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diy solar

Generac PWRcell system

Delmar

Solar Addict
Joined
Dec 9, 2019
Messages
817
Location
Lake Conroe Texas
Does anyone have experience with the Generac PWRcell system http://getpwrcell.com/? Both for the equipment and the company. Looks interesting that it should be seamlessly integrated with a backup generator for large loads (HVAC) or extended grid-down.

I have a personal connection with Generac by designing their portable generators and transfer switches in the 80’s. Otherwise I have no commercial involvement.
 
Clever... if you'll notice their claim "LARGEST ENERGY STORAGE CAPACITY ON THE MARKET TODAY!" is based on "storage cabinet capacity" and not usable capacity. It is a very big box. Form factor looks like it could also be rebranded Yiyen units.
 
It doesn't appear to be a diy option.
I’m a dealer/installer so that’s not a problem. when you own something and can dive into it daily you get a more intimate understanding of the unit and it’s nuances. I may be able to answer my own questions soon, as I should have mine up and running tomorrow.

I installed one last year and I noticed this week that one of Pv links said “low sun” for a few days so I went out today to look at it. When I restart the unit it seems to take a while for the Pv links to reconnect and sometimes it takes way longer than you would think for the cts to reconnect and show the power coming and going from the different devices. I’m wondering how long other people‘s units take to get going after a restart and if they have ran into any glitches.
 
I could go the dealer/ installer option.
But, I'm a cheapskate. lol
Unless I win the lottery, I will never own a tier one system.
But, I'm always curious about what's out there.
 
My fully-loaded, 18kWh PWRcell battery is behaving as if the capacity is about 6-8 kWh. Nothing in the system warned me about this. I just started getting high demand charges from my utility because my battery was nearly-fully-discharging (hitting minimum SOC) during peak hours, at which point it stops contributing and my grid demand skyrockets. I went back and analyzed the data from a few such incidents and found that the SOC dropped from 95% to 15% while only providing about 5 kWh to my home. So I called the installer and they called Generac, and they seemed to have admitted that some of the 6 modules are misbehaving. A visit is scheduled in about a week.

The system has plenty of data to provide a proactive warning about such a loss of apparent capacity. It just doesn't. Even if it didn't send an alert, it could at least compute the apparent capacity (the way that I did) and display that number. I suppose doing so would generate a lot of 'extra' service calls for Generac -- not financially advantageous for them. Many homeowners wouldn't even notice this problem ... until they had a power outage and the battery doesn't do the job that they thought it would.

My system is obviously not "DIY", so this might be the wrong forum. Happy to hear if there is a user forum for owners of non-DIY solar. Thanks
 
FWIW:

Generac is in the middle of some sort of a mess with lawsuits and bankrupt solar installers who (grossly?) oversold thier products. Early in 2022 we priced a few of thier systems out but found them to be overpriced for what they were. That may have changed and I'll admit we really didn't study them that deeply.

Now we're getting calls both by finance companies and owners to try to get systems going that were installed by bankrupt installers finished or going again. :oops: But since we don't know anything about them and are already booked out for the bulk 2023 we just have to tell people to keep calling around. Sucks but we learned a long time ago that these sorts of clean up projects are often miserable.
 
My fully-loaded, 18kWh PWRcell battery is behaving as if the capacity is about 6-8 kWh. Nothing in the system warned me about this. I just started getting high demand charges from my utility because my battery was nearly-fully-discharging (hitting minimum SOC) during peak hours, at which point it stops contributing and my grid demand skyrockets. I went back and analyzed the data from a few such incidents and found that the SOC dropped from 95% to 15% while only providing about 5 kWh to my home. So I called the installer and they called Generac, and they seemed to have admitted that some of the 6 modules are misbehaving. A visit is scheduled in about a week.

The system has plenty of data to provide a proactive warning about such a loss of apparent capacity. It just doesn't. Even if it didn't send an alert, it could at least compute the apparent capacity (the way that I did) and display that number. I suppose doing so would generate a lot of 'extra' service calls for Generac -- not financially advantageous for them. Many homeowners wouldn't even notice this problem ... until they had a power outage and the battery doesn't do the job that they thought it would.

My system is obviously not "DIY", so this might be the wrong forum. Happy to hear if there is a user forum for owners of non-DIY solar. Thanks
It’ll be interesting to see what they say about your batteries. Are they inside or outside? How old are they? How much throughput have they seen? Do you recharge them with the grid or just from solar? I switched mine from “self supply” to “clean backup” when we started getting cloudy days recently. Mine is set to only deplete the battery to 30% if there’s no grid outage. we’ve had a lot of cloudy days recently so I’ve only been making 1-9kwh on those days. If I was on self supply my batteries would be at 30% most of the week. I made 46kwh on Christmas Day though so when it’s Sunny and cold it does well.
 
It’ll be interesting to see what they say about your batteries. Are they inside or outside? How old are they? How much throughput have they seen? Do you recharge them with the grid or just from solar? I switched mine from “self supply” to “clean backup” when we started getting cloudy days recently. Mine is set to only deplete the battery to 30% if there’s no grid outage. we’ve had a lot of cloudy days recently so I’ve only been making 1-9kwh on those days. If I was on self supply my batteries would be at 30% most of the week. I made 46kwh on Christmas Day though so when it’s Sunny and cold it does well.
The battery and inverter are inside my garage, but this is Phoenix, so it can get very hot. The system is just over one year old. I use if for peak-shaving and there is one 6-hour peak period in summer and two (morning and evening) in winter. So I get some discharge during each peak period (probably averaging around 15%), then it recharges from whatever source is available. I don't worry about the source of the recharge, since I'm on a true net-metering plan. Using the system's TOU setting for my utility, the system is automatically in "self supply" during peak hours and then in "priority backup" during non-peak times. There is a different TOU setting that uses "clean backup" instead of "priority backup", but for me the difference doesn't appear to be important. (My solar is pretty limited -- peaking at around 6kW on a sunny day.)

So I'm doing three things to be 'gentler' on the battery:
  • Limiting charging rate to 2kW (before setting this limit, I was seeing it recharge at more than 8kW)
  • Limiting max SOC to 95% (Note: It sits at this level most of the time)
  • Setting a value of TargMaxImprtP (tuned each month) such that I discharge below about 50% probably 2-3 times each month.
What's NOT gentle is the heat in my garage in the summer. It is routinely in the mid-90s and I've seen it hit 104. I have not detected any case where the system has limited its own output due to the heat, but I'm not sure I would see this. I certainly wish that the Generac system would provide automated alerts or access to a system-event log. Having said that, my capacity issue did not appear in the summer (that I could detect anyway).

An aside: I've turned off "Outage Guard" after having been burned a couple of times by high demand charges. I was unable to see that Outage Guard was the culprit (again, no alerts or log available), but the system suddenly switched from Self Supply to Priority Backup in the middle of peak hours -- going from discharging to charging. This spiked my demand charge for the entire month. One month, I had a $51 demand charge, just because my power demand peaked for 30 minutes. With no help from Generac or my installer (after multiple emails), I finally found the culprit and turned the damn thing off.
 
It sounds Like you have it setup well. I bet your cooling fans run a lot! Is the filter underneath checked regularly? I’m sure with that phoenix heat you won’t want anything else causing heat build up.

Did they test individual battery voltages?

You could have a cell imbalance and need to do a vset to equalize the batteries.

What does your device page indicate your battery state is?
 

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It sounds Like you have it setup well. I bet your cooling fans run a lot! Is the filter underneath checked regularly? I’m sure with that phoenix heat you won’t want anything else causing heat build up.

Did they test individual battery voltages?

You could have a cell imbalance and need to do a vset to equalize the batteries.

What does your device page indicate your battery state is?
Thanks for the info. What is the source of that first graphic showing the imbalance problem?

On the inverter's battery page, the state is "standby".
 
@Rainwater01 - you nailed it. There's an imbalance. The tech from my installer explained: The system only measures state of charge on the first and last battery module in the series of 6 modules (actually, I was a little unclear on this part of the his explanation). Both of those are 'full' when the other four modules are not, so the system stops charging prematurely. He said that he needed jumpers to get around the fully-charged modules and allow the other 4 cells to charge, but he didn't have those with him. He has to get them from Generac. I was surprised at this.

This seems like a fundamentally poor system design, IMO. Maybe it's an issue with a series configuration -- the controller can't directly balance all of the batteries (?). If they were separately connected (in parallel), this might be possible, but then you only have about 47 volts to work with, I guess.

Do other battery brands have a similar problem?

I wonder if my SOC limit (95%) is causing a problem that Generac hasn't seen before. As installed, they set that limit at 100%. I set the lower limit in an effort to extend the life of the battery, but if it's causing a problem, I would not mind going back to 100%. I don't want to change anything right now, since I'm in the middle of this effort to resolve this issue. But it's something to consider for later, I guess.
 
@Rainwater01 - you nailed it. There's an imbalance. The tech from my installer explained: The system only measures state of charge on the first and last battery module in the series of 6 modules (actually, I was a little unclear on this part of the his explanation). Both of those are 'full' when the other four modules are not, so the system stops charging prematurely. He said that he needed jumpers to get around the fully-charged modules and allow the other 4 cells to charge, but he didn't have those with him. He has to get them from Generac. I was surprised at this.

This seems like a fundamentally poor system design, IMO. Maybe it's an issue with a series configuration -- the controller can't directly balance all of the batteries (?). If they were separately connected (in parallel), this might be possible, but then you only have about 47 volts to work with, I guess.

Do other battery brands have a similar problem?

I wonder if my SOC limit (95%) is causing a problem that Generac hasn't seen before. As installed, they set that limit at 100%. I set the lower limit in an effort to extend the life of the battery, but if it's causing a problem, I would not mind going back to 100%. I don't want to change anything right now, since I'm in the middle of this effort to resolve this issue. But it's something to consider for later, I guess.
Good. Now that they know what the problem is hopefully they get you going again soon! Normally every cabinet comes with 3 jumpers which you have to install one for each battery you don't use. I started with 3 at 9kwh so I used 3 jumpers. I upgraded to a full cabinet so I'm not using any now. Normally you would discharge all the batteries that have a higher s.oc. down to the same s.o.c. as the discharged batteries but you need at least three batteries to charge or discharge and you happen to have two that are higher than the rest so that makes sense that they're charging the four. If they rearranged the cells maybe they wouldn't need anything other than the typical jumpers that come with the cabinet?

I think the imbalance problem is common with lithium batteries or any battery for that matter. Maybe they test voltage from the first and last battery to get a total system voltage and your total voltage is high enough it's not creating an error. I've worked on a series of 8 6 volt lead acid batteries and you can put a probe on the first negative and move the probe from the first positive to the second positive and so on and each time and 6 additional volts are added every time you move towards the end of the series which is around 48 volts.

I'm not sure if the 95% limit is causing problems. It seems like a good idea in theory. Maybe heat and quick discharge/recharge times can cause that?

Let us know what you find out!
 
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