UK Source for reliable high amperage breakers?

P

phazaar

1 mW
Joined
Aug 10, 2018
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16
As per title, I've been using the breakers from Amazon (Qiorange things) rated for 300A (12V), and whilst the rating seems spot on, mechanically speaking they've proven unreliable in the extreme. Even with no terminals connected, 60-120 seconds after latching the breaker some of them just flip back to the unlatched position. I assume with more use all will start to do this.

I realise I could install 300A battery switches and dedicated 300A fuses in line, but space is tight and access is awful so circuit breakers are a much better option.

Any ideas for a more reliable option than the Amazon ones?
 
Good quality breakers at such high amps are crazy expensive.

IMO for critical use cases go with fuses.

Class T, MRBF and ANL type, from known-good makers like Cooper Bussman, Blue Sea

Not an area to skimp on.

Obviously incorporate current limiting into the normal-usage controls so CP is only triggered by kit at that level failing.
 
Also keep in mind that most breakers are not rated for switching duty. If you're using them as switches and they're not rated as such you will wear out the latching mechanisms quite quickly and they will not hold their rated current anymore.

Using proper switches, with fuses inline, will be cheaper and more reliable.
 
Hi all,

I am building a new 20s14p battery with a 100A BMS. i am not going to pull 100A ever, maybe 70A max. i should had purchase a 80A BMS!

However for safety purpose a circuit breaker is a good idea. i am thinking of this one found on ebay UK:

https://www.ebay.co.uk/itm/272566536852
100A DC Circuit Breaker MCB Solar Fuse 250v Single Pole 1P Ebike TOB1Z-125 C100.

Depending upon your requirement there are several circuit breakers available.

Petefr
 
Peterfr12 said:
i am not going to pull 100A ever, maybe 70A max. i should had purchase a 80A BMS
Click to expand...
No, the BMS does not usually **limit** your current, so even 200A would've been fine.

Pushing up close to the rated limit is stressful, threatens reliability & longevity.

Cheaper the unit, especially chinese, the more margin you want.

 
Peterfr12 said:
Hi all,

I am building a new 20s14p battery with a 100A BMS. i am not going to pull 100A ever, maybe 70A max. i should had purchase a 80A BMS!

However for safety purpose a circuit breaker is a good idea. i am thinking of this one found on ebay UK:

https://www.ebay.co.uk/itm/272566536852
100A DC Circuit Breaker MCB Solar Fuse 250v Single Pole 1P Ebike TOB1Z-125 C100.

Depending upon your requirement there are several circuit breakers available.

Petefr
Click to expand...
I am the vendor of the breaker linked to. Also available with 10% off if purchased direct using the discount code 'ENDLESS10':

https://torquetech.co.uk/collections/miniature-circuit-breakers-mcbs
 
phazaar said:
I realise I could install 300A battery switches and dedicated 300A fuses in line, but space is tight and access is awful so circuit breakers are a much better option.
Click to expand...
Keep in mind that the breaker will generally be spec'd to handle much higher than it's rated current for a long time before it pops. But it depends on the type; each has it's specifications for how long overcurrent and how far overcurrent.

The fuse will generally be spec'd to blow quicker than the breaker of the same rating...but it depends on the type.

So...it depends what you are trying to protect from.


Also, if you use a fuse or breaker on a voltage higher than it is specifically rated for, there is a chance (higher the farther overvoltage you go) that it will be unable to break the circuit when it pops, and plasma arcing across the contacts may either weld it shut, or simply continue arcing and cause a fire. (assuming whatever was trying to pop it didn't start it's own fire when it couldn't pop it in time).

FWIW, I use a breaker, mounted about a foot downstream of the battery pole, rated for something like 63A, IIRC, (for 24v, off a powerchair), on my SB Cruiser trike, and during various testing I pulled more than twice that current for up to 10 seconds without the breaker even thinking about popping. It has only popped so far once, during an accidental short while rewiring things (when I forgot I still had teh battery disconnect "on"). That was an instant pop.

I *also* have a 100A fuse actually *on* the battery pole, between that and the main positive cable, and that hasn't ever blown (the breaker popped before the fuse could in the event above).
 
john61ct said:
IMO for critical use cases go with fuses.
Click to expand...

