12V switching off.

[sydnsue]

I haven't found anywhere to buy one yet. I possibly could have bought one at the camper shop but after fitting the new battery and everything came back on I expected the problem was solved. We left Barcelona after buying the battery and from there we have been on motorways or rural stopovers. Today in Valencia and nothing of the sort around the centre. All designer shops and restaurants. As I said, on Monday we will be in Gandia where there is supposed to be a good motorhome workshop so I shall leave it to them.
Pulled into a site today for Valencia and all the 12V is working fine. The problem is now so intermittent I am wondering if it is something as simple as a bad connection. I'm not sure where to start , especially when it is all working. Grrrr.

 

[merl]

Gotta love those intermittent faults......NOT!

 

[sydnsue]

If you're anywhere near Benicarlo, Tambo Motorhomes are great. Not cheap, but thorough, and Ramon (Tambo) started as Motorhomers (think he may have worked at the Benimar factory), and built up the repair and servicing side. He brought a caravan fridge back to life in 2 hours when another 'engineer' said it was incapable of being repaired, and Ramon is skilled at taking the manufacturer system, spotting the weak point, and putting in an adaptation that will give a permanent fix. And you can park the M/home outside overnight if the same day fix is not possible. He always has at least 1 French/German/British M/homer 'xyz stopped working last night; we're on our 3 months Winter Sun Trip' in the 'Emergency Bay'! It was what spurred his business growth ...

Steve

We went past Brnicarlo a few days ago. It's a long way to turn back but thanks.

 

[sydnsue]

Can't find a full schematic for it so it's not easy to ascertain what could be happening with absolute accuracy. At first I thought one of the many 12v circuits could be overloaded and this was causing some sort of automatic power trip out but I really can't see any company trying to incorporate such a unit, after all you've got fuses to do that job anyway.
Your lights, pump etc are all taken back to the pdu as is the power from the leisure battery, it appears (from the only schematic I can find) the pdu has relays acting as isolation switches in the negatives. Personally, rather than struggling for 3 weeks I'd be tracing the negatives to lights, pump etc within the unit and linking them directly to the leisure battery negative and effectively bypassing the switching altogether enabling critical stuff to remain operational.
A multimeter would be really handy checking the above out!

Thanks for the trying Merl. Our dealer said something about the PDU switching off due to the lithium but it still did it after fitting the AGM. So much for the experts. I also thought about bypassing the PDU for lights and pump but that may be beyond my confidence level. I'm now favouring a loose connection but can't understand why the fridge lights appear but switching power on all goes dead. Surely if a connection was broken, the fridge would not light. Hopefully will see a workshop tomorrow.

 

[merl]

Thanks for the trying Merl. Our dealer said something about the PDU switching off due to the lithium but it still did it after fitting the AGM. So much for the experts. I also thought about bypassing the PDU for lights and pump but that may be beyond my confidence level. I'm now favouring a loose connection but can't understand why the fridge lights appear but switching power on all goes dead. Surely if a connection was broken, the fridge would not light. Hopefully will see a workshop tomorrow.

That depends on where the fridge gets it's ignitor power from, mine has a battery behind the igniter button. What puzzled me at first was that ALL power is lost when the unit clicks off, including the supplies that are supposedly "always on" but the schematic that I downloaded shows relays in the negatives of EVERYTHING including the circuits that are always on! Why they put a switch (relay) in a circuit that needs to be permanently on I can't grasp ATM but it means that it's possible to lose ALL power to EVERYTHING if the unit develops a fault. Crap design .
I reckon the issue will be with the circuitry that works the remote switching, it'll be very simple and probably a component that's become heat or voltage sensitive. Maybe that's why it worked fine with the replacement battery until you gave it a really good charging while driving?
If you open up the unit and see where the cables to all the appliances connect to, hopefully they are labelled up, that'll make things very simple. While you're on site why don't you ask a foreign camper for the location/ names of the equivalent of Screwfix/ Toolstation? They'll have a cheap meter and cable and connectors if you need anything like that to get the job sorted.

 

[wildebus]

That depends on where the fridge gets it's ignitor power from, mine has a battery behind the igniter button. What puzzled me at first was that ALL power is lost when the unit clicks off, including the supplies that are supposedly "always on" but the schematic that I downloaded shows relays in the negatives of EVERYTHING including the circuits that are always on! Why they put a switch (relay) in a circuit that needs to be permanently on I can't grasp ATM but it means that it's possible to lose ALL power to EVERYTHING if the unit develops a fault. Crap design .

The BCA PDU is not a very clever or good unit (IMO). I don't know of any diagrams being available for them, so it is very much a matter of sitting there with a notepad and pencil plus a meter and making notes of what happens when you do various things.

I reckon the issue will be with the circuitry that works the remote switching, it'll be very simple and probably a component that's become heat or voltage sensitive. Maybe that's why it worked fine with the replacement battery until you gave it a really good charging while driving?
If you open up the unit and see where the cables to all the appliances connect to, hopefully they are labelled up, that'll make things very simple. While you're on site why don't you ask a foreign camper for the location/ names of the equivalent of Screwfix/ Toolstation? They'll have a cheap meter and cable and connectors if you need anything like that to get the job sorted.

 

[sydnsue]

The fridge is weird. When the door opens, the interior light switches on but the panel lights go out. Close the door and the panel lights come on again. I don't think it's from a small battery because when the power button is pressed, it kills the fridge completely. Disconnecting and reconnecting the leisure battery brings the panel lights on again.
I'm in Gandia where there is a caravan workshop so I'm hoping they can do something. Even hardwiring the lights and the pump directly to the battery will get us home. Just hope they speak English. I have my friend who lives here but even his Spanish is so so.

