Leisure Battery Installation

WishfulDan

I wondered if anyone could double check this before I head out to Maplins.

I'm terrible with electronics and my experience of going to places like Maplins is, they're just as bad!

I suppose I want to know if this even makes sense, if I need to get a specific thickness of cable, do I need an isolator between the batteries or will the relay controlled by the alternator do the trick?


Worry Worry.

WishfulDan

The thing coming off the leisure battery is a fuse box and the four things in the back are lights

the two empty cables are for a 12v socket and maybe an inverter.

spaceHopper

WishfulDan wrote: »

I wondered if anyone could double check this before I head out to Maplins.

I'm terrible with electronics and my experience of going to places like Maplins is, they're just as bad!

I suppose I want to know if this even makes sense, if I need to get a specific thickness of cable, do I need an isolator between the batteries or will the relay controlled by the alternator do the trick?


Worry Worry.

It looks OK but normally the relay is controlled by the ignittion, google split charge relay. Also normally the batteries are about the same size so if your engine battey is 80ah then fit a 80 ah leisure battery.

The wiring for my camper is here it looks daunting but just focus on the battery
http://www.box.net/shared/hllysrxlql

WishfulDan

Wow thank you.

Yep I was thinking about that split charge relay (I drew the dashed line to indicate that I'd be pulling power from that cable that comes out of the alternator).

So do you think it would be a bad idea to buy a 125ah leisure battery if my starter is not the same? Is there any way of getting around this? ( I would love a big battery for the back)

Buford T Justice

WishfulDan wrote: »

Wow thank you.

Yep I was thinking about that split charge relay (I drew the dashed line to indicate that I'd be pulling power from that cable that comes out of the alternator).

So do you think it would be a bad idea to buy a 125ah leisure battery if my starter is not the same? Is there any way of getting around this? ( I would love a big battery for the back)

No reason why you can't have a bigger battery than the van one. The mains charger will be for the main charging of the battery, and the alternator will only be topping up when on the road if you will.

Which cable to you intend using on the alternator? Don't use the main one. There is another smaller light cable on the alternator that controls the battery light in the dash. When you put the ignition on, there is no power to it, and when you start the van and the alternator kicks in, it gives off 12V. You can use this one to control the split charge relay. that's what I did.

merc camper

A much safer and easier way to split the starting and leisure battery is to use a voltage sensing relay they are not expensive. An expensive but good option is a sterling battery to battery charger this is what I have in my van connected to 3 85 ah batteries.
There is no problem using a larger leisure battery than the starter.
Make sure u use large cables going to the leisure battery the further the battery is away the larger the cable needed to avoid voltage drop.

Buford T Justice

I've used 25A cable. Its not that large. tbh, you don't really need anything bigger than that, but be sure to have a suitable fuse on the supply.

The large cables that are used as standard battery cables are there as the current thats used to swing the starter in the van, it can be massive.

25A is loads to charge a leisure battery, even when its dead.

merc camper

25 A cable is very small if your leisure batteries are flat and you have a large alterntor. Standard altornator in vans are 75 A.
Volt drop calculator http://www.nooutage.com/vdrop.htm

Buford T Justice

merc camper wrote: »

25 A cable is very small if your leisure batteries are flat and you have a large alterntor. Standard altornator in vans are 75 A.
Volt drop calculator http://www.nooutage.com/vdrop.htm

In all fairness though, a leisure battery would want to be run seriously dead to take 75A from the alternator, not to mention that there would also be the main battery taking the load too. Most standard relays are also rated for 40A.

Chances are, if a leisure battery is very flat, it'll be charged by mains.

WishfulDan

Well, I went to Maplins looking for wires and the guy behind the till said "you know, I'm not very good with these kind of electrics, but there's a guy called Dave, he'll be in tomorrow and he can help you out".

So then I went to Halfords where after having asked everyone on the floor for a relay switch and a scotch block I found them myself, but wasn't sure if they were the right rating. No one to help.

So I went to a marine shop where a man knew everything. But had no parts.

I think it's going to be an internet job. Tomorrow maybe...

Buford T Justice

WishfulDan wrote: »

Well, I went to Maplins looking for wires and the guy behind the till said "you know, I'm not very good with these kind of electrics, but there's a guy called Dave, he'll be in tomorrow and he can help you out".

