# Leisure Battery and consumer unit questions



## Newbie84 (Apr 9, 2010)

Hello all

I am currently tidying up the mess of a consumer unit/leisure battery install in a ducato van conversion i have just purchased but i need a bit of help on a couple of issues

1. On the consumer unit the earth wires from the MCB and the two RCD's all go to a distribution block from which a single length of earth wire is currently dangling from - What do i connect this earth to, do i connect it to the negative terminal of my leisure battery or does this need to be earthed to the chassis? And does it need to be earthed to anything else eg. the gas lines on my built in gas hob?

2. What size/gauge wire do i need to use for the positive supplies from my leisure and starter batteries to my van/car switch on my consumer unit (leisure battery supply will be just over a metre in length and starter around 2 metres) Also do these both need to be fused before the switch?

3. Do my earth wires have to be the same size or could they be smaller

4. Can i use a 30A bosch relay that i picked up from a wreckers for my split charging relay or is a split charging relay totally different ie. heavier duty? Visually they look the same except i've noticed some of the relays come with two studs and nut obviously to accomodate the heavier gauge wires from each batteries positive supplies?

5. What size/gauge wire should the positive supplies (mentioned above) to the relay be? And what size should the relay trigger wire be?

6. I have found several split charging relay kits on the net the cheaper version being a "maypole" branded kit, are these good quality (they use a different looking relay to the square bosch type one mentioned above) or am i better off getting something like this - http://cgi.ebay.co.uk/Split-Charger...ervan_Caravan_Accessories?hash=item2ea6991efa

7. Does the leisure and starter battery have to be the same size (my starter is a 85 amp hour and i am looking at purchasing a 110 amp hour leisure) or is this just preferred? What are the consequences of having a bigger leisure battery than your starter?

Sorry for all the questions but im abit of a virgin to all of this and if anybody could help me out it would be greatly appreciated!

Happy motorhoming! 

Newbie


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## clive1821 (Mar 27, 2010)

I'll have a punt here if you are asking questions like this I would advise you to have an electrician view the job.. and make it conform to the 17th iee regs...

1) the earth wire should be bonded to the chassis 6mm from the common earth bus bar in the unit. Its good working practice to bond the hobs etc...

2) 10mm cable with be fine.. fuse both ends of the cable...

3) depending which earth wires you are referring to..... usually the cables coming into the unit are either 1.5mm 3 core or 2.5mm 3 core flex (not twin & earth)

4) 30a should be ok...

5) can't answer the question without seeing the loads the coil side of the relay 1mm twin will do

6) the main battery has nothing to do with the leisure side and they should be kept separated.... the leisure battery the bigger the capacity the longer the battery will last.... I have 250Ah leisure batteries AGM type...

this is only a guide but please get an electrician to advise you face to face and carryout the work... hope that is of help...


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## Newbie84 (Apr 9, 2010)

Cheers for the speedy reply Clive

Don't worry I shall be getting an auto sparkie to view all my work prior to setting out on any major excursion  

So just to clear things up

1. That would be 6mm "cable" from the common earth bus bar ? Also the cable the previous owner used was 6mm domestic type cable (very stiff with larger and fewer wire strands inside)....am i better off replacing this with flex? 

2. Im guessing you meant that the positive supplies should be "10 gauge" = 2.588mm not 10mm right? Also does it matter which end of the supplies is fused, im guessing the battery end as thats where the current flows from?

3. So some consumer units use 1.5mm? for the positive supplies and earths coming into them. So using 2.5mm should be well and truely sufficient

4. So there isn't any difference between a 30a relay from under the bonnet of any given car and the ones sold as split charging relays on ebay then?

5. 1mm twin means?

6. Any recomendations on split charging relay kits...? Are the "maypole" one's decent quality?

7. I realise they are totally different it's just that all the write up's on leisure battery installs i have read have stated purchasing a leisure battery the same amp hour capacity and age as the starter battery in the vehicle...i was just wondering why this is? 

Thanks once again


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## clive1821 (Mar 27, 2010)

mmm this is getting difficialt.... you really need someone that is qualified to do this work  i have also already answered the questions...

1) standard 6mm earth wire from the common bus bar in the consumer unit to chassi

2) you asked about the cables from the leisure battery to the main battery would be 10mm FUSED AT BOTH ENDS!! you do not take them to the consumer unit as that is mains and not 12v dc...

3) a consumer unit is a unit that has mains in it and distributes to your mains sockets and lighting as per 17th edition regs

4) as far as I am aware they should be the same.. 

5) 1mm cables to supply the relay coil....

6) i have no experience of the split charging but there are various ones on the market... don't use the cheapest...

7) there is no reason at all my main battery is a 80Ah and the leisure batteries are 250Ah just has more capacity, and they have solar, mains and "float charge" from the alternator, this is because you could easily damage the alternator if the charging current was not controlled....

As I have mentioned, I happy to help but you must get someone who is qualified to see the job at first hand and carryout this type of work.... its a skilled job.... when you are using mains consumer units.

Best regards Clive


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