PSA: EV batteries are A LOT bigger than smartphone batteries

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Zoomit

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Jun 13, 2015
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When I gave my sister her first ride in the Spark EV, the battery was low and naturally we talked about range. I plugged my smartphone into the 12v USB charger I have in the car, since the phone was low as well. My sister questioned if that was a good idea since the car was so low and she didn't want us to get stranded. I was dumbfounded with her concern as the battery sizes are about three orders of magnitude different.

My sister's lack of perspective and experience with EVs is representative of the average consumer's. So here's my Public Service Announcement about charging your smartphone with your car.

First and foremost, EV batteries are HUGE compared to anything with which the average person has experience. The Spark EV has a 18,400 Wh battery. A typical smartphone battery is about 11 Wh. The Spark EV battery stores 1,700x more energy than the phone's!

How much will charging the phone reduce the EV range? Not enough to care, but we can calculate it! Assuming an hour long drive at 4 mi/Wh efficiency, the car's drivetrain will use about 15,000 Wh. A 2.4A charger in the car will fully recharge a phone during that trip using about 11 Wh, ignoring conversion losses. The phone consumes 0.07% of the EV battery. That's equivalent to less than 250 ft of driving distance.

There are a number of factors that affect EV range that drivers should consider; such as temperature, winds, elevation changes, and driving style; but phone charging is not one of them. Charging a phone for an entire trip uses far less energy than a single, mildly-spirited, 50-Wh acceleration away from a stoplight.

If you're curious, here's the USB charger I use. I like it because it's capable (dual 2.4A) and small: http://www.amazon.com/gp/product/B00M6QODH2
 
Thanks, math is awesome!

But not all phones/usb devices can suck it up at 2.4A. So the range 'hit' is even less for them !!
 
Who's Hugh, and what does he have to do with anything?

BTW, that same argument applies to lights when comparing Halogen to LED, people assume the difference must be huge, but it's only a matter of a few feet of range...
 
Whats the output of the "cigarette lighter" outlet compared to the usb port? Is there a difference?

As a minimalist, this usb car charger looks like a great purchase. But if the factory installed usb port charges the cellphone just as fast, I'll probably just use that..
 
I don't recall exactly but I think the built-in USB port is only 0.5 or 1.0 Amps. It'll charge but it's intended to be a data interface. Most recent smartphones can charge faster using 2A.
 
Zoomit said:
... Most recent smartphones can charge faster using 2A.
Unless you have the new Nexus 5X. It can quick charge at "3A/15 watts during the middle of the SOC range", or some such language.
Kind of like my Spark EV w/DCFC (only that's at 48kW)!

I just got this phone when I went to Goggle Project Fi for my cell phone service. $20/month for smartphone service. It uses Sprint or T-Mobile or Wifi,, whichever has the best signal at the time. $10/Gb data.
 
Josy said:
But if the factory installed usb port charges the cellphone just as fast, I'll probably just use that..
One argument for using cig lighter charger is that USB connector is much more fragile. If that's broken, it could be expensive fix whereas the chance of cig lighter getting broken is much less. Also, USB port mating cycle is far less (maybe few thousand) where as cig lighter is practically infinite. Yes, I know few thousand is more than the life of the car, but the point is that USB is more fragile, thus more risk.

As for range, power coming out on USB port has to consider conversion efficiency. If car is 90% efficient, 5V/2A (10W) is going to suck 11W. But if using e-cheapo cig lighter, that may result in 50%, or whopping (!) 20W. Nothing to worry about.

But the lights could be more "substantial". At about 50W each at low power, that's 100W. At low efficiency (again, 50% as worst case), that's 200W. Assuming the worst case even when driving (it isn't), if you're driving for an hour, that's 0.2 kWh. At 5 mi/kWh at 62 MPH, that's 1 mile. By itself, it's trivial. But over the course of many miles, that's 1/62, or 1.6%. It's even smaller in the real world. "Substantial" is a subjective term.
 
I am guessing the cigarette lighter is connected to the 12 VDC battery ? Is that battery charged by the High Voltage battery ? Or by the AC charger , at the same time as the HV battery is charging from AC ?

I am guessing the Spark EV does not have a mechanical alternator to charge the 12 VDC battery ?

God bless
Wyr
 
WyrTwister said:
I am guessing the cigarette lighter is connected to the 12 VDC battery ? Is that battery charged by the High Voltage battery ? Or by the AC charger , at the same time as the HV battery is charging from AC ?

I am guessing the Spark EV does not have a mechanical alternator to charge the 12 VDC battery ?

God bless
Wyr
The aux power outlets (I don't think it actually comes with a cigarette lighter) are 12VDC. That battery is indeed charged from the high voltage battery.
 
The first thing the Spark asks when your range gets low is if you want to turn off the radio. Cracks me up!
 
SparkevBlogspot said:
One argument for using cig lighter charger is that USB connector is much more fragile. If that's broken, it could be expensive fix whereas the chance of cig lighter getting broken is much less. Also, USB port mating cycle is far less (maybe few thousand) where as cig lighter is practically infinite. Yes, I know few thousand is more than the life of the car, but the point is that USB is more fragile, thus more risk.

If you plan on using the USB port on a regular basis, I strongly recommend buying a short USB extension cable. Replace the cable when its connector wears out. You'll only have plugged into the car's port one time per cable replacement. You should do this with everything that's expensive, not just your car. I do this with my company's copy machine that prints from and scans to USB flash drives.
 
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