Hi guys

So for those using Pylontech, supplied cables to connect the Pylontech battery to the inverter is 25m2's...

So connection options are, connect battery/MPPT directly to Terminal lugs on Inverter or connect Battery/MPPT and Inverter to a Buzz bar... ok this is not the question though.

Between my panel combiner box and the MPPT my sparky asked that we install a dual pole isolator,

now ... the question... hehehe

are you connecting the batteries directly to the Inverter or Buzz bar, or are you installing a inline fuze and quick disconnect ?

G

Inline fuse with quick disconnect always

Not negotiable

I used this:

 

its a Jean Muller KETO-00 - in my case with 80A fuses.

its substantial and safe - you can pull the handle under load and the arcs are safely contained.

Came from The Power Store. 

Pylon’s are I’m sure safer than lead acid since I assume the BMS will shut them off it you short them.  But why take a chance since these batteries can push very many amps.

will speak to my installer and sparky tomorrow, got a price on exactly that same unit.

G

Fused disconnect between battery and busbar. I use Mersen but it is similar Jean Muller.

my installer basically got a completed back plate with everything on it...

My sparky did ask for a isolator (80-100Amp) after the buzz bar, before the MPPT.

Will speak to both, was also thinking the voltages etc calls for something between the battery and Buzz bar / or Terminal lugs if directly connected.

Just need to find out if the installers design already got something in place, included

G

Just now, georgelza said:

buzz bar

Have some sympathy for my OCD... It's a BUS bar... 🙂

no problem...I also suffer, thanks for the spelling correction.

G

20 minutes ago, georgelza said:

no problem...I also suffer, thanks for the spelling correction.

Some other things that get to me.

"Bare with me"... forget it, you can go skinny-dipping on your own thank you very much 🙂

"Could of"... ugh

"It begs the question"... Begging the question is a logical fallacy, you mean it "raises" the question.

But then I also understand that some writing is informal... so I suppress those tendencies 🙂

1 hour ago, plonkster said:

It's a BUS bar...

Ja it is, till it "buzzes" when you short shiite out. 😋

2 hours ago, georgelza said:

my installer basically got a completed back plate with everything on it...

My sparky did ask for a isolator (80-100Amp) after the buzz bar, before the MPPT.

Will speak to both, was also thinking the voltages etc calls for something between the battery and Buzz bar / or Terminal lugs if directly connected.

Just need to find out if the installers design already got something in place, included

G

Those are two different things. 

The MPPT gets fed from the solar panels, not the batteries. 

SO, you install a fuse between the batteries and the inverter. And you install a fuse between the solar panels and MPPT. An Isolator is not necessary between the MPPT and solar panels, but adds convenience in case of emergency. Let me explain, in some cases you have 2 or 4 or even 12 solar panel strings coming into a combiner box and then to the MPPT charger. Some people will install a fuse on each string (the correct way). Some people will then add another fuse on the combined strings, going into the MPPT, with a rating of slightly more than all the strings combined. OR instead of a fuse install an isolator. DC rated equipment is expensive. And generally bulky, due to the way DC arcs work and need to be safely contained. So few people install it. 

 

On the batteries side you have battery fuses, and sometimes an Isolator. Remember it's expensive and bulky. In the case of Lithium batteries, where they have On/Off switches and isolator isn't necessary. But fuses still are. If you have more than one battery string, leading to a busbar, put a fuse on each string. The NH00 type (those big white block) fuses are the preferred way to go. They can safely handle the arc and are quick to pull open in case of emergency 

some thinking, to be confirmed today with installer and pictures of his back panel and BOM...

 

multiple (

panel arrays -> isolator -> fuse -> quick disconnect -> bus bar A (this order of of components was requested by sparky)

)

bus bar A -> isolator ->MPPT  (this isolator was already requested by my sparky)

MPPT -> bus bar B

Battery/s -> bus bar B

Inverter Input -> bus bar B   (instead of connecting the MPPT and battery directly to the terminal lugs on the inverter they basically all meet/cleaner on bus bar B.)

with the Pylontech I have the on/off switch so that can be used to disconnect the battery, I can additionally if I want to "total safety just pull that plug in positive lead out of the battery pos terminal "once switched off"

but instead was thinking, good idea to place a fuse on the battery -> bus bar B line, and for total safety (instead of opening the battery cage and flipping switches on the battery) put a duel pole isolator between battery and fuse (means i can also isolate the fuse should i need to work on it (will require switching the isolator between bus bar A and MPPT also off, otherwise i have a new hair do...)

G

2 hours ago, georgelza said:

some thinking, to be confirmed today with installer and pictures of his back panel and BOM...

 

multiple (

panel arrays -> isolator -> fuse -> quick disconnect -> bus bar A (this order of of components was requested by sparky)

)

bus bar A -> isolator ->MPPT  (this isolator was already requested by my sparky)

MPPT -> bus bar B

Battery/s -> bus bar B

Inverter Input -> bus bar B   (instead of connecting the MPPT and battery directly to the terminal lugs on the inverter they basically all meet/cleaner on bus bar B.)

with the Pylontech I have the on/off switch so that can be used to disconnect the battery, I can additionally if I want to "total safety just pull that plug in positive lead out of the battery pos terminal "once switched off"

but instead was thinking, good idea to place a fuse on the battery -> bus bar B line, and for total safety (instead of opening the battery cage and flipping switches on the battery) put a duel pole isolator between battery and fuse (means i can also isolate the fuse should i need to work on it (will require switching the isolator between bus bar A and MPPT also off, otherwise i have a new hair do...)

