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harrison avatar image
harrison asked

Fusing Smart Battery Protect

Hi all,


another novice question.


just a quick question, I’m planning to use a 100a smart battery protect (SBP-100) to cut dc loads against under-voltage to prevent damage to the lithium batteries...

Do I need to in-line fuse directly before the SBP-100? With let’s say 100a fuse or less?...

It’s a 12v motorhome system, it’s fused (200amp) immediately after the batteries- goes up to the Victron lynx distributor And then the DC loads will be fused accordingly- but do I need to fuse from the +ive busbar to sbp with a 100a fuse. The 4 lynx connections will be used to connect and fuse the charging sources, dc/solar/ac-dc etc so my intentions was to use the un-fused m8 connections on the right hand side of the unit that would ordinarily be used to connect further lynx distributors.


so earlier on the system is protected by a 200amp fuse and the dc loads will be protected after the BP but does the SBP require fusing. I understand that fusing generally protects the wire/cables and not the device, I’ve oversized cables so that’s not an issue.


Also dc loads will be no where near 100a but it was just as cheap to buy a 100a over a 60a so I went for the 100.

Thanks for any advice

Battery Protect
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harrison avatar image harrison commented ·

Also, if I was to run an inverter (Cotek SP-1500w 12v) directly from the lynx distributor The Cotek manual says the inverter requires a 350a in-line fuse... if I was to run the inverter from the lynx distributor the main battery bank fuse would also require to be changed for a 350a fuse. If this was the case would I then be required to fuse before the SBP-100 because the main circuit protection has risen from 200a up to 350a fused main circuit.

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3 Answers
pekkaj avatar image
pekkaj answered ·

I would like to know also. BP 65 manual displays a fuse between BP and battery, but what size would be good? What happens to BP 65 if load exceeds 65A? Should it be protected from over current with fuse that is slighty smaller, let's say 60A?

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Fra avatar image
Fra answered ·

Same question. And more.

Why is necessary a fuse on the little negative cable of the BP?

Is not included.

Is sufficient a 300mA fuse on the remote contact if used? And not on the negative?


Thank you

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quantumquest avatar image quantumquest commented ·

> Why is necessary a fuse on the little negative cable of the BP?

I think it's necessary to prevent the situation where a fault in the BP's electronics lead to a short circuit with a resistance that generates a current low enough to not trigger the big fuse before the BP while still generating enough current to heat up the GND cable excessively.

Apparently it was not required in the previous versions of the manual. The problem I described may have happened and that prompted them to change the manual. They should really include the fuse in the provided cable.

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quantumquest avatar image
quantumquest answered ·

Yes, I think you do need a 100A fuse. I think the question you need to ask yourself is what would happen if there was a short circuit that produced a continuous current between 100 and 200A? You say that your cable is oversized, so it may be OK here. However, the BP itself is not rated for such a current, so it is likely to overheat and cause a fire.

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