A.C. operation while the car is parked.

I posted this in another thread and probably should have started a new one here. It is just observation of how the Prius A.C. behaves while parked. I thought that it was interesting. Actually, I think I bought this car as a science project.

I dropped off a fellow vet who needed a ride for testing at a VA clinic last week. It was 92 degrees and due to covid they wouldn't allow people to sit in the waiting room / lobby so I along with many other drivers parked in the shade on a lower level of the parking deck to wait for our patients.

I had the A.C. temperature set to 74 degrees and had a few hours to observe vehicle operations by selecting various parameters on my ScanGauge.

When I first got back in the car and pressed Start it initially drew about 8 amps. Traction battery current gradually dropped as the car cooled down and it stabilized at about 3 amps. The circulation fan ramped up to about 4 or 5 bars and it gradually dropped back to one bar as the car reached the 74 degree setpoint.

After the initial 10 minute cooldown, the ICE would run for about 2 minutes and then switch off for about 12 minutes. I began monitoring "SOC", state of charge of the battery and SOC would gradually drop. The ICE would start each time the SOC dropped below 40% . The ICE would switch back off when the SOC rose above 50%. Traction battery charging current was 20-25 amps.

I was trying to visualize what was going on. Correct me if I am wrong but with the ICE off, energy would be consumed by electronics, the A.C. compressor motor, the circulation fan motor, and a radiator condenser fan motor.

With the ICE running, energy would be consumed by electronics, the A.C. compressor, the circulation fan, the radiator condenser fan, the inverter coolant pump, ICE cooling pump and a second radiator fan.

I am not sure about the operation of the traction battery cooling fan. Once Start has been pressed does it run continuously probably at a low speed? I would expect that the fan speed is probably dependent on sensors on the traction battery. Or is the fan off until sensors on the traction battery call for cooling?

Is the 20-25 amp charge the actual generator current? Is the actual current going to the battery less than that in order to power those pumps and fans?

This was the first time that I had a reason to just sit in the car parked with the vehicle started for any length of time. It seemed very efficient to me considering I was sitting next to a Tahoe whose engine idled for hours and I could hear the distinctive click of the Tahoe's air conditioning clutch engaging and disengaging over and over.

 

I have to agree, what would it hurt to charge to 70% SOC? ICE duty cycle would then be something like 6 minutes on and 36 minutes off.

Thanks for the info. I don't know that I will be in a situation like that again but I will look into adding the Watts PID Xgauge to my ScanGauge.

 

Before I retired I worked in several Japanese transplant automotive plants. Their engineers are sooooo conservative, agonize over decisions, want to do some things in the most obtuse way and change their mind at the last minute. It may explain why things work the way our cars work the way they do.

I spent 3 months at Toyota Georgetown commissioning an e-coat paint line that we were commissioned to design and build. The project consisted of a body wash, basically a glorified car wash, an e-coat primer dip tank and a drying oven. Japanese automotives were tough to work for and Toyota may have been the worst . It is an extremely frustrating environment to build automation. You think that you have the drawings done and approved or you think that you have the code finished per the specs that they provided and then at the last minute things change. Their specs probably came from Japan and then one of their engineers on-site will decide that is not how he wants his system to work.

Case in point. The RFQ (request for quote) listed approved PLC's (programmable logic controller) for the Georgetown project. Alllen Bradley was on the list which made it easy for us. They are probably the most popular brand in the U.S. and we use a lot of Allen Bradley. We created the electrical controls package for the project using Allen Bradley PLC's and equipment. We took two months coordinating with their engineers and it took several hundred hours to creae a 30 page set of electrical drawings. I had made a good start on the three controls programs. We sent the drawing set to Georgetown for final approval. They came back approved as noted. I flipped through all the pages and there were few mark-ups until I got to the last page. On it were the instructions "Use Toyopuc".

I called to inquire about this comment. One of their engineers had changed his mind. This is when I learned that Toyota actually makes their own PLC. I had never heard of it and asked where I might find a distributor for it. Unlike Allen Bradley who can be purchased from electrical distributors in cities across the country, there is one distributor forToyopuc in the U.S. and it was in Chicago. We had to revise our electrical drawings, back to the drawing board literally, to reflect the substitution of a Toyopuc control system. My programming time was wasted. I called the distributor in Chicago to order the equipment. I told the distributor that I wanted 2 programming terminals, 3 PLC's, 48 of the 120 vac input cards and 35 of the 120 vac output cards and all the cables etc.

He took my order and then a few days later he called to ask me if I knew that their 120 vac output cards were not U.L. approved. I told him that I had scant information on anything Toyopuc and that I would have to call Georgetown as surely they must already know. The engineer at Georgetown replied "well then you can't use them then" .

He suggested that I switch all my output devices to 24 vdc. I explained that much of the equipment had already been ordered as 120 vac from vendors like Honeywell because of the long lead times in order to meet their timeline. He then suggested that I replace the 120vac output cards with 24 vdc output cards which are U.L. approved and then use a relay on each output to control the 120 vac devices. I ended up having to redo the drawings a third time including enlarging the control enclosures to accommodate nearly 300 ice cube relays.

