cool while traveling and so it is usually connected to the starter battery / alternator. However, it is possible to connect it to the hab. but there are pros and cons in doing so. You still need to control it through D+ in either case.

The upside in connecting it to the hab. battery is that you can use any excess solar power to reduce your gas usage with the right solar setup (sorry for repeating myself). This is the only upside that I can see.

The downsides are that the hab. battery will get a lower charge rate while driving and you risk damaging your hab. battery if there is a fault with the split charge arrangement that stops the alternator charging it. Your "remaining capacity" display (if you have one) might also be way out.

The reason for the lower charge rate is that extra the 10 amps or more will drop the voltage to the hab. battery while driving. Depending on the wire thicknesses, you could easily get another 100mV or so drop which will reduce the charge drawn by your hab. battery. There are lots of discussions about beefing up the split charge wiring to increase the charge rate for this reason, so adding the extra fridge current will not help.

If your split charge relay or fuse was to go open circuit, the 10Amps fridge current will discharge the hab. battery in a matter of hours - it maybe too late before you to realize it. Since the fridge uses a simple heater element (and there is no mention of any under-voltage cutout in the fridge manual), it will keep the load on the battery until its voltage is well below "safe" levels. Completely discharging the battery is not good and your battery may not survive it.
The game changes a bit if you have a B2B as this should maintain the correct charge voltage on the battery in spite of the extra fridge current.
user747Heavy
Posted: 11 December 2020 4:47 PM
Subject: RE: Another EBL/Fridge Problem
 
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Yet again thanks for the really invaluable information.

The idea of using spare solar certainly appeals but would need to be monitored very carefully, I'd suggest. I'm OK with the idea - but maybe not just yet.....................

For the time being that will probably be a non-starter because although I had thought of most of what you've given as examples of the down side of the present arrangement, I had NOT thought of the result of the split charge system failing. My main concern had been hoofing all the habitation battery charge and the fridge power through circuits on the EBL that were never designed to be that stressed.
There's a habitation battery warning light on the IT control panel but that's all it is. A warning light - and it doesn't come on until the battery is down to 10.8 volts, so pretty much on it's deathbed with a terminal illness.

Maybe we (and the previous owner) simply got away with it because the split charge system has always worked. I think I'll try and return the system to the starter battery configuration for now and look at some sort of monitoring/sensing system for a future project.
The whole setup doesn't look very professional the way it's been done, especially when you see the bill they got and the mess left behind.
I'll be sorely disappointed if I can't make a great improvement to it.
If anyone is interested, I'll file progress reports as I go.

Will
userplwsm2000
Posted: 11 December 2020 5:38 PM
Subject: RE: Another EBL/Fridge Problem
 
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Will,
Another option would be to add an external relay and fuses to mimic the relay inside the EBL.
The normally open contact should be wired to the starter battery, the normally closed to the hab., and the common to the fridge. The fuse to the hab. & n/c contact should not be fitted unless you intend to use the solar option.
The relay coil would need to be driven from D+ (also to the fridge D+). Just check the D+ source on the merc. can drive another relay coil (it needs to be buffered/boosted on a Fiat Ducato)
user747Heavy
Posted: 12 December 2020 3:59 PM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2020-12-11 5:38 PM

Will,
Another option would be to add an external relay and fuses to mimic the relay inside the EBL.
The normally open contact should be wired to the starter battery, the normally closed to the hab., and the common to the fridge. The fuse to the hab. & n/c contact should not be fitted unless you intend to use the solar option.
The relay coil would need to be driven from D+ (also to the fridge D+). Just check the D+ source on the merc. can drive another relay coil (it needs to be buffered/boosted on a Fiat Ducato)


Sorry, another War and Peace but in view of your suggestion above - and as a check of my understanding - how does this sound as a distillation of what's been said so far: (Don't be frightened of shooting holes in it, I'm not at my best with circuit diagrams)

As currently configured:
1. When the engine starts D+ from the alternator is fed into Block 2, Pin 3 to (try to?) energises both the fridge relays. The upper relay (in the diagram) swaps contacts over and tries to takes power from Block 2 pin1 to power the fridge heater element from the starter battery. At the moment it serves no purpose because its PCB track to Block 1 pin 1 has been cut. However, the lower relay also swaps contacts and that same supply (originally intended just for Block 1, Pin 2) is now fed to Block 1, Pin 1 as well, since the pins have been bridged. If the upper relay has failed, it makes no difference. If the lower relay has failed as well, then the output of the starter battery still cannot get to the fridge heater.......... and it probably has failed and is the reason the wires from Block 1, Pins 2 and 4 have been cut off and the 12 volt fridge heater is connected directly to the hab battery.

2. That same D+ input is fed out to the fridge from Block 1, Pin 3 to feed the AES, which in turn tells the fridge it can switch on the 12 volt heater element. The AES doesn't know or care what is supplying 12 volts - but as currently configured it's only the hab battery and therein lies part of the problem and the danger of flattening the hab battery if the starter battery/alternator output to the EBL is lost. If D+ is lost, the AES tells the fridge to switch off the 12 volt heater and go to gas/mains anyway.

3. The D+ signal at Block 2, Pin 3 feeds up to operate the Battery cut-off relay which, in turn connects the starter battery/alternator to the EBL through E20-3F (in reality a big lump of choc-block on the back of the EBL). I assume the alternator output is then routed to charge the hab battery across the 50 amp Shunt and by default replacing what the fridge heater element has been taking out of the hab battery in the present configuration.

