Level 2 EV Charger

So, as discussed earlier I have purchased a 2021 Chevy Bolt.  The stock 120v level 1 charger is too slow (my round trip to work is 100 miles).  I am getting about 3.5 miles/kWh, that makes my commute consume about 29 kWh of electricity.  The level 1 charger that comes with the car will charge at 8 amps or 12 amps (this is limited by the car, not the charger).  At 120 volts that comes to either 960 Watts (8 amps) or 1.44 kWh (12 amps).  So at the low charging rate it would take about 30 hours to replace the energy used in a trip to work.  Even at the higher rate it will take about 20 hours. And this assumes I don't want to use the car for anything else.  At first I could tolerate this because I don't drive to work every day, but I may have to again, so I needed a better solution.

Since I made my original decision to get a level 2 charger, I have learned that the stock charger can run at 240 volts.  This would have made my recharge after a trip to work take nine and a half hours, which might have been acceptable.  However, a trip to Galveston would end with me at home with about 10% charge; that would take about 20 hours; so, maybe going for the level 2 charger is a good idea anyway.

Having decided I wanted a Level 2 charger.  I read a little bit and chose the Juicebox 32 device. I knew I would be power limited, so I wanted a charger that was easily adjustable on its output level.  The Juicebox can be changed using the phone app and can be set in one amp increments.

A level 1 or level 2 charger is just some electronics and a big relay (called a contactor). Level 2 chargers seem to start around $500 and go up to about $700. The higher power ones are a little more expensive, but not a lot.  

I decided on the 32 amp version.  It will supply my Bolt with the maximum current that it can use and saves a few bucks.  As a plus, the Juicebox is easily detached from the wall and the 32 amp version uses a NEMA 14-50 plug.  (The larger ones are hardwired.)  This may make it possible to travel with if I can find a suitable outlet.

The problem is an outlet to plug it into.  It wants a NEMA 14-50 plug wired for a 40 amp circuit.  I can't give it that right now.  I have a small subpanel (breaker box) in the garage.  But it is only fed 30 amps.  This is why I knew I needed an easily adjustable unit.  The line for this little breaker box was originally run for a radial arm saw I had (it was a 220 only unit).  I used the saw a few times while building the house, but not much. When I needed power for the septic system (I did not know it would need power.) I stole the outlet and turned it into a subpanel with one circuit for the septic system (I don't think it pulls an amp).  The intention was to also put a breaker in for the saw.  Five years later, I realized I was not going to use that saw and gave it away.

Several years later someone gave me a hot tub; which for lack of a better place, I put in the garage.  (I have deck designed for it; now, if I only had time to build it.)  I configured the hot tub for a 30 amp circuit (it knows how to behave and draws a max of about 23 amps).  

So I figured that if I put the Juicebox on the same panel it would blow the breaker that supplies the subpanel.  And that is exactly what happened. I only wired it on 10 AWG wire so I set it to supply 24 amps and it worked for a couple of days. The hot tub is a very intermittent load; when the heater is on it pulls 22 amps, otherwise it draws less than one.  But eventually both devices wanted all the juice and the breaker blew. I turned the Juicebox down to 20 amps, and that worked better; but, eventually also popped the breaker. Now I have it running at 16 amps, which has not blown the breaker yet. But the breaker is still potentially overloaded. I would really like to get it on a 40 amp breaker so that it could supply the max 32 amps to the car.

Now a little about the wiring of this house. I built the house starting in 1997 and I wired it in accordance with the 1996 code. At that time Texas did not have licensing for electricians; and the power company would connect power to anything you wanted hooked up. (I spent a long time studying the code book.)  So, if the house's wiring sounds unusual, there is no one to blame but me. I did all the design and all of the wiring. It's still legal for me to do all the work in my own house. And I pretty much insist on doing it myself.

To start with the service panel is outside on a power poll. That is the way my electric company liked them at the time (1997). The local hardware stores sold main panels wired up to a meter socket and a conduit with the weatherhead on it; all wired for 200 amp service.  The electric company wanted you to buy one and leave it where you want the supply pole. They came out dug a hole, mounted your meter loop and tied it into the transformer. This seemed a bit odd to me at the time and odder now, but that is what they wanted.  My outside panel (the service panel) has one breaker in it: a 200 amp breaker that feeds the distribution panel in the house.  

When no heat or AC is running and my wife and I are working at our computers the house sits drawing 1300 watts or so.  (About 5.5 amps on each 120 volt leg.) That makes 200 amp service seem silly until the AC, hot tub or the heat pump heat strips come on.

The distribution panel (technically a subpanel) is at one end of the house (the end near the power poll) and is a pretty full 20 slot box (which can hold up to 40 half size breakers).  However of those 40 slots 8 are taken up by two full width tandem breakers that feed other panels and one half size tandem that feeds a box in the well house.  There are several full width slots taken up by GFIC breakers and several taken up by half width tandem breakers for special appliances (a dryer and two ovens).  So there are 23 circuits in the box and 4 empty half size slots.

