A New Roof

Before I could install a solar system I needed to have a new roof done. I could have probably gotten a few more years out of the asphalt roof, but I didn’t want to rip off the panels to redo it. So after a few months of quotes and scheduling I had a local roofing company come and replace it while I continued doing research on exactly what solar system I wanted. The cost was around ~20k.

Batteries Are Heavy

Once all the equipment was delivered, I had to figure out how to actually move the batteries into their final resting place. They weigh 300 pounds, and though they have some ropes to help you break them out of their shipping containers, that didn’t work for moving them. I settled on using some moving straps, which worked great. Two people would lift with the strap, while a third helped position the battery by the wall.

The batteries themselves are mostly supported by the feet, with the wall attachment used to stop them from falling over and to hold the inverter (which is considerably lighter than the batteries).

You’ll note I used Unistrut to mount the batteries and inverter. This was after I had already started building it with wooden 2x4’s, and then read in the battery installation manual to not use flammable materials. Woops. Always read the installation instructions. At least I didn’t get too far before I realized my mistake.

One other thing I will mention is I didn’t realize I was sent the outdoor version of the EG4 batteries until I had already mounted them. This shouldn’t be a problem because I was installing them inside the garage, but the cable shroud was for the indoor version and they are not interchangeable. A quick call to the seller and they shipped me the proper shrouds.

It would have been much more of a problem if I was sent the indoor batteries and needed them for an outdoor installation. Luckily, the electrical specs of the batteries are identical, they just have slightly different housing. The takeaway here is to really make sure you sent the proper equipment before you install it.

And even though the equipment I was using was outdoor rated, I installed the inverter and battery in the garage for a few reasons:

• The inverter is outdoor rated, but is supposed to be shaded. I would have had to build an overhang to shade it in the afternoon. There is also a small shed that would have had to be removed where it would have been installed.
• The garage has less extreme temperature swings.
• It is more protected from purposeful and accidental damage.

Of course, the main con is the system takes up room in the garage. Some shelves that used to be there had to go. I also had to install a heat detector in the garage that is networked with smoke detectors in the house because of batteries inside the garage.

Wiring is Simple When You Have Someone Else Do It

In theory, wiring the inverter and batteries isn’t too difficult. But it is not what I would consider trivial either, and I am far from an expert of electrical work. Now is a good time to mention I didn’t do this alone. My dad has a lot of experience with electrical work and did all the wiring on this job (don’t worry, I held the flashlight). Also, when I say “I” did something, it really was “we.” I think this is where many homeowners would probably outsource because dealing with 240v can be daunting if you have never done it. Lucky for me my outsourcing only cost me lunches.

The manuals of the inverter and batteries are very detailed and provided all the schematics for how to wire everything together. It is extremely important to follow them exactly. For example, it is imperative you use wire ferrules for all the connections inside the inverter to make sure each connection is solid and won’t come loose.

Here is a simplified overview of how the core components connect together.

So battery 1 is the “main” battery that is hooked up to the inverter. Batteries 2 and 3 each connect to battery 1. Here are some close ups of the sides of the batteries.

When this was first wired up, I had no solar panels and the inverter essentially just acted in pass-through mode. The only time the batteries would kick on is in the event of a power outage (though this has yet to happen — PG&E is generally pretty stable in this area, especially in the winter. Summer is another story though).

I could have used the batteries to “peak shave,” where I charge them during low rates and discharge them to load during high rates. I didn’t really care to do this that much though because my end goal was to have my panels charge them completely anyway. Also, I couldn’t figure out how to do this in the EG4 software. User error, no doubt. I’m sure I could have done it if I called support though, but I didn’t care enough to follow up.

Lastly, this is also when I installed the new subpanel. I also took this opportunity to run a new dedicated 20A circuit to my server rack, since the rack was right next to the new subpanel.

Voltage Issues

I did have to call support for a voltage issue I started seeing as my batteries sat around for a few weeks while I worked on getting my panels installed. The battery state of charge (SOC) stated that it was at 90%, but I was getting a low voltage warning on my batteries.

After calling Signature Solar, they mentioned this can happen if your batteries sit around for a while without charging or discharging. They had me re-calibrate the SOC with the voltage by having the inverter treat the batteries as lead acid for a few charge cycles. By this time I did have one string up and running, but not enough to completely run my loads and charge the batteries.

I had to manually change the charge and discharge settings every couple days to get the batteries to fully charge and discharge (100% and 20% respectively). After cycling my batteries 5 times over a couple weeks my batteries have been running smooth.

