Fuse sizes for additional leisure batteries (1 Viewer)

Feb 14, 2021
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Milton Keynes, UK
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II have 3 Leisure batteries of 90AH each. 2 and 3 are close to each other but number 1 battery is about a metre away.

I need to put a fuse inline between the Number 1 and number 2 batteries. (I understand I don't really need to between 2 and 3 as they are next to each other with very short cable)

I also have an inverter. 1500/3000 watt. I have a 300amp fuse on the positive cable to this inverter. Inverter is connected to positive of battery 3 and negative of battery 1.

So the question is - What size fuse do I need on the positive cable from battery 1 to battery 2? Do I need 2 fuses - one near the terminal of each battery? I have 50mm2 cable and as I said about a metre length. - maybe 1.5 metre?

Does it need to take into account the draw of the inverter?
 

pappajohn

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Aug 26, 2007
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Yes, a fuse at both ends of the positive link cable.
If you only use one and the cable shorts to earth only one battery is protected, the earthed live wire is still live at the unfused battery.
I would use the same size fuse as the inverter fuse as the inverter will still draw the same current no matter how many batteries are linked.
Also, if possible move the neg cable to the last battery, leave the POS as it is, and link between battery earth's.
It equalises the draw on the three batteries.
 

Lenny HB

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Oct 18, 2007
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The fuse should be of a lower rating than the cable, main function of a fuse is to protect the cable from overheating.
 
OP
OP
VXman
Feb 14, 2021
3,711
8,009
Milton Keynes, UK
Funster No
79,219
MH
Burstner Lyseo 727G
Exp
19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
The fuse should be of a lower rating than the cable, main function of a fuse is to protect the cable from overheating.

Yes. The cable is rated to 400amps. That's why I used a 300amp for the inverter cable. Just wasn't sure if the battery link cable needed to be the same.
 

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