Re: 12V electrics problem


"METWO" <metwo@xxxxxxxxxxxxx> wrote in message
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"Pete" <sryjdyky@xxxxxxxxxxxx> wrote in message
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"Woody" <harrogate3@xxxxxxxxxxxxxxxxx> wrote in message
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"Pete" <sryjdyky@xxxxxxxxxxxx> wrote in message
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"Woody" <harrogate3@xxxxxxxxxxxxxxxxx> wrote in message
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"Pete" <sryjdyky@xxxxxxxxxxxx> wrote in message
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Hi

The 12V side of my caravan have stopped working.

According to the caravan's meter, the battery has no charge, so
maybe the battery has conked out, but I would have thought the 12V
electrics would function while the battery is still connected and
being charged. Wouldn't the charger power the 12V electrics as well
as charging the battery?

The battery is less than 3 years old. Is that how long they last,
or is it my fault for keeping it on charge all the time? We keep
the caravan at home, and the charger is left on all the time. Maybe
that's not a good idea? I keep the cells topped up with de-ionised
water, but maybe I should allow the battery to partially discharge
before recharging it?

Thanks

Pete



We don't keep our battery on constant charge - not a good idea - and
it dies about a week after we get home. However, put the mains on
for 24 hours and its back up.

Sounds like your PSU has died and is not providing supply to the
system or to charge the battery. Daft question, but has your power
input protection - RCD or MCB - tripped? Do the mains lights in the
van - if you have any - work when the mains is on, or failing that
is there any supply from a 13A socket, again if you have any?

Have you checked the fuses?


--
Woody

harrogate three at ntlworld dot com



Thanks for your reply Woody

The power protection is OK

The mains lights work, as do the 13A sockets

It's the 12V lights and the pump (which I assume is 12V) that don't
work

All the fuses on the 12V side are OK

Pete




Then it must be your PSU/charger. If you don't have a voltmeter (and
they are very cheap these days) try connecting a 12V flasher bulb
across the output of the PSU with and without the battery connected.
Also make sure if it has an input (mains) fuse that is externally
accessible that it is not blown.

Whatever happens DO NOT open up the PSU. If it is a modern switched
mode unit there will be capacitors in there with 300-400V or more on
them and they can hold that charge for quite a time.


--
Woody


I purchased a multimeter. I charged the battery up and it seems to be
OK

The charger gives out around 5V, dropping to 0.5V at the battery
connectors

I presume the charger should give out just over 12V?

Pete




Ooh dear, that looks problematic. The battery should read around 13.2V
when charged and settled (13.8V on charge and immediately after.) If the
charger is only outputting 5V and 0.5V across the battery then you have
a serious problem.

Disconnect the battery and see what voltage you find on the cables with
the mains on, and see if voltage is present see if the lights will work.
Whilst disconnected check the battery volts. You could have an internal
short inside your battery which is causing the power supply/charger to
protect itself and switch its output off. Conversely some charger units
need to see volts from the battery before they will start to charge -
even a 'flat' battery will show some volts, usually about 10V or above
if no current is being drawn.

You could try connecting your car battery onto the caravan - with jumper
cables if you like - and see what happens. Disconnect the -ve on the car
before connecting to the 'van just to make sure you do no damage. Check
the battery volts before connection, then after connection but before
switching the mains on, and finally after the mains is on. You may see
12.6V or 13.2V across the battery stand-alone; this voltage may drop
slightly when connected to the 'van (check if the lights work) but
should rise to around 13.6-13.8V when the mains is on. If it does then
your charger is OK and the battery is a fault.

If it looks like the battery take it to a battery specialist and as them
to check it. For a small charge they will probably give it a short fast
charge and then load test it. If it is nadgered then you are in the
right place to buy a new one! Oh, and get a 'leisure' battery, not a car
battery as they are designed to have different load and usage patterns.


--
Woody


Thanks very much for all your advice Woody. Your suggestion that I buy a
multimeter has saved me a few hundred quid

I'm fairly confident that the battery is OK, because since I charged it
up, I've been using it for a couple of days in the caravan without any
problems

That basically narrowed it down to the charger

I rang a few caravan sales / repair companies, and due to the charger
being an integral part of the power supply system, the whole lot was
going to need replacing at around £350 plus fitting. Unfortunately none
of them could do the work this side of August due to them being so busy

I therefore rang a local mobile caravan repairer - Dr Caravan Mobile
Services:

http://www.caravandoctor.bravehost.com

The reason for the shameless plug is that, even though he knew I was
prepared to pay him to do the repair, he gave me an idea that saved me
hundreds of pounds and earned him nothing at all. He suggested I buy a
cheap leisure battery charger and fit it permanently into the caravan. I
suppose I should have thought of that myself, but I didn't!

£35 pounds an an hour later, the problem is fixed

Cheers

Pete


Hi Pete,

I don't want to put the mockers on the saving, BUT, that's why the caravan
manufactures put a PSU in the van, so it will run the lights, pump etc,
and
a charger (only) won't so don't use any 12v power when using the charger.

what you need is a regulated PSU (power supply unit) that is regulated to
13.8 Volts, and as higher amperage as you can get (20-50Amp)

Metwo


Thanks Metwo

I'm using the caravan for 2 weeks as of next week, so it looks as if I'll
have to use the battery with the charger disconnected then recharge as
necessary while we're out and about

Then I'll need to get the experts to repair it when I get back

Cheers

Pete


.

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