power supply replacement

[paulllewellyn123]

Hi folks, new here so please bear with me. Just bought a Lunar 516, 1995. Plugged it into the mains and no center lights working. Looked at the breaker rcd and oh! the power supply unit has gone awol. I dont think i will get an original replacement so does anyone know of a compatible item that i could buy please. Its a KT 125 SM. Many thanks. Paul Llew

 

[SteveW]

I don’t know your van, but… My advice would be to dump the idea of using typically rubbish caravan electrical parts and fit a decent Victron charger. May not cost any more than a spare part. In another league. Bluetooth interfaced. Very configurable in terms of voltages, charging parameters etc, supports lithium if you want in the future too,

Steve

 

[Dustydog]

Contact these guys. They can repair / re manufacture most PSUs

Apuljack Electronics

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www.apuljackelectronics.co.uk

 

[Jcloughie]

I don’t know your van, but… My advice would be to dump the idea of using typically rubbish caravan electrical parts and fit a decent Victron charger. May not cost any more than a spare part. In another league. Bluetooth interfaced. Very configurable in terms of voltages, charging parameters etc, supports lithium if you want in the future too,

Steve

How would that assist with the OP’s mains power supply problem?

John

 

[SteveW]

How would that assist with the OP’s mains power supply problem?

John

I gained the impression he had no working 12v PSU?

 

[paulllewellyn123]

Yes, the power supply has gone, some previous owner must have removed it, and i need to replace it. cheers lads

 

[RogerL]

As a short term measure, just use a smart charger directly onto the battery - did me proud for 17 years in our first caravan so can be a long-term fix too.

 

[paulllewellyn123]

please feel free to correct me if im wrong chaps, but shouldnt the lights work from a mains 240v connection without a battery on the van. they dont work and cant work without the transformer being in place. Of coarse if i connect a 12v batt then the lights work. We only ever go to a camp site with 240v hookup and so never had need for a batt in the past.

 

[Gralay]

please feel free to correct me if im wrong chaps, but shouldnt the lights work from a mains 240v connection without a battery on the van. they dont work and cant work without the transformer being in place. Of coarse if i connect a 12v batt then the lights work. We only ever go to a camp site with 240v hookup and so never had need for a batt in the past.

Usually most of the lights are 12v the 2 lights in the lounge area in line with the lockers (wall lights) are the only 240v lights.
Hope this helps
Gra

 

[Jcloughie]

please feel free to correct me if im wrong chaps, but shouldnt the lights work from a mains 240v connection without a battery on the van. they dont work and cant work without the transformer being in place. Of coarse if i connect a 12v batt then the lights work. We only ever go to a camp site with 240v hookup and so never had need for a batt in the past.

Your van will have two circuits.

1. A mains which normally only does a couple of lights, supply's the sockets, is an option to heat the water and to supply the PSU (Power Supply Unit), which, in turn, powers the 12 volt system and keeps the battery charged.

2. A 12 volt circuit which does most of the lights, a radio and a few outlets. This is supplied by the battery and/or the PSU.

Therefore, if you use 12 volt you may not have the mains powered lights. And you will be time limited depending on battery size.

You can just use mains and rely on the PSU. BUT. It is recommended that you always have a battery attached to smooth out fluctuations. Even if it it only a small one.

If the PSU fails and you have no battery. You will lose most of your lights. You could use a smart charger as suggested earlier. But you would definitely need a battery. Also, a smart charger is perhaps 2amp compared to about 20amp for a PSU. So not man enough.

You need to identify just what has failed. If it is the PSU they are interchangeable. BUT. Might require an electrician.

John

 

[paulllewellyn123]

Thanks John, yes you are correct in saying the 2 lights in the lounge area are 240v (the only ones which work at the moment). PSU has been removed previously for some reason. I didnot realise that a batt should always be connected, we have never used one on our previous van (bailey pagent cd) always gone where there is power hookup. will get a small leasure batt for the job, still need to get a psu tho
paul

 

[RogerL]

You could use a smart charger as suggested earlier. But you would definitely need a battery. Also, a smart charger is perhaps 2amp compared to about 20amp for a PSU. So not man enough.

