Battery charging and 240 to 12v supply problems

[dinglefoot]

Hi My first post and I need some advice please.
I have recently purchased a Lunar Delta 640 ew after owning a Delta twin 590/4 for some 17 years without any battery / 240 /12v troubles with the old Zig unit.
This last weekend I used the caravan on a site with electric hook up 85% of the time I use sites without electric.
24 hours into our stay I noticed the 12v lights starting to dim, we had been using the 12v lighting and heating fan quite heavily not worrying as we thought the battery was being topped up by mains electric.The electric / water tank gauge was working on the water side but the needle did not move on the voltage / condition function.
As it happens I always carry a spare fully charged battery with me and when changing it I checked if there was any output from the battery connection clamps ......nothing was showing on the meter with the 12v unit light illuminated.
With the fully charged battery connected the battery condition meter needle just moved slightly when pressed and the flat battery symptoms still existed with dim lights and slow water pump, can I say the factory fitted radio did not work.
The 3 RCDs were all set OK the one that feeds the charger also runs the fridge and that was working fine on 240v.
On setting off for home I plugged the 12s socket in and drove home, upon arriving at my storage disconnecting my 12s plug I checked the 12 v battery condition meter and it showed a fully charged battery lights were bright and radio was working again.
Any ideas ? Unfortunately there is no electric at my storage so I cant check it until I go away again.

 

[Damian]

It sounds like your charger is not working.
You need to measure the voltage at the battery terminals with no power connected.
Then connect power, make sure the rcd is ON and the MCB's are on, and the charger is on (if it has a switch on it) then measure voltage at battery terminals again.

The first reading with no power and a fully charged battery should be around 12.8v

Second reading with power should be at least 13.6 up to 14v

If the voltage stays the same for both , the charger is not charging which may be a simple fuse problem, or a more serious charger problem

 

[dinglefoot]

Thanks for the info I did try switching the 12v switch on and off with the 12v lights on to see if there was any difference in brightness as I switched but none. I have checked all the fuses I could find and they are all OK. Do you know if there is an internal fuse ? As I said the Fridge and the charger are on the same trip, the box is live as the 12v switch illuminates when on.

 

[HenryB1]

I had a similar problem on my last Abbey caravan. When I arrived home and had access to a multimeter I found that I had pulled apart an in line fuse under the fixed bed when sliding chairs into the bed locker from outside.

 

[dinglefoot]

I will look under the fixed bed locker to check any fuses may be a possibliity Thanks