Should Electric Cars Have Visible Charge Indicators For The Public?

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2013 Fiat 500e live photos, 2012 L.A. Auto Show

2013 Fiat 500e live photos, 2012 L.A. Auto Show

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It's a standard fitting on most plug-in electric cars: a visible light to show when it's recharging, often with a different indicator for when it's done.

Those lights, often on top of the dashboard and visible through the windshield, aren't yet standardized.

They come in red, orange, and green; some flash, some are solid.

And some other plug-in cars--the Tesla Model S and Ford Focus Electric among them--have a ring of colored lights around the charge port itself, rather than on the dash.

Now the low-volume 2014 Fiat 500e has a new wrinkle: an externally visible state-of-charge indicator that shows the battery's percent of charge.

It's similar to information that's available to owners on most plug-ins' touchscreen displays, often via a smartphone app for the car as well.

The low-volume Honda Fit EV also shows state of charge on a tiny display built into the car's remote control key fob.

Turns out, though, that not every electric car owner thinks the Fiat 500e approach is a good idea.

Tom Moloughney, who now drives a BMW ActiveE and previously had a Mini E, wrote:

I don't like the outside state-of-charge indicators, and don't want one on my car. I think a snappy smartphone app (I mean it works and it's instant!) would be all I need. I don't want others walking by knowing my SOC.

I can imagine it will lead to people unplugging you because they "really needed to charge badly and saw that you were almost full anyway."

I don't mind so much if the state of charge is shown somewhere inside the car, so you can quickly look inside and see it--but I definitely don't want something outside the car like what this pic shows. No way!

Honda Fit EV electric car remote-control key fob showing battery state of charge

Honda Fit EV electric car remote-control key fob showing battery state of charge

Enlarge Photo

"I think an external indicator that only shows if it is complete could be useful," suggested ActiveE driver Jon Jasperson, adding, "otherwise I do see a lot of charges getting interrupted."

Other owners, though, weighed in to disagree, saying that external lights were useful and appropriate in a large number of situations--and that they'd never experienced anyone unplugging their electric cars during a charge.

What do you think?

Should electric cars show their battery state of charge to the public at large?

Should they show only a light when the charging is complete?

Or is battery state of charge no one's business but the owner's?

Lave us your thoughts in the Comments below.


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Comments (31)
  1. I have no problem with being unplugged if I am completely full so I'd be in a favor of a light that showed that (either on the car or on the charger itself).

  2. I understand your frustation but honestly there should be a way to allow other drivers to be able to use the charger once your car is completely full, in particular if you are absent for several days.

    Some sort of valet parking, or self parking car without driver and induction plug, would be good way to solve this issue.

    What do you think?

  3. Funny this article should pop up days after my leaf was unplugged at the airport just a few hours after I had left it and with only about 70% charge. I didn't find it too funny though when I recieved the text telling me the car was unplugged. I just barely made it back home thanks to this fine individual. I can see where this person probably thought I had enough because the last light was blinking.

  4. An external indicator to show charge "Status" is meaningful. Tells if PEV is plugged-in, charging, or if charging is complete. Useful info to a casual observer.

    Showing the SoC ("State" of Charge) level is much less useful as it lacks context. Example: if only 40% SoC is desired to complete final leg of trip. What will an indicator show when this 40% SoC is reached (displayed as 100% of needed charge)? Is the driver going to stand around, or run out to car ever so often to check SoC value? What does it cost to have a detailed SoC indicator?

    Expect most drivers would appreciate the experience of having a notification (smartphone, or text msg) vs. direct observation of vehicles SoC.

  5. Showing a light is silly.

    Plus, I want other people to unplug my car EVER without first contacting me...

  6. Fob tells me SOC when I’m nearby. Phone app gives SOC and charger status from anywhere. Note on the dash tells others what time its OK to unplug my car, and my cell number if they have a question. Problem solved :)

  7. With the Tesla Model S you have tend to have enough range (minimum 150 miles to 230 to 265epa with 85KWhr) to get back home before you have to charge again so someone unplugging you at a public charging spot will be less of a problem. However with all the other EV's out there with the seemingly manufacturer agreed upon range of 75 miles or so this will mean people will want to unplug you since they will often have to charge during the day just to make it home if they have to travel more than 40 miles from their home charging unit.

  8. Awww, come on. You make it sound like you're showing your bank account balance on the windshield : )

  9. There should be at least 5 lights. The 3 of the leaf is too coarse.

  10. I think this is going to become a huge problem as e-cars become increasingly popular. For Elon to have three Superchargers between DC and Boston is fine when the New York Times is the only one trying to use them (at least two of them), but what happens when someday there are 50 Tesla S's a day on that Interstate? It's not impossible...

  11. If there is demand for charging infrastructure, someone will step up and install it.

  12. Here is an easy way to be courteous to other EV owners. Just put on your inside windshield that you will be done charging at x time and will return to PU your car for the next person. There is always a work around.

