The batteries are in our uninsulated shop, unfortunately. They weigh a whooping 108 lbs so I can't move them. They have R19 insulation packed around them because it's been cold this year. This is our first few months with the system up and running. The lowest the temp has been in the shop in the area of the inverters has been 38F. I live in SW Washington and this year the temps have been down to 16 at night a few times. Whenever there is potential for below 32F outside, we put propane heaters on to be sure we don't drop too cold.
This was another issue I had with them last week which is when I met Mr. Honey who you probably talked to. My batteries are laid out from left (by our shop/garage door) to the right which is in the middle of the shop wall well away from any doors or drafts. I'm putting a pic up for you to see. The top two pieces of insulation were removed for the picture as I was working on the BMS warning light with Fortress. They sit up on a bit of a shelf which is supported by 2x4's for extra strength. Each 5 battery section has 4 pieces of insulation one on the back, one on the front and two to close in the top allowing only gaps for the battery cables. The temperature, according to the thermometer on the wall next to our Sol-Arks (closest to the garage door) said 38F at it's lowest overnight. Anyway, I had shut the system down because of low power. Their stated storage temp is 20F. When I brought the batteries back online, I had 4 of my newer batteries in the middle of the line up (from the left, it was batteries 6-9) showing a BMS warning light (flashing red instead of the normal green). I worried and at the time didn't know how to see what the alarm was so I called Fortress and was walked through how to see the alarm. It was for a warning that the temperature was getting too low. Funny that it was low in the middle when it had been wrapped in insulation all night and it wasn't that cold in the shop! That's how I met Mr. Honey who informed me that I should just let the system stay on so it could keep itself warm. And this is when I asked about their parasitic load.
When we read the specs on the batteries, it says operating temperature min was 32F and storage was 20F. We don't normally have very low temps so we hadn't been worried until these guys told us they needed to be in a warm environment. I was like, "WTF?!"
Nothing is as advertised. And their stated "efficiency" is a fraud if they eat 30 watts.
I will get them back up to full and start my testing on Saturday when my husband is available to work with me.
Again, thank you so much for all of your help!
As I keep digging into this, I'm beginning to get the idea that the problem isn't the batteries.. Of course, without your testing results being available yet, and without any data, I'm relying on a combination of experience, technical know, and social media information.
Social Media
If those modules really had such a high self-consumption, I would think that you would not be the only one complaining about it. Loosing 14% of your power reserves to self consumption would surely show up on someone's radar. Folks who operate off-grid are pretty intensive when it comes to knowing where their energy is going, and I have to believe that someone, more likely everyone, would be raising alarm bells.
Experience
Secondly, any storage device that loses 14% of its own energy reserves PER DAY, wouldn't make it off the engineering table.
Technical Know
I'm guessing you have some other problem, or combination of problems. All battery technologies are based on chemistry, and as such, all batteries lose capacity when they are cold. Lead acid is absolutely horrible and can lose 50% of its charge capacity at 30 degreesF. Lithium is significantly better, but not magically so. Cold temperatures in the low 30's can zap the capacity of a lithium battery by 10% to 15%. So keep that in mind.. It would be a good idea to maybe tape a surface mount thermometer to the case of one module to monitor them. This way, you know if that case is down in the 30 degree range, you can expect a 10% drop in storage capacity. On the upside, cold operation just above freezing will extend the battery life.
My next concern is based on you.. As you have indicated that this kind of stuff isn't your wheel house, I'm going to assume, based on my experience with others in similar situations, that your comprehension of energy draw is probably not up to the requirements needed to manage an off grid system. To make a long story short, I'm going to postulate that your household appliances (refrigerators, heaters, phone chargers, televisions, etc), probably draw a lot more energy than you think they do. You said you ran a 2.5 ton heater? Is that a heat pump? Because that is a MAJOR HUGE load.. gigantic energy hog. Heat pumps are just air conditioners running in reverse and they are the axis of evil for anyone living off grid.
Among my other thoughts are
1) your charge and discharge profile settings in your inverters. You need to make sure your inverter is set to charge your batteries to full voltage. Fortress power recommends a charge voltage of 54.4 volts. A little math says their modules are set up as 16 series units and 54.4 volts divided by 16 = 3.4 volts. That's just a hair on the low side for most folks running phosphate cells. Phosphate cells can be charged to 3.65 with most folks going to 3.6. Kind of odd that Fortress is limiting it to 3.4. I would make sure the settings in your Sol-Arks are set for 54.4 volts and I would make sure to verify that voltage with a multimeter when your cells reach 100%.
2) Shut down one of those Sol Arcs and leave it off for now.
3) Purchase a kill-o-watt meter and check every single thing plugged into your home. I was stunned when I found my fridge pulled a whopping 5kW or more. Cleaning out the coils reduced it to 3.5kW, which was still more than I expected. A kill-o-watt meter will help you identify the energy hogs in your home.
4) Fortress power advertises their modules as 5.4kW, then the specs say 5.374kW (close enough), but their charge voltage of 3.4 per cell does not take advantage of that capacity. I might have to inquire about that being included in the capacity spec or not.
5) And lastly, one unfortunate truth you're not going to like.. and I suspect this is the real problem.. I live in Michigan and winters here are solar horror shows. Our solar array is 12kW in size and we use a 25kWh lithium battery. Between late November to the end of January, our solar system barely makes enough daily power to run the fridge for that day, let alone the computers, lights, television, or a freaking heat pump. There's just no getting around it.. when the days get so short and the angle of the sun gets so low, I'm lucky to see my 12kW solar system making 2kW of power. And while we can generate up to 80kWh in a single day in the spring, I'm lucky to see 5 to 7 kWh's a day during the December-January solar nightmare months.
I have included December's solar generation graph for you so you can see what a 12kW system does in Michigan.. it's kind of pathetic.
You might need to add more solar, or you might have to suck some energy from the grid for those months. One solution we use is to heat with wood, which cuts down our energy use in a huge way.
Something else we did that surprised me.. (and as an engineer a bit embarrassing). In 2021, we replaced all the 30 year old windows in our home with the new energy efficient ones. And WOW.. the difference is staggering.
I bought a thermal rifle scope some time back and I remember looking at my home from a distance.. the outside walls of the house were gray, (that means cold in a thermal scope), while the windows were all bright red and orange, which indicates a heat source. I just thought "hey, its a window, its going to bleed heat, that's probably normal" Then we replaced the windows and I took the scope out to look at them again.. the windows are now gray too.. We were losing crazy amounts of heat through them, and they were heating up the house in the summer forcing more cooling. I have most certainly noticed the difference in our energy monitoring.. it is significant. Just something to think about.
