# sizing circuit breakers to high-amp controllers



## dtbaker (Jan 5, 2008)

I would love to have some of the EE types clarify ratings and 'suggested' configuration for circuit breakers needed for the new modern controllers that output way more juice than the old Curtis..... 

In my first EV, I went with a suggested package including curtis 1221c and the '200a' two pole GE circuit breaker. This has worked just fine as the max amps of the 1221c rarely if ever actually hit 400a, and continuous almost never is even at 200a for very long, even at highway speed. 

First, I would appreciate a comment on whether I wired correctly in using the GE basically as a single-pole by running the pack - thru one side, and pack + thru the other. seems to have worked fine, but is this correct?

I am asking because I am considering upgrading the controller to a soliton Jr in my next build, which could hit a peak of 600a (for a little while without water cooling), but won't have a whole lot more continuous amps normally. I am wondering if it would be appropriate to use this same circuit breaker, but as a parallel-pole by splitting either my pack - or + and running one of them thru the GE unit using both poles.... I THINK this would provide coverage for 400a continuous, 800a peak; am I correct, or making a mistake?

The thing I don't know is whether each of the two poles on the GE unit can carry 200a continuous, 400a peak; and be safely used in parallel to effectively carry up to 400a continuous and 800a for brief periods.... or if I need to pay a lot more to use TWO airpax '250a' single-pole in parallel.

Secondly.... is it 'safe' to have the circuit breaker just on one side of the main traction pack? Does it make a difference whether its the + or - side?


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## piotrsko (Dec 9, 2007)

TESS did a reply somewhere the other day about fuses. Got to get him to post his replies to the WIKI.

Circuit breakers break on a 200% load after i think 2 minutes. They are thermally operated, so the hotter they get the faster they open. been a lo0ng day with the flu so the reply isn't guaranteed accurate, but the maker should provide the actual specs on their data sheet.

Oh, BTW breakers should be rated in max watts, but they aren't. They are rated like switches.

I by tradition break the + side since most of my stuff can have spurious grounds which would nullify and protection from transients.


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## dtbaker (Jan 5, 2008)

I would hope the traction pack doesn't ever have 'spurious grounds', but would go with the breaker on anyway.


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## coulombKid (Jan 10, 2009)

piotrsko said:


> TESS did a reply somewhere the other day about fuses. Got to get him to post his replies to the WIKI.
> 
> Circuit breakers break on a 200% load after i think 2 minutes. They are thermally operated, so the hotter they get the faster they open. been a lo0ng day with the flu so the reply isn't guaranteed accurate, but the maker should provide the actual specs on their data sheet.
> 
> ...


Typically the breaker is considered tripped when amperage hits 150 % of rating so the 200 % claim above sound credible. I've got 200 amp breakers on my shop that hit 400 when I start the phase convertor and again when I start the big three phase loads but each transient only exists for 1 to 2 seconds. Here in Phoenix we have some brutal summer ambient temps so all my copper got the bolt cutters and an up-grade when I moved here. Where in the car they are makes a big difference. When we've had rated breakers in a panel on the west side of a plant we've had to add Vortec thermal coolers to the enclosure to operate normally even though all installation was to code.


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## electricmini (Oct 21, 2008)

You really need to look up the tripping characteristics for the breaker - there are many different types!

As an example, I have two Heinemann GJ1P series breaker, one rated at 500A the other at 600A. You'd think they would behave in pretty much the same manner, right?

No, one has a rapid trip characteristic (the 500A one) so it will trip in just a couple of seconds at 200% overload, the other has a much more general trip curve, and will take approx _*10x longer*_ to trip at 200% overload

FWIW, I'm using a 600A std trip Heinmann GJ1P on my front pack (Exide Maxximas), with a 250A GJ1P on the rear pack of Hawkers(mainly because they are zombies already).
The 600A breaker has 3 poles, but they are all linked together internally so you can't actually use it as a 3-pole breaker
(hence the 1 in the GJ1P bit of the part number, that denotes the number of poles).
This is in a 132V car, with a Z2K, car weighs around 4000 lbs
There is also a GE Redspot 355A HRC fuse in each pack, as a last-ditch line of defence.

In general, I wouldn't try using separate breakers in parallel to try to get a higher rating - there's no guarantee that the currents will divide evenly between the breakers
(because you can't control the wire-to-breaker connection resistances tightly enough),
this will likely lead to it tripping at a lower current than you expect.

The big Heinemann breakers crop up regularly on Ebay - look for ones from the GJxP series (I searched for "Heinemann breaker")


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