What if:

4. If the D+ isn't very robust and proves difficult to boost: The Battery cut-off relay is a FRC3A, 14 volt 70 amp item and is already controlled by D+. It has the usual terminal numbers: 30, 85, 86 and 87. It's readily accessible at the moment, so to avoid extra load on D+, is it a sensible/reasonable/feasible option to make use of the (No 30) switched output terminal of that relay to operate a suitably rated and low holding current changeover relay to latch in the starter battery/alternator output to run the fridge when driving? The input cable to Block 2, Pin 1 could be suitably spliced whilst maintaining it's connection to the EBL and fed onward to the fridge 12 volt heater using the existing 6mm square cables.
Looking for snags with that idea:
a. If the D+ input at Block 2, Pin3 fails or blows its fuse, the Battery cut-off relay opens, isolating the starter battery/alternator from the EBL and also switching off the fridge 12 volt heater input because the AES has lost the D+ input and tells it to switch it off. It will try for mains/gas - and probably won't get it because I'm driving and don't travel with the gas on, so start sounding the alarm on the AES.
b. In the unlikely event that the 50 amp fuse on the starter battery/alternator input at E20-3F fails, the extra relay will unlatch because the actuating and holding circuit from the Battery cut-off relay terminal 30 would be lost. The fridge will lose its 12 volt heater supply input from the starter battery/alternator but the AES will continue to think it's got it because D+ is still active, so doesn't switch to gas/mains. If the hab battery is connected to the normally closed terminal, it will try to use that but if the fuse is pulled as you suggested, it can't draw power. We would end up with warm beer - but not a flat hab battery.
If we are moored up for an extended period I can put the fuse back in easily enough since that is the time we would most likely benefit from the solar system helping the fridge. I was already in the process of arranging for a switch on the S+ line from the solar so I can control it.
In my experience there's probably less chance of that 50 amp fuse popping than there is of a failing alternator faithfully producing a healthy D+ output to fool the system, even when it's main 12 (14.4) volt output is well below par and barely holding up the starter battery, let alone a hab battery as well.

5. An alternative to point 4 above is to cut the PCB track links from Block 2, Pin 3 to the fridge relays, or physically remove the relays from the PCB. It would probably lighten the load on D+ enough to operate another relay - but is perhaps a bit perilous in terms of collateral damage to the PCB if all does not go well. I know a 'man who can' and he did an excellent repair to an Alde main board for me some years ago but I don't see it as a straightforward option getting the job done under the Covid rules and more expense if my point 4 is sensible.

A couple of questions:

i. What is the purpose of the Block 5, Pin 8 connection to Block 2, Pin 1? I've a feeling someone has told me but I can't find it. I can also see Block 2 Pin 1/Block 5, Pin 8 have a connection from the mains charger through the Charging relay B1, on through a diode, then a component I can't identify.
ii. What is that unidentified component and what is its purpose?
iii. Is Block 3 just the connection point for any additional charger to feed into the EBL?
iv. Just to muddy the water a bit more: when I first started investigating, the cable connected to Block 2, Pin 1 was looped through the original LR1218 solar charger/regulator Starter battery charging terminal.

Will

Edited by 747Heavy 2020-12-12 4:02 PM
userBruceM
Posted: 12 December 2020 4:21 PM
Subject: RE: Another EBL/Fridge Problem
 
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I won’t attempt to provide an opinion on all your options, there are those much better technically qualified on this forum than I to do so.

I will however say two things

1/ Yes, Block 3 is for an auxiliary charger- eg via a generator. In my case, as I have an EBL 99 whose solar provision would have potentially exceeded that of my EBL 99 solar socket, my solar regulator is connected to the equivalent of your block 3 as it has the higher current rating.

2/ Rather than make further changes to the EBL’s functional design, would it be wiser and perhaps kinder to the next owner of the van to either have your EBL repaired or even swap it for a reconditioned unit and wire the fridge in correctly?
userplwsm2000
Posted: 12 December 2020 8:31 PM
Subject: RE: Another EBL/Fridge Problem
 
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747Heavy - 2020-12-12 3:59 PM
...
What if:

4. If the D+ isn't very robust and proves difficult to boost: The Battery cut-off relay is a FRC3A, 14 volt 70 amp item and is already controlled by D+. It has the usual terminal numbers: 30, 85, 86 and 87. It's readily accessible at the moment, so to avoid extra load on D+, is it a sensible/reasonable/feasible option to make use of the (No 30) switched output terminal of that relay to operate a suitably rated and low holding current changeover relay to latch in the starter battery/alternator output to run the fridge when driving? The input cable to Block 2, Pin 1 could be suitably spliced whilst maintaining it's connection to the EBL and fed onward to the fridge 12 volt heater using the existing 6mm square cables.
Looking for snags with that idea:

Unfortunately this won't work. Terminal #30 on the relay is the common contact and will always have a voltage on it - either from just the starter battery or both batteries joined together (the "battery cut-off relay" is also known as the "split charge relay").
On the Fiat Ducato, the D+ (from the converters socket) can only drive one small relay so this is usually boosted by another relay somewhere to drive the split charge, auto-retracting step, B2B etc. I don't know the D+ drive capacity on the Merc. chassis. Perhaps this has a higher current drive?

747Heavy - 2020-12-12 3:59 PM
...
5. An alternative to point 4 above is to cut the PCB track links from Block 2, Pin 3 to the fridge relays, or physically remove the relays from the PCB. It would probably lighten the load on D+ enough to operate another relay - but is perhaps a bit perilous in terms of collateral damage to the PCB if all does not go well. I know a 'man who can' and he did an excellent repair to an Alde main board for me some years ago but I don't see it as a straightforward option getting the job done under the Covid rules and more expense if my point 4 is sensible.

I would not recommend trying to remove the relays with just a soldering iron as it is possible to damage the through-hole plating on the PCB. These can be removed easily with a hot-air gun with a controlled temperature to heat up all the pins simultaneously.

