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Robert Noel Reddington
Grand Master
Username: bob_uk

Post Number: 907
Registered: 5-2015
Posted on Sunday, 27 March, 2016 - 06:55:   Edit PostDelete PostView Post/Check IP

I have just wired up a Transit van with a aux battery and split charging.
The van is used for a weekend as a base for fishing and touring Dorset. The owner lives in Dorset.

The owner cut a hole in the van floor and fitted a large box flush with the floor. Inside he has fitted a battery, 30 amp mains charger, 1000 watt inverter, circuit breakers, split charge relay and a small compressor for an air bed. Plus a 1000 watt petrol genie which can be placed away from the van to make it even quieter. Plus led interior lighting. Warm white.

My job was to wire the kit in. All nice and easy. The split charge relay is voltage sensitive. When the relay detects 13.3v it connects to the aux battery. To charge without running the van engine has two options the genie or mains when he is at home or on a camp site. Also the relay can be overridden so the mains charger will also charge the engine battery. ( it is a Ford Transit diesel not the best of starters from cold)

The inverter will run a microwave. However it's best to start the genie to take the load off the battery. Micro waving is quick so genie only needs to on either direct to microwave or say 30 mins if running on inverter to top up battery.

The charger is an Absaar 3 stage 30 amp automatic jobbie, these aren't cheap but first class quality. The relay is marine quality and the battery is AGM. Again not cheap. The bits cost 600. The genie a used Suzuki 1000 watt with a 6 amp 12v output and 240 acv. The reason for only 6 amps at 12v is because Inside the control panel is a small transformer and small rectifier running off the 240 acv bit. I have tried the 12 v output on my similar generator and it will charge a battery but not very fast. Still the feature is of some use. The genie starts easy. 8 hours on full tank. The genie fits under the passenger double seat. The work the owner did is very good not bad for bricklayer. No side windows.

The equipment works well and should be problem free. On test at a fast idle the aux battery had 14.3v and the engine battery 14.4v which is bang on the money. He's very pleased and gone fishing.

I quite like the idea of this van. It's cheap and very useful. I would have based it on a Renault Espace though. Nobbly tyres and don't go off the gravel into stupid places.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 920
Registered: 1-2008
Posted on Sunday, 03 April, 2016 - 01:42:   Edit PostDelete PostView Post/Check IP

I added a split charge relay to the secondary towing socket on my little Rover cabrio, but on my Dodge day van I've placed the 'new' battery in the back and wired it into a roof mounted 40 watt solar panel. Although both feed into a power socket (cig lighter) in the back of the van, current from neither is appearing at the front battery. I can only conclude that there must be a diode somewhere in the circuit, but I'm buggered if I can figure out why.

Preventing a current drain from the car battery might be a good idea, but makes adding the rear socket a waste of time unless it only works with the engine running (it doesn't). Preventing a rear battery from boosting the car battery is moronic at best. I'm putting in extra wiring so that the solar panel/leisure battery can keep the car battery fully charged at all times. If necessary I can add another 40 watt panel on the roof as I ensured I had the fitting space for another when I designed the roof mounts.
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Robert Noel Reddington
Grand Master
Username: bob_uk

Post Number: 935
Registered: 5-2015
Posted on Sunday, 03 April, 2016 - 09:13:   Edit PostDelete PostView Post/Check IP

The best way for charging the aux or domestic battery is a second alternator if possible.
The next best is a voltage sensitive relay because it has no voltage loss.
Most alternators are battery sensed.
The shadow is battery sensed via the ammeter shunt to the regulator.

With one alternator this can cause the charging voltages for one of the batteries to be wrong. Usually too low for the aux. If the aux is pumped up a bit then the engine battery gets overcharged. If a diode is used the forward voltage drop of 0.6v means if the engine battery is charging at 14.4 then the aux will be 13.8v. This is not a problem as long as say once a month the aux battery is charged via a mains charger for 12 hours. Else due to undercharging the battery will fail.

Scotky diodes have a lower forward voltage drop.

On the Transit day van the volts for charging comes direct via a fuse close to the engine battery. The wiring to the aux battery was the front to back battery wire from a mini which is quite heavy cable. The aux battery is quite close to the engine battery to keep the supply wire as short as possible. Which gave us 14.3v at the aux battery. Which is a 100 amp hour agm. Which is laid on its side to keep the height low.

I have not had much luck with solar panels.

The guy with the day van is very pleased and the system was tried and tested over a long weekend fishing.

Next I am going to wire the interior lighting when he has fitted this track light led system. The track goes down the centre of the roof. It has 5 little Led light pods with switches fitted to the pods which slide up and down the track. It uses 1 amp. Also fit USB charging thingy and a selection of different sockets to get 12v. Such as cigar lighter and wander lead plugs.

Also he's going to fit front swivel seats and throw the bench seat out. He's got 2 BMW leather front seats from the bone yard. Should look good.

Check that the split relay is correctly wired. Some relays have an earth as well.

Another way of split charging is to use the alternator warning lamp to control the a relay. This method is the old way and no voltage drop. But this can interfere with the operation of the regulator which is why it's not used much, especially modern smart alternators that are controlled by the ecu. No No.

On some Dodge alternators there is a small hole in the back. This leads to the rotor field windings. If a screw driver is inserted it shorts the rotor to earth and the alternator should go full power. This is an official GM way of testing alternators, neat idea. The rotor windings are modulated by the earth side of the rotor windings via the brushes of course.

How about a fan on the roof from a boat that charges the battery. It will cause drag and a wee bit of extra fuel because you don't get something nothing.

We obey the laws of thermodynamics on this site.
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Jan Forrest
Grand Master
Username: got_one

Post Number: 922
Registered: 1-2008
Posted on Sunday, 03 April, 2016 - 23:24:   Edit PostDelete PostView Post/Check IP

Oddly, for some unknown reason, the Dodge car battery can lose virtually all charge over a couple of days if not used. It shouldn't as I replaced the battery less than a year ago and I've eliminated all the static drains that I can find since then. I'll have to see if it continues after I've rewired the connections from the solar powered leisure battery. If it does I'll have the alternator checked for internal drains, which I am given to understand can happen if there's a knackered diode in the pack.

Just off to Halfrauds to get an inline fuse holder to make the circuit safe.