# Fuse ratings multi battery and inverter?



## ched999uk (Jan 31, 2011)

We have 3 leisure batteries. Original one and 2 additional ones. The 2 additional ones are each connected back to the original by 120amp cable with a 60 amp fuse at each end. 

We would like to fit a 1000watt inverter as they are on offer at Maplin for £100. But it can pull 100amps on full load!

The problem I have is I can't find any 100amp fuses that fit the AGU fuse holder.

I am wondering whether I actually need to change the 60amp fuses or not. As in theory a total 100amp load should pull 33.3amps from each battery???

So any ideas if I need higher rated fuses or not?

Thanks for any help.


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## airstream (Jan 7, 2009)

*not easy*

Hi, 
The draw will be more or less equal on all three batteries and 
depending how the three batts are connected will detemin on how the load is shared

Correct way is not always or ever used!, most common way pos and neg taken off one battery call it "A" with the other one/two/three in a parallel daisy chain results in battery "A" providing the greater share of the load whilst the last battry in the chain the least

If the batteries are connected so that the three are in a parallel daisy chain with say the pos taken from battery "A" and the neg from the last battery in the chain both the load and charging are shared a little better

Still means your fuses will need uprating - battery cable fuses are there to protect the cables and should be rated a little less than the cable rating, appliance fusing should be integral or local to the load

Good Luck

Ray


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## ched999uk (Jan 31, 2011)

Cheers.
Battery A is original location. Battery B +ve is connected via 2 fuses to Battery A +ve. Battery C +ve is connected via 2 fuses to Battery A +ve. Load connections are from Battery A. Negatives same i.e. all back to Battery A.

Current fuses are 60amp but I can't seem to find any 100amp ones to fit my holders. I can find them in America but expensive.

Appliance (inverter) is internally fused.

Thanks for your help.


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## Ian_n_Suzy (Feb 15, 2009)

Hi,

http://www.ebay.co.uk/itm/Line-Maxi...arts_Vehicles_CarParts_SM&hash=item41614f665b

Looks like you can buy it complete with the holder for under a fiver.

GOOD LUCK


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## Ian_n_Suzy (Feb 15, 2009)

or http://www.ebay.co.uk/itm/100-AMP-1...arts_Vehicles_CarParts_SM&hash=item4150aa2598

http://www.ebay.co.uk/itm/1-x-100-A...arts_Vehicles_CarParts_SM&hash=item3a6eb23376

A couple without the holders if you have a Maxi Holder yourself.


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## ched999uk (Jan 31, 2011)

cheers I may have to go down the maxi route. I wouldn't use fuse holder shown as you then need to connect to the tails from the fuse holder. But thanks for maxi fuse type reminder. I forgot about those haven't use them since the 80's . 
These are what I have: http://www.maplin.co.uk/water-resistant-fuse-holder-30428


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## rod_vw (May 10, 2005)

These are AGU fuses at 100Amp I don't know if they are exactly what you need but have a look.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&clk_rvr_id=311261071073&item=380297394925

Personally I prefer the 'Blade' type but if you don't need to change the fuse holders then go with the type that you have.

Rod


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## ched999uk (Jan 31, 2011)

Cheers Rod, I hadn't found those. 
The problem I have with blade types is getting the 20mm2 cable in the crimps.

Cheers for the link. I think I will order a couple of sets.


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## airstream (Jan 7, 2009)

*mega fuse/holders*

Hi.
Mega fuse and holders can be purchased from vehicle wiring proucts 
mega fuses go up to 175 amps www.vehicleproducts.co.uk

Also should have mentioned that the cable length between batteries is also a major factor in how the load/charging is shared between batteries - ideal is all cables are the same length and size

If your take off battry is metres away from the other two (you have to count up both cables to determin volt drop) at 100 amps draw you could lose 1 or 2 volts between batteries

Ray


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## rod_vw (May 10, 2005)

The other choice is to use these http://www.vehicle-wiring-products.eu/VWP-onlinestore/fuses/fuses.php#strip and build your own fuse mounting if necessary. That is a solution that I have used in the past. VW use strip type fuses in the high current circuits as I suspect do many other vehicle manufacturers,

Rod


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## kandsservices (Sep 5, 2010)

try here http://www.ebay.co.uk/itm/250880513800?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
kev


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## airstream (Jan 7, 2009)

*strip fuses*

Hi, 
I would be careful if using strip fuses at anywhere near the fuse rating and I think the max cable size for the strip fuse holder is 16mm and the holder has small m5 connections ? - is the max strip fuse rating 100A?

Strip fuses at near fuse rating can get hot and should not be used in battery compartments with open cell batteries

I would go for the safer option of the mega type holder and fuses

For info at 100amps 20mm cable has an approx volt drop of 0.08v per metre on a cable run of 2mtrs ie 1 mtr + and 1mtr - = 0.16v

However will you ever use he inverter at its maximum rating? the only time we get close is for "the hairdryer" and then only with the engine running! so my installation is well overspec in both cable and fuses

Better safe etc

Regards Ray


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