747Heavy - 2020-12-12 3:59 PM
A couple of questions:

i. What is the purpose of the Block 5, Pin 8 connection to Block 2, Pin 1? I've a feeling someone has told me but I can't find it. I can also see Block 2 Pin 1/Block 5, Pin 8 have a connection from the mains charger through the Charging relay B1, on through a diode, then a component I can't identify.
ii. What is that unidentified component and what is its purpose?
iii. Is Block 3 just the connection point for any additional charger to feed into the EBL?
iv. Just to muddy the water a bit more: when I first started investigating, the cable connected to Block 2, Pin 1 was looped through the original LR1218 solar charger/regulator Starter battery charging terminal.

i. Block 5 connects to your display unit and pin 8 is used to monitor the starter battery voltage.
ii. This is a PTC thermistor to limit the charge current going to the starter battery to about 2 Amps.
iii. Yes
iv. The LR1218 has a separate output to trickle charge the starter battery. Block 4 pin 2 on your EBL is not connected but on later EBLs, pin 2 is connected internally to the fridge power input (Block 2 pin 1 in your case). As mentioned previously, this pin normally has a dual function 1) to provide power to the fridge when driving and 2) to trickle charge the starter battery when not driving (from solar or EHU).
Although not mentioned in Schaudt / Votronics wiring diagrams, I would suggest fitting a 2A fuse in this line (from the solar controller) otherwise it is only protected by the 20A fuse near the starter battery.

Edited by plwsm2000 2020-12-12 8:32 PM
user747Heavy
Posted: 12 December 2020 8:31 PM
Subject: RE: Another EBL/Fridge Problem
 
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BruceM - 2020-12-12 4:21 PM

I won’t attempt to provide an opinion on all your options, there are those much better technically qualified on this forum than I to do so.

I will however say two things

1/ Yes, Block 3 is for an auxiliary charger- eg via a generator. In my case, as I have an EBL 99 whose solar provision would have potentially exceeded that of my EBL 99 solar socket, my solar regulator is connected to the equivalent of your block 3 as it has the higher current rating.

2/ Rather than make further changes to the EBL’s functional design, would it be wiser and perhaps kinder to the next owner of the van to either have your EBL repaired or even swap it for a reconditioned unit and wire the fridge in correctly?

Thanks for the response.
Ref 1/ Ta, it's what I thought.

Ref 2/ Yes, it would certainly be kinder and I've certainly had my quota of head scratching misery thanks to the person who perpetrated this particular act of butchery plus a few others I've corrected. I'm not moaning about my plight, it was bought cheaply enough and I knew there were some issues I won't be leaving the same mess, whatever happens. If I don't replace the EBL and put things back to standard, I'll certainly document what's been done and altered so any future owner doesn't have the same 'mare. That said, I have no intention of changing the motorhome - ever. I am of an age where, if I can, I will make this one last until a time when It's just not right for us to be going motorhoming any longer.
With regard to it being a wiser option? Hmmm. I can't resist a challenge to sidestep obstacles and repair things - not at the expense of safety, I might add. I'd sooner spend the money on fuel and travel than in someone's workshop, especially when you look at what the 'professionals' did to it for a princely sum.

Will
user747Heavy
Posted: 13 December 2020 7:07 AM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2020-12-12 8:31 PM

747Heavy - 2020-12-12 3:59 PM
...
What if:

4. If the D+ isn't very robust and proves difficult to boost: The Battery cut-off relay is a FRC3A, 14 volt 70 amp item and is already ............................
Looking for snags with that idea:

Unfortunately this won't work. Terminal #30 on the relay is the common contact and will always have a voltage on it - either from just the starter battery or both batteries joined together (the "battery cut-off relay" is also known as the "split charge relay").
On the Fiat Ducato, the D+ (from the converters socket) can only drive one small relay so this is usually boosted by another relay somewhere to drive the split charge, auto-retracting step, B2B etc. I don't know the D+ drive capacity on the Merc. chassis. Perhaps this has a higher current drive?

747Heavy - 2020-12-12 3:59 PM
...
5. An alternative to point 4 above is to cut the PCB track links from Block 2, Pin 3 to the fridge relays, or physically remove the relays from the PCB. It would probably lighten the load on D+ enough to operate another relay - but is perhaps a bit perilous in terms of collateral damage to the PCB if all does not go well. I know a 'man who can' and he did an excellent repair to an Alde main board for me some years ago but I don't see it as a straightforward option getting the job done under the Covid rules and more expense if my point 4 is sensible.

I would not recommend trying to remove the relays with just a soldering iron as it is possible to damage the through-hole plating on the PCB. These can be removed easily with a hot-air gun with a controlled temperature to heat up all the pins simultaneously.

747Heavy - 2020-12-12 3:59 PM
A couple of questions:

i. What is the purpose of the Block 5, Pin 8 connection to Block 2, Pin 1? I've a feeling someone has told me but I can't find it. I can also see Block 2 Pin 1/Block 5, Pin 8 have a connection from the mains charger through the Charging relay B1, on through a diode, then a component I can't identify.
ii. What is that unidentified component and what is its purpose?
iii. Is Block 3 just the connection point for any additional charger to feed into the EBL?
iv. Just to muddy the water a bit more: when I first started investigating, the cable connected to Block 2, Pin 1 was looped through the original LR1218 solar charger/regulator Starter battery charging terminal.

i. Block 5 connects to your display unit and pin 8 is used to monitor the starter battery voltage.
ii. This is a PTC thermistor to limit the charge current going to the starter battery to about 2 Amps.
iii. Yes
iv. The LR1218 has a separate output to trickle charge the starter battery. Block 4 pin 2 on your EBL is not connected but on later EBLs, pin 2 is connected internally to the fridge power input (Block 2 pin 1 in your case). As mentioned previously, this pin normally has a dual function 1) to provide power to the fridge when driving and 2) to trickle charge the starter battery when not driving (from solar or EHU).
Although not mentioned in Schaudt / Votronics wiring diagrams, I would suggest fitting a 2A fuse in this line (from the solar controller) otherwise it is only protected by the 20A fuse near the starter battery.

