I really need to update this section there are several bits I am not happy with: I would not put the battery under the bed now, I would put it in the engine bay like everyone else! Also, this was a type 1 alternator install - I need to document a type 1 dynamo install (the only difference being where to connect the purple wire) and a type 4 install. However, as a stop gap and to show my slightly updated methods, I have created a temporary set of additional information to help you along the road to Leisure Battery Nirvana! To view these pages, click here.
The idea of a split charge circuit is to charge both the leisure battery and the main vehicle battery whilst the engine is running AND the alternator/dynamo is charging.
Once the engine stops OR the alternator stops charging, the main battery is disconnected from the leisure battery.
The leisure battery is used whilst camping so that electrical items not drain the MAIN battery needed to start the vehicle!
This topic is the one of the most popular area of discussion in the forums, and also the most misunderstood and most complicated in appearance. I am therefore taking the opportunity to write my own "dummies guide" on the subject, making it as clear as I can.
The secondary fusebox is designed to distribute 12v positive from the leisure battery to you camping accesories such as interior lights, fridges, invertors etc.
The job of a fuse is to protect the wiring in an installation from catching fire. The fuse is essentially a small strip of metal which will get hot and melt in the case of a short or overload, breaking the circuit long before the cables can burn. Of course, the fuse and wire need to be of the correct rating at all times.
The most common mistake people make when thinking about leisure battery installations for the first time is that the term fusebox refers to the fusebox already in the vehicle. This is not the case: you will need a secondary fusebox if you plan to run more than one internal device. I will always refer to this fusebox as the Secondary Fusebox to avoid confusion.
The diagram below shows a simple diagram of how the secondary fusebox relates to the leisure battery installation.
If you consider yourself a bit of a dummy with electrickery, don't be put off by this drawing; it's really very simple.
Below is a set of photos showing a real-world example of a secondary fusebox.
The idea of the link is to "common up" the live feed coming in from the leisure battery, as you only need to connect this wire once to the common side of the fusebox. Of course, you can use 5 small bits of wire to do this job, but for the sake of a quid or so, this is much neater and easier to work with.
Once you open the fusebox, you will need to assemble it.
Use a screwdriver to prise open the 4 catches.
The fusebox, opened.
The fusebox with the common rail installed. I am not sure if this is the way it was designed to fit, but it looked wrong poking outside of the box....
And now with the 6 fuses installed. They will need to come out again for the final installation in the van, there are two holes in the back of the fusebox to allow you to screw it to a wooden cupboard etc.
You should now see that you only need to connect the thin wire from the +ve of the leisure battery to one of the terminals at the bottom, and you then have 6 seperately fused "output" terminals to run to each piece of 12v equipment.
For the record, my equipment will include:
1. Internal Light
2. "Bedside" spotlight
3. 12v socket for coolbox or invertor
4. Radio and Amp
In order to connect the leisure battery to the charging circuit, we need a relay. A relay is simply a small box containing an electro-magnet and a switch.
When there is no power connected to the electro-magnet, the switch remains open. But as soon as the power is connected, the electro-magnet pulls the switch on.
How does this help us?
Well, one of the pre-requisites of a leisure battery installation is that the leisure battery needs to be connected to the charging circuit when the engine is running to make sure there is enough charge for the days camping, but to disconnect the leisure battery when the engine stops so that all your nice 12v equipment is powered purely from the leisure battery and is not draining your vehicle's main battery.
So, if we take a feed from the alternator charging circuit that goes live when the alternator is charging, and connect it to the electro-magnet of the relay, we can use the relay's switch to connect and disconnect the leisure battery from the charging circuit.
So, we now have a leisure battery, a relay and a bunch of wires. Now we need to put it together.
Consider the diagram below:
When the alternator starts to spin i.e. the engine is running, the thin wire in the diagram becomes live, activating the electro-magnet of the relay and pulling the switch on. This now connects the leisure battery into the charging circuit, and both the batteries start to charge.
When you get to your destination and you stop the vehicle, the alternator is no longer spinning, so the electro magnet in the coil is deactivated and the switch opens, disconnecting the leisure battery from the charging circuit. The other thin wire at the top of the diagram is the positive feed to the fusebox - you can now kick back and switch on all your twelve volt gear safe in the knowledge that even if you flatten your leisure battery, you will still have a full charge in your main battery to start the vehicle and get you home!
