Prius Prime Plus in my hands

Getting ready for a drive to Knoxville, I filled up after the 3d tank:

I think it took about 8 gallons, not that I really care.

Bob Wilson

 

Because it is a trip out of town, I want to make sure we're not held up by a flat:


So I used the space inside the spare tire:


Later,
Bob Wilson

 

A Trip Report

Many years ago, I bought a Gen-1 pack from a wreck early into my Prius NiMH battery experiments, Prius Battery Photos, that was gathering dust in the shed after gifting our Gen-1 Prius last year. Then @gittarpikk in Tennessee reported he needed some Gen-1 modules for his 2001 Prius and a plan formed on how to recycle my unused Gen-1 pack to maybe help a 2001 Prius get back on the road.

Huntsville to Knoxville and Back

@gittarpikk lives about 214 miles away, easily a day trip, just outside of Knoxville. Leaving at 3 AM to avoid driving into the Sun rise, I arrived about three hours later. But recent rains and no clouds, there was significant fog for all but the city sections of the trip. But with the radar collision detection and dynamic cruise control, it was non-stop ... perhaps driving a little faster than the law would allow. The fog revealed that the brights project an impressive 'box of light' down the road but I was a little too busy to take a photo.

Arriving shortly after dawn, we got the pack onto a hand cart, it weights about 90 lbs,, and discussed where my Gen-1 module rehydration experiments and where I stopped. The root cause of Gen-1 module failure is overheating of the "O" ring on the battery terminal that is visually evident by the black smear around the B+ terminal. In normal operation, an NiMH battery generates a small amount of 2H{2} and O{2} gas from electrolysis of the KOH. If the "O" ring is intact, this gas will recombine over night to water, sustaining the electrolyte. But charging an NiMH battery is exothermic and makes them get hot enough to melt and weaken the "O" ring letting the gas leak out. Over time, this dries out the KOH which leads to low capacity and eventually, a spot heating short of the plastic separator in one of the six cells that short kills module.

My experiments found that rehydrating the module, it has a shared gallery between the six cells, and cycling the module leads to recovering full capacity. BUT I was never able to solve how to close the hole(s) drilled to inject the water. My last speculation, not tested, was to drill a hole in the useless, pressure relief valve (the actual one is the "O" ring!); inject the water, and; using a pair of modules, connect them with vinyl tubing tightly clamped. If the internal voltage does not lead to a 'short' via the vinyl tubing, it should provide pressure relief for the failing "O" rings and allow a pair of modules to return to service.

The other approach, plastic welding, is a technology @gittarpikk is well aware of so he may have more success than I did. The plastic case is exceptionally resistant to epoxy and I was not able to secure a stainless steel nut plate. But the problem of the weakened "O" ring remains. Since @gittarpikk has the technology, an avid RC hobbyist, and understands the technology, it made sense to 'clean our my shed' and gift him the spare traction battery. We then went for a cuppa coffee and @gittarpikk did the driving while I made a few suggestions.

Prius Prime Test Drive

A good test drive should consist of two sections with a break in between. The first drive is feeling out the steering, brakes, and mirrors of this strange car ... getting over the newness. Take a break so everyone gets a chance to calm down. Then the second drive is where the 'good stuff' gets covered. So the coffee break broke the drive into two and gave us a chance to discuss 'plugshare.com' and EV economics.

On the way back, we paid attention to the different driving modes: HV, Charging, EV, and discussed EV Auto. We also had a chance to do a few maximum accelerations with and without a charge and continue to explore how dynamic cruise control works. I still remember my trepidation when I first used dynamic cruise control and if he felt any, @gittarpikk hid it well. After an hour, it was a little after 8:30 AM (all times are Central Daylight) and it was time to head home.

Home Again

On the way back, I took biology breaks as needed and arrived about 3.5-4 hours later. I stopped at my favorite Star Market/Propst mini-shopping center; put an hour charge on the car, and; bought a pair of rather excellent Porter House steaks and fresh corn on the cob for dinner. Home again, my wife and her two dogs were happy to see me and I took a nap.

There is an old joke that if you lock your wife and dog in the trunk of a car. The dog will be happy to see you when you open the trunk. Happily, my wife and her two dogs were glad to see me when I arrived.

Rested

I enjoy the irony of a 2017 plug-in, Prius Prime, Gen-4(+), delivering a salvage traction battery pack to help a 2001 Gen-1 Prius get back on the road. It was ~7 hours; driving ~475 miles; ~67 mph block-to-block, and; about 8 gallons of gas. Hopefully everyone is happy again and the salvage, spare pack might help a 2001 Prius return to service.

