Greetings,

I got a couple of single and double pole PV DC circuit breakers from AliExpress for use as DC battery disconnects for 48VDC 5KVA Axpert inverters. The 1P and 2P polarized MCBs are rated 220VDC/125A and 440VDC/125A respectively with "+/-" markings on top pole(s) as shown in the first image. 

From the look of it, the 440VDC/125A double pole breaker appears to be two single pole 220VDC/125A breakers side-by-side with a handle tie and perhaps an internal common tripping mechanism and opposite magnetic poles for DC arc extinction (hopefully). 

Should this be the case then it should also be possible to connect the 440VDC/125A 2P breaker in parallel as shown in method D to increase the current rating to somewhere near 250A, of course using same length cross connection cables and assuming an equal internal resistance between pole pairs.

The reason I want to try this is because I cannot get hold of any DC MCB rated above 125A for use as DC battery disconnects for 24VDC systems. What is your take on this? Your views and/or comments are welcome. KW

Will this help you?

https://www.aliexpress.com/item/50-300A-AMP-Circuit-Breaker-Dual-Battery-IP67-Waterproof-12V-24V-Fuse-Manual-Reset-Car-Circuit/32967621269.html?spm=a2g0s.9042311.0.0.3da24c4dmBIsA4

Hi, for strictly 24VDC yes although I 'd prefer one that can be installed inside a DIN-rail enclosure. Thanks

OK, to address your paralleling question the answer is no, it won't work reliably.

Unless you can perfectly match the impedances of both current paths so as to ensure perfect current sharing.

With impedances of the MCB's being this low the introduction of a milli-ohms will make a huge difference in the respective current paths.

That means one MCB will trip sooner, but once it does trip the other one will follow suit.

So while you will desensitize the MCB somewhat, expecting protection at 250A is unrealistic.