One of the oven circuits was for a range in the kitchen and is a 50 amp circuit.  I considered repurposing it for the charger (there is a place in the attic I could cut it, install a box for a junction and tie in a new cable to the garage. But after thinking on it, I decided not to.  If I ever need to replace my gas cooktop with an electric range, I would have to tear out sheet rock to replace the line.

Unfortunately, that main distribution panel is at the end of the house opposite the garage and the kitchen and the laundry room.   Since the house is 74 feet long, it was necessary to put a subpanel at the far end of the house.  This is a 12 slot box, all of the breakers are half size.  It currently has 19 of the 24 positions filled (two of which are a tandem breaker for the small panel in the garage.  This subpanel is fed by 60 amps and would have to have sheet rock cut out to add circuits.

So what do I want in the future? Well when I move the hot tub to it's deck, I would like to supply it with 50 amps (the max it can be configured for) and I would like to feed the charger with a 40 amp circuit so I can run it at 32 amps.  It appears then, that I need a 90 amps panel.  

With 75 degree terminations and THHN conductors I could use 3 AWG copper or 2 AWG aluminum. But, it is about 150 wire feet to get from the distribution panel to the garage.  (If I don't want to repair sheet rock.)  At this length and current voltage drop becomes an issue. However, the circuit will seldom operate at 90 amps. The car charger will draw 32 and the hot tub will draw max about 22 amps when not in actual use. So the actual load will be 54 amps.  So, lets use 54 amps for the voltage drop calculations. With 3 AWG copper I'm looking at 3.2% voltage drop which is OK, but that much copper is pricey. With #2 aluminum the drop is 3.99%, a little high.  With #1 aluminum the drop is back to 3.2 which I can live with.  So I chose #1 aluminum.  I have an order for 180 feet for 1-1-1-3 of SER cable into my electrical supplier.  I will get it Tuesday and start the project.

The first stage is to install the new subpanel, then I will continue to the next phase of rewiring the NEMA 15-50 on a 40 Amp circuit.

Installing the Subpanel

Main Panel Work

Sunday, April 18, my wife was out of the house all day, so I shut off the power and moved some circuits around in the distribution panel. Now I have a place for my new breaker. It was all pretty straight forward except that I was using my emergency generator to power the lights while I worked. And I found that over the winter it had gotten water in the gas, so of course it ran until I had a bunch of stuff pulled out of the box and then died. I had to clean the fuel filter and the carburetor bowl to get it going again. (Sometimes I just want all of the gasoline engines out of my life.)

Getting Stuff Together

Tuesday, April 20, I got my cable. I picked it up in the Bolt. It should have been a piece of cake. But the supplier got it shipped on a spool. The spool weighed as much as the cable and would not fit in the Bolt. The supplier pulled it off the spool and made a nice coil out of it that fit easily in the Bolt. (BTW: it's Summit Electric Supply in Austin, I used to use the one in San Antonio.)

Last night I went to Lowes and got most of the rest of the components I need. I probably could have gotten them all from Summit, but I find Lowes' web site much easier to use and they have more GE stuff listed (all my panels are GE).

I am now short one neutral lug of having everything. They say it'll be here Wednesday (the 28th).

Running the New Cable

Saturday, April 24, I started running the cable.  The first struggle was getting the whole thing in the attic.  It was a pretty day outside, so of course, it was very hot in the attic.  Unlike many modern houses, the attic is floored.  This makes working up there easier.  But it is a mess and the center is taken up by a room, that makes things harder.  

The 1 AWG by 3 conductor cable is not easy to work with.  It's important to not allow it to form twists as you uncoil it; so, you have to unroll the coil not just pull it out.  One side of the attic has cable supports that hold most of the cables that feed the circuits in the house. So I ended up unrolling a little of the cable and then feeding down the cable supports and repeating the process until the cable ran the full length of the house.

By the end of the day I had it run the length of the house.  So on Sunday I fed it into the main breaker box.

The next weekend I finished the cable run and installed the box.  The cable still needed to go down to the first floor (through the chimney chase) and across the single floor wing of the house to the attic above the garage. This was a lot of physical work but pretty straight forward.

Wiring in the Garage

At this point the cable was directly above where I wanted the box in garage; so, a few holes and I was ready to install the box. I used a mid size box with 16 half size slots.  I used up four of them for the 50 amp tandem breaker for the 14-50 outlet.

I then ran a 8 AWG three conductor cable to the 14-50 outlet and connected to it.  The 8 AWG cable is good for 50 amps at 75C. Both ends are terminated to 75C terminals and the breaker is alone in the box and should not need to be derated.  So, the circuit should be both safe and legal for 50 amps.

A Year Later

So, it's been a year since I did the install and everything has been just fine.  No sign of heating at the plug or the charger when running at max power.

I have found that in the summer I want mostly to run the charge at 24 amps. This is because of the car not the charger. The car builds up a lot of heat charging at 32 amps when the temperature is above about 95 F. This makes the AC run to cool the battery.  It probably doesn't hurt anything, but I would rather not get the battery that warm.

In the winter the car used more power mostly for the heater and I put the charge level back up to 32 so it would charge a little quicker. I'll probably turn it back down in June or so.

Other than that it's been pretty uneventful. Everything has worked just the way it should.