Spreading electric car chargers will do little good if they don't work.

Studies repeatedly show that one of the most important things needed to spread adoption of electric cars is to install more public chargers for them.

Expanding public charging infrastructure makes it more convenient to own an electric car, makes it possible for electric-car drivers to make longer trips with less range anxiety, and raises awareness of electric cars for other drivers.

CHECK OUT: What kind of public electric car charger do you rely on most often? Twitter poll results

One of the biggest complaints we hear from our electric-car driving readers, though, is the frequency with which they arrive at a public charger only to find it doesn't work.

(This is a separate problem from chargers being "ICE'd," having a gas-powered car (internal combustion engine, or ICE) parked in their designated parking space so an electric car can't park there. That problem seems more intractable.)

To get a handle on part of the problem that seems easier to solve, we decided to try to quantify the former problem—chargers that simply don't work when electric cars do park there.

Our Twitter poll this week asks: "How often do you encounter a public electric-car charger that is out of order?"

Choices include: half the time, 25 percent of the time, 10 percent of the time, or infrequently.

Previously we learned that when our electric-car driving Twitter followers use public charging, they most often use common Level 2 chargers rather than the DC fast chargers that networks are rapidly installing now.

DON'T MISS: Twitter poll results: More electric cars get charged at work than at public chargers

In another related poll, we learned that the vast majority of our followers who drive electric cars today do most of their charging at home or at work. Fewer than 10 percent relied primarily on public charging.

That could change as more public chargers—and more public DC fast chargers—come on-line. That development is expected to enable more apartment and condominium dwellers to drive electric cars. It may not happen, though, if the available public chargers aren't reliable.