Second system extension extension.

[Tinbum]

And there is a small cable (with the green fuse) which goes to a DC Disconnector Contactor to take the Pylontechs out of circuit when they go over voltage.

Does that fail safe if the fuse blows?

[nowty]

And there is a small cable (with the green fuse) which goes to a DC Disconnector Contactor to take the Pylontechs out of circuit when they go over voltage.

Does that fail safe if the fuse blows?

No, its because I integrated two separate systems using 2 different Lithium Battery chemistries. The Pylontechs (19kWh) are 15 cell Lithium Iron Phosphate and have a max voltage of about 53v, but I take them out of circuit above 50v (SOC 85%) so they live longer.

The other two parallel batteries are re-used growatt 14 cell Lithium Cobalt Manganese (24kWh each) which have a max voltage of 58v but I limit them to 55.2v (SOC 90%).

So as the voltage rises above about 51v, the Pylontechs are taken out and don't come back in until the growatt batteries drop to about 50v SOC 50%. Eventually as the voltage drops, the Pylontechs automatically drop out at about 48V SOC 10%. The growatts keep going until 46v SOC 10% where the Sunny Island wont discharge them any further.

In practice in Summer the Pylontechs are out of circuit the whole time, its only Sept to April they get cycled unless I have a grid outage and then I'm glad I have them in reserve.

EDIT - Sorry Tinbum I understand your question now, yes if I lose power to the DC Disconnector Contactor for any reason, the Pylontechs are taken out of circuit so yes, I designed it failsafe. Normally open contactor rated to 200A DC.

[Joeboy]

Thanks Nowty, how many beers is that I owe u? I will view back in Scotland as just image gifs on my phone the noo.

[Andy]

And as an example, this is my positive DC Distribution point. I do have another negative one, just don't have a picture of it.

That's great to see a real world example thanks. Where did you get the dc buses or did you make them yourself using copper sheeting? I tried pricing separate dc busbar/fuses vs the Victron Lynx distributor and they come out very similarly priced at the end of the day.

[Andy]

..... and to Andy, your going to need to do something similar with that Bigboy Victron if you are going to use Pylontech batteries with their 25mm cables.

Thanks, it is something like that I am hoping to do.

[Stinsy]

And as an example, this is my positive DC Distribution point. I do have another negative one, just don't have a picture of it.

Note,
The black cable is actually a 70mm positive cable back to my Battery Inverter.
The thinner cable at the bottom of the picture is 25mm to my Victron charge controller and supplementary / emergency battery charger.
The other 3 red cables at the top are 50mm cables to each parallel battery.
And there is a small cable (with the green fuse) which goes to a DC Disconnector Contactor to take the Pylontechs out of circuit when they go over voltage.




EDIT - Now I have a picture of my negative DC Distribution point. I don't bother fusing that end but some people do both ends.

I'm surprised you don't have a 400A busbar chamber nowty!

[Joeboy]

Our son took delivery of upgrade charge controller today so good to go on our return.

As I say not a natural sparky, exemplified today in the shower when penny dropped on the 3840W/109V that is the PV Sum pre charge controller conversion in comparison to the post charge controller result. Funny old thing power conversions eh? Thin vs thick in cabling as the volts drop and the Amps ramp up.

I say this to show my lag with no embarrassment and maybe catch someone passing through.

[Stinsy]

The principles are simple once you grasp how Volts / Amps / Watts work. It turns out that doing ‘A’ level physics all those years ago was a good idea after all.

[Tinbum]

The principles are simple once you grasp how Volts / Amps / Watts work. It turns out that doing ‘A’ level physics all those years ago was a good idea after all.

Yes a good education is great. I do think, nowadays, they should base it more on the principles of how to do things a lot more than just remembering facts. If you know the basic principles then the internet is a great teacher and library.

[Stinsy]

The principles are simple once you grasp how Volts / Amps / Watts work. It turns out that doing ‘A’ level physics all those years ago was a good idea after all.

Yes a good education is great. I do think, nowadays, they should base it more on the principles of how to do things a lot more than just remembering facts. If you know the basic principles then the internet is a great teacher and library.

I always was rubbish at memorising stuff. It is all easy once you understand the underlying principles.

A friend’s son had been told by his GCSE maths teacher to memorise a table of trigonometry values (sin 60, cos 30, tan 45, and all the other combinations).

I showed him how you could figure it out on the fly if you need to, if you understand the underlying principles. His teacher had the whole class mindlessly memorising a table of values rather than teach the underlying principles that would enable them to quickly figure out any one of the values decades later if they need to.

My friend told me the problem was: his son’s maths teacher is a bit thick. When did they start hiring dim people as teachers?

I learned loads of cool stuff that I still know all these decades on. Haven’t found an application for the vast majority of it. The electrical stuff is an exception.