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Squeaky Visitor plus Solar and EV Update

Squeaky (Their call is an almost continuous squeak)

There I was, sitting in my chair having a quite coffee and reading a book and we had a visitor, A fantail came in through the back door, did a couple of circuits around our kitchen, checked out a vase of flowers as a possible nest site, and eventually back out through the door it came in through. Maori legend tells us this can be a harbinger of death, but I’ve also heard that if they depart the way they came in then the prophesy is negated….. Iris & I are both very fond of these busy little birds, and they’ve been quite numerous these last couple of weeks, There were 5 flitting around us on the Golden Bay wharf as we left for Ulva.

The increase in numbers is to be expected as they come down from the higher parts of the Island in the Autumn. They do good work for us under our back veranda which has a white ceiling…. a great place for small insects, which the fantails are very diligent about hoovering up

Battery connections to draw power for back up solar system

Cable from Battery to connection plug. Installed by Tansley Electrical

 

Feed to Inverter inside workshop. From there via underground cable to

Cable from car to inverter set up inside workshop. From there via underground cable to “Roxburgh” where all the P/V electronics and batteries live

Electronics inside our PV shed

The Rotary switch on the left centre allows me to transfer Back up power source from gen set to car inverter. The Sunny Boy has to have input amperage re-set when changed.

Electronics and Battery Shed

Our Nissan Leaf EV

As well as being able to fuel our EV off our solar system I’d realised we had a potential extra 40 odd KwH to supplement our solar power batteries. But how to access it was a bit of a puzzle. EV’s actually have two separate batteries. The biggie is the traction battery, in our case 450 volt Lithium Ion with 40kwh capacity which is charged from our household mains, via a small wall charger unit. And there is also a much smaller 12 volt lead acid battery which powers the wipers, lights, radio, heaters etc. It is charged via a 1.4 kw (I think) charger from the main traction battery.

V2H…. Vehicle to home.

So two potential sources of power as a back up for our solar system. When we bought the car I had planned to connect a 12 to 230 volt inverter to the auxiliary battery, and feed that into our SMA Sunny Island, effectively mimicking our existing back up Powertec Inverter gen set. I would of course only be able to draw around 600 to 1000 watts, bearing in mind the car can only charge the battery at around 1400 watts. The SMA Sunny Island allows me to program a maximum output from the back up generator source, so no issues there, I thought. But there was an adjustable parameter I couldn’t work out … reverse current. So I ignored it. Initially the system worked, then the 12/230v inverter shut down, re-loaded and then shut down again and died.  Iris was NOT happy… $600 down the gurgler.  I eventually decided the issue was the reverse current, but couldn’t get any sense from SMA as to what and why the reverse current function was there for. But if at first you don’t succeed try again, and after several queries to Google AI, each one modified from the previous query I found that I could turn the reverse current feature off. So then had a long talk with a techie at Vectron and decided too try again. I went for a Vectron Phoenix Inverter 12/1200.  I set the Sunny Island to 2.5 amps (575 watts)…. It loaded right up, with no issues. With around 150 watts over our household load at that time.  But then our water pump started and the unit shut down, and then re started and ran OK. This happened again and it refused to load, although on checking the inverter it ran a belt sander, so was OK. After scratching my head I decided that the inverter for some reason wasn’t “seeing” our solar system as a load, so I added a small load parallel to the SMA Sunny Island system. And it worked just fine. I’ll probably up the output to around 800 watts. Not much, but all I really need is a trickle charger to keep slightly ahead of our household standard draw of around 400 watts.  So a very happy camper, as we can now keep our system “happy” even on cloudy days. After a few runs I’ll get a better idea of just how many hours I can get out of the car, without getting below a State of Charge (SoC) of around 40%. But so far it looks like around 26-28 hours if the car is fully charged.

I’ll probably fit a run timer so I can have the system run for a set time in the evening and then turn off.

Using The Traction Battery Directly

When the first inverter blew up I gave some thought to using the 450 volts of the traction battery directly. Our Sunny Boy solar inverters accept from 60 volts up to around 600 volts, so the traction battery at 450 volts is right in the sweet spot. And using a Sunny Boy 5, set to (say) 2kw would mimic a standard solar array. And of course would give me a “spare” Sunny Boy if I ever needed one. Also less parasitic loss than the other option. But extracting power from the cars traction battery looked to be a real project, and I really didn’t want to screw up our car. I still think this would be the better option, but I’d need to know a lot more about just how the power management system of the car works. The car has two separate charging plugs, and one, the ChAdeMO is actually designed to work with a two way charging system. These are available overseas But VERY expensive, and again difficult to get any meaningful info on them