# question

## Fuse on Positive Battery Lead - Multiplus II 48v / 3000

The Quick Install Guide for the MultiPlus II suggests a fuse. I carefully cut all my cables throughout the 8-battery array, including the parallel leads and the battery leads the same length.

I did not provide for a fuse.

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It's always a good idea to have a fuse!
Especially good to have one as close to the battery as possible, any faults downstream will then be mitigated by the fuse.

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Thank you. When I insert a fuse, should remove a section of the cable as long as the fuse, or is there a more scientific way of measuring to ensure that the two cables (positive and negative) remain equal in resistance (I think)?

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Warwick Bruce Chapman ·

If you are aiming for the technical ideal of matched resistance you'll have to take into account the resistance of the protection device - practicalities of installation usually negates technical ideals. You should be able to find the resistance of the fuse in its specification, that'll allow a best guess calculation as to how much length to remove.

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Warwick Bruce Chapman ·

There’s no need to match the positive and negative resistances. The idea is to match positives in parallel, and negatives in parallel, as much as possible.

(Separately, it’s a good idea to minimize overall resistance.)

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With one multi plus its no big deal to insert the fuse in the cable making the cable longer is no issue,

all that will happen is a very slite extra voltage drop,

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Maybe use a battery terminal fuse. Those put the fuse as close to the battery as possible (good) and might let you not have to cut your wire.

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Thank you. That’s a great idea. Do you have a specific one you prefer using?

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Warwick Bruce Chapman ·

I like the Blue Sea ones.

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A batt isolator is also useful too. 'Matched resistance' doesn't apply in the case of batt > inverter wires, but between multiple batts to keep them in balance, yes.

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Thank you. That is helpful to know.

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