Seems to be a bit of confusion on this, on a FreedomWon battery, where the battery has a built in breaker, is an (external) fused battery disconnector still required? Or Is it deemed good practice, or not at all ?

With multiple batteries it becomes quite a significant additional cost. 

Anyone care to provide a concrete answer on this matter?

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FreedomWon themselves say its not necesarry as their batteries have a breaker built in. As per their installers manual as well, 

https://www.freedomwon.co.za/wp-content/uploads/Freedom-Won-Lite-Home_Business_52V_Installation-Manual.pdf

Quote

The Lite range includes an integrated battery DC breaker/isolator that breaks the positive cable continuity inside the battery. This breaker, on all Home and Business models, is rated for a 36kA fault (short circuit) current. The system therefore does not require another DC isolator or breaker except where required in relation to conformance with the Clean Energy Council of Australia battery design Best Practice Guide, which states that, should the internal battery isolator not offer isolation of BOTH the positive and negative terminals of the battery, an external isolator is required that can isolate both the positive and negative cables/terminals of the battery.  

 

However , according to an electrican this is required, as per the following draft regulations: 

According to the electrician, EXTERNAL means not built in to the battery / inverter . So even the PV strings should have an isolator, apart from the built in isolator the sunsynks have. 

 

https://powerforum.co.za/topic/9976-latest-regulations-legislation-for-pv-combiner-box/

 

Edited March 29, 20231 yr by abd7

Having deployed a heap of Livoltek as well as FreedomWon Batteries. They both have DC MCBs that offer great protection & I have tested both. The FreedomWon takes it a step further with that ABB breaker which is just in another class as compared to many other cheaper options. It even integrates with the Orion BMS to trip as a function of the SoC at 10% SoC left. 

Protection to me is the following: In the event of a single failure will the existing infrastructure have sufficient protection to not cause a fire or not be damaged. 

Let's discuss this in the following way: Let's say you have a cluster of Batteries in Parallel like a Trio of FreedomWon batteries & they are 3 X 10/8s. So 10kW = 200A DC discharge rating at 1C. So 200A X 3 = 600A DC draw capability. 

So each battery has a 200A ABB DC breaker. If one trips, the other 2 still have protection. So no problems to over stress the remaining units. The inverter will Power trip & probably spit out DC_Bus under Voltage or something similar. 

These batteries are integrated via Busbar, so you connect & disconnect via this isolated Bus Bar. For sure before you work on such system the Inverters & DC battery Bus is isolated & the bus Bar is not powered at all. All isolators off & the inverters are depowered. The Sunsynk 16kW MAX further even has a seperate Battery DC MCB inside of its wire basket. 

So to me you can fork out for the 600A Keto fuse set but it is serving absolutely no good purpose except hanging like a decoration. Or you can also add 3 X 200A ketos & once again they offer zero value. 

Similarly on any Sunsynk Inverter there is a PV DC isolator on each machine. So you remove the inverter & want to isolate that PV inverter strings. Your first point of PV DC disconnection point is the inverter. There after the fuses. You isolate & remove the inverter so the question is now how to isolate the PV string? Pull out the fuses & remove the fuses. Absolutely no way that that PV Array can now use energy. How is fitting a DC isolator externally going to add better safety & value than 2 empty fuse housings? 

I see 3 profound issues here in our Solar installation work here in SA: 

1) Lack of access to the latest SANS code docs. 

2) Lack of fundamental understanding of why to do something, just we interpret & follow like sheep. 

3) Master electricians that are placed to uphold the Code of fundamentals that so many of them are not qualified or comfortable to signing off on. I say this with the most utmost respect to them. I really take my hat to off to some Gentlemen that I have asked to carry out an assessment or inspection & that have shared their discomfort at working on DC systems as well as the Neutral/ Earth bonding required when a Sunsynk needs this bond during Islanding. 

We have a far way to go yet. I guess it's like politics & religion. Everyone has their own belief. 

On 2023/03/29 at 4:47 PM, abd7 said:

Seems to be a bit of confusion on this, on a FreedomWon battery, where the battery has a built in breaker, is an (external) fused battery disconnector still required? Or Is it deemed good practice, or not at all ?

With multiple batteries it becomes quite a significant additional cost. 

Anyone care to provide a concrete answer on this matter?

