48v battery breaker suggestions?

What amperage are you looking for?

Yes, the vast majority of "DC" breakers on eBay/Amazon are horrible quality Chinese junk units with fake ratings, etc.  I wouldn't touch them with a 39.5' pole...a high-amperage DC arc is something you do NOT want to play with.  Check YouTube for videos of improperly rated (or reverse-biased) DC breakers catching fire--it's not funny.

I like to dig around eBay for used/new old stock Airpax magnetic trip breakers.  The advantage of magnetic trip over heat-trip is...well...they aren't affected by heat, and often trip much faster.  Most of the DC-rated ones are rated at 80vDC, 10kAIC (10,000A interrupt current), and often have a "sense switch" that you can use to detect if the breaker is tripped.

• If you're looking for >250A, search for GJ1P-series breakers (sort by price, haha, they're expensive brand new!)  Should be able to nab a good, solid breaker for < $40/ea.  (These are the huge ones that Sean has.)
• If you're looking for <150A, search eBay for "Airpax DC breaker."  (I'm seeing 20A through 150A on a casual search.)  KEEP IN MIND: Most of these are removed from old equipment...READ THE SPECIFICATIONS BEFORE BUYING!  Make sure they're 80vDC rated.  Sellers don't always advertise them right--or understand what they're selling.  You should be able to get what you want for < $25/ea.  (All of my breakers are this size/style.  I have 5 10A, 1 each 40A, 90A, 150A.)

There are other breaker brands besides Airpax out there (I have one Heinemann 40A DC breaker); if you want to search for "DC breaker" and weed out the 15,381 results of resellers marketing Chinese garbage...you likely will find some pretty decent breakers for a good price.  But it'll take some time.

As an example, here's a link to an Airpax breaker that the seller didn't include much info on.  If this is the size you want, you can probably get a better price than a seller who knows what they're selling: https://www.ebay.com/itm/AIRPAX-LELHPK11-1RS4-30452-80-V-Circuit-Breaker-80V/274720081826   I looked at it, and noticed that it has as 50,000AIC rating--which is really good.  Amperage isn't listed on the nameplate, and they don't show the toggle...but from the "Trip Amps" and the part number, I can infer that it's probably an 80A breaker.  (Trying to find the manufacturer spec sheet also can be very handy...though most of these will have custom options that aren't in a manufacturer spec sheet).

Another thing to keep in mind with most of these magnetic DC breakers...POLARITY IS IMPORTANT.  The terminals are usually marked with text on the label closest to the terminal, you're looking for "LINE" and "LOAD."  Line goes to battery positive, Load to the...well...load 😉

One other thing you might want to check is the "Delay" rating.  A magnetic trip breaker with no delay will trip instantly upon a surge...so they usually use some fluid in the "trip mechanism" (often called "hydraulic magnetic trip") to slow the response down.  There can be several different kinds of trip curves as a result...but for practical purposes, this usually can be ignored.

DC breakers can also be marked as Bat and Aux as are the ones made by Bussmann. Some are only rated for 42Volts which is fine on a 24 Volt system while others are rated at 48 Volts.

For what it's worth, I've been able to successfully break a shorted HV string of panels using TOMZN DC MCBs and confirmed that it wasn't a fluke by sacrificing one on the altar of testing by reversing the current and causing immediate failure and destruction of one.  In terms of current, apart from dropping a lead acid bank across one in a similar test I have no way of actually testing the current handling ability and certainly no way of testing their claimed 6000A+ break rating.

TOMZN's DC MCBs all seem to be C curve, which means instant trip via the magentic side of it needs > 5 times their rated current.  I have seen the trip time curves vs ambient temperature & current graphs floating around the internet but again no way practical way to validate what they say.

That's very good to know, as I have tandem TOMZN MCBs on all my solar arrays...they advertise 400vDC ratings, and I'm not sure whether to take that at face value or with some salt.

Did find a YouTube video showing that even those breakers are getting "scam treatment", though they're reportedly easy to identify by a very low weight.

Yes, I saw BigClive's clip.  Nothing surprises me these days when it comes to stuff coming out of China.  The fakers even fake lead acid batteries by putting dead weight in the bottom of the case, which can't be that much less than the cost of making a genuine battery but they still do it.

I purchase the breakers direct from TOMZN via Aliexpress, so hopefully the genuine articles make it to me (so far, so good).

Tomzn are fine. In Europe they use a lot of them. As long as you order from the official Tomzn store you will get the real breakers. You can also use the magnetic hydraulic (black color breakers) from midnite or bluesea but they are very expensive compared to the Tomzn.

Just to chime in - there are also alot of nonpolarized DC breakers. Midnight solar sells alot of both (would like to hear what <a contenteditable="false" data-ipshover="" data-ipshover-target="/profile/2-sid-genetry-solar/?do=hovercard" data-mentionid="2" href="/profile/2-sid-genetry-solar/" rel="">@Sid Genetry Solar thinks) but here is a link to their product offerings.

I have a question though. Say I want to totally disconnect my panels from the SCC and I need to use polarized breakers. Typically breakers have a (+) sign, where the higher potential voltage is supposed to enter. How I would use this breaker on the positive wire is straightforward - the positive from the PVs enters the (+) side of the breaker. But what about when I want to add a polarized breaker to the negative wire? Should it be reversed, with the wire coming from the SCC entering the positive side of the breaker? 

