Tesla Motors: The Pros and Cons of Plug-In Hybrids

What he's saying is a good point that I had not thought of (I'm guessing it's the CEO writing the blog). This is a good opportunity to dig a little deeper.

There seems to be three cases. In all cases the driver drives 12500 miles per year and charging occurs only at night and not at work/carpool parking etc. during the day. Assume the car gets 300 miles per charge+fillup.

Case I: driver charges batteries only after electricity is all used but before gasoline is used. This case is possible if the charge in the battery pack equals the work commute plus some errand-running -- and the car is plugged in every night.

Case II: driver charges only once gasoline is used up; said another way, they use all their electricity then all their gasoline before they fill up the gasoline tank and plug in the car. That's (12500/300) = 41 charge-fillups per year.

Case III: somewhere in between -- sometimes all the electricity is used (and then some gasoline) and sometimes only a bit of electricity is used before a recharge

In case I, the driver will fully discharge the battery every day. If the batteries are designed for 500 cycles, then the driver gets 500 / 300 or about a year and eight months of driving before the batteries need replacing.

In case II, the driver will fully discharge the battery every 9 days (365 days / 41). With 500 cycles, the driver gets 500 * 9 or about 12 years of driving before needing to replace the batteries.

In case III, we could make some assumptions and get some number in between 1 year eight months and 12 years, which I'm guessing is what the car manufacturers did so that they can say that the batteries last the life of the car. There's one more factor to add in which is whether the 500 number goes up if the batteries are only partially discharged before they are replenished (which seems likely to me but I'm not a battery expert). But we'll ignore that to keep things simple.

There you have it: if you just use batteries and your batteries last only 500 discharge cycles, you will be going through a lot of batteries. If you dip into your gasoline before charging, you will extend the calendar life of your batteries. I would be in the group of people who would avoid using gasoline and run solely on grid electricity whenever possible. Which means I'd better budget for extra battery packs every two years or put in extra batteries through an after market modification to lessen the frequency of battery replacement.

Bottom line: for us greenies, full electric seems the way to go. For everyone else, a plug-in hybrid will do the job.

I believe they may being missing the point that a plug in hybrid is a transition technology from the age of don’t forget to fill up the tank to don’t forget to plug in the car. It seems like such a simple transition, but hey I’m still typing on QWERTY keyboard.

What makes current hybrid batteries last over 250k miles is that they never are drained all the way, like a cell phone battery. Most of the time, they only drain to 50%. The problem with PHEVs is that they drain the battery to 0%. This puts a lot of strain on the battery and lowers its lifespan.

Why would you think that you would have to drain the battery to 0% before charging? I doubt people would drive 250 miles every day and then fully recharge every night. It would be like a cellphone. You use some of the charge and then top off at night.

I think the deal with the battery is that Li-Ion batteries last the longest when they are kept out of their extremes of capacity. Toyota programs the Prius to keep the batteries between 20 and 80% of charge at all times, that's a big part of why it lasts so long. A plug-in hybrid will be getting topped all the way up at night, which evidently is bad for this type of battery.

Don't ask me why, I'm just regurgitating what I've read on the subject.

One thing I don't hear discussed often with plug-in hybrids is what their impact would be on the electric grid. I have a friend who works for a company that expands the capacity of current power lines, and he tells me that the system is already stretched to the breaking point; power companies aren't investing enough in expansion and maintenance, and their engineering work force is approaching retirement age and they can't find replacements. If plug-ins are to be successful, someone's going to have to take a look at the improvements that will have to be made in the electric power grid to satisfy this new demand. Who is that someone?

http://greendrivinghandbook.com

You are right, Leszek, but I still think it's better to upgrade the grid (which we have to do anyway) than to keep burning all that oil. Probably less expensive (in many ways) too.

What I think is missing here and it seems is missing from most plug-in hybrids is the idea of only using the gas engine to generate electricity not trying to tie it into the power train. I think it would be easier to only setup a small gas engine in the back of the car that would kick on when the batteries get down to around 20% and just charge the car up to around 60% then turn off again.

I seem to remember an article about a hybrid mini someone built a few weeks ago that does something similar and it got 80 MPG. True the engine would require maintenance but if the car was plugged in every night it would not run very often and most users would be fine with only having it done once a year. Also since most people do not drive anywhere near 250 miles in a day I would think the car would be fine with only enough batteries for 100 miles.