---------------------------------------

FreedomWon themselves say its not necesarry as their batteries have a breaker built in. As per their installers manual as well, 

https://www.freedomwon.co.za/wp-content/uploads/Freedom-Won-Lite-Home_Business_52V_Installation-Manual.pdf

 

However , according to an electrican this is required, as per the following draft regulations: 

According to the electrician, EXTERNAL means not built in to the battery / inverter . So even the PV strings should have an isolator, apart from the built in isolator the sunsynks have. 

 

https://powerforum.co.za/topic/9976-latest-regulations-legislation-for-pv-combiner-box/

 

I have been wondering the same thing and noticed in the Freedom Won installation manual that a 2 pole breaker is only required in Australia where both the positive and the negative battery cables must be broken. Currently in my situation introduction of an additional fuse on positive from the battery to the busbar in the DC connector box (if installed in the box) only introduces cabling difficulty, additional cost and more unwanted resistance. If I install an additional fuse not in the DC busbar box but closer to the battery I end up having to cut my battery cables really short which I am not keen on as I might move in the next couple of years and might require longer cables when reinstalling. So for me the additional fuse seems redundant and unnecessary when considering the Freedom Won's built in breaker. The only justification ofcourse would be if you want to break both positive and negative since the Freedom Won only breaks live but we are not in Australia and most Victron schematics I have seen only fuses the positive not the negative.

The SANS extract you reference above seems to be targeted at the PV side of the system. Here an additional 2 pole isolator makes sense since with the isolator embedded in the inverter, if you remove the inverter for some reason, there is no way of isolating the fuses. Take into account you cannot disconnect fuses under load due to arcing, they have to be isolated first with an appropriate DC isolating device (has to be correctly rated and don't use AC isolators) and then the fuse can be removed/replaced. 

   

1 minute ago, Star Harvester said:

I have been wondering the same thing and noticed in the Freedom Won installation manual that a 2 pole breaker is only required in Australia where both the positive and the negative battery cables must be broken. Currently in my situation introduction of an additional fuse on positive from the battery to the busbar in the DC connector box (if installed in the box) only introduces cabling difficulty, additional cost and more unwanted resistance. If I install an additional fuse not in the DC busbar box but closer to the battery I end up having to cut my battery cables really short which I am not keen on as I might move in the next couple of years and might require longer cables when reinstalling. So for me the additional fuse seems redundant and unnecessary when considering the Freedom Won's built in breaker. The only justification ofcourse would be if you want to break both positive and negative since the Freedom Won only breaks live but we are not in Australia and most Victron schematics I have seen only fuses the positive not the negative.

The SANS extract you reference above seems to be targeted at the PV side of the system. Here an additional 2 pole isolator makes sense since with the isolator embedded in the inverter, if you remove the inverter for some reason, there is no way of isolating the fuses. Take into account you cannot disconnect fuses under load due to arcing, they have to be isolated first with an appropriate DC isolating device (has to be correctly rated and don't use AC isolators) and then the fuse can be removed/replaced. 

   

Just to clarify, if you remove the inverter and connect whatever other load or perhaps another inverter without built-in isolator, in future you no longer have a way of isolating PV without removing fuses or even live cables. Breaking a circuit under load via removal of a fuse/cable is a bad idea, just look at the warning on most DC fuse holders...

See the below as well from freedomwon, clarifying this matter 

However, I've dealt with a few electricians who won't issue a CoC without the fuse disconnectors. 

So it would be best practice if its affordable / easily installable 

Thanks for this, that answers it then. The multi battery with total kWh > 5 x kVa inverter rating requiring suitable fuse/DC breaker to each inverter is interesting since a short circuit fault in a Victron without the Victron triggering an overload error is something which I haven't ever considered to be honest. Then again, I suppose it is one of those what-ifs which could happen theoretically, especially during installation if the cables/batteries are not handled properly. 

As a side note, they mention fuse OR DC rated breaker. If a breaker is used it should be bi-directional i.e. non-polarity sensitive. I see many polarity sensitive breakers being used out there which can only operate correctly in one direction where current is always from source to load and wiring must be done accordingly (usually indicated by + and - or arrows on the breaker itself). This is obviously not appropriate between inverter and battery if one considers another what-if of a short on the battery side during charging from grid and an even more unlikely "what-if" of the inverter not triggering an overload to break the fault current.