Howzit from muldersdrift - DIY install

I am David and I stay in muldersdrift and I am currently installing a DIY victron system at my home.
I’m sure I will have lots of questions. Just want to check where would be the correct place to post the install as it is about all of it from db’s to panels and all the victron bits between.


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Welcome David
Best is to do a search quickly (this forum software has a great search). Many of those questions have been answered.
For anything else you are welcome to post those questions here in your introduction thread, or if they are specific to a topic (say inverters, or batteries) in those categories. There is no wrong way to do it.

Oh and by the way a DIY Victron system is the best option in my view. :smiley:

I have already split my DB and added changeover switch for generator

If you know how much power you use, then you are halfway there. For a home it will be either a 3000KVA (Multi II 3k) or the 5000KVA (Multi II 5k) model. Or more if you want to go big.
I know @GVC is looking to upgrade his 3k kit to a bigger one, so that is an option as well.

so far I have bought the following
multiplus II 5000
octo Gx
ET112 power meter
2 x lithium SA batteries 52v 100ah
and cables.

Welcome David! Will follow your build thread with interest. I also went the DIY route but must say your work on the dbs thus far is excellent!

So I have a question regarding the coms cables such as the and rs485 cable, can I run them in the same trunking as the DC cables? I’m thinking that the DC supply shouldn’t interfere but has anyone had problems doing this. It will just be much easier than trying to route separate trunking’s as they cross each other.

Far as I’m aware, not a problem.

DC and AC in same trunking can be a challenge.

yes that I am aware, going to keep all AC and DC separate

RS485 is an industrial protocol made to handle quite a bit of interference, so that one is fine.

RS232 is the not so robust family member and might give you issues. Also the max cable length are shorter. ( = RS232) You do get converters that you can use if it is an issue that will convert to RS485 on the one side and back on the other.

Also DC does not have a frequency like AC, so that will have less interference.

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Thanks for the info
Yeah the cables I got are 1,8m so cant route them too far which is why i want the GX device next to my MPPT and inverter and above the batteries but that means cables are going to be running together. The RS485 needs to go to main AC DB so will have to route it separate but it has a 5m lead.

That is fine. The RS485 can go up to 1000m. Mine was 10m along the AC cable without issues

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Managed to do some installing this weekend and set up power meter. Octo had been working well then just wouldn’t connect online. After 3 hours of head scratching realized that once set up first time I should have change IP address setting to manual then it keeps the settings.

Sketched in my plans for other bits to add still.

Got a question regarding the temp sensor that comes with inverter. It says to connect to one of the terminals on the batteries but the lithium’s I have already have temp sensors, should I still just connect it to the first battery?

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You can skip it if the batteries already have temp sensors and publish that data to the GX system. You can also add it and choose which one to use in your system setup

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No need to connect the sensors. They are for lead acid batteries. For Lithium batteries, the BMS will do temperature compensation (if it has such a thing, usually they don’t, it’s simply not a thing for LFP batteries) and instruct the rest of the system what voltage to charge to (again… if they bothered… I haven’t seen a single manufacturer yet that cares).

The only exception is when it is really cold. Lithiums should not be charged below 5°C. Again, a good BMS will handle this for you, and you still don’t have to connect any sensors.

You can connect the sensor to one of the temp connections on your GX device, and use it for general information unrelated to charging…


Nice installation so far. Please post the final result as well.

yes i will

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I have been trying to work out my first solar panel layout as its on my only north facing section of roof and its a weird shape. I want to have a MPPT that will be suited without needing to upgrade or add panels as I cant add more facing north, unless I build a frame on the ground.

I have come up with 8x 435w panels which will be easiest to install or I could get 9x 360w but then its complicated installing. I would either have 4 strings of 2 panels or 3 strings of 3 panels. Im leaning more towards the 4 strings of 2 panels (435w panels)

In the victron MPPT calculator it says the 150/60 is best suited but its actually 40w less rated than the 8x435w panels.
the 150/70 will also work but is a bit more expensive, should i just upsize or should i not bother about the 40w as the panels probably wont be working 100% all the time. Any thoughts?

Aaah ok, for a moment I was confused. 4s2p usually means 4-series 2-parallel, ie two strings of 4 modules each. You mean the reverse… 2s4p :slight_smile:

4 series will put you somewhere around 180V-200V open circuit, which is too much for a 150V controller. Hence my confusion.

I would not worry about the 40W difference. PV modules rarely make STC (standard test condition) values in this country. It’s too hot most of the time :slight_smile:

Note that each string will push up to 12A or so, so 48A on the PV side, which is quite close the the maximum (50A) for that controller. So carefully look at the Isc (current, short circuit) value of the modules you want to use, make sure they don’t add up to over 50A.

If you live in an area that never sees low temperatures (eg Western Cape), you can go 3s3p. I have a 3s array myself, which is fine as long as I never go below -7°C. Which hasn’t happened in over 30 years…

ah sorry you right, yes what I meant is 2 panels in series and parallel 4 times

  • Opt. Operating Current (Imp): 10.85A
  • Short Circuit Current (Isc): 11.35A

so it is pretty close to the 50A but just short

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