On another note:The other electrical engineer from my company was approached by a Japanese engineer to inform him about a water leak on a pump motor. He replied that he did not do plumbing, he was electrical but he would find a pipe fitter to look at it. The Japanese engineer was offended and replied you work for "XYZ" everything on this project is your responsibility. He complained about my colleague to our general manager and he was removed from the job. My company sent a replacement but that didn't know anything about the job so I was pretty much on my own for the next couple of weeks. As if working 70 hours a week wasn't enough lets make it harder.

I liked working in Honda plants as there was more cooperation and fewer surprises.

I was so happy when that project was done.

 

In 1990, Honda announced a new manufacturing plant would be built in East Liberty, Oh. We received a $45 million order for the paint shop mechanicals. The lion's share of that was to design and build the paint booths and drying ovens but about $5 million dollars was for electrical equipment. There were 260 fan and pump motors up from 1/2 hp up to 250 hp, 100 Honeywell single loop temperature controllers and Honeywell control motors, Mitsubishi PLC hardware and Westinghouse easy-starts for motors over 200 hp. I was going to have to write 24 control programs for the 13 paint booths, 10 drying ovens and a sludge treatment plant. The PLC's would all be networked together and linked to their Central Control Room. At the peak of construction there were 165 electricians out of the union hall in Columbus running pipe, pulling wire and making terminations. Sprinkle in a bunch of pipe fitters running water and gas lines and it was like an ant hill.

After about 8 months of construction we got to the point that we could begin to power up the first of our control panels, the Honda's paint shop manager had instructed his maintenance associates to shadow us and learn how the equipment worked. I would be stooped over a terminal making some program change and when I stood up I bumped into an associate that had been looking over my shoulder. I would reach for a start button and an associate who was observing would beat me to it. By the time we had the programs in all the ovens and booths the associates had the equipment running when we got there in the morning. They had taken over and were making their own adjustments on limit switches, temperatures, pressures etc. The associates had a morning meeting and after that meeting, their team leader would give me feedback on items that they would like to have work a little differently. I felt good walking away from that project.

When we did the Georgetown project, the Toyota associates sat in their break room. The first time we fired up the drying oven there was oil smoke burning off of some of the panels and rising in the bay. One of the associate called me from the break room and asked if I could have someone turn on the overhead exhaust fans. In the time it took him to get me on the radio he could have walked the 50 yards to the switch and done it himself. When we were ready to turn the project over, the associates questioned who was going to train them on the equipment.

Just a difference in philosophy.

 

I didn't mean to imply that Toyota was the worst automotive to work for. It was just that project. We experienced more problems at any of the big three plants for projects that we had there than Toyota, Honda, Mazda or Nissan.

Typical was one GM install. I signed in and was waiting at the gate for an employee to escort me to their casting department. I was going to install a ladle (robot) that dipped molten aluminum from a furnace and poured it into a die-cast machine. When the employee arrived, the first thing he said was "You aren't taking that tool box into the plant". I always had a small startup toolbox with my meter, hand tools, tape, labels, wire ties etc. I took the toolbox back to my car.

I got to the ladle and began the checkout of the connections to their die cast machine. I found two wires that needed swapped. I had to find the area supervisor and requested an electrician. He got on his radio and about 15 minutes later an electrician arrived in an electric cart. He swapped the two wires and left again. A few minutes later I discovered another pair of wires that were reversed. I tracked down the supervisor and explained that we had quoted 3 days of startup time to commission the ladle but without tools and with a roving electrician it would probably take more like 3 weeks. The supervisor called and requested that an electrician be assigned to assist me.

My electrician arrived but after about a half hour, he said he had to see someone and he would leave his tool belt there and he would be back later. He said if anyone questioned me about using tool to explain that he was covering me and it was OK. I didn't see him the rest of the morning but since I had his hand tools I was fine. Union shops just added another layer of difficulty to start-ups.

 

To add to my observations of the PriusV while in Ready mode and sitting. I was waiting for my wife at the Post Office today and seeing the parking lot was full, knew she had a wait ahead of her. I decided to observe how the engine cycles on and off in colder weather to keep the engine temperature up to provide cabin heat.

It was an indicated 38 degrees out and the console temperature setpoint was 72 degrees.

While driving the ICE coolant temperature reached 105 degrees and the console indicated that the interior fan switched on at one bar. At 110 degrees the fan speed increased to 2 bars and 115 degrees increased it to 3 bars. The temperature eventually reached 160 degrees and I noticed that the the console fan speed display showed four bars. As the cabin warmed up the fan indicator dropped to three bars and then to two bars.

While sitting in park the ICE switched off and the coolant began cooling off. With the fan at two bars, the ICE switched back on when the coolant temperature dropped below 115 degrees and it switched the ICE back off when the coolant temperature exceeded 130 degrees (15 degree span).

As the cabin approached 72 degrees the console fan display dropped to one bar. At one bar, the ICE switched on at 110 degrees and off at 125 degrees. Still a 15 degree span but with the lower range.

With the 38 degree ambient, the ICE ran about 3 minutes on and 3 minutes off in either case.

While the engine was running I switched the ScanGauge to display Gallons per Hour and the engine was consuming fuel at a rate of .4 gph so with the 50% duty cycle it would consume about .2 gph. Lower ambient temperatures would force the engine to consume more to maintain the cabin temperature but .2 gph, less than a quart of fuel, at 38 degrees is pretty remarkable.

I marvel at all the scenarios that the engineers worked through to get to this final product.