Ref 4. Doh! OK, didn't work that one through. I'll go get my donkey ears. (Sticking to the excuse that I struggle reading circuit boards)
Looks like a mimic relay as you suggest is the simpler solution. I assume it's OK to bleed a little bit of (suitably fused) power from the input to the EBL from the alternator to use as the supply for the relay?

Ref 5. Copied. Leave well alone. Out of curiosity I'm going to test the functionality of the relays on the PCB, even if only to see what has been damaged.

Ref i to iv. Copied and thanks.

Will
user747Heavy
Posted: 13 December 2020 2:14 PM
Subject: RE: Another EBL/Fridge Problem
 
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"Ref 4. Doh! OK, didn't work that one through. I'll go get my donkey ears. (Sticking to the excuse that I struggle reading circuit boards)
Looks like a mimic relay as you suggest is the simpler solution. I assume it's OK to bleed a little bit of (suitably fused) power from the input to the EBL from the alternator to use as the supply for the relay? "

Oh, that was badly worded. I'll try again

I'll fit a Mimic relay as a substitute for the internal fridge relay system.

In order to produce a beefier D+ signal, I assume it would be OK to bleed a little bit of power (suitably fused) from the alternator circuit that feeds into the back of the EBL at E20-3F, on the 'starter battery (batt 1)' terminal, maybe even where it comes into Block 2, Pin1, by using a small relay controlled by the D+ signal which at the moment comes into Block 2, Pin3?

Hope that sounds better.

I got out a spare, small, 12 volt battery I keep topped up for testing things and tried the D+ circuit as it is. All the relays seemed to operate correctly. However: according to my my DMM there seems to be a short, not just continuity, across some of the relay terminals that shouldn't have a connection when the power is disconnected. Didn't want to push my luck and burn something else, so I've left it alone. There was probably a good reason the track was cut, D+ messed about with, then the whole project abandoned and the fridge wired direct to the hab battery. I think perhaps I've just found the reason. I've opted for the Mimic relay alternative that plwsm2000 suggested above and put the box back together.

Will
userplwsm2000
Posted: 13 December 2020 3:29 PM
Subject: RE: Another EBL/Fridge Problem
 
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I am not familiar with the Mercedes electrics so I don't know if you can just add another relay to the D+ (perhaps someone more familiar with the merc. sprinter could help?)

It is possible that "normally open" relay contacts have been welded shut giving you a continuous reading on the DMM. These relays are rated at 30A and as the fridge heater element is mainly resistive (not inductive) this suggestes that it was caused by very high current rather than through high voltage arcing (from inductive emf). It is possible that the original fridge had a dead short causing the pin damage and relay damage (just a guess). The 20A fuse should have blown but it is not uncommon for people to try a bigger fuse to attempt to fix the problem.

You only need to modify / repair your setup if you intended to make use of the excess solar output. The LR1218 does not have this feature so you would have to change your solar controller to a Votroic MPPT250 (or larger) or some other controller that has the AES control output.
As has already been said, unless you need this feature it might be best to leave alone for now.
userplwsm2000
Posted: 13 December 2020 3:34 PM
Subject: RE: Another EBL/Fridge Problem
 
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Will, I just re-read your post and you did not say what relay contacts are short. Just to point out the main power relay (not the fridge relays) in the EBL is a bistable (or remanence) type that keeps its on/off state even after power has been removed.
user747Heavy
Posted: 13 December 2020 4:03 PM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2020-12-13 3:29 PM

I am not familiar with the Mercedes electrics so I don't know if you can just add another relay to the D+ (perhaps someone more familiar with the merc. sprinter could help?)

It is possible that "normally open" relay contacts have been welded shut giving you a continuous reading on the DMM. These relays are rated at 30A and as the fridge heater element is mainly resistive (not inductive) this suggestes that it was caused by very high current rather than through high voltage arcing (from inductive emf). It is possible that the original fridge had a dead short causing the pin damage and relay damage (just a guess). The 20A fuse should have blown but it is not uncommon for people to try a bigger fuse to attempt to fix the problem.

You only need to modify / repair your setup if you intended to make use of the excess solar output. The LR1218 does not have this feature so you would have to change your solar controller to a Votroic MPPT250 (or larger) or some other controller that has the AES control output.
As has already been said, unless you need this feature it might be best to leave alone for now.

There is evidence of some 'creative' electrical work in other areas, so the bigger fuse scenario would be no great surprise. A good deal of the maintenance was a bit 'hammer and molegrips' standard.

The solar regulator I have is a Votronic SR330 - with the AES line. I know there are many who think trying to use the solar is more trouble than it's worth and you run the risk of flattening the hab battery if it's not monitored but I'll have a go. The Frankia's predecessor had a similar but slightly smaller solar system and it was not unusual to see it pushing 15 or 16 amps at the battery if we were loading the system up. I am also fitting a switch to that line so that I'm in charge of the 'if and when'. I fitted it because I was 'in there' fitting the new solar panels, etc, and it only entailed the addition of 5 metres of wire and a £1 rocker switch with a LED warning light on it.
This whole mess came to light in the process of fitting the solar.

Will
user747Heavy
Posted: 13 December 2020 4:14 PM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2020-12-13 3:34 PM

Will, I just re-read your post and you did not say what relay contacts are short. Just to point out the main power relay (not the fridge relays) in the EBL is a bistable (or remanence) type that keeps its on/off state even after power has been removed.

