question

frederic avatar image
frederic asked

Expansion MEGA fuses

Hello

Will the 58V MEGA-fuse series expand?


I’m asking because:

The connection cables of Pylontech 48V are 4AWG, which is about 21QMM.

When I did my cable calculation, that’s about 63 Amps when in a cable tray with 40 degrees C.

That would mean it could charge/discharge 2 batteries at 25A each, 50A in total. A fuse of 60 Amps would be perfect in this case.

If I fuse this at 125A, the minimum available at 58V, the cable is not protected from 63A till 125A if a fault would occur.


So I hope an expansion will soon arrive.


thanks in advance

Frederic

fuses
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5 Answers
Alexandra avatar image
Alexandra answered ·

@Frederic

Pylontec cables are different to other battery cables. Their insulation has a higher temperature rating, and a few other things that make them special.

Their 4AWG are rated for 120A. (It is stated in their manual). So the megas are perfect for them.

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wkirby avatar image
wkirby answered ·

Indeed, I am using a 125A MEGA fuse with my Pylontch cables.
Like Alexandra said, the insulation is rated at a higher temperature and so the overall current rating is elevated, 105°C IIRC.

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esa69 avatar image
esa69 answered ·

In the case that you use a 125A fuse then the cable will be the fuse, also I have seen tests with Victron Fuses where a fuse will blow not at 125Amps, but a much higher rate then 125 Amps and can be as high as 250Amps, so your 120Amp wire is now the fuse

I fully agree with Frederic to use a much lower fuse, like 63A or the next 80A Fuse and not the 125 Amp. And off course 48 volt version not the 12 or 24 volt versions


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ahtrimble avatar image
ahtrimble answered ·

Problem is trying to find a 60a or 80a MEGA fuse for a 48v system. Anyone find a supplier yet?

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hominidae avatar image hominidae commented ·
search fur MEGA fuses from littelfuse...they offer 60A/80A@70V as well as the other ranges.

Sources are Digi-Key (some are only available in large batches, not single pieces though) and I've seen these on ebay, too.

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esa69 avatar image esa69 commented ·
Let me know if you need some, I have 60Amp 80Amp and 100Amp on stock with 70Volts, got them from a friend. Let me know how many you need and I will check price and how much we can send you (ps to where needs to be shipped?)


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kevgermany avatar image
kevgermany answered ·

What people are missing is that the BMS in the lithium batteries will cut the output if overloaded.

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