NB: This page shows the very first install I did on my old Devon camper - I have done things a little differently on my new camper, Woody. For a start I used a relay from a scrapyard (cheaper) and put the battery in the engine bay of the camper on the opposite side to the main starter battery. A charging battery will give off hydrogen fumes, so putting it under the R&R bed may not be the best choice! Also, it takes up valuable storage space. Also, in this install I used a car battery, which is ok but now I have a 110amp marine battery which is a good combination of starting/leisure battery.
I ended up giving in and picking up a relay from Halfords for a whopping £16. OK, I could have got one from a scrappy for nothing but there were three reasons why I didnt:
1, I had the money on me, and figured why not get a new relay that will last the life of the van.
2, It is pre-wired so that you do not need to worry about what type and colour of cable to buy.
3, The wires are fixed, and not connected by spades which can work loose and cause shorts.
You will note later that the relay has two thick power wires running out of the relay - Red and Dark Green. The dark green is to connect to a fridge to give it 12v when driving, but to kill the power to the fridge when parked as this would flatten the battery very quickly!
Then a big gulp and take a drill to your pride and joy - 2 little holes in the RH side of the engine bay, 2 self tapping screws and bingo. A solid mount in just the right place.
(NOTE: Make sure you do not push the drill in too far and that you know where the fuel tank is located!!!)
The relay screwed into place on the RH side of the engine bay.
Note that the short, black earth wire can just be clamped under one
of the self-tapping screws for a good connection. Crimp an eyelet on
to it first, mind.
Once this is done, take the lime-green wire with the fuse holder on it and connect it to the positive of the vehicle battery. It should reach without being tight. Clamp it down good and hard now.
The purple "trigger" wire can now be run to the alternator over the holey panel above the engine bay. It's cable-tie time!!
The cable ties in place over the engine bay to take the alternator wire.
Thanks to the person who though the holey stuff was a good idea. It is
perfect for cable ties.
The alternator wire should run neatly across these ties and "drop" over the alternator where a faithful old scotch block connector can be used to "intercept" the little wire that dishes out 12v when the alternator is doing its thing, i.e. charging!
Here you can see the purple cable running to the alternator. Neat, huh?
This wire drops down neatly into place. Use a scotch block to connect
the purple wire to the wire coming off the alternator. Scotchblocks allow
you to cut 1 wire into the other without causing any damage to the original.
The next job is to run the red and green wires neatly over to the other side of the engine bay. At first, I though about using the holey plate again, but then realised that there were some metal clips in the bay just above the engine hatch.
Here the red and green wires are being clipped up on the RH side of the
engine bay and then fed into the clips to start their journey across the engine
..And along and along (this was taken from inside the engine bay...)
Until you get to the LH side of the engine bay. Use a cable tie to do the
last little bit onto the holey plate bit.
Guide the wires underneath the wheel well (you might want to put the battery
in this side of the engine bay - I wanted mine under the R&R bed!)
Drill a small hole in the drain grommet to feed the wires into the van.
Like this. This is inside the wheel well inside the van.
Run the cables under the R&R bed to your leisure battery.
My leisure battery sits inside a purpose built plastic box from Towsure that
comes complete with a nice red lid. Drill a coupla holes in the bottom and use
two woodscrews to fix it to the floor so it wont s-l-i-d-e about!
Here, you can see the earth wire of the leisure battery in the quick-relaease clamp.
Note that I have reversed one half of the clamp to make a tight fit for the thin cable.
The live side of the leisure battery clamp with a couple of very nice fuseholders
from Towsure - you will need to buy 2 30amp blade fuses from Halfords for these.
One fuse connects to the main feed from the relay (the thick green wire) and the other
connects to the secondary fusebox feed. This protects both sides of the circuit from
fire caused by shorts or overloads. Very sensible!
Let's now finish off the inside of the circuit and test it all!
Firstly, make sure all connections are good and that you have not trapped any wires or have any dodgy crimping going on! Good. On we go.
If you want to test the alternator charging circuit that turns the relay on,
set your trusty multimeter to the first DC range above 12v .
sitck the positive probe of your multimeter here, and the negative probe to a
good earth. It should read 0.00v
KEEP YOUR HANDS WELL CLEAR and get a buddy to start the engine. Rev slightly until
the red light on the dash goes out.
Now CAREFULLY put the probes back where you had them. All being well, the multimeter should read around 13.5 volts, like below. If the red light on the dash comes on, the multimeter would drop to 0.00v. With the purple wire connected to the alternator, this would mean that the relay would not come on to charge the leisure battery UNLESS the red light had gone out, and this terminal was actually dishing out 13.8v, making the relay click on!