Only Make That Mistake Once

Now’s a good time to go over the mounting solution I used: Ironridge. My solar planner put in my system and roof specs into some software, which kicked out a bill of materials (BOM) I could give to my local Platt. That BOM ended up being a little bit off but was close. I had to order a couple more bolts and also returned a few rails that I didn’t end up using. The Ironridge system wasn’t cheap (I think around 2.5k for all the pieces), but it is extremely high quality, and this is something I want to last for years.

Using a chalk line, I marked the rafters I would be using as the mounting points for the rails. Ironridge does sell a model that allows you to not have to use rafters, but I opted for the rafter model that uses less screws.

Once the rails were installed (making sure to seal everything with outdoor rated silicone), I made my first mistake (related to the panels) that would have to be corrected later: I didn’t plan out all my wiring and run it before actually mounting the panels. Things like the wiring to the Tigo TAPs and ground wires. Why does this matter? Well, it is code that no wires touch the roof, and it is a huge pain to fix it afterwards. I ended up having to take some panels back off to fix it, but not all of them.

On later panels I ran the ground wire and communication cable for the TAP, as well as prepped each panel with cable clips as they were installed. It is much easier to cable manage as you go instead of having to fix it later. Luckily, I only made this mistake on the first string.

Wiring the First String and Optimizers to the Inverter

Each panel in the string is wired to a Tigo TS4-A-O optimizer, with each optimizer wired to the next one in the string. My first string (south facing) has 12 panels. I then ran a positive from one end of the string and the negative from the other end into a junction box (pictured above). Inside the junction box they are connected to metal clad (MC) cable, which runs through the attic to one of the inverter’s MPPT hookups.

The reason for using MC cable + junction boxes are so I didn’t have to work with metal conduit. I also think it ends up looking a lot nicer because you don’t have long metal conduits running all over your roof. The downside is you have to crawl around in the attic to route your wiring. The end result looks pretty great though.

Aside the positive, negative, and ground wires, you’ll notice there is also a white cable coming out of the junction box. That is for the TAP. The TAP provides the avenue for wireless communication between the CCA and the optimizers. This is critical because when the ESTOP is pressed, your panels need to turn off for fire safety. It is also wired into the inverter/batteries. This means at the press of a button all solar, inverter, battery, and electrical loads are shutoff.

Each TAP is daisy chained from the previous TAP. Tigo has excellent documentation on how to wire up the TAPs and CCA.

Tigo Software Setup

The Tigo software is pretty straightforward. You add information about your panels, inverter specs, and the serial numbers for your CCA and all the optimizers. Then the system scans for the optimizers, which you can associate on your system view so that the layout matches the panels on the roof, like this:

I did run into a weird issue where Tigo’s system was reporting missing or incorrect types of optimizers. I called Tigo about this and they recommended waiting a couple hours. Sure enough, a few hours later everything reflected correctly in the web and mobile apps.

The last thing to do before I could start using my system was to make sure my ESTOP was hooked up to the CCA and my inverter. I followed some tutorials on YouTube to do this.

Now I was ready to start charging my batteries and running my load from solar.

EG4 Software

Similar to Tigo, the EG4 software is pretty straightforward and defaulted to a lot of reasonable settings. These are a few settings I had to change:

• Battery type to Lithium
• PV input mode to however many MPPT hookups I was using
• Off-grid mode to enable (temporary until I had PTO)

Based on manufacturer support, I setup my batteries to charge to 100% and discharge to 20%.

I did have to do a firmware update for the inverter. You can use the mobile app to do this, but I highly recommend just upgrading firmware through the web UI — it’s much more reliable. I kept having issues with the mobile app firmware update failing. My understanding is that is more useful for locations where you have no internet access. Updating the firmware will cycle the inverter and cut power to your loads for a few seconds.

I also had to update the firmware for the screen on the inverter, which required using a USB drive. Again, I ran into a few issues here but eventually got it working by using an old USB 2 drive with FAT32. This had to be done because after the inverter firmware update, the screen was displaying incorrect wattages. The screen firmware update fixed that. I’m not quite sure why the screen requires a local firmware upgrade, versus the inverter itself that can be done over the internet. Here’s what the screen looks like:

You’ll notice in the above screenshot the inverter is in “Backup Power” mode because I have offline mode enabled, so as to not bleed power back to grid. It would also look like that in the event of a power outage. Once I got my PTO I was able to turn that setting off and it now looks like this: