A used plug-in hybrid vehicle

[Nords]

Flush with photovoltaic success, I'm eagerly anticipating my next infrastructure project. I could start it tomorrow but we have a couple years before deadline and money is not a huge concern. While we wait for the technology to mature, let me seek the counsel of you experienced geeks engineers.

Our kid plans to take her driver's license exam in just 758 days (you have been warned) and she came up with an interesting variation on her parent's car proposal. Instead of driving our 1993 Ford Taurus wagon (two tons, 102K miles) she wants to pay us her $5000 car fund to share a Toyota Prius. When she goes to college (almost certainly on the Mainland) we'd buy her out and she'd use the money for her own beater.

Spouse and I are happy to support our kid's initiative. Not only is it a good idea, it gives me an opportunity to spend more money boost the battery pack (if necessary) and convert the car to a plug-in. I'd be happy to hack the software to minimize the engine use but hey, it's my kid's gas money.

I'm seeing Hawaii Prius prices of $11K-$13K like this one. I remember some concerns about the batteries on the early models but I don't know how that's turning out or whether it's an issue on the later models. I've also heard of aftermarket booster packs that should give us a greater range, although that might not be necessary on Oahu.

What intrigues me the most is being able to recharge the car on photovoltaics. The most expensive part of an array is the inverter, but we'd upgrade to a 4-6 KW inverter (or buy another 3 KW one) and add another couple kilowatts of panels. We'd be dumping huge kilowatt-hours into HECO's grid by day and building up annual credit which we'd take back at night or whenever we plugged in the car.

Here's a couple questions:
- How do I determine a car's mpk (miles per kilowatt)?
- How many kilowatt-hours would I be dumping into a drained battery pack to fully charge it?
- I know a Toyota Prius is the most popular hybrid, but would we want to shop other hybrids?
- How accurate is the manufacturer's range estimate? I'd drive a battery pack with as low as 100 miles between charges.
- How long are the battery packs lasting? Anyone heard of recent problems?

 

[eridanus]

1) An internal combustion engine is only about 25-34% efficient. That 34% is for high-end engines (i.e., you don't have one).

A gallon of gas is 33.3 kwh. Take your per kwh charge and multiply = what a "gallon of gas" costs from the grid.

Now you need to figure out what the car can get with a gallon of gas. Let's say a Pruis, which is kinda Civic-like, can get 35 mpg highway. At 25% efficiency, that's ~140 miles if it were 100% efficient.

The conversion of electrical to mechanical energy with a battery is about 80%.

80% * 140 miles = 112 miles on a "gallon of gas"

See above for what a gallon of gas costs from the grid. At $.10/kwh, you're talking about 2.97 cents/mile.


2) Good question.

3) Unknown at this time.

4) As of the last time we had a thread about the Prius, Toyota had only replaced battery packs due to accidents. They are supposed to last 10 years and can be replaced for $3000.


Edit: Amended numbers. Using EPA numbers for BTUs (113500/3413).

 

[wabmester]

Prius plug-in hybrid

 

[poboy]

http://www.evworld.com/view.cfm?section=article&storyid=898

Steve Lapp's solar assisted Prius, interesting read.

 

[Nords]

Thanks, guys, I'm going to keep an eye on that.

Spouse pointed out that today's stock market gains could've paid for the whole project... then she asked me why I'm prowling through junkyards looking for the Taurus' replacement rear-wiper switch. I knew there was a good reason for marrying her!

Steve Lapp calculates 125 watt-hour/km or 4.8 miles/KWhr. I'm going to have to keep chewing on the rest of the capacities if the Prius doesn't fully charge its batteries.

As much as I admire Lapp's work, I have to say that the guy never thought of hauling a longboard on his roof. Sure, maybe the board will fit inside the Prius, but he could've mounted the PV panel on his hood!

 

[sailor]

- How do I determine a car's mpk (miles per kilowatt)?
- How many kilowatt-hours would I be dumping into a drained battery pack to fully charge it?

Easiest to determine empirically of course after you get the Prius.
My advice is to buy a kWh meter on eBay (less than $50) and use it to track just prius charging.
Than it's easy, read odometer and kWh meter and voila: mpk = miles driven / kwh used

There was a poll on EV list a while ago about efficiencies and i think best conversions were in 100 Wh/km range (old Karman Ghia conversions come to mind for some reson)

How many kWh per pack it's up to you - depends on how big of a pack you install nad coulombic efficiency of particular battery chemistry.