Now, with the engine off, check the voltage at the leisure battery.
Should get a reading of 12v.
Now fire up the engine again, and make sure the red light is off on the dash.
The meter should now read just over 13 volts again.
Congratulations - your leisure battery will now charge when you are driving along.
If any of these test fail, go and have a cuppa and come back. Test all your connections,
check your wiring and have another go. Try these common mistakes first:
So now you have a battery under your R&R bed that charges when the van is running. How do you get the power out? Remember right back at the start I talked about the secondary fuse box? Well, now is the time to use it!
On the inside of the bed box, in front of the battery, I sited my secondary fuse box. In the pic above, you can see the main fused wire from the leisure battery positive terminal. This is the main 12v feed into the fuse box. The two wires you see coming out of the top of the fuse box are the first two items I have connected: the condition meter and the 12v socket.
On the other side of the bed box is my 240v socket (hookup details coming soon!) To the right, you can see a 12v socket, bought from Just Kampers. This can be used to feed the fridge or an invertor, phone charger etc.
Above the 240v socket, is my home-made battery condition checker. This is basically a JK battery condition meter and a 12v rated rocker switch mounted into a standard socket box. When you want to monitor the battery, flick the switch on and the meter shows into the green... and as the battery gets used up, the meter will drop. Also, it can be used to show that the battery is charging - switch it on and start the engine, and the meter will go all the way to the right! Neat, huh?
Is the fuse on the leisure battery circuit blowing and you don't know why?
There are two main reasons.
1. The relay is being energised when the ignition is switched on. This connects the leisure battery to the starter battery through your charging circuit.Good job you fused it correctly, otherwise you would be looking at a lot of melted wire right now! Check that the relay is being energised by the charging of the alternator and that the previous owner or some numpty garage hasnt wired the relay to the positive of the coil!!
2. The leisure battery is too flat. If the leisure battery has been completely flattened over a weekend of camping, when you first start the engine, the leisure battery will draw as much current as it can to reacharge. Sometimes, this current will exceed the rating of the fuse and it will blow. You may have to recharge the battery on a mains charger at least partly before replacing the fuse and trying again.
A lot of people ask about which is the best battery to buy. Some people will tell you that the best battery by far is a proper leisure battery, while others will swear that they camped in Europe with no hookup running off a standard car battery with no ill effects. Whilst both viewpoints are valid, there are a few points you should be aware of to be in a position to make a decision for yourself.
|Car Battery||Leisure Battery|
|May sustain damage if run flat||Designed to be run flat|
|Cheap (especially if second hand!)||Can be expensive|
|Will recharge quickly||Can take a long time to recharge|
|Standard size||Can be large (ok, I'm reaching now!)|
If you want my advice (and I guess by visiting this page you might) then I would say this:
Is money an issue? (when isn't it?) Is your main starter battery a bit old and of dubious reliability? Well, start there and treat your self to a new battery. Shouldn't cost you more than about £30 and you will get the advantage of knowing that your ability to start the van is at its best and you will can use your old battery as a temporary leisure battery to check your charging cicuit. Other than that, most scrapyards will sell you a battery for a fiver or so, again a useful standby until you can afford a "proper" leisure battery. Of course, you may find that a car battery is more than adequate for your lighter usage applications. A leisure battery of about 60AH (ampere hour) will cost you about £45.
My first leisure battery install used an old car battery I found in the back of my garage. Worked fine for a bit of light invertor use and lighting etc.
So, you want to know how long your leisure battery will be able to run your appliances? Here are some calcs that might help.
Have a look at the transformer on the laptop (the box between the mains plug and the plug into the back of the laptop)
It'll have printed something like "Output 18v, 4A" Multiply the volts by the amps to give you a wattage figure - in this case 72. So you are drawing 72 watts, and then add 20% for inefficiency (it gets warm, for example", so call it 90 watts.
Your leisure battery is rated at 85Ah and is a 12 volt battery. At peak it has/had (when new) 85 x 12 watts (1000 give or take) total capacity. Take off 20% for age (assuming it's fully charged).
Are you using an invertor to give you 240v to plug in your laptop transformer? Take off another 10%.
So you have available say 700 watts - and you are drawing 90. Divide 700 by 90 - about 8, and that's the number of hours you should be able to run for.
You can adapt these calcs for any device for which you know either the wattage or the current (A) draw.
(With thanks to "artist" on JK forums.)