12 v electrics

Catcher · May 20, 2007

The 12v electrics on our van stopped working - absolutely nothing. (Fortunately I was only doing a few jobs on it at home)I plugged in the mains lead and the mains side of things worked fine. I assumed that through the charger the 12v side would work but again nothing. I removed the battery and charged it overnight using a mains charger. After replacing the battery the 12v side worked fine.

My question is... why didn't the 12v side work when the mains were connected? Does the battery have to have some charge in it for it to work through the mains? (I think the battery was very low)

Thanks

Catcher

RonD · May 20, 2007

As the battery was completely flat the caravan charger would probably stop working (shut down)as it can only supply around 12amps, hence no 12v on your van. By charging it overnight the battery would not need such a high current to charge it and the van charger should maintain it now.

Ron

Catcher · May 20, 2007

Thanks for your reply Ron, that explains it.

Regards

Catcher

ProfJohnL · May 20, 2007

Hello Catcher,

Further to Ron's suggestion, If the battery was so low as to cause the charger to limit and stop running, then the battery could be damaged.

However there are some other possible causes. Most chargers have an input and output fuses to protect the wiring in the event of a fault. If a fuse has blown, then the battery will not charge.

If the fuses are ok, then the charger may be damaged. To check:

Disconnect the battery, (Make sure the battery leades do not touch each oterh or any oterh metal parts to the caravan). Turn on the charger, and see if any of the 12V lights or fans work. If they do, then the charger is ok. Tuen every thing off and reconnect the battery.

If the appliance don't work then the charger is likely to be faulty.

Catcher · May 20, 2007

John, thanks for your reply. I must admit I was wondering about the charger. We've only had this van for a few weeks and the thought did cross my mind as to whether it was working properly. When I had the problem I found a fuse near the control box. It was a very old looking fuse in a brown plastic (bakerlite?) holder that looked much older than the van (1999). The local caravan dealer had never seen anything like it. When dismantling it I broke it (it had fuse wire in it) so replaced the whole thing with a new holder and fuse. The van is still under warranty so I will check it as you suggest before contacting the supplying dealer. I can't help thinking though that the test you suggest would be the same as having the mains connected with the flat battery as in my original post and the 12v side didn't work then - or am I missing something?

Damian · May 21, 2007

Catcher, some vans will not work on 12v if there is no battery connected, they are an integral part of the system.

To check if your charger is working, with all electric off, measure the battery voltage.

Now turn on the 240v and make sure the charger switch is "on", then measure the voltage atthe battery terminals.

If there is around 13 to 14 volts, the charger is working, if no difference, its not.

ProfJohnL · May 21, 2007

Hello Catcher,

Yes there is a difference, and your last note added some useful information. As the caravan is post 1998, the system in the caravan will not be a simple charger, but a more sophisticated beast called a regulated power supply.

Prior to 1998 many caravans used a relatively simple battery chargers. These produced an unstable dc current which could have voltage peaks as high as 22Vand lows of 0V. If these earlier systems were used without a battery, some sensitive appliances could be damaged by the voltage spikes. A battery was needed to provide current and voltage smoothing.

The modern power supplies can be 'intelligent' to the extent that they can sense the load they are connected to, and if it is too current hungry, they shut down. - So if your battery is faulty, then the power supply may be reacting to it and turning off. By removing the battery, you are eliminating that part of the system, and the power supply may be able to function satisfactorily and run some of the 12V appliances in the van.

That will at least prove if the power supply is working or not.

I have to point out though, my suspicion is that the supply is not working or an associated fuse has blown. This is partly supported by the apparent non-standard fuse installed. This suggests that a previous owner has had a problem of some sort.

Catcher · May 21, 2007

Many thanks for the helpful replies. I have tested the voltage at the battery with mains disconnected and it read 12.66 volts. I tried it again with mains connected and it still read 12.66 volts. This would suggest that the power supply is faulty doesn't it (or could it be the intelligent charger shutting down)?

The power unit has 'Power Centre II' on it and the only switch (apart from 4 circuit breakers) is an un-marked rocker switch which I presume is to switch between car and caravan battery. I might just try your last suggestion John of seeing what happens without the battery, but not tonight!

Regards

Catcher

Damian · May 21, 2007

Catcher, by not having an increase in voltage at the battery with mains on indicates that either the charger is not working at all, or there is a break in the cable or fuse blown, but it is unlikely to be a fuse as there normally is not one in the charging cable from the charger.

When you put power on, you should have had at leat 13.5 volts at the battery terminals.

Catcher · May 28, 2007

Thanks for all the replies. I've decided the charger is definitely not working. As the van is still under warranty it will be sorted by the dealer.

Regards

Catcher

chenzhen · May 19, 2016

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