Off-Grid Solar Install

[PV1]

Time to expand again.

We've been thinking of putting some kind of pergola or canopy over the rear patio. I thought, "why not take advantage of it and boost solar capacity?" I've been designing a system made up of 10 SolarWorld 320 watt panels, 4 Tesla Model S battery modules, and an Outback GS4048A Inverter to provide off-grid i-MiEV charging, as well as some interior lighting, and possibly the fridge as well.

4 Tesla battery modules will give me 21 kWh of storage (~18 kWh usable) at just shy of 48 volts nominal. The 4,000 watt inverter provides 120/240 volts, and will allow full power level 2 charging for Bear (Koorz is plugged in once a week at 120 volts, 8 amps). I am also going to off-grid one light on each floor of the house for coverage during a power outage. Depending on which method works better, I would like to either use an automatic transfer switch or a modified UPS to keep the fridge running from battery power when the grid goes out, but use grid power when available.

Total cost will be around $13,000, but the Solar Federal Tax Credit drops it down near the cost of a straight grid-tie system. Besides being a learning experience, it's quickly becoming necessary to expand our solar generation, as this year was the first where demand exceeded generation in the summer, and it'll only get worse as the climate de-stabilizes. Plus, since this system is a mini version of WK057's system on TMC, it can scale up and take the whole house off-grid should that be necessary.

https://teslamotorsclub.com/tmc/threads/plan-off-grid-solar-with-a-model-s-battery-pack-at-the-heart.34531/page-33#post-1013666

Section below will serve as a summary of specs, links, and other useful tidbits of information.

Equipment Pictures (a collection of pictures of the equipment as I receive them. Also includes pictures of testing.):
https://www.dropbox.com/sh/tmj7298pl9q9z3q/AABFAxKKS1RJb1IxXsEBY7Qba?dl=0

Wiring Diagram:
https://www.dropbox.com/s/8cl77cna418cr87/Equipment%20Wiring.png?dl=0

Completed System Pictures (automatically updates as I progress. As of 12-27, there are no pictures here.):
https://www.dropbox.com/sh/88rt7xelrd7s8g5/AAC_cW2N-fAsuX0yYo79b5Zfa?dl=0

 

[jray3]

Please post pics o progress. Few PV modules are designed to make raintight roofs, and one that came close is out of production (Silicon Energy Cascade Series). The leader seems to be http://www.floriansolarproducts.com/, who turns beautiful bifacial modules into the glass panes of a greenhouse-style roof.
My second array is relatively raintight, using solid uni-strut as rails that also act as rain gutters, with aluminum cap strips sealing the longitudinal gaps.
http://karmanneclectric.blogspot.com/2015/11/solar-washington-part-deux.html

Unless you've got some anti-consumer grid tie or peak demand billing, I don't see the reason to do the double conversion and run PV through a stationary battery in route to EV. Sure, battery backup may be desired, but why run the pack through any extra cycles?

 

[PV1]

Will do.

I don't really care if it is perfectly rain tight, but I'd put a bead of silicon caulking or rubber gaskets between the panels to stop water from coming through. We mostly want it for shade as the patio is too hot in direct sunlight.

Being lithium ion, sitting idle at high charge isn't that great for them. I figure they'll easily last 10 years or more, as they aren't seeing any temperature swings or high currents. The voltage range is just as conservative as the i-MiEV. I do want to start transitioning away from being totally dependent on the grid, and this seems like a good starting place (granted, running the A/C is likely a better fit, but the i-MiEV is a fairly predictable load).

 

[PV1]

Small update. Instead of ten 320 watt panels (72-cell), I can get a better deal on the smaller 60-cell panels rated at 300 watts. Not only do these panels fit the dimensions of the pergola better, I end up with more power for the same area (3.6 kW instead of 3.2 kW), and the array runs at a higher voltage which reduces amperage. Also, because I'm now using 12 panels instead of 10, I can wire them so that only one string of panels at a time moves into the shade as the day goes on (patio is on the east side of the house, so I'll have morning to early-afternoon production for this array).

The array is wired 3 panels in series, and 4 strings in parallel. These go to a Midnite solar combiner box, then to a Midnite Classic 150 charge controller. This charges the Tesla modules, wired 2 in series, 2 strings in parallel. In all, the pack is 12s148p (total of 1,776 lithium ion cells). Nominal voltage is 44.4 volts, with a capacity of 21.2 kWh and a higher power output than I could ever use (500 amps / 22.2 kW, but likely capable of much more) :lol: . With a pair of 80 amp fuses, one on each string, they feed an Outback GS4048A power inverter, which will provide up to 4,000 watts of 120/240 VAC to the EVSE, lights, and fridge (total load is close to, but less than 4 kW).

The plan was to start next spring, but the election results bumped up the timetable on at least buying the equipment (30% FTC may not survive next year). I still haven't decided if the system will have any grid connection or not. That will depend on energy deficit/surplus.

 

[PV1]

Major components ordered! Just about everything else is available locally.

Now to start making some room for everything.

 

[Phximiev]

Do you already have the Tesla pack?

I'd like to see pics when you have time.

 

[PV1]

The modules are ordered, but haven't shipped yet. The main pack has already been disassembled by the seller, and I'm only getting 4 of the modules that were inside the pack.

This is what a module looks like.
https://www.dropbox.com/s/210nrgi1ytt87vm/Firefox_wallpaper.png?dl=0

 

[Phximiev]

Are these the EVWest modules? I saw they were selling a group of modules from a pack.

 

[PV1]

No. They are coming from a seller in New York. I think EVWest is selling modules from the Smart ED, whereas I'm using Model S modules.

