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Discussion Starter #1
I am currently using a single 250 amp circuit breaker as an emergency cutoff. It has worked well. I am moving up to a better controller and may go to an amperage level that trips this breaker. I would like to retain this emergency cutoff option. I looked into 500 amp breakers, but they are 1000s of $!.

I can get a second 250 amp circuit breaker for about $90. My question is, can I put the two breakers in parallel so that each is only handling 250 amps if I am drawing 500?

I know that they don't trip until a longer sustained load. The one I had never tripped when I went to 300 amps briefly. For now it is mainly a theoretical question because I may not even need it unless I start tripping the single.
 

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Why not just use a contactor and fuse? The LEV/EV200's can break like 900A.

Paralleling circuit protective devices is not recommended. They do not neccessarily share current equally, and when one trips, the other has the full 500A going through it, which could be beyond its limits.
 

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Discussion Starter #3
Why not just use a contactor and fuse? The LEV/EV200's can break like 900A.
I have 2 contactors, the first one on in the aux position through an inertia switch and the second one on in the key run position. I also have a fuse. I just liked that added emergency cutoff capability with a red handle that anyone could see and it is a nice way to cut power when working on the car.

Paralleling circuit protective devices is not recommended. They do not neccessarily share current equally, and when one trips, the other has the full 500A going through it, which could be beyond its limits.
If one tripped and all 500+ amps were directed to the remaining one it should trip very soon after I would think.
 

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Hi PAK

If one tripped and all 500+ amps were directed to the remaining one it should trip very soon after I would think

The issue is that it might try to trip and weld itself together!

I have had some overloaded contactors stick closed
 

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I have had some overloaded contactors stick closed
I guess I had that happen once too.

There is still a fuse that is really the first layer of protection. It blew before the breaker tripped when my logisystem controller just died.

I just found these manual disconnects referred to in the sticky above. http://www.gigavac.com/catalog/power-products/manual-disconnect-switches

These look like a good option, I just don't know how much force is needed to turn them. The current choke cable I have easily throws the circuit breaker, not sure if it would work on this switch since it requires more of a twist than a pull. Anyone use one of these who can tell me about how much force is required?
 

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Hi PAK

If one tripped and all 500+ amps were directed to the remaining one it should trip very soon after I would think

The issue is that it might try to trip and weld itself together!

I have had some overloaded contactors stick closed
Exactly! It could trip, but it may not be designed to handle a huge surge that goes from 250A to 500A, and could weld.

The other thing, is you need to link the circuit breakers so they trip at the same time.



I guess I had that happen once too.

There is still a fuse that is really the first layer of protection. It blew before the breaker tripped when my logisystem controller just died.

I just found these manual disconnects referred to in the sticky above. http://www.gigavac.com/catalog/power-products/manual-disconnect-switches

These look like a good option, I just don't know how much force is needed to turn them. The current choke cable I have easily throws the circuit breaker, not sure if it would work on this switch since it requires more of a twist than a pull. Anyone use one of these who can tell me about how much force is required?
I think you're going down the right path, with that manual disconnect. You're protected (fuses and contactors), you just want ease of disconnect. You could use a huge Anderson plug rated for full pack voltage,
 

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Quote from PAK65
I just found these manual disconnects referred to in the sticky above. http://www.gigavac.com/catalog/power...nnect-switches

These look like a good option, I just don't know how much force is needed to turn them. The current choke cable I have easily throws the circuit breaker, not sure if it would work on this switch since it requires more of a twist than a pull. Anyone use one of these who can tell me about how much force is required?


I bought one and when turning it to off it is spring loaded and snaps to off - should be easy to use with a pull wire... I am thinking about using it as emergency shut off but I am a little concerned about arcing at high amps,

The other option is a Heinemann circuit breaker or just a Heinemann disconnect switch- The only place I know that has them is canev - they also sell a red knobbed manual disconnect.
 

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We use EV200s, LEV200s, both Kilovac (Gigavac) in all out battery packs. They are only ~$90-150+ from Digikey. You can also use (make) an economizer to reduce coil hold current dramatically. As others have said, DON'T parallel breakers, and make SURE they can handle the DC squelch / off current / arc !
 
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