I've got an array which, when paralleled, will be up to 90 volts and 60 amps, and I was hoping to figure out the cheapest, safes and easiest way to fully disconnect and protect it when I need to. I have each individual string fused on the positive wire. 

My two cents of advice is that you should contact the breaker manufacturer or check the product datasheet to ensure you wire it the right way or be prepared to do your own polarity tests and possibly write off the breaker in the process.  The magnet orientation is the critical part as it has to push any arc towards the trap.  If the current is flowing the wrong way in relation to the magnet and the other side of the ganged breaker also flows the wrong way the arc will be push back into the contact area rather than the trap on both sides and fires ensue.

If you can rely on the breaker simply being two identical single breakers being ganged and want to break the + and - wires you would normally place both the array wires on the + sides of the breaker.  That way the current flows through one breaker in the wrong way, ensuring that regardless of wiring errors or even a fault where power can flow back into the array, the current can be interrupted.

2 hours ago, TheButcher said:

My two cents of advice is that you should contact the breaker manufacturer or check the product datasheet to ensure you wire it the right way or be prepared to do your own polarity tests and possibly write off the breaker in the process.  The magnet orientation is the critical part as it has to push any arc towards the trap.  If the current is flowing the wrong way in relation to the magnet and the other side of the ganged breaker also flows the wrong way the arc will be push back into the contact area rather than the trap on both sides and fires ensue.

If you can rely on the breaker simply being two identical single breakers being ganged and want to break the + and - wires you would normally place both the array wires on the + sides of the breaker.  That way the current flows through one breaker in the wrong way, ensuring that regardless of wiring errors or even a fault where power can flow back into the array, the current can be interrupted.

 

Some are even marked that way from the factory when you get them in 2 pole versions with a common trip. Eaton/Moeller breakers as an example are marked that way. The left one is marked + on the top and - on the bottom while the right one is marked - on the top and + on the bottom.

Here's the confusing part.  If you put the most positive wires on the + terminals of that breaker, and then follow the current flow through it, is that causing reverse flow through one side so that regardless of current flow direction at the time of the breaker opening any arc pulled will 100% be forced into the trap on one side ensuring successful break of the current?  ie, one side has the + and - labelling reversed in relation to the arc magnet

Some breakers have the + on both breakers at the bottom, and some reversed like this.  Unless you understand how the magnets are set up you can't be sure it will function properly.  That's why I advise people to check the manufacturer's information about how to wire them up.

5 hours ago, wpg205 said:

I have a question though. Say I want to totally disconnect my panels from the SCC and I need to use polarized breakers. Typically breakers have a (+) sign, where the higher potential voltage is supposed to enter. How I would use this breaker on the positive wire is straightforward - the positive from the PVs enters the (+) side of the breaker. But what about when I want to add a polarized breaker to the negative wire? Should it be reversed, with the wire coming from the SCC entering the positive side of the breaker? 

That would be my hunch.  Uneducated country bumpkin opinion 😉

Also worth noting that polarized breakers on the battery side of SCCs (solar charge controllers) are quite an interesting conundrum.  It could be argued that breaker positive goes to the SCC positive (breaker negative to the battery positive terminal), as that's the way power normally flows through it.

But there's an issue: the one and only way that an SCC battery breaker can trip (if properly sized!)--is if the SCC internally fails and shorts out the battery through it's FETs.  Suddenly the tables are turned, and the breaker must break the full battery voltage (and current!) the other way.

Interestingly enough, if a power supply has an electrolytic capacitor on it close to where you short the wires out, it is pretty nigh impossible to pull a DC arc.  SCCs inevitably have a fair amount of filtration right at the battery terminals...so breaker polarity may not matter as much in this case.  With that in mind, I do have the SCC battery breakers on my system mounted breaker positive to battery positive.

Have had an MPPT blowup trip the battery breaker.  (And because I tandemed the solar input and battery breakers together, this also disconnected solar from the MPPT, so it had zero power potential on it.)  One of those mysterious blowups--I was tweaking the charge voltage configurations on a Morningstar Tristar TS-MPPT-60.  Had done it 4-5 times already (still not accepting the settings because I hadn't set the DIP switches right)...and the final time, after updating the appropriate setting registers, I sent the MODBUS Restart command (like before)...it restarted, did the power-up sequence...followed by a deep "pop" and simultaneous bright orange flash--tripping the breakers.  Fortunately, Morningstar replaced it under warranty...and very quickly at that.  To this day, I'm scared to touch the charge settings in the replacement unit...37,000 hours on it so far.

It would be interesting to cut them open to find out. The Kayal brand is also marked that way. Eaton branded ones are marked as 48/60VDC and 277/480VAC on some FAZ-NA models. Reason they may be able to get away with either direction is that they are both magnetic and thermal.

Feeling around with a small bar magnet is usually enough to tell you which way the magnet is oriented then check on the other side of the set to see the 2nd one is facing the same direction.  I'd still check with the manufacturer, checking is only confirmation of what the manufacturer says IMO rather than the only check.

The regs here say thou shalt fit a non-polarised breaker but I think that is really more directed at transformerless grid tied inverters where there is a potential (tickets still on sale, I'm here all week) for rectified mains voltages to appear on the panel wiring so any breaker must be able to handle current in and out of the array.