Understood. Afraid the EBL's back together and I'm going to be a bit of a wimp and stick to the extra relays to sort it out - but before I commit myself I will try the idea of fitting another relay onto the D+ without boosting it and see how it copes.

If the whole thing looks like getting too unwieldy, I'll simply get the EBL repaired, or get a reconditioned item. It's good to have a go at solving problems, though................ and I sure have learned a LOT about EBLs

Will
user747Heavy
Posted: 14 December 2020 8:22 AM
Subject: RE: Another EBL/Fridge Problem
 
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....... and a bit of your last post I didn't actually answer:

The 'short' seemed to me to be across the outputs of the upper fridge relay - but it was only me probing with a DMM. It would, I think, explain the cut track.
Another thing that has pinged into focus is the Scotch-Loc on the D+ output at Block 1, Pin 3. If whoever was trying to get the fridge working on the starter battery when the engine was running had tried to trigger a relay from that output and found it wasn't strong enough, they may well have given up and just wired it straight to the hab battery, then added the 'just-in-case' switch to the AES 12 volt supply, so it could be isolated regardless of what the EBL was doing.

It's all theorising but to my very much improved but still limited understanding of the EBL: It fits quite nicely.

Will
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Posted: 2 January 2021 1:53 PM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2020-12-12 8:31 PM...................
...................
iv. The LR1218 has a separate output to trickle charge the starter battery. Block 4 pin 2 on your EBL is not connected but on later EBLs, pin 2 is connected internally to the fridge power input (Block 2 pin 1 in your case). As mentioned previously, this pin normally has a dual function 1) to provide power to the fridge when driving and 2) to trickle charge the starter battery when not driving (from solar or EHU).
Although not mentioned in Schaudt / Votronics wiring diagrams, I would suggest fitting a 2A fuse in this line (from the solar controller) otherwise it is only protected by the 20A fuse near the starter battery.

I've just been looking at the 07/2019 published installation instruction leaflet for my Votronic SR330 solar regulator. It seems to show a 5 amp fuse on the Starter Battery trickle charge output you suggest as per the above could do with some protection. (I've tried clipping the diagram but can't get it below the 100Kb limit in any readable form.)
I think I'll hedge my bets and fit a 3 amp fuse. I somehow can't see the regulator output being as high as 5 amps.

Will
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Posted: 11 January 2021 4:59 PM
Subject: RE: Another EBL/Fridge Problem
 
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Update, and observations welcomed:

I have done the following:

1. Fitted a D+ booster relay
2. Fitted a ‘Mimic’ relay to replace the function of the EBL internal ‘absorption’ and ‘compressor/AES’ fridge relays
plus:
3. Fitted a Votronic SR330 solar regulator
4. Fitted a Votronic 200A Smart Shunt and display
5. Installed secondary fuse boxes to protect the additional wiring for the relays and the supplies to auxiliaries such as a fridge cooling fan, Smart Shunt feeds, etc.
6. Installed a Habitation Battery (Batt 2) negative terminal busbar (see #3)

The D+ booster relay is triggered by the D+ signal wire (see #1) that originally fed into the EBL Block 2, Pin 3. The output of the relay is fed back into Block 2, Pin 3 to maintain the D+ signal for the EBL but its main use is to trigger a ‘Mimic’ relay (suggested in previous posts) to connect the alternator feed to the fridge 12V heater when driving.

The output power for the D+ booster relay is obtained from a 1.5mm2 fused spur (see #1) taken from the original connection point on the back of the EBL at E20 3F. E20 3F is fed power via the original 50A fused, 10mm2 wire from the Starter Battery (Batt 1) into the back of the EBL. That 3A fused spur also provides a 1A independently fused reference feed for Batt 1 for use by the Smart Shunt.

The Mimic relay is an 80A 5 pin, with a diode snubber across 86/85 and has:
Batt 1 (starter battery) connected at terminal 87a [NO]
Batt 2 (habitation battery) connected at terminal 87 [NC]
Fridge heater 12v heater connected at terminal 30 [Common]
Output of D+ booster relay connected at terminal 86
Batt 2 negative busbar (see #3) connected at terminal 85
Power consumption is ± 130mA, so about 1.7W. I soak tested it with a bench power supply and it gets warm to touch but no more. When fitted, none of the wires/connectors got warm after the engine had been running with the fridge on for 30 minutes. Happily, that includes all my new (very carefully made) crimps on the terminals in the Mate-n-Lok connectors.

As found (during my investigation into the fridge wiring problems) the connection from Batt 1 (starter battery) into the EBL Block 2, Pin 1 was via a secondary ‘breakout’ connector. I believe this breakout connector is probably part of an accessory kit that was, in turn, part of the original installation of the LR1218 solar regulator.
The original feed (Frankia fitted) from Batt 1 to the original Block 2, Pin 1 connector is by 6mm2 wire. From the breakout it was then only 4mm2 to the LR1218 solar regulator (now removed), then back from the LR1218 to the EBL, again by 4mm2. I replaced the 4mm2 wire that originally went to the LR1218 with 6mm2 and used it as the Batt 1 supply for the Mimic relay (terminal 87a) to use for the 12v fridge heater when driving.
The 4mm2 wire that originally took the power from the LR1218 back into the EBL is now connected via a 3A fuse to the Batt 1 output of the new (Votronic SR330) solar regulator - but see #2.

#1 The D+ booster relay has a coil resistance of 75 Ohms (at rest), ie 160mA-ish of power consumption to operate it. Its holding current consumption hasn’t been tested. Does that seem a reasonably light load on the D+ circuit? I have no way that I can see of testing the original EBL relays to measure if they consumed as much power - especially since they appear to be shot.

