Tesla powerwall 1 - DIY electronics. Has anyone here built it?

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Hanssing

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So I was wondering if anyone in here has tried to build something connection to DC-side of a normal GTI?
With or with-out step-down for DC-DC charging.

I know a guy in Denmark did, with cheap chinese GTI's, a step-up DC-DC booster and so forth. But powercompany then knowcked on his door and forced him to take it down, as it was not allowed without permit :)

Essentially its the electronics allready inside the low-voltage battery inversters:


Anyone DIY for GTI's?
 

Wolf

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Not sure what your question is but my (4) GTIL are running from the battery bank which solar charges.
Wolf
20210804_190152.jpg
 

Hanssing

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Sorry, I was probably not clear.

What I am asking, is if anyone has taken a standard non-battery Solar GridTiedInverter (GTI) with a DC-bus of say 250-500VDC, and made their on step up/ step down (48VDC <-> 350VDC) on the to the high-voltage DC-side for the panels. This can then inject during nighttime etc.

Essentially what you get when you buy an MP_Solar Hybrid inverter, just DIY for the powerwall part.

IIRC this was the buissnessmodel for Tesla Powerwall 1.
 

Hanssing

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Wolf, I just reviwed your setup-thread.
You do PV Panel String -> Solar Charger -> 48VDC Bank -> SineInverter to 230 VAC Mains
So always in series, through lowvoltage DC-bus, correct?


What I am asking about is more like this:
Code:
PV Panel-string High DC Voltage -----------------> PV-Inverter 230VAC Mains
                                          |
Battery 48VDC---- DIY Booster-------------|
               |-- DIY Stepdown Charger-- |


The reason for the question is reuse of non-hybrid inverters (like reuse of cells), is possible in this way.
Where the old and used GTI inverter then runs with a DIY battery injecting on the solar-side.

A secondary reason, is that it would allow for any type of voltage, on the battery, so instead og staying at 14S (16S for LFP), one could increase to 100VDC or xxx VDC on teh battery as one sees fit, of course using the right breakers and stuff.
 
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Korishan

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Probably not a good idea to connect your batteries directly to the PV array. You need a charge controller to make sure you pull from the PV as much as possible, and to isolate the PV from the batteries. The PV will drain the batteries at night.

You can always have more than one inverter running off the battery bank(s). The only issue is that the output circuits need to be isolated, unless the inverters are designed for parallel connections.
Another thing you could do is configure the GTI to run off of the Batteries, and then inject into the Mains side of the inverter. Altho, I'm not sure how safe this overall as several safety features may get overridden this way.

Boosting 48VDC battery up to PV voltage will require a LOT of current coming from the battery. So this is not feasible or safe.

What would the Stepdown charger be charging?
 

Hanssing

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Korishan,

What I am asking is not if you can buy a solar charger/inverter like wolf - if money is no object just buy COTS - but then why are we talking DIY-Powerwall here at all.

>What would the Stepdown charger be charging?
A stepdown charger, would be charging the battery (Buck converter), like in wolf MPPT-solarchargers. ITs just electronics, coils, IGBT/Mosfet, DSP/FPGA/Arduino and so forth.

So have people been building their own from scratch, just for the fun of it, and secondly have anyone tried to just do the DC-side of it, as doing the mains-connected Sine-side is hard, and illegal in most contries.

>Boosting 48VDC battery up to PV voltage will require a LOT of current coming from the battery. So this is not feasible or safe.
Huh? You are aware that it will not require more power than what you are using on the mains (+conversion-losses) - is just an inverter..... Energy-conservation principle applies, we are not breaking any physicslaws here. Everyone have high power-drain, and by doing you own electronis you get to decide the inverteroutput, but you get to do it using an old inverter that is not a hybrid model running on batteries. :)

I think the answer to all my questions is no: Unless anyone here has been dabling in their own power-electronics above 300V?
 
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Wolf

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Unless anyone here has been dabling in their own power-electronics above 300V?
I don't thing dabbling would be the correct vernacular, working with voltages over 150V DC let alone >300V. We are not talking about old style TV and Radio HV transformers with low current here. Although still enough to set your ass back a couple of feet and possibly kill you.
As DIY with array voltages in the ≈120V or so is dangerous enough. I know there are some with long runs from array to controller location to storage and they are running 400+V DC to keep wire size manageable. Although old (2001) this is a good NEC (suggested practices) read regarding solar installations wiring and voltages. https://www.solaris-shop.com/content/NEC.pdf
Personally I'm going to leave anything over 100V DC to Victron or some other reputable charge controller manufacturers. Now if you are an EE and that is what you do for a living more power to you, as you are well aware of the dangers of high DC voltage. My one and only mishap so far with 48V nominal was a Snap-on wrench. There was a bright blue flash and luckily the wrench did not permanently attach to the terminals and become the fuse. Taught me a lesson about insulating wrenches.
Wolf
20210724_224500.jpg
 

Hanssing

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Yeah, well I actually hold an M.Sc. EE. but no where near Power-electronics back in the day :) more control-theory and modelling as my professional field.

Anyway It's purely an academic thought on paper for now.
 
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