A smart charger doesn't need to be as powerful as a PSU - ours was 3.6A with the battery providing the rest and then recovering when lights, pump, etc not in use - as I posted, we managed for 17 years like that - just an old car battery and a smart charger was all we used.

 

[RogerL]

Thanks John, yes you are correct in saying the 2 lights in the lounge area are 240v (the only ones which work at the moment). PSU has been removed previously for some reason. I didnot realise that a batt should always be connected, we have never used one on our previous van (bailey pagent cd) always gone where there is power hookup. will get a small leasure batt for the job, still need to get a psu tho
paul

If you're always on EHU, an old car battery will do - just to smooth the voltage out.

 

[paulllewellyn123]

As an aside, we just bought the van, 1995 model Lunar 516 for 300 quid. Inside is great, but has several issues, fridge gone, gas feed pipe underneath the van has been cut and blanked off, water heater has been disconnected, prob due to a leak, PSU gone. Fortunately, most of this can be solved using our bailey pagent cd as a donner van, and scrap what is left of it. Its coming along nicely, new skylights installed, the alluminium strip running down the centre of the roof has been removed and resealed. Seats from the pagent fit quite nicely, so they will be going in when all the work is complete
paul

 

[Jcloughie]

A smart charger doesn't need to be as powerful as a PSU - ours was 3.6A with the battery providing the rest and then recovering when lights, pump, etc not in use - as I posted, we managed for 17 years like that - just an old car battery and a smart charger was all we used.

I think it only doesn't need to be as powerful if you have sufficient battery (The OP had none), and you monitor the use. I had a week of this. My PSU failed and I had an Aldi smart charger with me. I used this for a few hours a day and limited my use during this time. I may have been being over careful. But I guess that PSU’s are 20ish amps for a reason.


John

 

[RogerL]

I think it only doesn't need to be as powerful if you have sufficient battery (The OP had none), and you monitor the use. I had a week of this. My PSU failed and I had an Aldi smart charger with me. I used this for a few hours a day and limited my use during this time. I may have been being over careful. But I guess that PSU’s are 20ish amps for a reason.


John

A PSU needs to be able to supply all 12v items simultaneously, hence the 20A ouput - in the same way that people manage off-grid, the battery also needs to be able to supply that same rate - however that rate isn't sustained continuously so a smart charger of 3.6A is able to supply enough long term power to prevent the battery going flat.

 

[ProfJohnL]

.... I guess that PSU’s are 20ish amps for a reason...

Yes- there was an NCC technical document that advised manufacturers should fit a mains powered Power Supply Unit (PSU) capable of running a number of items in the caravan without a battery, which is why during the 1990's caravan chargers (which needed a battery to smooth the current delivery) where replaced with 'proper' power supplies with smoothing and regulation. These started with about 8A units and have steadily increased in capacity as the range of standard bells and whistles increased with each new model. Typically 12or 16A units with some specials rated at 20A began to get fitted.

Theoretically modern (post 2010) caravans do not need a battery unless you have a caravan mover, but as is always the case with caravans, you can't assume anything will always be the case, so a battery can usually help.

 

[Jcloughie]

A PSU needs to be able to supply all 12v items simultaneously, hence the 20A ouput - in the same way that people manage off-grid, the battery also needs to be able to supply that same rate - however that rate isn't sustained continuously so a smart charger of 3.6A is able to supply enough long term power to prevent the battery going flat.

I agree, and that is why I said it needs to be monitored. It may be OK, but I would worry if I applied more than the chargers output to the circuitry. I don't know if the battery would take up the shortfall, or if the charger would be overloaded.

Yes- there was an NCC technical document that advised manufacturers should fit a mains powered Power Supply Unit (PSU) capable of running a number of items in the caravan without a battery, which is why during the 1990's caravan chargers (which needed a battery to smooth the current delivery) where replaced with 'proper' power supplies with smoothing and regulation. These started with about 8A units and have steadily increased in capacity as the range of standard bells and whistles increased with each new model. Typically 12or 16A units with some specials rated at 20A began to get fitted.

Theoretically modern (post 2010) caravans do not need a battery unless you have a caravan mover, but as is always the case with caravans, you can't assume anything will always be the case, so a battery can usually help.

No doubt you are right. But whenever the topic of the need for a battery has been discussed before, the advice is invariably to use a small battery.

John