12v

[Practicallycaravanned]

Hi - I have a 1980s caravan with 240v distribution (sockets, lights, fridge).
All is fine (we always stay at a site with an EHU), except the water pump/tap is 12v!
Can anyone recommend a suitable 240v to 12v power supply?
Or (it seems a lot more of a faff), should I fit a 12v leisure battery, charged by a 240v to 12v power supply? The leisure battery also be charged from the car 12v?, but would need clever switching etc.
Has anyone done similar and can recommend suitable kit?

 

[ProfJohnL]

Hi Practicallycaravannd

Most caravans from the 1980's usually had the facility to have a 12V battery and to recharge it from the internal 230V mains system, and to recharge from the car when towing. Whilst they were far less sophisticated than todays you may well have such a facility already in the caravan.

However to answer your question, it is possible to have just a 230Vac to 12V power supply, but you really need to know what the power draw of your water pump is, as whatever 12V power supply you choose must be able to meets the pumps starting inrush/stalled current.

IF you have an inboard displacement pump (Whale and Sureflow models were quite common in the 1980's) Ideally you need a power supply with a peak current capability of 12 to 15A. IF your using a submersible pump then your PSU will need to have a peak rating of about 10A.

Such power supplies are available but will tend to be quite expensive, and realistically overkill for just running the water pump.

As an alternative solution, consider getting a 6Ah 12V gel battery and a Aldi or Lidl smart car battery charger (usually available 2 to 3 times year) , Use the charger to keep the battery safely and fully topped up all the time and the battery will have more than enough capacity to run the pump when it s needed intermittently.

 

[Practicallycaravanned]

Hi ProfJohnL,
Many thanks for replying.
The caravan (Eriba) has been owned by my father in law for most of it's life and I'm fairly confident it hasn't been messed around with too much (especially the electrics - he wouldn't go near them).
However, there is evidence (a short cable with battery post connections on one end, rolled up in a cupboard) that there was a leisure battery inside the caravan at some point. There is no evidence of any charging system, especially one that was 'factory fitted'.
I like your 'alternative solution'. However, if I connect a leisure battery to the 12v 'distribution' in the caravan as it is at the moment, it would connect to the cars 12v system (when the caravan is plugged in to the car). I could install an 'isolation switch' to separate the two systems, but I know that I (or my wife) will soon forget to switch it, so I don't like that idea. Also, I think a split charging system thing is a bit overcomplicated for our needs?
So......, I'm planning to cut the wire to the cars permanent 12v and have a totally separate 12v system in the caravan. (Note, the fridge will still be connected to the cars ignition-switched 12v for towing in the usual way).
While the caravan is at home on the driveway and at a caravan site with EHU (we don't plan on staying at a site without an EHU), the battery charger will be constantly keeping the leisure battery charged up and so can use it for the pump/internal lights.
Sorry, I'm repeating all what you said, but I'm just thinking it all out as I'm writing. I think the only thing different/additional to what you wrote is my plan to cut the wire to the cars permanent 12v (to stop the two 12v system fighting/draining each other etc) . I don't see any problem with that. Do you???
The caravan has only a 12v pump (used very infrequently) and dual 12v/240 lights (2 bulbs in each light and completely independent cabling), so the 12v for the lights will be very infrequently used.
We have a whale submersible 881 pump, which I think (the caravan is in a million pieces as I'm currently welding the chassis and repairing the wooded floor) connects to a 'socket' on the outside of the caravan.
So yes, I like your simple solution for a small 'leisure battery' and cheapish charger, plugged in to the caravan 240v socket.
Many thanks for your help and sorry for the waffle.

 

[ProfJohnL]

Thankyou for the added detail. Eriba were a continental manufacturer, and the specifications of UK caravans of the day often had more bells and whistles, which correspond to the differences in the way we caravanned. So I'm not surprised the Eriba does not have a built in
battery charger.

I can see no problem with disconnecting the permanent 12V feed from the car, but may I suggest don't remove the wire, just disconnect it in side the caravan and ensure the end is insulated and label it, so the option is there should you or a subsequent owner wish to reinstate it.

With regards to the battery and charger, I deliberately suggested an Aldi or Lidl charger for two specific reasons. Firstly smart multistage chargers are specifically designed so they can be left connected to a 12V battery and will automatically boost the charger when necessary but more importantly will fairly precisely limit the float charging (long periods when the battery is full)to 13.8V to keep the battery in good condition without overcharging it.

The second reason is that both Aldi and Lidl chargers are refreshingly cheap compared to the likes of Nobo and CTEK and for light duties such as yours they will do perfectly well.

Cheaper chargers may not have the safe float charging for 24/7 operation.

 

[Practicallycaravanned]

Thankyou for the added detail. Eriba were a continental manufacturer, and the specifications of UK caravans of the day often had more bells and whistles, which correspond to the differences in the way we caravanned. So I'm not surprised the Eriba does not have a built in
battery charger.

I can see no problem with disconnecting the permanent 12V feed from the car, but may I suggest don't remove the wire, just disconnect it in side the caravan and ensure the end is insulated and label it, so the option is there should you or a subsequent owner wish to reinstate it.

With regards to the battery and charger, I deliberately suggested an Aldi or Lidl charger for two specific reasons. Firstly smart multistage chargers are specifically designed so they can be left connected to a 12V battery and will automatically boost the charger when necessary but more importantly will fairly precisely limit the float charging (long periods when the battery is full)to 13.8V to keep the battery in good condition without overcharging it.

The second reason is that both Aldi and Lidl chargers are refreshingly cheap compared to the likes of Nobo and CTEK and for light duties such as yours they will do perfectly well.

Cheaper chargers may not have the safe float charging for 24/7 operation.

Thanks for you to help. Yes, I’ll identify/tape/terminate any unused wires. I’ll also produce a wiring diagram that I will keep updated and keep it with the caravan. Cheers….