battery wireing/starter and leisure

[backstay]

many thanks to all who have helped me in the past,perhaps someone can clear up a little problem that was highlighted the other day.I left my side lights on and flattened my battery,my van is a vw autosleeper trooper t4.I called out an engineer who jump started me,but first he tested both the starter and the leisure batterys.While he was working under the bonnet and I was trying the starter key as directed,the 30amp fuse that is under the bonnet located on the bulkhead melted.I believe that this group of fuses are for the convertion side of the van,while the vw base vehicle fuses are just inside of the van close to the steering wheel.An aquaintance said that the fuse was doing it,s job and protecting the wireing circuit.I happended to have a replacement 30 amp fuse ,we put it in place and there has been no trouble since.So,all this seems to make scence perhaps someone can confirm this or put me right. The engineer questioned why all my wireing take offs came from my starterbattery and not the leisure battery.I would have thought that the starter battery releases it,s power in a rush to turn over the starter motor,while the leisure battery releases it,s power slowly .My friend suggested that the main battery is charged while the engine is running and the leisure battery is trickle charged from the main battery if this is case I still can,t under stand why my take offs for the camper side of the van are,nt connected to the leisure battery.Perhaps someone can put me right on the above points and set out exactly how it all works on simple laymans language,many thanks,backstay.

 

[Deleted member 207]

"Usually" the leisure battery supplies power to all the campervan bits - fridge, lights, water heater, etc.

The leisure battery (in a simple circuit) can be isolated from the starter battery by a solenoid that gets its on/off orders from the alternator's signal terminal (the wire that turns out the alternator warning lamp on the dash).

If there is no solenoid cutting power from the leisure battery and the starter battery then you will continually drain both batteries.

leisure battery circuit into Google will get you plenty of diagrams.

 

[Deleted member 3011]

Are you certain which battery is which? Only asking because in some vehicles, both batteries are in the engine compartment.

It is possible that the fuse blew because your mechanic (engineer?) bridged something out so that either the starting current was being provided by the house battery, or he connected both batteries together via the fuse and the inrush current from the charged battery into the flat battery was too much for the fuse to handle. :Likely his mistake that did it.

Checking what you have would take anyone armed with a cheap multimeter about 5 minutes doing some simple test involving measuring battery voltage while switching on various loads in the house and on the vehicle.

 

[Hawkmoon]

Are you certain which battery is which? Only asking because in some vehicles, both batteries are in the engine compartment.

It is possible that the fuse blew because your mechanic (engineer?) bridged something out so that either the starting current was being provided by the house battery, or he connected both batteries together via the fuse and the inrush current from the charged battery into the flat battery was too much for the fuse to handle. :Likely his mistake that did it.

My thoughts as well Tony.

 

[NicknClair]

There could be a couple of reasons that the 30A fuse "Melted" on the bulkhead. One is that when the engine has gone to start, the transfer/split charge relay from engine to leisure has kicked in (or maybe stuck) allowing leisure battery power to feed the engine thus trying to take more power to assist in the large demand of amps needed to start.
Two, is that your leisure battery condition might be questionable (or have had a faultly leisure battery in the past) as if it is starting to struggle, the split charge system is constantly feeding a poorly/low battery, plus the average of 12-15A needed for your fridge. Eventually the 30A fuse will get so hot, it just melts rather than blows. Have the leisure battery checked (just in case and simply repace the fuse, you should then be back to normal.

Rgs

Nick

 

[Firefox]

Caravan loads must come off the leisure battery and it must be isolated from the starter battery when you are parked up by a relay or a switch.

Otherwise you will not start after a few days camping

Check you have identified your batteries correctly (by following the heavy wires back from the starter motor)

 

[Deleted member 5816]

Battery connections

Backstay it may seem that your camper is fed from the starter battery because on an Autosleeper you will have at least connected to the starter battery
1 the fridge wiring via the relay
2 the split charge wire
3 the relay for the power cutoff when driving
4 the feed wire to the leisure control unit.

if you are so mindfull remove the positive connection to the leisure battery and check what works and what does not

Alf

 

[backstay]

re battery wireing .

many thanks to every one who has offered advice to my most recent camper problem. I,m amazed how far afield the replies have been sent from,all the information will be acted on(when the snow clears!).I did put anoyher 30amp fuse in and to date there has been no problems,the van is due to go to a garage to have a sump problem fixed and I will make further enquiries there putting all the points raised by members,thanks folks ,backstay.

 

[The Grand Wanderer]

Melting fuses

Hi,
The main cause of fuses melting is resistance,normally if the load demanded through them is too high they blow straight away.
Resistance causes heat and thus melting and sometimes fireing of the plastic cover of the fuse.
Resistance is often caused by corroded conections, as the current cannot flow easily heat is generated. Bit like a rusty bolt when undoing it, it gets hotter the tighter they are.
As a matter of good housekeeping every year, all battery connections and associated wiring should be cleaned and lubricated with vaseline or cooper grease, particularly the final earth connection between the earth strap and the van body.
Wanderer