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NH fuse in parallel?? aka NH knife blade fuse aka DIN NH blade fuse

I think the NHA is referring to the fuse holder dimensions and not the fuse....not sure though,,,, but I believe all the bottom dimensions are fuse holder size dimensions????
Old thread but I'll throw in my 0.05$.

The FIRST thing you need to determine is which fuse tripping characteristic you are going to use:
- aR: semiconductor fuse, ultra fast, short-circuit protection ONLY (NO overload protection !), HIGH power dissipation
- gS: semiconductor fuse, very fast, short-circuit protection and overload protection, medium power dissipation
- gBat: semiconductor fuse, quite-very fast, short-circuit protection and overload protection, medium power dissipation
- gR: semiconductor fuse, relatively fast, short-circuit protection and overload protection, medium power dissipation
- gG: general purpose fuse, slow, short-circuit protection and overload protection, low power dissipation

Check:
- Prospective Short-Circuit current vs Clearing Time Curve
- Peak Limiting / Let-through Current Curve
- Pre-Arcing I2t value (take it with a pinch of salt - the value is typically given for AC circuits under some controlled conditions)
- Arcing I2t value (take it with a pinch of salt - the value is typically given for AC circuits under some controlled conditions)

THEN:
- Check the power dissipation of your fuse at the operating current (including unbalance: 20-30% unbalance is typical) and check that the fuse holder can withstand it
- For aR fuses you need to MASSIVELY oversize the fuse with respect to your operating current, simply because the power dissipation is HUGE
- For aR fuse a Breaker (or other fuse) OVERLOAD protection is required.

What I did for operating current of 100 ADC:
- Fuse aR 315A NH1 (1 for DC+, 1 for DC-)
- Breaker type Schneider Electric C120H-B100 (2P)

You won't protect much if you are planning on installing a gG fuse ...

At the very least go for gR.

I would NOT go below gS / gBat. aR is preferred but make sure you have overload protection though some other means !

In the future I might change for operating current of 100 ADC:
- Fuse aR 200A-250A NH00 (1 for DC+, 1 for DC-) and/or Fuse gBat 125A NH00 (1 for DC+, 1 for DC-)
- Breaker type Schneider Electric C120H-B100 (2P)

For the same Fuse Tripping Characteristic and Nominal Current, a NH00 fuse will have a lot LESS power dissipation than a NH1. Similarly NH1 will have LESS power dissipation than NH2. And so on.

EDIT 1: When paralleling fuses, besides the current unbalance issue, you also need to be aware that the I2t value of the "equivalent fuse" (the I2t delivered to the load/inverter/charger/etc in case of a fault) is the SUM of the I2t of each fuses.

So for instance 3 x 100A fuse will give you 300A operating current (ideally, WITHOUT considering unbalance / current sharing), but 3 x (I(t)
)^2 where I(t) is extracted from the fuse Prospective Current vs Clearing Time Characteristic.
 
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Are these NH fuses and holders same, or similar to RT16 fuses? And has anyone tested these cheap AliExpress versions and know whether they are worth using?

I don't know ... But if you plan on using a non-brand Fuse from China, you better do some tests to make sure they work correctly, BEFORE you deploy them ...

I already saw many videos of cheapo Chinese Fuses, these small automotive 1-16A Blade Type Fuses, where the non-Brand version would NEVER melt. And here we are talking a much dangerous situation ...

EDIT: from the Picture it's a gG Fuse. No matter how "fast" or "quick" they claim to be, it's like the SLOWEST fuse you could possible deploy on a Battery. aM is not a thing ...
 
Fuses in parallel don't behave the way you think. The current does split through them but only close verse dead even. It totally messes up the time verse current curves so it is unpredictable. And if one blows it will blow the other.

If you parallel fuses you have to test them and identify the curve to use.

The only exception to this is when the mfg matches fuses together and makes them together then they provide a time/current curve set for the grouping.
 
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