#2 As far as I can see from the EBL wiring schematic, now that the original connection into Block 2, Pin 1 from Batt 1 (for the 12V fridge heater) goes directly to the Mimic relay and not into Block 2, Pin 1, the trickle charge for Batt 1 from the solar system (or from the EBL when on EHU), now has no connection to Batt 1. If I take a 1.5mm2 link (fused 3A) back to Batt 1 connection to the EBL at E20 3F, it should suffice for the minimal current flow (2A max) back into Batt 1.

#3 The original battery terminals looked like Spaghetti Junction. Apart from the skinny cables to the old 1200W inverter there were plenty of just plain scruffy, nasty, badly made crimped connections, To make a much tidier job of the wiring and to make the fitting of the Smart Shunt easier, I’ve fitted a battery negative busbar.
In the process it’s also made a lot neater job of the wiring for the Eberspacher diesel heater, the air suspension compressor, the new 500W inverter and various other ‘add-on’ circuits the old girl has gained over the years.

If anyone can shoot holes in the setup, please fire away!

To add to the above:
I've seen various comments on other forums that motorhome converters frequently do not follow fridge manufacturer's installation instructions.
Turns out Frankia is no different:
The external vents were the L200 type and for this fridge they ought to be at least L300s to get rid of the much higher volume of heat generated. The power consumption of the fridge is 170 Watts on 12 volt, 190 Watts on 220 volt. That's almost 50% up on the old 120 Watt units that were the base option on the motorhome - and they used the same vents.
Whoever replaced the fridge compounded the issue since the new fridge doesn't have a dedicated gas burner flue like the old one, it passes the gas exhaust out with the flow from the heat exchanger. As a consequence the frame of the upper vent is so damaged by heat that it has gone crispy.
There is no gas dropout fitted at the rear of the fridge, even though it is recommended by the manufacturer. The lower vent is positioned so that it makes a 50mm lip above the base of the housing. Any gas leak would have to build up above that level before it could start to escape.
There is no heat deflector at the top of the fridge housing. Whether it was removed and not replaced when the fridge was replaced, I can't tell.
I've bought two L300 vents and I'll also be fitting a dropout vent and a heat deflector.

Will

Edited by 747Heavy 2021-01-11 5:12 PM
userplwsm2000
Posted: 19 January 2021 7:02 PM
Subject: RE: Another EBL/Fridge Problem
 
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Will, Thanks for the pm. I thought it best to add my comments to this thread in case it is of use to someone else.

747Heavy - 2021-01-11 4:59 PM
The output power for the D+ booster relay is obtained from a 1.5mm2 fused spur (see #1) taken from the original connection point on the back of the EBL at E20 3F. E20 3F is fed power via the original 50A fused, 10mm2 wire from the Starter Battery (Batt 1) into the back of the EBL. That 3A fused spur also provides a 1A independently fused reference feed for Batt 1 for use by the Smart Shunt.
You will still be relying on the 50A fuse to protect this new 1.5sqmm wire (before it gets to the new 3A fuse). An unused output on Block 6 (eg circuit 4 on pin 8) would have been preferrable with a smaller fuse fitted.

747Heavy - 2021-01-11 4:59 PM
The Mimic relay is an 80A 5 pin, with a diode snubber across 86/85 and has:
Batt 1 (starter battery) connected at terminal 87a [NO]
Batt 2 (habitation battery) connected at terminal 87 [NC]
Correct that the starter battery should be connected to NO. but this is on relay pin 87. NC is 87a. Is this just a typo?

747Heavy - 2021-01-11 4:59 PM
As found (during my investigation into the fridge wiring problems) the connection from Batt 1 (starter battery) into the EBL Block 2, Pin 1 was via a secondary ‘breakout’ connector. I believe this breakout connector is probably part of an accessory kit that was, in turn, part of the original installation of the LR1218 solar regulator.
This was probably the solar charger output for the starter battery. What you have done seems ok to me.

747Heavy - 2021-01-11 4:59 PM
#1 The D+ booster relay has a coil resistance of 75 Ohms (at rest), ie 160mA-ish of power consumption to operate it. Its holding current consumption hasn’t been tested. Does that seem a reasonably light load on the D+ circuit? I have no way that I can see of testing the original EBL relays to measure if they consumed as much power - especially since they appear to be shot.
I am not familiar with the Merc. chassis but the D+ on the Fiat convertors socket can only drive one relay (and it also switches the 0V pin). The FRA2C relay coil spec. is 133mA at 12V and there were two of them on your EBL. Assuming you removed these relays, it should be fine. If you have not removed the old relays, then you just need to check the merc. D+ is capable of driving another 160mA or so.
My Frankia is fitted with a Schaudt AD01 (for Fiat chassis) that has a number of "booster" relays for D+, external position lights, ignition etc. I noticed that the Merc version (AD02) has the same boosters except for D+ so I would assume that the merc. chassis doesn't need this extra relay?
user747Heavy
Posted: 20 January 2021 11:34 AM
Subject: RE: Another EBL/Fridge Problem
 
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plwsm2000 - 2021-01-19 7:02 PM

Will, Thanks for the pm. I thought it best to add my comments to this thread in case it is of use to someone else.

747Heavy - 2021-01-11 4:59 PM
The output power for the D+ booster relay is obtained from a 1.5mm2 fused spur (see #1) taken from the original connection point on the back of the EBL at E20 3F. E20 3F is fed power via the original 50A fused, 10mm2 wire from the Starter Battery (Batt 1) into the back of the EBL. That 3A fused spur also provides a 1A independently fused reference feed for Batt 1 for use by the Smart Shunt.
You will still be relying on the 50A fuse to protect this new 1.5sqmm wire (before it gets to the new 3A fuse). An unused output on Block 6 (eg circuit 4 on pin 8) would have been preferrable with a smaller fuse fitted.