When I said about space being limited, what I actually meant (and should have said) was access space. It's a HELL of a lot easier to reach a breaker and flip it with your arm wedged between a drawer runner and a 2x4 than it is to unscrew a cover, pull out a blown fuse, and fit a replacement :lol:

I agree though; fuses would be better, but it's always going to be one compromise or the other, and in this case, I don't really mind expense (as long as it's not utterly extortionate, like the £12,000 ones I found haha!).

dustNbone said:
Also keep in mind that most breakers are not rated for switching duty. If you're using them as switches and they're not rated as such you will wear out the latching mechanisms quite quickly and they will not hold their rated current anymore.
Click to expand...

To be honest, I thought this was why the first one failed as I'd been using it to isolate and re-isolate a circuit during testing. Then two of them failed when they hadn't been latched/unlatched ever... Proper Chinese quality ;)

I'm not looking for switching duty though, just to avoid the need to replace fuses if there's a problem.

danielrlee said:
I am the vendor of the breaker linked to. Also available with 10% off if purchased direct using the discount code 'ENDLESS10':

https://torquetech.co.uk/collections/miniature-circuit-breakers-mcbs
Click to expand...

Thanks for jumping in here with that, super helpful :) Couple of questions before I order, if I may...

1) How do you wire into these? Is it a screw clamp or something different? And what wire size can they take?
2) You mention using them in parallel to up the rating - I've seen them used that way in marine environments - are you able to provide any distribution block-type things to connect them in parallel reliably? I don't have much fabrication equipment.

Cheers all!
 
phazaar said:
danielrlee said:
I am the vendor of the breaker linked to. Also available with 10% off if purchased direct using the discount code 'ENDLESS10':

https://torquetech.co.uk/collections/miniature-circuit-breakers-mcbs
Click to expand...

Thanks for jumping in here with that, super helpful :) Couple of questions before I order, if I may...

1) How do you wire into these? Is it a screw clamp or something different? And what wire size can they take?
2) You mention using them in parallel to up the rating - I've seen them used that way in marine environments - are you able to provide any distribution block-type things to connect them in parallel reliably? I don't have much fabrication equipment.
Click to expand...
These breakers feature screw clamps for securing conductors. The 3-63A breakers have a 7mm wide cable entry point and the 80-125A breakers have a 10mm wide cable entry point.

I do not stock any sort of distribution accessory for these breakers. You would have to create your own harness to wire them in parallel.

Dan
 
Keep in mind a 12v rated breaker may fail catastrophically at 20s voltage if it trips. You need one designed for that voltage.
The Sur-ron uses one like in the link posted and it has been trouble free for me. They use it to switch the battery and there is no precharge circuit.
 
Have you got the current / time delay charts for them?

Or have you tested yourself at what currents+time they actually trip at 12/24/36/48 volts?
 
i got a few pictures of scooters that burned down due to those breakers failing, they are pretty standard on chinese scooters/mopeds. often you only see the reguar 240VAC version wich usully just melt before bursting into flames.

fun stuff.

use a megafuse rated at 150% of max load that the controller can have. if that frocker goes you got a major problem and should not try and just reset the breaker. and a fun fact: a megafuse will not burn your scooter down.
 
If they're DC rated they should have a mechanism to extinguish the arc. That (along with simply scale of supply) is why DC breakers cost more than AC ones, they are more complex.

AC interruption ratings depend on crossing the 0V point in the AC waveform, simply separating the contacts enough limits any arc to 1/2 an AC cycle (1/120 or 1/100 of a second).

That never happens with DC so you get the meltdowns described above when the incorrect breaker is used. The contacts pull apart, an arc is stuck, and said arc continues unabated until enough of the contacts burn off that there is no longer an arc path. By then you have a huge mess, which may or may not be contained to the breaker housing.

A properly rated DC breaker should do exactly what it says on the tin, they're used in industry all the time, nothing inherently sketchy about them.

A fuse is not different in needing to be correctly rated for DC interruption, for exactly the same reasons.
 
Sadly most manufaturers use the ac version. I only saw a dc version on a scooter once, and that was becayse the dealership replaced it themselfs.
 
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