Luxpower_Gilbert
Luxpert @Luxpower USA Team
If the battery is far to full, 12kw plus the ac couple.
EG4 18kPV Q+A general thread
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zanydroid
Solar Wizard
Sorry, I don't understand what the 12kW+AC couple refers to. That sounds like the max amount of grid sell or supported AC load
Some other brands recommend AC couple to be no larger than the minimum of charger rating and inverter rating.
Luxpower_Gilbert
Luxpert @Luxpower USA Team
if the ac couple is more than 12kw for example. 20kw ac couple system. 20-12=8. 12kw will charge the battery and 8kw will support the load and the rest will sell to grid.
Quattrohead
Solar Wizard
Can you also have them work on the frequency for timekeeping, my clocks lose at least 5 minutes a week off grid.
I keep seeing mention of suddenly stopping a large load (EV charger, 4 ton AC unit, etc.) can cause some brief power to export back to the grid, but also it looks like there's some updates happening that might have fixed that? Is this still an issue to be concerned about with the 18kPV?
I'm looking at a large build that would be self sufficient for 99.X% of the year, but ideally I'd like to have the grid feeding into the 18kPV for those extremely rare times (once or twice every few years) my array & battery wouldn't be able to keep going. However, if it has a chance to backfeed that's not an option as it just adds more cost and easily 3-6 months waiting for the utility company to approve it.
I'm looking at a large build that would be self sufficient for 99.X% of the year, but ideally I'd like to have the grid feeding into the 18kPV for those extremely rare times (once or twice every few years) my array & battery wouldn't be able to keep going. However, if it has a chance to backfeed that's not an option as it just adds more cost and easily 3-6 months waiting for the utility company to approve it.
zanydroid
Solar Wizard
I'm sure you've seen my technical analysis and opinions on this on the other threads so I won't repeat them.
If you really are sized big enough to not draw from grid why not double convert? The reduction from 100% efficiency of pass through to 80% of double convert sucks but you will rarely pay it.
NEM3 is pretty solar friendly IMO.
PG&E pre approved my new NEM2 in March 2023 in not much more than a month and did PTO on my old NEM2 in November 2022 in about a month too. You can look up the costs assessed to get to PTO, pretty sure it's less than $500
Your AHJ permit will likely take about as long as the initial pre approve. My AHJ has decided to discount solar permits pretty heavily.
That leaves planset ($750 is what I paid in May) and engineer stamp if your AHJ requires ($300 for a basic design). TBH if you are DIY for first time you can call the $750 tuition to teach and derisk the project, I was happy to pay it.
It does suck that your $20k project (18kpv, powerpro, $10k of panels and balance of system) increases by $1500 in soft costs, but in the grand scheme of construction overhead that is under 10%, less than the California sales tax on the materials...
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zanydroid
Solar Wizard
If they are using bad real time clocks not much firmware can do if truly off grid. The IT solution to this is to have a atomic clock receiver (which could just be a LTE or GPS receiver, no monthly plan necessary) that hosts a timesync server. And then either you add an external script to force the inverter to resync time, or LuxPower implements the client (it's all open source and free) to do this against the timesync box.
zanydroid
Solar Wizard
Yup, this makes sense for on-grid and I have no worries about it. I want to understand your guarantees for off-grid better.
The worry is if you max out the 16kW AC coupled, and it's outputting at 100% to satisfy 4kW of loads and 12kW of AC charger. If the loads turn off then there is risk of overvoltage damage until the FreqWatt or relay can react quickly enough. Or the AC charger has surge charging capacity to compensate and sink the current.
This also depends on the BMS capabilities on the connected battery, for instance the PowerPro defaults to 100A charge, 200A discharge on a single battery. Now given the PowerPro surge spec I think AC coupling in 10-12kW on a single battery should be safe since I would be surprised if F-W response is too slow. This also does not require me to know the LuxPro AC charger's surge rating, since the continuous rating is enough to satisfy this.
With two PowerPro, as long as LuxPro AC charger surge can match the PowerPro BMS surge ratings (possible? the inverter can handle a lot of surge on the opposite side) 16 kW AC coupled is probably safe.
If you have a section/page number in the manual on the official guidance I'm happy to read through it. Maybe @Markus_SignatureSolar has guidelines for tested / sane combinations with PowerPro (in one or two battery configuration).
I have the EG4 18kpv inverter only issue I am having is light flicker from time to time when it switches the loads from grid to off grid .I am pretty sure it’s software issue but was wondering if anyone else has had this issue
Zapper77
Renaissance Man
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That's normal. The transfer time is fast but not fast enough to prevent dimming when switching power source.
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Quattrohead
Solar Wizard
I'm still not particularly thrilled about the regulation although it is way better than it used to be. Also even though the inverter knows the correct time it absolutely cannot provide the correct frequency to keep my clocks in time, I lose 5 minutes plus a week. To be fair the Solark 12K did the same damn thing not quite as bad though.
zanydroid
Solar Wizard
Ah that kind of frequency, right. Maybe one solution is to implement inverter version of time error correction (which the grid is required to do; grids these days are allowed to deviate from 60hz but I believe TEC forces them to run at opposite correcting frequency). It would have to be something custom for off grid AC coupled system solar, like let the frequency float during the day to do frequency-watt, and then at night compensate for the positive and negative drift introduced by that.
You still have clocks that use AC frequency for timing? All of mine are on DC wall warts (or an AA battery). I think most of them get the time signal from the national clock or a NTP server.
zanydroid
Solar Wizard
They could be cherished collectible vintage AC clocks handed down in the family or whatever.
I own zero AC clocks so I was initially confused by the post about clock drift.
There’s some kind of medium frequency or whatever atomic clock signal that is broadcast for time sync, it’s used by things not on NTP, GPS, or LTE. Which are expensive.
Well NTP is not expensive since WiFi enablement is basically free now, but the cost comes back because the config is obnoxious to maintain across a dozen devices
Quattrohead
Solar Wizard
Stove, microwave and the all important to Mrs QH coffee pot ?
Zapper77
Renaissance Man
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I will pay attention to this. I haven't notice a loss in time. Looking at the stove and microwave, the time is 1 minute slow. But it's been a few weeks since the last firmware update.
Just advertise the NTP server from DCHP. Ideally, make your router the NTP server and have it sync upstream.
zanydroid
Solar Wizard
What if WiFi stops working ?
What if you want to rename the network.
I have two freaking generations of SSIDs right now because I don’t want to hunt down random IoT devices still using the old one.
I can’t recycle the old SSID because I’m running a mix of new managed and old unmanaged WiFi access points, and putting both on the same SSID means the crappy old APs will hose the nice features on the new APs
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Luxpower_Gilbert
Luxpert @Luxpower USA Team
Are we talking about the time on the inverter? Mine pretty accurate, i set the time advance on the seconds digit, while looking on my phone with the clock app i the will try to press the set button when my settings on the inverter match on my phone clock.
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