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View Full Version : P-LTD - Maga-Fuse - Limited AMPs Thoughts



Darin Jordan
02-02-2016, 03:10 PM
The idea has come up from time-to-time of building a "P-LTD" rule system around the idea of limiting the AMPs allowed to be pulled through a power system. The idea isn't new. It's often used for Airplanes, etc.

I was picking up a new 40A fuse for our Tahoe last night at O'Reilly's Auto Parts, and came across these "Littlefuse MEGA-FUSE" packs.

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http://www.littelfuse.com/products/fuses/automotive-passenger-car/high-current-fuses/298.aspx

Data Sheet available here:
http://www.littelfuse.com/~/media/Automotive/Datasheets/Fuses/Passenger-Car-and-Commercial-Vehicle/Bolt-Down-Fuses/Littelfuse_MEGA_Datasheet.pdf

They come in ratings from 40A all the way up to 220A.

The dimensions for these particular ones are:

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These particular ones are "slow blow", which seems appropriate for this application. The size seems to be appropriate for many applications as well. I could easily fit this into a system in a Hydro, Sport Hydro, OPC Tunnel, etc.

If one really wanted to, they could use the supplied Maga Fuse holder as well:

http://www.delcity.net/store/MEGA%C2%AE-Fuse-Holder/p_795652


Looks like you can pick them up for around $5.00 each:

http://www.delcity.net/store/MEGA-Fuses/p_800374.h_800375.t_1.r_IF1003?mkwid=se6pKVrgO&crid=38094426869&mp_kw=&mp_mt=&gclid=COvV9v3i2coCFZRcfgod0XoC1w


Would be an interesting test to build in a 100A fuse to a P-LTD system and see how the system responds, watching for heat build-up, resistance, voltage drop, and general performance.

Would be another interesting test to build a similar setup using a "hotter" motor and review the same data.


The theory would be that you design a set of rules around the idea of simply failing the system, via the fuse blowing, if you exceeded a certain power level. I think you'd still want, or NEED, to specify a general motor SIZE range, or maximum, but otherwise, might be able to leave the rest open to the competitor's judgement.

If you push it too far, the fuse pops, and you're done.

Just regurgitating an old idea, but I think it's worthy of discussion.

Any thoughts?

ray schrauwen
02-02-2016, 03:46 PM
Can they be soldered? I know thermal fuses can't. Found out the hard way...

May require crimped connections.???

Darin Jordan
02-02-2016, 03:47 PM
Can they be soldered? I know thermal fuses can't. Found out the hard way...

May require crimped connections.???

Great questions. I'll buy one and find out...

Darin Jordan
02-02-2016, 03:53 PM
Here is another interesting option from the same manufacturer:

http://www.littelfuse.com/products/fuses/automotive-passenger-car/high-current-fuses/bf2-32v.aspx

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Doby
02-02-2016, 05:00 PM
You would need to "spec" the fuse, wouldn't you? I'm sure they are not all created equally.

Darin Jordan
02-02-2016, 05:37 PM
You would need to "spec" the fuse, wouldn't you? I'm sure they are not all created equally.

Certainly, to the part number.

T.S.Davis
02-02-2016, 05:53 PM
Any indication what the resistance is on them?

Darin Jordan
02-02-2016, 06:17 PM
Any indication what the resistance is on them?

Varies by AMP rating... looks like the 100A is 0.720 mΩ.

Looking at the specs closely, I don't know of the "slow-blow" fuses are the right way to go. The blow time is pretty long. Unless you want to use the load ratings, and spec like an 80A fuse, which is supposed to blow in 5-10 seconds if you exceed 135% of it's rated capacity, or 106A for more than 5-10 seconds.

Some thought would need to go into implementation.

jaike5
02-02-2016, 09:37 PM
How about pb/aq 60 amp esc's to keep all things equal and simple !!!

Cheers, Jay.

Darin Jordan
02-02-2016, 10:29 PM
How about pb/aq 60 amp esc's to keep all things equal and simple !!!

Cheers, Jay.

2 problems.

1) a "60-Amp" ESC isn't really a 60A ESC
2) You are suggesting an $80+ fuse. I'm discussing a $5.00 fuse.

Doby
02-02-2016, 10:36 PM
That $5.00 fuse is actually $6.50 Canadian.

jaike5
02-03-2016, 08:31 AM
Your rtr boat comes with a $80.00 plus fuse (esc ). If your building from scratch you have to buy an esc any way. plus they are water proof, and quite forgiving if you mistakenly ( or not ) over prop.
Cheers, Jay.

Darin Jordan
02-03-2016, 11:25 AM
and quite forgiving if you mistakenly ( or not ) over prop.
Cheers, Jay.

And, therefore, not really a "limiter"...

The point would be to ABSOLUTELY limit the available current, regardless of the ESC or motor used. Limit it to something well below what would otherwise damage the system, as well as limit it to a reasonable level of performance so as to limit the advantage that some motors might have over others.

Again, just an idea. Really not worth arguing about without some real testing.

Darin Jordan
02-09-2016, 09:15 AM
Picked up a few things to play around with. Going to see about their resistance, ability to be soldered, and may set something up on my test bench to run these and get some data.

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