I am not that up on Li-ion but my understanding is the reason that charging to 100% does no damage but the real problem is that it must be done VERY slowly so for a hybrid car its just not worth the work.

It all sounds great, but I do wonder about the viability when the only electric vehicles I've seen in the UK are 10mph milk floats!

"One thing I don't hear discussed often with plug-in hybrids is what their impact would be on the electric grid."

The effect isn't likely to be of any significance in the short term (5-7 years) if you consider the effect hybrids have had on oil dependence - negligible.

In less than 5 years thin-film and concentrating solar power technologies will be cost-competitive to the grid and will slowly take over from it. Not to mention other renewable energy sources such as wind that are expanding at a great pace and will contribute on their own.

As to the grid burden issue: I think that most people will charge their cars at night, which is when the grid has the least strain during peak times (the air is cooler, so less AC). On a tangential issue: if more electric companies switch to pricing models that charge more for electricity used during peak times, it would further encourage electric car drivers to plug in at night.

1. There's no question that using generated electricity is a more efficient way to move us around than burning gas; you're talking net efficiencies of about 25% or higher motive efficiences using electricity generated by fossil fuel, vs. about 12% by burning gas. Using alternative electricity sources swings the balance even more. But the grid isn't capable now of handling the extra demand, and it's not being upgraded in any rational fashion. If plug-in hybrids are really coming, the grid needs to be worked on now, but it's not.

2. Having worked in the semiconductor industry, I can tell you that if a startup announces a breakthrough technology, there's about a 2% chance it will make it to market, and less than 1% chance it will meet or exceed their hype. As much as I'd like to see solar contributing substantially to our electric requirements in 5-7 years (or other alternatives), it's very unlikely. People have been announcing major breakthroughs in solar cell technology for 20 years now, and all of them were going to make solar competitive in 5-7 years; not yet. George Monbiot, no tool of industry, says that alternative sources simply aren't going to be able to meet our energy requirements anytime soon without massive reductions in consumption.

3. The greatest burden on the grid comes in summertime when people get home, crank up their A/C, and start using their appliances. If they do the natural thing and plug in their cars at the same time, they're adding to demand at the worst time. It's potentially an easy problem to solve (put the charge circuit on a timer), but will people put up with the loss of convenience, not having their car fully charged at all times?

http://greendrivinghandbook.com

Actually, the greatest burden is in the summer afternoon to early evening. If people plug in after dinner or after taking the kids to soccer or whatever, rather than as soon as they get off of work, most people will not hit the peak time at all.

Hey guys, nice post. However the photos of the Tesla were not atributed properly. Those photos were taken by me and were not Tesla handout shots. Could you please give Popular Mechanics credit...thanks!
--Ben Stewart/Popular Mechanics

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editor note: Absolutely! Sorry ben, will update with full credit.

1) Martin Eberhard, the Tesla CEO, is an electrical engineer who has quite a bit of experience with batteries.

2) The charger Tesla bundles with the car has a timer you can set to turn on later at night. You plug it in when you get home and it begins charging at say, 1AM. That *is* off-peak.

3) The batteries do last longer if you don't discharge them all the way to zero before recharging them. The full EV with the bigger battery pack makes that easier.

I think the biggest challenge facing EV's uptake is recharge times. If you could pull into a service station, work, etc. and recharge your batteries (fully or partially) within, say, 5 minutes, you would eliminate one of the big consumer concerns associated with an electric car. My understanding is that there are batteries that are capable of charging to 80% capacity within a short time, but that it shortens the life of the battery. My understanding is that even now, getting 75% to 100% is just as long as getting from 0% to 75%. If they could improve the recharge time while maintaining the battery life, that would be a huge win.

Pros
Perception moves closer to the potential future of cars as consumer electronics where customers switch brands frequently to follow technology. The beginning of behaviorial change, possibly the biggest hurdle that electrics face from the users standpoint.

Cons
The mix of the grid changes constantly and differs by locality, region, state, country, etc. Conducting WtoW analyses is a moving project with no end, which weakens argument data against other disciplines or expert that are not engineers.

i want to become a vegan, got any ways that will help

i want to become a vegan, got any ways that will help

Sure. Stop eating animal products.