Bob Wilson

 

It was dynamic cruise control and accident avoidance in our BMW i3-REx that led me to buy a 2017 Prius Prime. Before I was interested but after using it in the BMW system, it became a hard requirement after two weeks with our 2010 Prius:

	characteristic	2014 BMW i3-REx	2017 Prius Prime
1	sensors	optical	optical and radar
2	heavy rain	turns self off	turns self off
3	warm-up	1-3 miles < 50F	not seen freezing and above
4	low speed	20 mph	28 mph
5	come to stop	yes	yes
6	resume from stop	+1 mph resume	+1 mph resume
7	false positives	shadows across road also cresting overpass with sign at night	none
8	lost lead vehicle	tight cloverleaf curve	tight clover leaf curve
9	lead vehicle turns (*)	comes to a near stop	comes to a near stop

* - As the car turns, the rear part comes to a relative velocity of 0 mph to the following car direction of travel. Our wide-vision, primate eyes see the car is leaving the lane, something neither the optical nor radar sensors can detect. This causes a false positive for a non-moving, object in the lane. An experienced driver will override the alarm and use the accelerator to maintain speed as the vehicle leaves the lane.

Bob Wilson

 

Trip summary for July 9:

• 467.5 miles
• 58.8 MPG

Bob Wilson

 

I'm starting to look a CHARGE mode duration and fuel burned. So I drove on the Interstate spur, 75-80 mph, to Decatur, 35 miles, for breakfast. When the SOC dropped to 0%, I reset 'A tripmeter' only to see impossibly high MPG, !44 MPG, which confirms what others have reported. The car continues on EV during the engine warm-up cycle. I continued resetting until the early tripmeter reading became more normal, ~50 MPG.

I parked so the front of the car was in shade, 90F, but the rear was in sunlight. The A/C was on, 76F, auto, and I put the car in "P" and CHARGE mode. The engine came on so with the windows up, I went to breakfast:

	time	miles	MPG	SOC %	gal
1	10:13:59 AM	10	59.7	0%	0.1675041876
2	10:49:49 AM	10	26.2	17%	0.3816793893

In summary:

• 17% SOC increase
• 35:50 mm:ss or 35.83 minutes
• 0.214 gallons of gas (CHARGE and A/C at 76F, in 90F heat, 50% shade)

Rough order of magnitude in 90F, 50% shade, 76F A/C:

• 2.11 min/%
• 0.0126 gal/%

Based upon this ad hoc, non-optimal test:

• 1 gal to reach 80% and keeping cabin 76F in 90F heat
• 168.8 minutes (2:48 hh:mm) to reach 80% SOC

On the way back to Huntsville, I ran the battery to 0% SOC using EV and then put the car in CHARGE. Halfway to my appointment, ~11 miles ~10 minutes, the 75-80 mph car was already at 16%.

These are by no means definitive results due to the 90F temperatures, sunlight, and limited range of some metrics. This was practice to figure out how to conduct more accurate benchmarks.

Bob Wilson

 

I have to do well documented tests at different speeds.

The car was in P in 90F and estimated 50% shade with A/C set to 76F. There are so many variables not controlled, it was ad hoc and imprecise. For example the integer %SOC would set some folks hair on fire because there could be a .0-.9% variation in the true SOC.

Bob Wilson

 

Answers don't come free:

The Graybeard engineer retired and a few weeks later the Big Machine broke down, which was essential to the company’s revenue. The Manager couldn’t get the machine to work again so the company called in Graybeard as an independent consultant.

Graybeard agrees. He walks into the factory, takes a look at the Big Machine, grabs a sledge hammer, and whacks the machine once whereupon the machine starts right up. Graybeard leaves and the company is making money again.

The next day Manager receives a bill from Graybeard for $5,000. Manager is furious at the price and refuses to pay. Graybeard assures him that it’s a fair price. Manager retorts that if it’s a fair price Graybeard won’t mind itemizing the bill. Graybeard agrees that this is a fair request and complies.

The new, itemized bill reads….

Hammer: $5
Knowing where to hit the machine with hammer: $4995​

Bob Wilson

ps. I'm waiting on a call ... FYI, I did not knowingly leave a 'time bomb' and tried to document everything I had learned. But my experience is every 6-18 months a 'difficult' problem will reveal itself. If the product I supported is still working, I've got anywhere from 3-15 months before I 'get the call.' <GRINS>

If the product is still running, I've been lied to and ... my bill will be appropriate.

 

I suspect there is an optimum, maximum efficiency rpm/load. A little under that would be an ideal operating point to start CHARGE mode that would bring the engine efficiency into the peak, efficiency range.

Bob Wilson

 

Tell them,"Please have the service manager check the charging cable over night. I've heard on PriusChat that the Toyota charging cables have a problem."

FYI, Toyota charging cables must have a problem because they are not checked to make sure they work overnight. Toyota claims they only work 10,000 times so something must be marginal.​

Anyone else have a problem with the Toyota charging cables? Perhaps that Toyota does not test them as part of Prime prep?

Bob Wilson