Cool project anyway and I'm assuming you have seen PRIUS+ site: http://www.calcars.org/priusplus.html

 

[shtg42012]

Nords, we have a three year old, 6 kW grid-tied system (36 Sharpe 165 & two SB 2500) here in SoCal and we went with net metering. Our NEM rate schedule is based on a 9am-6 pm M-F time frame so we put back a fair amount of kWH back into grid on weekends (and holidays) that we do not get any credit for.

My FIL has a 2004 Prius (that one day he will have to give up, I hope to be first in line) and I thought about what you mentioned in your post. We do more short errands on weekends, could charge up rather than give SCE free juice (which really bugs me). Coversion cost & availability is key but maybe by the time FIL is ready to give up his Prius, this will come down.

Would be fun to do local short errands in the Prius on PV generated charge!!

 

[Nords]

Easiest to determine empirically of course after you get the Prius.
My advice is to buy a kWh meter on eBay (less than $50) and use it to track just prius charging.
http://www.calcars.org/priusplus.html

Well, the whole point of this exercise is to do the engineering analysis and to know the costs before we whip out a credit card.

We have a Kill-A-Watt but I haven't found a 240V version, although I've read that a lot of the charging seems to be on 120V lines. Hot stuff.

Thanks for the website-- more studying!

Nords, we have a three year old, 6 kW grid-tied system (36 Sharpe 165 & two SB 2500) here in SoCal and we went with net metering. Our NEM rate schedule is based on a 9am-6 pm M-F time frame so we put back a fair amount of kWH back into grid on weekends (and holidays) that we do not get any credit for.

God bless Hawaii's alternate-energy lobby, led by the solar contractors. They agitated long & hard with HECO to start the net-metering program, and then they lobbied all over again to get the books shifted from a monthly rebate balance to annually.

So now, with just a few hundred more watts of spouse-approved panels ("And this time I really mean it, honey!") we'd be able to build up a surplus bank during the summer that'd get us through the winter and totally flatten our electric bills.

When we expand this system I'm buying at least a 4.5 KW inverter, if not 6 KW. But right now we're running out of photovoltaic real estate faster than we're running out of inverter capacity.

 

[Nords]

We're considering bottom-fishing for a used 2001 Prius. Help me find the flaw in my logic.

Here's the Craigslist ad: http://honolulu.craigslist.org/oah/car/220692187.html
The owner had posted it last month before reposting this month, so the car's been on the market for six weeks with presumably no takers. We'll learn more about that when we test-drive it.

85K miles in five years is extremely high-mileage driving on this island, although it could have been shipped here from the Mainland. If we buy it then the car will only rack up 3-4K/year for the remainder of its life so it's not that big a concern unless the car's been beaten to crap.

I see that the 2004 Prius is a significant improvement over the 2001 with a better battery pack and more horsepower. I'm not sure those improvements are important to us either.

The only major difference between the 2001 & 2004 models that might matter to us is the air conditioning. I'm getting the impression that the 2001 A/C works best when the engine runs but I see that the 2004 will run the A/C off the engine or off the battery. Am I correct and is this a significant performance difference? The reason I ask is that I can modify the battery pack (or replace it) and convert the car to a plug-in whose engine would seldom run. But if the A/C is crap without an internal combustion engine then it's not worth the plug-in conversion.

Anyone here know any other differences between the 2001 & 2004 models? Toyota's 11MB "brief" addresses the engineering more than the driver's experience.

 

[wabmester]

Nords, given your recent power outage, I would have thought you'd be more interested in this Prius mod than a plug-in hybrid mod:

PriUPS

 

[Patrick]

Nords, you might want to subscribe to the EV Discussion List here: http://www.madkatz.com/ev/evlist.html

There are lots of engineers and other people on the list who would probably be happy to crunch the numbers with you and offer helpful suggestions.

 

[Lakewood90712]

A co-worker has a 2006 prius. The a/c will run w/o the gas engine running. Even parked. The engine will start to protect the battery in this mode.

Also, the second generation Prius has a huge windshield and rear hatch glass. Makes a great solar heater ! and this car is white with the tan interior.

 

[BigMoneyJim]

My BiL has a 2006 Prius. The AC compressor is electric and works great. I can't speak for the older model.

From what I've read, I'm under the impression that the battery longevity is helped by the fact that the batteries are never fully charged or fully drained. I wonder if charging them up from the plug will reduce battery life?

My oversimplified summary take on the Hybrid Synergy Drive system is that the battery is there to store and later deliver the gas motor power that would normally be wasted, and it wasn't designed with external charging in mind.

But the base of my hybrid expertise is a few hours riding in my BiL's car and a handful of hours reading about it on the internet.