Point taken, it is effectively inappropriately protected for that 1/2 metre run, isn't it. I'll investigate - but if, for example, Block 4, Pin 8 is used does that not mean the supply for the output of the D+ booster is from the hab battery? At the time it seemed appropriate to obtain the boosted D+ from the same source as the original, ie the starter battery/alternator, or does it not really matter where it gets its supply from? I can see that there is little chance that the system would be required to function without the hab battery installed. Either way it would be easy enough to fit an inline 3A fuse to protect the cable at the point where if emerges from E20 3F.


747Heavy - 2021-01-11 4:59 PM
The Mimic relay is an 80A 5 pin, with a diode snubber across 86/85 and has:
Batt 1 (starter battery) connected at terminal 87a [NO]
Batt 2 (habitation battery) connected at terminal 87 [NC]
Correct that the starter battery should be connected to NO. but this is on relay pin 87. NC is 87a. Is this just a typo?

Yep, a typo. I made myself a diagram, made a notation error, corrected it - then promptly repeated the error in the above text.


747Heavy - 2021-01-11 4:59 PM
As found (during my investigation into the fridge wiring problems) the connection from Batt 1 (starter battery) into the EBL Block 2, Pin 1 was via a secondary ‘breakout’ connector. I believe this breakout connector is probably part of an accessory kit that was, in turn, part of the original installation of the LR1218 solar regulator.
This was probably the solar charger output for the starter battery. What you have done seems ok to me.

Yes, it was said solar charger output for the starter battery, with a (almost certainly an original Schaudt) breakout connector forming a loop in the Frankia original 6mm2 run to the EBL with quite skinny cable.


747Heavy - 2021-01-11 4:59 PM
#1 The D+ booster relay has a coil resistance of 75 Ohms (at rest), ie 160mA-ish of power consumption to operate it. Its holding current consumption hasn’t been tested. Does that seem a reasonably light load on the D+ circuit? I have no way that I can see of testing the original EBL relays to measure if they consumed as much power - especially since they appear to be shot.
I am not familiar with the Merc. chassis but the D+ on the Fiat convertors socket can only drive one relay (and it also switches the 0V pin). The FRA2C relay coil spec. is 133mA at 12V and there were two of them on your EBL. Assuming you removed these relays, it should be fine. If you have not removed the old relays, then you just need to check the merc. D+ is capable of driving another 160mA or so.
My Frankia is fitted with a Schaudt AD01 (for Fiat chassis) that has a number of "booster" relays for D+, external position lights, ignition etc. I noticed that the Merc version (AD02) has the same boosters except for D+ so I would assume that the merc. chassis doesn't need this extra relay?


Understood. Seems a bit surprising, considering the almost infinite variety of alternators available, that Fiat should need the boost and Merc not so. A base vehicle cost function and/or converter's option? A job for a very wet week but maybe I can find the spec of the Merc/Frankia fitted alternator if I dig deep enough.
I'm afraid I took the easy option of sidestepping the original D+ output capability question by assuming it wasn't good enough to operate additional relays but see below, because:

I think I didn't explain what I'd done well enough.
The original D+ booster relay trigger circuit from the alternator (originally into the EBL at Block 2, Pin 3) has been rerouted as the actuating supply for the new D+ booster relay (terminal 86). It is now the only job of that D+ output from the alternator. The boosted output is now used to trigger the fridge mimic relay and is also fed (fused 2A) back into the EBL at Block 2, Pin 3 so that all the original functions of the D+ circuit (eg, step retraction and starter battery cut-off relay) are still available.
I've since had a chance to test the new D+ relay. It draws <140mA holding current at 12 volts. By my calculation, using your figures for the FRA2C relays, I've effectively almost halved the original EBL load on the raw D+ output from the alternator?

The whole exercise has thrown up yet another question. After a (very rough and ready) check, the alternator doesn't seem to produce much over 13.6 volts at the hab battery terminals. I think I need to disconnect the solar, run the hab and starter battery down a bit, then try again - at both ends of the charging circuit. The alternator is almost certainly as old as the vehicle's now 18 years, so entitled to be a bit tired, I guess.

Once again, thank you for your help and patient explanation. It's very much appreciated.

Will

Edited by 747Heavy 2021-01-20 11:36 AM
userKeithl
Posted: 20 January 2021 12:05 PM
Subject: RE: Another EBL/Fridge Problem
 


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747Heavy - 2021-01-20 11:34 AM

...maybe I can find the spec of the Merc/Frankia fitted alternator if I dig deep enough.
Will

Will,

If you enter your VIN on http://mbepc.net/f/vin/ you will get your full Data Card showing exactly how your MB chassis was built, including your alternator spec.

747Heavy - 2021-01-20 11:34 AM

The original D+ booster relay trigger circuit from the alternator...
Will

When you get your Data Card look for 'EK1 Terminal strip for electrical connection' otherwise known as the Body builders terminal. If you have this option it will be located underneath your drivers seat approximately in line with the handbrake lever. One of the three terminals is a D+ feed rated at 10 Amps.

Keith.



(EK1 Terminals.jpg)



Attachments
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Attachments EK1 Terminals.jpg (101KB - 6 downloads)
user747Heavy
Posted: 20 January 2021 12:27 PM
Subject: RE: Another EBL/Fridge Problem
 
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What a star!
Thanks, I'll look.

Will
user747Heavy
Posted: 20 January 2021 12:44 PM
Subject: RE: Another EBL/Fridge Problem
 
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Rats!
'No Data Card Available'
Thanks for the 'nice try', though.

Will ;)
userKeithl
Posted: 20 January 2021 12:50 PM
Subject: RE: Another EBL/Fridge Problem
 


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747Heavy - 2021-01-20 12:44 PM

Rats!
'No Data Card Available'
Thanks for the 'nice try', though.

Will ;)

PM me your VIN and I'll try a few others for you.

