Charging, going small

Charging, going small

Perhaps range isn't the real issue. Maybe we should think more about the availability of recharging stations and the time it takes to charge.

What is better, stopping for a ten-minute charge every 200 miles, or being able to go 400 miles but then having to spend an hour sitting at a Supercharging station? Does it being free make this long stop so much more alluring?

What happens when lower cost models come out and Tesla wants a much larger market that includes condo owners and renters? They can't install home chargers. How are they going to charge up if not at home? Will they be happy sitting for hours a week at some weak charger?

Perhaps the answer is a battery that you can quickly and cheaply charge up at most any gas station. Not free, but a lot cheaper than gas and with all the other advantages of an electric car. People will be happy enough to get the occasional free charge when they come across a Supercharger, and this will be a viable option for long trips. And they are great advertising for Tesla.

Monetizing charging will bring in more chargers at no cost to Tesla and allow for a wider customer acceptance.

Perhaps a fast-charging 200 mile battery would be lighter and cheaper than the holy grail 500 mile battery. Now you have a cost advantage to go along with more convenient charging. I would presume also that chargers that can charge a smaller battery are not as expensive to put in as those fancy Superchargers that have to force-feed giant batteries. The cheaper the charger and its installation, the more profitable they get. More chargers equals more electric cars and it just all gets better for everyone.

If capacitive batteries are what it takes to do this, and these are expensive to make, perhaps going small would at least minimize the cost some and allow for their use.

Tesla could also mass produce an appropriate turn-key, easy to install metered charger that would be attractive to gas station owners, perhaps free with a piece of the action, to get these put in everywhere.

So, maybe ubiquitous charging stations and quick-charging batteries with modest ranges are what we really need for the near future at least, to get this going. Later there will be other alternatives.

ghillair | June 5, 2013

you raise several interesting points. I believe an owner of a townhouse or condo should be able to work with their HOA to install a charger for their unit.

As to charging for apartment renters, I am in an apartment partnership. The managing partner manages 8,000 apartments in six states. At a meeting last month I asked when upgrading a complex where thinking of installing chargers? They said not currently, but are following the market an will probably start in a couple years. They see it as an amenity that would attract clients and provide enough additional rent to be profitable.

Paul Koning | June 5, 2013

Quick charging batteries would be great. If they existed, people would be using them for all sorts of things. But they don't exist.

You may be thinking of supercaps (you mentioned "capacitive batteries"). Those are not batteries. Yes, they charge quickly -- but their capacity is a tiny fraction of what a battery of that size will hold. And the price isn't all that much lower (if it is lower at all). So if you're looking for a Model S with 20 miles range, that technology may work. If you want 100 miles, it will not.

carlgo | June 5, 2013

Musk brought up the subject of fast charges. He evidently studied capacitor technology in school. He is a rocket scientist!

A high school girl won a prize for using caps in some way that enabled her to charge her iPhone in a few minutes. She may be a future rocket scientist.

I'll just guess that caps are involved in future fast-charging technology. If they choose to not call the energy storage unit a battery, fine with me. Doesn't matter.

The only point is that I think fast charging is at least as important as pure range.

Brian H | June 6, 2013

You must deal with a) large volume (space) required for capacitors with equivalent energy storage, and b) very heavy cabling to provide the power flow implied by large energy transfer in short time. So -- cables like stiff firehoses and a car-full of capacitors.

At cellphone size, the trade-offs may be workable. At automobile size, not so much.

Paul Koning | June 6, 2013

Here's an easy way to look at it. Suppose you have a storage device that holds 85 kWh (as the current Model S battery does). But unlike the current battery, it can be charged in 5 minutes -- the "as good as filling a gas tank" goal.

That translates to 85 * 12 kW charging power, in other words 1 MW in round numbers, if charging is 100% efficient. If the storage device is 1000 volts (well above what is currently used) the charge current is 1000 amps. The wires for that would be an inch in diameter, give or take.

Now suppose the charging system is "only" 95% efficient (here too, well above what's currently likely). You'd get 50 kW of power loss during the charge; that lost power is converted into heat. That's the rough equivalent of 5-10 home ovens running full blast. The cooling system of the energy storage/charge device has to be able to remove that heat from the car. A cooling system fit for a good size truck is about right for that work load.

The trouble is that liquid chemical fuels are just a very compact way of storing energy, and that stored (potential) energy can be transferred with very little power. Neither of these are true for electricity. It's certainly possible for electric cars to be adequate for many purposes, but many of the limitations we're currently seeing are not a simple matter of a bit more engineering.

carlgo | June 7, 2013

Interesting information.

Can caps be charged more quickly than batteries and are there heat issues when charging them quickly?

Can caps be charged up quickly and in turn charge up or augment a conventional battery (I think this is how the iPhone charger works and I also think that idea was mentioned here for cars)?

Musk indicated fast charging was coming soon and it does not seem to involve battery swaps. What is left? Caps? Superconductivity? Or, as some believe, mere range extenders like air-metal batteries, or something mechanical like a flywheel?