# Fuses and holders to protect leisure batteries



## sirhandel (Mar 5, 2008)

I have 2 leisure batteries (12v each) in parallel charged by a solar panel. I have read recently in MMM that they should be protected with separate 25A fuses in case one of the batteries fails. I assume the fuse holder should be attached directly to the pos terminal on each battery but can anyone recommend a suitable source for these holders and fuses?


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## wug (May 19, 2011)

Yes, in-line from the Positive. You want a 50A maxi fuse and fuse holder. You can get them in Halfords or cheaper on eBay. Fuse Holder


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## trek (May 1, 2005)

some ideas here ?:-

vehicle wiring products : fuse holders

look for the MAXI fuse holders


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## listerdiesel (Aug 3, 2012)

Thinking back over the years, I have never had a battery main feed fused and never had any issues, but of course there are situations where it might be useful.

Look at vehicle batteries, they aren't fused.

Our three batteries are not fused directly but feed fuseboxes which then feed the sub-circuits. Even the 5000lb winch isn't fused from the trailer battery set as the current can go well up in the air if the cable jams as it did on Sunday evening when loading the engine.

I'd not get too worked up about it, you are adding another bit of voltage drop and something else to go wrong. Plus you need to carry a spare fuse.

The other thing to think about is under what conditions the fuse is going to blow. What are you going to do to knock out your main battery feed? Smaller circuits should be fused appropriately, 5A for lighting, 10A for power (water pumps etc etc) so outside of those items, how are you going to blow your 25A or 50A fuse?

If you dropped something across the battery terminals, the fuse wouldn't help, it would only help if you shorted out the cabling between the battery and the fusebox. Work out a risk assessment to see how you could do that, and it probably comes down to 'never'.

YMMV

Peter


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## sirhandel (Mar 5, 2008)

listerdiesel said:


> Thinking back over the years, I have never had a battery main feed fused and never had any issues, but of course there are situations where it might be useful.
> 
> Look at vehicle batteries, they aren't fused.
> 
> ...


Tks for your response Peter. My original question arose after reading an article that Clive Mott wrote in MMM Aug2013 :
"As a failed short circuit cell on one battery will try to discharge a second paralleled battery fit individual fuses to each battery before paralleling to protect against this scenario".
His accompanying diagram shows fuse values of 25A.
Thanks again.
sirhandel


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## listerdiesel (Aug 3, 2012)

In the industry we use steering diodes when paralelling large banks of batteries, but generally cell or battery failure is pretty rare, they tend to die away rather than go short circuit, and if just one cell goes it probably wouldn't generate enough current to blow that fuse anyway.

Peter


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## sirhandel (Mar 5, 2008)

listerdiesel said:


> In the industry we use steering diodes when paralelling large banks of batteries, but generally cell or battery failure is pretty rare, they tend to die away rather than go short circuit, and if just one cell goes it probably wouldn't generate enough current to blow that fuse anyway.
> 
> Peter


OK Thanks

sirhandel


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## drcotts (Feb 23, 2006)

THe latest caravan council info is that you should site any fuses outide the battery box or cabinet in which they are house for risk of explosion when the fuse blows and the spark ignite the Hydrogen gas

this is for lead acids of course with removable caps.
even vented batteries can let some gas out the top


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