12v inverter fuse

Does a 12v 1200 watt inverter need a class T fuse? or is a 250 amp inline ANL fuse good enough?

It's the SOURCE not the inverter that dictates fuse type. The source is where the voltage/current originate.

A 12V lead acid may have a potential short circuit current of 12V/3mΩ = 4267A. A LFP 12.8V may be 3X that or more due to their lower internal resistance.

e67 said:

Does a 12v 1200 watt inverter need a class T fuse? or is a 250 amp inline ANL fuse good enough?

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A lot of people consider Class-T fuses to be of much higher quality, but an ANL fuse could work (people use them for car stereo amps all the time). I've had ANL before where it partially melted, then later it completely melted, overheated, and I wasn't even over-currenting it. I would prefer either a quality brand breaker or Class-T fast-blow fuse now.

Also make sure to use a quality brand like Bussman or something, so you know the rating is real and tested, instead of buying no-name fuse/breakers.


But as far as size (you mentioned possibly 250a) for over-current protection, the fuse is there to protect the cable from melting the insulation off and starting on fire, so it depends on the size cable you will run.

For a 1200w inverter you might need around a 150a fuse, so you need a cable that is roughly 20% higher ampacity rating (following the 80% fuse/breaker size rule, where the breaker/fuse should be 80% of the cable max ampacity rating, the max temperature that the cable can safely operate at)...

Ref:

It's about the AIC rating.

ANL is typically around 6,000A, i.e., if you pass MORE than 6000A through it, it may not fuse.

Class T is typically around 20,000A

so with a LiFePo and 12v I need a classT between the battery and the inverter, and nearer the battery..yes??

e67 said:

so with a LiFePo and 12v I need a classT between the battery and the inverter, and nearer the battery..yes??

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that is the recommended practice.

so 12v 1200 watt, probably only use 800 watts max.....what size T fuse?

e67 said:

so 12v 1200 watt, probably only use 800 watts max.....what size T fuse?

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Something like this:

1200 AC watts / .85 conversion factor / 10.7 volts low cutoff = 131.94062671797691 service amps

A bit higher to cover for load startup surge. Maybe 150a fuse, so the cable should have a good ampacity to safely support 20% higher than the fuse, like maybe a 1/0 cable. Longer lengths can cause more voltage drop and require larger gauge.

This would be better than nothing, yes?? with 2 awg cable??
cause I ordered this a few days ago...

e67 said:

This would be better than nothing, yes?? with 2 awg cable??
cause I ordered this a few days ago...

https://www.amazon.com/dp/B00FSKYNSC/ref=dp_iou_view_item?ie=UTF8&th=1

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Then you might want to protect it using a 100a fuse (roughly the 80% rule, just estimating without calculator).

ordered 100 amp fuses.thanks