 

[Phximiev]

EVWest may be selling both. I mentioned it because of a recent video regarding EVWest selling them.

See:

https://youtu.be/4_AGSYsVCJs

They may still have some available?

 

[PV1]

Tesla makes the Smart car battery modules, but they are different than Model S modules (and more expensive per kWh). The Smart modules run higher voltage, but have fewer cells. I don't see the Model S modules on EVWest.com.

Apparently, there are a lot of Smart EDs being parted out, given the parts that EVWest has.

They look like fun guys to hang out with, though.

 

[PV1]

Battery modules have shipped. Should see those early next week. FedEx Ground right to the house .

The inverter and charge controller are being shipped by pallet due to weight, so that will be dropped at my work, and I'll break the pallet down and load everything into the i-MiEV (ought to handle 100 lbs. of equipment, right? :lol: ).

The solar panels will arrive at my friend's place on a pallet, but those will be picked up in the truck, likely on Saturday if they arrive in time.

 

[pbui19]

PV1- looks like a fun project. I briefly scanned the Midnight 150 charge controller, it doesn't seem to have lithium charge profile. Am I missing something ? the Outback inverter has lithium charging option. Does the Tesla pack already have built-in BMS ? may be the 150 can be programmed to stop below 40vdc ? then you can top off with the Outback.

 

[PV1]

The Classic has a custom setting that I can use and set the charged voltage manually. I plan to only charge the bank to 49.2 volts (4.1 volts per cell). I'll also be disabling the equalizing function and temperature compensation (which shouldn't be an issue anyway, as my basement holds a pretty stable 65 F) to prevent over-charging. I can safely go to 50.4 volts, but operating voltage range of the pack is 42-49.2 volts (3.5-4.1 V/cell).

The modules each have a BMS board on them that appear to function on their own. I have a lithium balance charger that I'll use to make sure all the modules are balanced and at the same charge level. Given that they came out of relatively new packs, they should already be balanced (especially if they're all from the same pack). I may end up using the "Garcia Bros. BMS" :lol: , given my voltage range and relatively low current draw.

The Outback's charger uses grid power to charge the battery bank. That's not the goal of this system. Ideally, this system is off-grid, but if it does end up needing a grid connection to be reliable, then I'll need to figure out which method allows for the following:

1. Runs independently on battery/solar power.
2. Automatically connects to grid to support loads when batteries deplete. Automatically disconnects when batteries are charged.
3. Grid does not charge the batteries.
4. Automatically connects to grid to sell excess solar power when batteries are full. Automatically disconnects when excess is no longer available.


As a bonus feature, I'd like to give the system control of interior lighting circuits for dusk to dawn operation for the pair of lamps that we leave on all night.

 

[JoeS]

PV1, you're going with a fancier system than me, undoubtedly better in the long run. Your voltage levels are right on for 12 Li(NMC?) series cells. In my case, I have three parallel strings of 4S 12v AGMs, 16S LiFEPO4, and 14S Li(NMC), each string of similar capacity, intending for them all to play nicely off a single charger at a max charging voltage of around 56v. Need to finish instrumenting this setup to see how well they share both charging and discharging currents before proceeding further - exactly where I was a year ago before being rudely interrupted :evil: .

 

[PV1]

I believe they're lithium cobalt oxide, but I'm not certain. Each module is 6s74p, and the battery will be wired two parallel strings of two modules in series, for a combined 12s148p cell configuration. At full output, each string has just over 50 amps draw, making for less than 1 amp per cell.

While I'm actually less than 48 volts "nominal", the inverter shuts down at 40 volts input, or 3.33 volts/cell, keeping the batteries from getting near a critical level. I should be able to program the inverter to shutdown at 42 volts, leaving that bit at the bottom for when I really need it, and to not stress the cells more than necessary.

I could've went for a cheaper off-grid only inverter, but knowing that someone else used the same components and everything worked together, I felt the few extra bucks was worth the peace of mind.

Batteries were delivered to the house this morning :mrgreen: ! Right now, they are in the back of Koorz. If they were hooked up, total range would be 140 miles while only adding an additional 220 lbs. :lol: .

 

[PV1]

https://www.dropbox.com/sh/tmj7298pl9q9z3q/AABFAxKKS1RJb1IxXsEBY7Qba?dl=0

Garcia Bros. BMS it is :x . The modules don't have the BMS board on them. But here are pictures.

 

[PV1]

Also, according to my charger, 3.33 volts per cell is just over 5% charge. That's the lowest the inverter will go before shutting down. I'll see sometime later what 3.5 volts per cell is considered, as that will likely be my "dead battery" point.

Right now, I'm trying to bring the first module up to about 10% charge. One bank of cells are just a hair higher than the others (.02 volts).

I just got word that the solar panels have arrived at my friend's place. I'll be picking those up Saturday.

 

[PV1]

I put 1.5 Ah into the module in about an hour, hardly moving the voltage, but I ran out of time last night. If I were to fully charge a module, it would take my lithium charger over 100 hours at full bore. It's only a 50 watt charger :lol: . Even running at 40 watts, it was getting warm.

I also emailed the seller. She said they recently started removing the BMS boards when they add their balancing connector as the boards don't appear to work outside of the car, but offered to send them to me if I wanted them, which I do.

Just as I about hit Submit on this, a box showed up containing the MATE3 control panel, combiner box, PV breakers, and charge controller. I wasn't expecting these until next week (thought they would've been with the inverter, which will be delivered on the 27th).

It's satisfying to finally have the Classic in my possession. When I was dreaming about building a solar car (before the i-MiEV), I followed the Classic's development with anticipation.

Can't wait to get everything hooked up and tested.

 

[pbui19]

how about posting a block diagram so we can follow your train of thought ?