G

Tell him to do it this way:

 

PV array -> fuses -> Isolator -> MPPT. You don't need a busbar for this. Generally the fuses are installed in a combiner box, which has a busbar to connect the multiple fuses to a single output. 

Batteries -> fuses -> inverter. IF you use that fuse disconnect that @Elbow showed, it would act as an isolator as well. 

I bought (direct from Mersen in Industria West) a 2 pole fused battery disconnect. Along with 125A fuses it came to just under R600.

Not much for the peace of mind.

2 hours ago, PaulinNorthcliff said:

Along with 125A fuses it came to just under R600

That's a very good price.

1 minute ago, plonkster said:

That's a very good price.

Yeah, I was pleasantly surprised.

Sales guy was, like: "So how many do you want?"

But this is their direct to public price.

On 2019/05/03 at 7:30 AM, PaulinNorthcliff said:

I bought (direct from Mersen in Industria West) a 2 pole fused battery disconnect. Along with 125A fuses it came to just under R600.

Not much for the peace of mind.

Do you have model number etc. want to try and source this

My one concern is that most of the Mersen and Jean Muller fuses available seem to be AC fuses without any proper DC rating to them.

This is a big no-no for me.

My Mersen is rated 220V/250A DC.

https://ep-us.mersen.com/sites/mersen_us/files/DS-IEC-Low-Voltage-GP-Multibloc-Size-1-ST8-NH-Fuse-Switch-Disconnector-EN.pdf

 

On 2019/03/28 at 5:29 PM, Jaws said:

Inline fuse with quick disconnect always

Not negotiable

OK.... I have one of those (installed by a business, I didn't DIY). Question is WHY? Why is this a good thing to have? Why might I need to rapidly isolate the battery pack?

On 2019/08/08 at 11:27 AM, Ingo said:

My Mersen is rated 220V/250A DC.

https://ep-us.mersen.com/sites/mersen_us/files/DS-IEC-Low-Voltage-GP-Multibloc-Size-1-ST8-NH-Fuse-Switch-Disconnector-EN.pdf

 

250A is way too much for use with a Pylontech. The idea of a fuse is to blow long before any electronics get damaged.

2 hours ago, CarlT said:

250A is way too much for use with a Pylontech. The idea of a fuse is to blow long before any electronics get damaged.

I thought fuses where to protect the cables?

Like with my 24v system. Needs a 300amp fuse on a 50mm2 cable.

Fuse is there to protect the cable from melting / burning.

9 hours ago, CarlT said:

250A is way too much for use with a Pylontech. The idea of a fuse is to blow long before any electronics get damaged.

 

6 hours ago, The Terrible Triplett said:

I thought fuses where to protect the cables?

Context. Fuses are used to protect electronics, but then they have to be quick blow. Other ways are electronic fuses (they go high impedance when they heat up), or just plain circuit breakers. You can also design the power supply to be current limited, so that anything bad that happens simply can't blow anything up. But within the context of intelligent batteries such as the pylontechs, the battery contains its own form of a circuit breaker: on high current it will disconnect. So it's more about protecting the cables.

I do however think that unnecessarily oversizing a fuse (even if the cable is much thicker) is a lost opportunity. If you can give the electronics a bit more protection by sizing the fuse to the actual current (+10% or so) that it needs to do... why not? It probably won't do much, most fuses of this size won't blow nearly quick enough to save malfunctioning electronics, but why not? Smaller fuses are cheaper too 🙂

Edited August 14, 20196 yr by plonkster

6 hours ago, The Terrible Triplett said:

Like with my 24v system. Needs a 300amp fuse on a 50mm2 cable.

That's why mine has a 160A fuse. I know the recommendation said 300... 160*24 ~= 4kW. Fuses like these take several seconds to blow at twice their rating, and the inverter can only peak at 6kW for a second. I rarely get close to even 3kW, and when grid tied only to 2.4kw.

🙂

 

10 hours ago, plonkster said:

 

Context. Fuses are used to protect electronics, but then they have to be quick blow. Other ways are electronic fuses (they go high impedance when they heat up), or just plain circuit breakers. You can also design the power supply to be current limited, so that anything bad that happens simply can't blow anything up. But within the context of intelligent batteries such as the pylontechs, the battery contains its own form of a circuit breaker: on high current it will disconnect. So it's more about protecting the cables.

I do however think that unnecessarily oversizing a fuse (even if the cable is much thicker) is a lost opportunity. If you can give the electronics a bit more protection by sizing the fuse to the actual current (+10% or so) that it needs to do... why not? It probably won't do much, most fuses of this size won't blow nearly quick enough to save malfunctioning electronics, but why not? Smaller fuses are cheaper too 🙂

The short-time current rating of cables are probably orders of magnitude higher than for the electronics.

Yes, the Pylontech is designed to switch itself off on high current (100A for 15s if I'm not mistaken), but why take the chance? The Pylontech is significantly more expensive than most anything else in the setup. Therefore I want to protect it.

From Pylontech's datasheets, the US2000 has a recommended charge/discharge current of 25A and a max charge/discharge current of 50A, while the US3000 has 37A and 74A respectively.

Ideally your fuse will blow before you reach these maximums.