Safe and unsafe guerrilla electric car charging at apartment buildings

We’re now at the electric vehicle adoption stage where people are trying all kinds of crazy things. In this case, a South Africa automotive news site has posted this video giving extremely bad advice for apartment dwellers to charge their electric car. The tactic they recommend, lowering an extension cable out the window of ones apartment down four floors to the parking area – this has several problems including tripping hazards, an overloaded extension cord catching fire, and the lack of weather protection for the connectors. The apartment manager would rightly have a conniption fit seeing what this guy has done.

I’m sure their tongue was firmly planted in cheek, and this was meant to be a bit of fun. But — it’s a bad idea. I say that as someone who lives in an apartment, is on my second electric car, is no way no how going back to driving gasoline, and whose apartment manager has expressly forbidden charging at home.

That’s my situation – my EV Soul to the left under the carport, my apartment to the right, and a fire-lane in between.

Let’s go over this in a little more detail than I did above. The video below shows:

A nice rundown of the BMW i3 – 19 kiloWatt-hours of electricity costs 30 Rand, so while I don’t know the Dollar-Rand exchange rate that sounds like a small mount of money
Apartment is four floors above parking area, and his assigned space is not in a parking stall in the building but on the strip on the other side of the parking area.

The extension cord he used looks like any old cord you’d have lying around. The initial problem with this is whether that cord is designed to handle 12 amps continuous current? Presumably that portable charger he showed is designed for 240 volt 12 amps, but it might be 16 amps or more?

Ampacity – or the capacity of a copper cable to carry current

This chart shows the ability of a cable to carry current. I got this from the solar power design course I’ve taken. It shows that the cord may well be able to handle the current, because 14 gauge wire is recommended for currents up to either 15 amps (in conduit) or 20 amps (not in conduit). You’ll also see from this chart that the thicker the wire, the more current it can handle – 10 gauge wire is rated for either 30 amps (conduit) or 60 amps (no conduit).

Maybe the wire itself is suitable for the current, what about the power socket on the end? Is it also rated to handle the current? What about the power outlet in the apartment? The packaging for the extension cord should indicate its rated capacity. Exceeding the rated capacity runs the risk of overheated connectors and extension cord, and therefore a fire.

Another consideration is the length of this wire run. The longer the run the greater the voltage drop and therefore the less effective this is at charging.

Another consideration is the physical safety of a particular cord run. In my case the cord would run across the parking lot. Cars would be driving across it all day, and people could possibly trip while walking along the sidewalk in front of my apartment.

In this guy’s case, the cord is dangling down swinging in the wind. It’s draped across where cars drive to get to parking places, blocking their path. It presents a tripping hazard for anyone walking through. The cord could smack into windows or the building causing damage. Well, this is a sturdy brick building and an extension cord won’t cause damage, but what if the building were made of something else – wood siding could be damaged by an extension cord repeatedly smacking it as the wind causes the cord to swing around.

Another consideration is weather protection. The power outlet in the apartment might not be designed with ground fault protection, for example. What happens if there’s a sudden rainstorm? Does the cord short out causing a fire?

Don’t get me wrong, I’m not against doing guerrilla charging — but you must do it safely. There are ways around all those problems, in some cases. This guys specific case, and my own case, aren’t ones that lend themselves to guerrilla charging attempts. Let’s go over what would make this safer:

Study the fine print ratings on the portable charger, so you understand the continuous amp rate it runs at.
Make sure to use suitable extension cord – the thicker the better.
Make sure the connectors on each end are rated to handle the current.
You may have to chop off the connector supplied with the extension cord and install a better quality plug that’s designed for the power level.
Run the extension cord through a safe path.
If you must run the cord across a walkway, use a cord protector to limit the tripping risk.
Determine whether the indoor outlet has ground fault protection, and if it doesn’t buy an add-on ground fault protection doohickey.
120 volt charging is better than no charging.
Learn the location of all fast chargers in your vicinity.
Make sure to get fast charging support on your car — because you’ll need it.
Be willing to pay for public charging, at fast chargers.
An ideal situation are apartment complexes where your car parks next to the apartment, rather than across the parking lot.
Avoid the temptation to plug into a random power outlet you see in the carport.
Talk to your building manager about installing a regular supported charging station.

If you do the guerrilla charging thing without consulting the building manager, think about the conversation which’ll ensue when your surreptitious charging is discovered. The more effort you put into doing it safely and with consideration for others, the more chance you’ll have of surviving the encounter.

Over on VisForVoltage, I’ve written a guide on safely using an extension cord to charge an electric car. It goes into a little more detail on specific equipment you might use.

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About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.