Keith.
user747Heavy
Posted: 20 January 2021 1:18 PM
Subject: RE: Another EBL/Fridge Problem
 
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Thanks.

PM sent.

Will
userKeithl
Posted: 20 January 2021 5:04 PM
Subject: RE: Another EBL/Fridge Problem
 


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Problem sorted with Will's VIN, I'm sure he will be back soon with more questions

Will, the 'stock' alternator on a T1N Sprinter was 90 Amps.

Keith.
user747Heavy
Posted: 21 January 2021 10:51 AM
Subject: RE: Another EBL/Fridge Problem
 
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Keithl - 2021-01-20 5:04 PM

Problem sorted with Will's VIN, I'm sure he will be back soon with more questions ..............

Keith.

I'll have you know I resemble that remark!

Thanks for the info, Keith.

Will
user747Heavy
Posted: 27 January 2021 10:04 AM
Subject: RE: Another EBL/Fridge Problem
 
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BruceM - 2020-12-11 11:03 AM

I’ve found this a fascinatingly informative thread and a great insight into the workings of the EBL’s fridge electronics.

Whilst I’ve nothing practical to add to the superb insight provided by the other posters I still wonder why use of the EBL refrigerator AES output was abandoned. As I see it, the AES fridge output probably failed (relay defect?) so the absorption fridge circuitry was repurposed for this function. This may well have been a professional ‘repair’. This makes me question why when the new fridge was installed, it didn’t make use of the EBL fridge output?

If you have the inclination and time, it would be interesting to measure the voltage on Block 1 pin 2 (AES +ve output) both with the vehicle engine off and the engine running to see if if the appropriate +ve voltages are present. If not then I guess the EBL repair was insufficient and abandoned, if it is present then the mystery remains.

Reading back, I realise I haven't done this.
That said, I think, even if the correct voltage appears at the output, the apparent damage to the internal relays is sufficient proof of why it was abandoned. Probably they cut and linked the tracks, only to find the relays were stuffed anyway. Nice try, no banana!
When I get the chance, I'll measure it, even if only out of curiosity. It may be a while - but there seems to be plenty more lockdown time left to fill................

Will
user747Heavy
Posted: 27 January 2021 10:28 AM
Subject: RE: Another EBL/Fridge Problem
 
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BruceM - 2020-12-12 4:21 PM

I won’t attempt to provide an opinion on all your options, there are those much better technically qualified on this forum than I to do so.

I will however say ..................

.............. Rather than make further changes to the EBL’s functional design, would it be wiser and perhaps kinder to the next owner of the van to either have your EBL repaired or even swap it for a reconditioned unit and wire the fridge in correctly?

I'm in the process of putting together a wiring diagram that I'll put with the vehicle documents and tape another copy in a sleeve to the underside of the seat base that houses the EBL.
If nothing else it will remind me when, hopefully on the very rare occasion, I go to look in there.
Add to that, I don't think I'd want to inflict on anyone the amount of effort required to understand what the hell had gone wrong in the first place!

Will
user747Heavy
Posted: 27 January 2021 10:40 AM
Subject: RE: Another EBL/Fridge Problem
 
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Right!

The problem is solved - well, at least gone away!

Everything now works as it should, albeit in a somewhat non-standard way. When I look at the amount of extra wiring, relays and fuses, it shows just how compact and efficient the Schaudt EBL units are when you take into account the desired end result.
My only criticism of them is that they are maybe not as robust in some areas as they could be and would benefit from better overload protection devices that cannot be circumvented by the congenitally daft owner, ie, fixed, resettable circuit breakers on some circuits.
I have only one problem left to solve, it's not something caused by the 'meltdown' of the original fridge/EBL, it's a problem caused by the poor design and inefficiencies of the Dometic AES system. In short, when the solar S+ triggers, the fridge switches to solar, even if the EHU is on line. Que?
The S+ line from the solar is now switched but I think I favour the 'failsafe' option.

The last thing I have to do is thank all the Forum members who's knowledge, skills and endless patience have allowed me to sort this problem out. Without your help it could have been an expensive visit to a repair shop and in the current environment, not likely to have happened anytime soon. In the process I've learned far more about Schaudt EBLs than I ever anticipated - or hoped I would need to ........... plus it's something to keep me occupied and sane(ish) during Lockdown.
There are too many to list and thank but I must offer particular thanks to Alan (Alanb) and Paul (plwsm2000). You, Sirs, have the patience of Saints.

Will.
ps Keithl: Quite correct, I've found another! INCOMING ...................
userAlanb
Posted: 27 January 2021 2:00 PM
Subject: RE: Another EBL/Fridge Problem
 
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Thanks appreciated Will, but more due to pwlsm2000.

May I praise the intention to leave details of modifications.

Alan
user747Heavy
Posted: 27 January 2021 3:23 PM
Subject: RE: Another EBL/Fridge Problem
 
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Alanb - 2021-01-27 2:00 PM

Thanks appreciated Will, but more due to pwlsm2000.

May I praise the intention to leave details of modifications.

Alan

Modesty is an admirable character trait - but OK, agreed, plwsm2000 has awesome knowledge, no denying it.
Reference the diagrams: This is by no means the only 'issue' I've had to resolve. The poor old thing has had quite a bit of inexpert modification over the years.
The wiring diagrams for this motorhome simply don't exist, even for the original layout. Frankia only responded with a 'Nein', very polite but 'Nein'.
It seemed only fair to give someone a clue to my work and modification, especially considering all the effort put into getting there. It was bad enough when I had an idea/inkling regarding what had happened and a lot of help resolving it. Now it's basically a fair proportion of the guts of an EBL laid bare and in more robust form, so to the uninitiated? a potential 'Whhaaaaaattt?'. Run away............

Will
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