Leisure battery inline fuse size

[fred flintstone]

I have a 2001 Pilote Pacific and have just replaced the leisure battery with 2 brand new 110ah batteries.

They are next to each other and I joined them together with wire that is approx 6mm diameter.

I realise there should be a fuse somewhere near the batteries but there isn't one that I can see.

I want to fit inline fuses, or breakers, to my new wires and need to know what size inline fuse I should fit?

Any ideas what size is best?

 

[PhilandMena]

20 Amp should do it. Put it as close to one of the batteries as possible.

 

[mustaphapint]

I put 50 amp fuses in mine.

 

[PhilandMena]

That's quite a lot. 20 amp should do it as the on board charger is unlikely to exceed this current and a bigger draw is unlikely to occur unless it's a short, and if it is a short you need to protect your wiring and services as quickly as possible. I'm not a sparky but this is the level of protection fitted to my motorhome from new, so I assume the builders knew what they were doing.

 

[Wagoneer]

Clive Motts is the electrical expert on MMM and this is what he recommends:

http://www.motts.org/second leisiure battery.htm

So, 25 amp fuses as per your particular configuration.

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[PhilandMena]

The above advice is OK. Technically the fuse size would be determined by the cable size (amp rating) and the amount of current passing through the cable. If you can obtain 25 Amp blade fuses and fell more comfortable fitting them, go with that, you will be protected.
I'm of the view 20 Amp blade fuses are easier, cheaper and more readily to obtain. You could always fit a 20 Amp fuse and if it blows fit a 25 Amp. However, I'm of the view it would take a short (earth fault) to blow both.

 

[pappajohn]

As both batteries are right next to each other, and providing there is absolutely no possibility of the link wires touching earth either by chaffing or impact damage you wont need a fuse.. ..but its always good practice to fit one if possible.

 

[Lenny HB]

50 amp is standard in German vans.
If the cable you used is only 6mm dia it sounds far too small.

 

[pappajohn]

Probably as big as, if not bigger, than the wire feeding the vans fuse box.

To link the batteries should take less than 1/4 mtr and 6mmsq will carry 60 amps over that run.

 

[Bart]

I've got an 80 amp fuse fitted to mine .. Ofc that's the feed going to my b2b charger.

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[mustaphapint]

If you've got a reasonable size inverter fitted, say 1500 watts, you can easily draw over 100 amps even if it's only for a short period. So you could potentially draw 50 amps or more from each battery. That was my logic anyway.

 

[fred flintstone]

Phew, lots of replies. Plenty of food for thought.
The main reason I asked was because I was having a problem with my Schaudt unit. Udo Lang said to check the 5 amp and the 50 amp fuses on the leisure batteries.
I have no fuses anywhere near them, which I thought was strange. All fuses in wardrobe are fine.
Pilote must have hidden them
I think I will start at 30 and if I have to will go higher.
Thanks for all your input.

 

[PhilandMena]

Fairly sure you will have a fuse on the positive lead from the original Leisure battery. It will probably be an 'in line' fuse or in a fuse box along with other fuses protecting other services.

 

[peterc10]

I don't have a fuse between mine at all, as I am not sure what use it would be. I use 25mm starter battery cable between the batteries and I have a 2000W inverter that my wife uses for her hair dryer. And I have wired my battery bank in the way Hymer recommend to allow even loading, i.e. the positive leads connected to one battery and the negative ones to the other.

 

[funflair]

I have 4 batteries in two banks of two, the close coupled batteries are not fused between them but the +ve runs are fused at 150 or 200 amps to run inverter at up to 3000 watts.

Martin

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[PhilandMena]

Interesting comments on here. I too have a 300 W Inverter and have fitted a 60 Amp fuse (as stated in user instructions for the inverter) on the pos cable between leisure battery and Inverter. I also have a pos to pos lead between both batteries with an inline 20 Amp fuse. (Installed from new). It never dawned on me that if more than 20 Amps was drawn by the inverter the 20 Amp fuse would blow leaving the inverter drawing power from only one of the leisure batteries. This has yet to happen by the way and I am unlikely to add a bigger load to the Inverter than I have been in the past.