# Second battery cable size hymer 544



## Goldwinger (May 10, 2005)

Well I have the batteries sorted, I have the fuse holder sorted. the only question I have left is the cable size 16 mm sq is recommended, I don't have a problem buying it, if you have already completed this task, can you tell me 16mm is just over half inch in old money will it fit ok into the fuse holder from Farnell as recommended by Mr Clive.
Lastly to all the people that have given info on second battery installation on this site a great big thank you.


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## Techno100 (May 8, 2010)

What rating is the fuse holder? 16mm is cross sectional area not diameter so it's more like 6mm or 7mm across


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## Goldwinger (May 10, 2005)

Thank you for the very fast reply, now I understand, the fuse holder is made by littelfuse and will carry a 25 amp fuse.


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## Techno100 (May 8, 2010)

You could use smaller cable for 25 amp but I prefer the mechanical strength of bigger cable :thumbup:


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## Techno100 (May 8, 2010)

Actually without seeing it in the flesh you may struggle to get 16mm cable in a 25 amp rated fuse holder.
If however Clive has suggested 16mm and this fuse holder then it is very unlikely that they won't fit


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## Goldwinger (May 10, 2005)

Thank you again, we are just down the road at Shipley.


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## Techno100 (May 8, 2010)

Goldwinger said:


> Thank you again, we are just down the road at Shipley.


I is just up the road at Armley :wink: no not the nick :lol:


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## Goldwinger (May 10, 2005)

The fuse holder is a maxifuse holder recommended by Clive.


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## Techno100 (May 8, 2010)

Goldwinger said:


> The fuse holder is a maxifuse holder recommended by Clive.


Like this :roll: http://www.cbsonline.co.uk/product/IN-LINE_MAXI_FUSE_HOLDER_MAXFH


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## Goldwinger (May 10, 2005)

No have a look here www.farnell.com/uk then enter maxifuse, sorry unable to do it any other way.


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## Techno100 (May 8, 2010)

I think you'll seriously struggle to terminate 16mm2 cable to those screws? I'd hazard 6mm with yellow insulated crimp lugs at best.

How far apart are your battery +ve's


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## Goldwinger (May 10, 2005)

Well the cable is now on order, I have the yellow connectors waiting I will let you know. Thank you for your interest Techno100.


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## Techno100 (May 8, 2010)

Goldwinger said:


> Well the cable is now on order, I have the yellow connectors waiting I will let you know. Thank you for your interest Techno100.


If you have yellow connectors their maximum cable size is 6mm2


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## Techno100 (May 8, 2010)

Further contributions will require copious use of the tab on the left 







:wink:


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## Goldwinger (May 10, 2005)

The entry area is 9mm and the copper connector area is 11mm across on the fuse holder,I do have a number of crimp and solder end connectors,


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## Techno100 (May 8, 2010)

To be honest if your going to use 16mm cable and your load is never going to be above 25 amp you don't need a fuse unless there is a risk of mechanical damage to the cable?
If you are going to put a 25amp fuse in line regardless then 6mm cable is adequate and probably as big as that fuse holder is physically designed to accommodate.


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## Techno100 (May 8, 2010)

If you want to proceed with 16mm cable AND a fuse? you'll need something like this
http://cgi.ebay.co.uk/MIDI-fuse-hol...CarParts_SM&hash=item588d1f1072#ht_1364wt_901


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## Goldwinger (May 10, 2005)

Thank you for that, I will send for one, cheap as chips.


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## Techno100 (May 8, 2010)

Yes but you need to buy a fuse separately. Same seller stocks a choice.
You'll need 16mm crimp lugs with 5mm or 6mm holes as well and a ratchet crimping tool. 
I have a ratchet which you can drop by and use if needed.


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## Goldwinger (May 10, 2005)

Right, will look in to all that, and be in touch.


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## clive1821 (Mar 27, 2010)

I would also recommend that unless the batteries are contained within the same compartment, most definatley put a fuse at both ends of the cable joining the batteries on the +ve ends the first most basic requirement for you own safety, with 16mm cable you will be fine to fuse them at 50 amps....


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## Techno100 (May 8, 2010)

Clive what is the theory behind a fuse at both ends being any safer?


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## Goldwinger (May 10, 2005)

Hello Clive, Techno100, has been very helpful, I have read your posts on fitting a second battery, mine will be under the passenger seat, My plan is to use 16 mm sq cable ( on order ) also using a maxifuse on both ends however If there is a connecting problem I will order the one recommended by Techno100.


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## clive1821 (Mar 27, 2010)

Ok cool no probs its just very important to fuse both ends well done, just did not want you to have any issues.... best regards Clive


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## pieterv (Feb 3, 2009)

The fuses are for when the cable connecting the + terminals breaks, and touches something that is connected to - or vehicle metal (since that is -). Without a fuse sparks can fly and large currents flow causing overheating and possibly fire.

If you only fuse on one side of the connecting cable, this can still happen if the other unfused side (after a break) shorts.

So fusing in this case is recommended when there is a risk of breaking of the cable, not just to protect the cable from too high currents in normal operation, which is what fuses are normally for.

Pieter


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## Goldwinger (May 10, 2005)

Clive, following your diagram on fitting a second battery, is it necessary to join into the cable which goes from the first battery to the motor home or is it ok to connect to the + on the first battery. 
If that makes sense.


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## clive1821 (Mar 27, 2010)

Yep different Clive sorry, but yes conect +VE to +VE and -VE to -VE... Pieter has the correct answer.. always fuse BOTH ends of the conecting cable ( the +VE cable) just think each battery can a pontential bomb... once saw a ring spaner short accross a battery and what a sight it melted the spanner..... best regards clive....


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## Techno100 (May 8, 2010)

With most vans with the exception of panel conversions there is no metal in the hab area and no chassis earth to cause a short. All my hab circuits have their own negative wire. So I'd say it depends on your particular installation.
Also the risk of accidentally breaking a 16 mm cable IS extremely unlikely


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## pieterv (Feb 3, 2009)

My reply was meant to be to the question "why fuse both ends?".

Of course, if there is no possibility of a short, you might want to decide to leave the fuses. On the other hand there is always going to be one point where you can short to minus, isn't there, even in an area where there is no vehicle or other metal? 

So if you don't fuse maybe cover not just the plus terminals of the batteries, but also the minus.

But indeed a sturdy cable won't just break.


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## Techno100 (May 8, 2010)

pieterv said:


> On the other hand there is always going to be one point where you can short to minus, isn't there, even in an area where there is no vehicle or other metal?


Not if the cables are the correct length and routed correctly so they cannot reach the wrong terminal.


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