 

[sydnsue]

Now you are all going to tell me why didn't I do this first. I started removing fuses on by one and pressing the power button. The power kept disconnecting until I removed the fuse labeled space heater. The power stays on. Clearly the heater has a problem. Not sure why it would react when it's not switched on.
So being in Spain with 30 degrees we will not need it so the heater will be a problem to sort when back home. Good news for now especially as I don't need a workshop now.
Thanks everyone for your assistance. My next post will be about how to fix a heater. I think it is Whale. I have separate water heater and space heater which is a good idea for once.

 

[merl]

Now you are all going to tell me why didn't I do this first. I started removing fuses on by one and pressing the power button. The power kept disconnecting until I removed the fuse labeled space heater. The power stays on. Clearly the heater has a problem. Not sure why it would react when it's not switched on.
So being in Spain with 30 degrees we will not need it so the heater will be a problem to sort when back home. Good news for now especially as I don't need a workshop now.
Thanks everyone for your assistance. My next post will be about how to fix a heater. I think it is Whale. I have separate water heater and space heater which is a good idea for once.

Bah, I nearly suggested that but thought it was a silly idea.

"At first I thought one of the many 12v circuits could be overloaded and this was causing some sort of automatic power trip out but I really can't see any company trying to incorporate such a unit,"

I reckon I must have put the idea into your head subliminally

Still can't understand why a fault would make it switch off rather than take a fuse out but hey ho, always learning

 

[wildebus]

Bah, I nearly suggested that but thought it was a silly idea.

"At first I thought one of the many 12v circuits could be overloaded and this was causing some sort of automatic power trip out but I really can't see any company trying to incorporate such a unit,"

I reckon I must have put the idea into your head subliminally

Still can't understand why a fault would make it switch off rather than take a fuse out but hey ho, always learning

It is a strange one isn't it. You would suspect that to be more the behaviour of a bad battery?

However ... here is a possible explanation .... Fuses as we all know have a certain rating. However, as we also know, that rating means the fuse will blow if the rated current is exceeded for a certain time and they will cope with higher currents for a short duration and big power surges for shorter durations still.
Then we have a Lithium Battery that has an internal BMS that has a maximum allowed current and if that is exceeded the battery will turn off.
Is it maybe the heater has a short circuit on the 12V side (maybe there is a ventilation fan that has failed and shorted out?) and the fuse copes with the current surge longer than the BMS takes to turn the battery off?

That doesn't fully cover the fact that the same problem happened on a Lead Battery which of course has no BMS. But I maybe have an explanation that could cover both battery types and and something that I can get my own motorhome to do if I am not careful!
I have an Extractor Fan Roof Vent in the kitchen which I can set to pull air in or extract. My Hab Electrics are supplied via a Regulated Supply with a limit of 18Amps (actually via a Victron Orion). If I have the fan on and I switch it from IN to OUT (or vice-versa) too fast, that seems to create some kind of short or surge and the Hab power is killed as the Orion overloads. So in MY case, it is not actually the battery that is turning off but a regulator turning off. The reason is known and problem repeatable (of course, I don't think I have a fault, it is just a design thing with the fan).

 

[sydnsue]

Spoke to soon. Power is off again. Heater fuse is still out. Sort of good news as a new heater is £1200. Tried pulling all fuses again but no joy. Even the fridge is off now. This has to be something in the PDU. We are having to use sites now just for the fridge.

 

[merl]

It is a strange one isn't it. You would suspect that to be more the behaviour of a bad battery?

However ... here is a possible explanation .... Fuses as we all know have a certain rating. However, as we also know, that rating means the fuse will blow if the rated current is exceeded for a certain time and they will cope with higher currents for a short duration and big power surges for shorter durations still.
Then we have a Lithium Battery that has an internal BMS that has a maximum allowed current and if that is exceeded the battery will turn off.
Is it maybe the heater has a short circuit on the 12V side (maybe there is a ventilation fan that has failed and shorted out?) and the fuse copes with the current surge longer than the BMS takes to turn the battery off?

That doesn't fully cover the fact that the same problem happened on a Lead Battery which of course has no BMS. But I maybe have an explanation that could cover both battery types and and something that I can get my own motorhome to do if I am not careful!
I have an Extractor Fan Roof Vent in the kitchen which I can set to pull air in or extract. My Hab Electrics are supplied via a Regulated Supply with a limit of 18Amps (actually via a Victron Orion). If I have the fan on and I switch it from IN to OUT (or vice-versa) too fast, that seems to create some kind of short or surge and the Hab power is killed as the Orion overloads. So in MY case, it is not actually the battery that is turning off but a regulator turning off. The reason is known and problem repeatable (of course, I don't think I have a fault, it is just a design thing with the fan).

Yes, it's something unusual for sure and as you say can't be the BMS cutting out because it does the same with the replacement AGM.
It's similar to a mains RCD tripping because of an earth fault but obviously there's no such arrangement on the 12v side, when you think about it MUST be current related and therefore there must be some sort of additional over current circuitry that's cutting the 12v off, and because the 'electronic fuse' works way faster than a conventional fuse the conventional fuse doesn't have time to blow.
Alternative theories welcome

 

[merl]

Spoke to soon. Power is off again. Heater fuse is still out. Sort of good news as a new heater is £1200. Tried pulling all fuses again but no joy. Even the fridge is off now. This has to be something in the PDU. We are having to use sites now just for the fridge.

AHH, the genuine explanation is just a coincidence and there's not an addition fail safe!!! I love electronics