  13. Exactly - this problem was solved at least 10 years ago.

    Still, I think some sort of standardized status light (charging/charged/waiting-to-charge) would be useful.

  14. Charging station availability in the SF Bay Area has become increasingly unreliable over the past year. I leave a note (with my cellphone number) by my iMiEV's filler letting anyone in need of a charge know when they can unplug me (I usually try to get back to the car and move it by that time, anyway), and I would appreciate knowing when I can unplug someone else's car so that I can charge mine without disrupting them. Having an externally-visible SOC indicator (and, at the very least, a "full" indicator) can help those of us who NEED to charge, and I suspect would also be appreciated by owners of those cars without having to resort to smartphones. With a limited resource (charging station) we need to learn to share. PHEVs please take note.

  15. Why share it? Why NOT push for more charging stations? If we continue to share it, then they won't install anymore of them...

    Please don't discriminate against PHEVs just b/c they have an engine. You can always call a tow truck...

  16. I have not used public charging before (and so might be off with this), but my Volt sets off an alarm if its unplugged while locked. I assume this is to prevent someone from stealing my standard charger. Is this not the case with other cars?

    How about the public charger just sense when finished charging (which I'm guessing it could tell by the low flow rate), turn off (which would encourage people not to use the charger just to sustain a full charge), and indicate on the station itself when it's off, available for use, and may be unplugged?

  17. You can turn the Volt plug alarm off on the center touchscreen in the car. It will alarm if any plug (not just the portable 120V unit) is removed from the car while it is locked. I disabled the alarm on my Volt in case I am not able to immediately move it away from the charger once it is fully charged.

  18. I'm not sure all Volts can do that. I have a 2011 and have not seen that setting. I have a relative with a 2013 and there are a number of small differences like that.

  19. I don't think charge indicator layouts need to be standardized, but the meaning needs to be. The Ford charge lights are very easy to understand, but it doesn't necessarily need to be in a ring layout (could be a line of lights). At least something that is less cryptic than a Volt charge light.

    Drivers who are uncomfortable having other plugins unplug their vehicle should not be using public charging in the first place. If your car is done charging, you either have to be ok with someone unplugging it or (better yet) move your car away from the charger.

  20. What if it is on a extreme cold day and the car needs the power to keep the battery at the right temperature so its range don't drop...

    You know that temperature control is critical for BEV's range.

    Where do you draw the line?

  21. I agree with the idea you might want to keep your car plugged in to keep the battery conditioned but I don't think this is a fair use of a public station. Better you should use your 120/emergency cord for that once you've used the fast public charger to fill 'er up.

  22. Assuming this is a 120V outlet available nearby.

    Public stations are "public". It means everyone paid into it. I don't see why the BEV owners gets a "priority dip" on it. Just b/c they choose to drive a "limiting car"?

    Sure, I agree that "hogging" a place without charging is absolutely wrong. But if the car is continuing to draw power, then it is okay by me. But if the car is full and it is NOT drawing any more power from the charging station, then it should vacate the spot.

  23. @Joe Foerster,

    Also, Tesla S can't keep its battery temperature constant at -20 degree temperature plugged into a 120V outlet. A 120V is ONLY rate for 12A sustained power. That is ONLY good for a heater of 1.4KW. NOT enough when it is extreme cold.

  24. Having a Charging Status light is sufficient for public charging. The gaffe of unplugging someone who is still charging is easy enough to avoid then. I don't need to know that you're "nearly done", just that you're not done.

  25. I have a Volt, so i never *need* to charge to get home. That said, I still *want* to charge if I can, if it's convenient, and if it's cost effective. Some of the flat-rate stations I've seen are priced too high and not practical to use in my case. Nevertheless, if I'm on a longer trip it is usually cheaper and more efficient to charge when I can instead of just letting the range extender do it all. The answer is more stations, not EV drivers getting upset with PHEV drivers charging up.

  26. Exactly! That is my point. We are all here to use electricity and save gas. So, there is NO reason why one gets a priority over the other. Sure, Volt has that capability, but it is a choice. BEV chooses NOT to have that capability so it doesn't have to haul the weight around... Like I said, they can always call a tow truck...

  27. Living in Vermont where there are very few charging stations, I like the idea of a universal "Fully charged" light--i.e., a light that illuminates when the state of charge set by the driver has been attained (in the case of a LEAF, 80 or 100%). I have no problem with someone disconnecting the charger if the car is charged, and I'd like the opportunity to do the same. It will help us all maximize the usefulness of a limited number of charging stations.

  28. Does my gasoline car show how much fuel is in my tank to the public? Showing your SOC to the public is unnecessary.

  29. Let's energize cars with H2 fuel cells, beginning their use with the heating gas pipeline network, and its "natural" gas dealers.

    They don't involve unsupervised plugging in or unauthorized unpluging.

  30. That gas network exists now.

  31. The 2013 Nissan LEAF makes unplugging a moot point. It has a lockable charge port that can be set to automatically unlock when the charge is complete.

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