No, it means that the PV inverter doesnt invert the PV Dc voltage to AC, then back to DC to charge the battery. PV DC Voltage is provided directly to the battery, without additional converting/inverting losses.
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Discussion: Powerwall 3 [Speculation / Discussion etc]
- Thread starter n.one.one
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Matt-FL
Member
3' separation, that's a significant difference. Trying to picture what that would look like in my case with 4 PWs, that's close to 20' of wall space.
Yeah, unit is only 48A output.
11.5kW export + 5kW simultaneous charging would be 16.5 kW (if the internals support that).
Possible architecture:
PV -> boost -> HV DC rail -> inverter -> AC
Battery -> boost -> HV DC (discharge)
Battery <- buck <- HV DC (charge) <- PFC boost <- AC
With HV DC around 600V
The four power levels could correspond to 0,1,2, or 3 MPPT with additional power stages. Base unit then has the birectional 5kw in 5.8kw out AC/DC and DC/DC battery blocks. Battery could potentially feed PV blocks for more capacity.
Only if the UL 9540A testing is not accepted are you required to put 36" between the ESS units.
FWIW, this testing is performed for every unit since Powerwall 2 AC. I haven't seen it yet for PW3 but I know it is coming. If this wall space is a problem the testing should be completed soon to make it not a problem.
how about my 7 powerwalls, that are all lined up now
I assume you know that PWs can be stacked (I believe it's a maximum of 3 deep). So your 4 PWs would only be the width of 2 with the required 3 feet in between.
Here's a photo.
Yah, his system was installed in 2022.
The PW3 likely isn't stackable.
Whether powerwalls can be stacked, or not, and other requirements, depend entirely on ones Local Authority having Jurisdiction (AHJ), and when they were installed.
In some places, they can be stacked, in others, they cant be.
jgleigh
Member
I was probably thinking of the opposite where you have a much larger battery and smaller solar system so there's never enough solar energy to charge the batteries.
Jeremy3292
Active Member
I believe this removes the ~10% conversion loss from solar to battery, as noted in Tesla's PW+/2 specs.
The conversion was never a big deal to me honestly. I'm happy with choosing micro-inverters and looking at all the posts here on single inverter failures, the PW3 being DC would've been a non-starter for me already. At least it's LFP, but maybe there will be a PW4 that upgrades the PW2/+ to LFP finally.
Jeremy3292
Active Member
I think it is also cheaper to manufacture than an AC coupled system. So Tesla gets $$$ savings from LFP cells + DC coupled in PW3. My guess is PW3 is easier to install as well, further $$$ savings.
All grid-tied solar inverters support DC coupling to solar panels and AC connection to the grid. PW3 not supporting AC coupling with third party inverters doesn't result in meaningful manufacturing cost savings. It's the same HW components. It does save some firmware development and testing but since Tesla has already done the work for PW2 it's unlikely the main reason. It's more likely that Tesla, like Enphase, is further pursuing a walled garden approach to lock in customers to their proprietary product portfolio.
What's the exact reference for this conclusion? I am doubtful, as it makes little sense technically.
Cheers, Wayne
See the quoted Tesla doc:
Discussion: Powerwall 3 [Speculation / Discussion etc]
Now I'm really torn...might have to go with Powerwall+/2 over waiting for Powerwall 3. I have a feeling installs aren't really gunna happen until at least April 2024 and even then probably going to be a limited supply. So realistically could be almost a year from today. If I can get my order...
teslamotorsclub.com
It makes little sense technically to me as well but business motivation often trumps all else.
OK, thanks. But the worst case technically is this:
(a) In grid following mode (utility is up), the GW equivalent simply will not support CTs to track other solar inverters. So the PW3 charge behavior will ignore the other PV, you couldn't set it up to charge only from solar and count the 3rd party solar in that configuration. If you place the "house" CTs accordingly, the other PV will just appear to be a negative load, so the PW3 will still adjust its discharge behavior to only cover net load.
(b) In grid forming mode (utility is down), the grid forming inverter will not support AC charging of the batteries and will shut down if the attached microgrid has a net power production. I guess this is possible but seems pretty stupid. If this is the case, you just have to interconnect your other PV outside the GW so it won't be on the microgrid.
Cheers, Wayne
WidowMaker03TX
Member
It may have that requirement to handle switchover to isolation better. The solar inverter may or may not kick off on transition.See the quoted Tesla doc:
Discussion: Powerwall 3 [Speculation / Discussion etc]
Now I'm really torn...might have to go with Powerwall+/2 over waiting for Powerwall 3. I have a feeling installs aren't really gunna happen until at least April 2024 and even then probably going to be a limited supply. So realistically could be almost a year from today. If I can get my order...
It makes little sense technically to me as well but business motivation often trumps all else.
Plus, the system may go for zero net current before the gateway disconnects, having other sources available complicates that.
Matt-FL
Member
Oh yeah, agreed. My four Powerwall 2s are stacked in pairs, taking up about 7' of wall space.
I was referring to the callout that the PW3s (possibly) cannot be stacked and need 3 feet in-between.
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