So then I went to Halfords where after having asked everyone on the floor for a relay switch and a scotch block I found them myself, but wasn't sure if they were the right rating. No one to help.

So I went to a marine shop where a man knew everything. But had no parts.

I think it's going to be an internet job. Tomorrow maybe...

25A Cable, Inline Fuse, 25A Fuse, Spades & Lugs, & a single throw 25A Relay

Aidan_M_M

Modern campers run at least 50a relays between batteries...

boardsiebob

WishfulDan,

I have this installed in mine
http://www.conrad-international.com/TWO-TBATTERY-CHARGER-80-A.htm?websale7=conrad-int&pi=856040&ci=SHOP_AREA_14724_0310070

and cable:
http://www.conrad-international.com/SINUS-LIVE-BK-10P-BATTERY-CABLE-SET.htm?websale7=conrad-int&pi=372155&ci=SHOP_AREA_32410_0300033

is cheap 5 euro delivery

I put a 80A fuse in the line also.:)

Saruman

Sorry to hijack the thread...
My leisure battery charges when the engine is running, that is grand however it does not charge when plugged in to the mains.
Anyone any ideas? I know it will be hard to offer specifics as all campers are different and mine is a conversion (did not do myself). A pointer in the right direction would be greatly appreciated.

paddyp

Fingers McGee wrote: »

In all fairness though, a leisure battery would want to be run seriously dead to take 75A from the alternator

Actually the largest current is at about 25% charge not uncommon to see this level of charge in leisure batteries.

Beyond this the internal resistance increases and limits the charging current.

While the alternator may limit its charge current; when your relay kicks in after starting the engine its only the resistance of your wiring, relay and the internal resistance of the batteries that limits the current between the charged main battery and the discharged leisure battery. You can under certain conditions have large currents especially with my agm leisure batteries. Thats what the fuse is for :-p

Agm leisure batteries have tiny internal resistance

Theres no such a thing as 25A cable. You size the cable by CSA according to acceptable loss ie 2 or 3 %, method of fixing and length. By making the cable as short as possible you can reduce its size. A 25A cable over 2m (from under the bonnet to under the drivers seat) could be as little as a 10A cable by the time you reach the back of the van (yes I've seen leisure batteries inside the back door!)

WishfulDan

I went to a local auto dealer in Derry and bought most of what I need. I got a 'Ring' inverter

http://www.shopwiki.co.uk/Ring+300W+-+Power+Source+Inverter+-+Tesco.Direct

and a split charge relay.

I got fairly heavy wiring for the battery and simple car audio wiring for the lights in back.

Should I be worried? The guy seemed quite confident, the relay came pre wired and he gave me a load of fuses and a fusebox.

Fingers crossed now I don't burn the van down.

£60 for the lot though

Irishgoatman

There was an earlier thread on this subject.

My posting then was that I had fitted a solar panel on to the roof (I have a flat enough roof) that only needs daylight to keep a battery charged, it cannot over charge because no charge going in at night, and it is working perfectly. Even now with the short days it is still keeping the battery charged. Once I put the camper in the barn for the winter I will, of course, have to top the battery up from the mains now and again.

You can get panels in various sizes and voltages. For me it was the simplest way.

Buford T Justice

Saruman wrote: »

Sorry to hijack the thread...
My leisure battery charges when the engine is running, that is grand however it does not charge when plugged in to the mains.
Anyone any ideas? I know it will be hard to offer specifics as all campers are different and mine is a conversion (did not do myself). A pointer in the right direction would be greatly appreciated.

Do you have a mains charger fitted to the van?

Irishgoatman

Fingers McGee wrote: »

Do you have a mains charger fitted to the van?

No. When it's laid-up I just intend to run a normal battery charger to it every so often.

Do you have a better idea ? If so I'd be very interested.
I'm very much an amateur when it comes to campers electrics.

I will of course disconnect the solar panel from it (just 2 crocodile clips).

Irishgoatman

Hi Fingers Magee,

Sorry, Just realised that your last question was probably not meant for me.

Saruman

Fingers McGee wrote: »

Do you have a mains charger fitted to the van?

Very probably, I do not... I will have to have a good look at the electrics when I have a spare, dry weekend.

Thanks for the tip.