How we improved our EV charging station sharing with HipChat, AWS and ChargePoint API

Financial Engines TechBlog
Financial Engines TechBlog
7 min readApr 3, 2016


By Alexander Yavorskiy

Have you ever noticed that there are never enough EV charging stations at work?

You probably have if you own an electric car or a hybrid. Electric vehicles and plug-in hybrids have come a long way and are steadily growing in popularity. A combination of government incentives and exemptions from carpool lane rules make them a great choice for commuters. As a result, it is a common employee perk in Silicon Valley, for a company to offer free or subsidized charging at work. However, it seems the number of available charging stations always seems to be dwarfed by the growing number of electric car drivers. Even if there are several chargers, the process around sharing the chargers between employees is never perfect and someone inevitably gets stuck without enough juice to drive home.

At Financial Engines Sunnyvale, CA headquarters, we have four charging stations managed by ChargePoint Network. At the time of this writing, there are roughly 35 EV drivers trying to get a charge on a daily basis. At first, our “sharing” process didn’t quite work. First, there was no visibility into when people plugged in and out. Our offices in Sunnyvale are far enough from the charging stations that you cannot see if there is one available at any given point. Second, not everyone bought into the whole “sharing” idea, and sometimes cars would continue to occupy the precious charging spots long after their car was fully charged.

EV Concierge to the rescue

By experimenting with various options, and with a little bit of coding and iterating, we developed a nifty system that is fun to use and works much better — so much so that on most days, by late afternoon we have chargers available and nobody is questioning that “sharing” concept anymore. We call it — EV Concierge.

EV Concierge is an automated assistant that monitors our charging session availability, manages orderly queue of drivers who need a charge and occasionally shames you into moving your car in time for others to get a charge.

How it works

At the center of the system, we have HipChat, which is already used by nearly everyone in the company for daily collaboration. We set up a dedicated room, called “EV Charging” and that is where all the magic takes place.

It all starts with an employee typing an “ev add” command to put themselves in the queue. He (let’s call him Dave) does it right there in the HipChat window, the same way he would post a short message. In response, the system will put Dave at the bottom of the queue and display a complete listing of the queue in the same HipChat window. Now Dave knows where he is on the list.

In the background, we have a monitoring process running (EV Concierge), which is communicating with ChargePoint network via XMPP protocol and listens as people plug-in and plug-out. In response to these events, EV Concierge notifies everyone in the room about a change in charger availability and also informs the next person in the queue that it is his or her turn. That is how Dave knows that it is his turn. EV Concierge will automatically remove Dave from the queue as soon as it detects that Dave has actually plugged in.

Growing feature list

Adding new features to EV Concierge and using it daily has been equally fun. There is something to be said about being able to interact with your customers and iterate on the solution on a daily basis. Iterative development does not get better than that! Since basic functionality was put in place, we enhanced EV Concierge with a number of useful features. Here is a complete list:

  1. ev add/remove/list — driver queue management
  2. ev suspend/resume — keeps your place in the queue but lets person behind you go ahead of you. This is useful when you are stuck in a meeting.
  3. ev next — calls out next person in the queue. This happens automatically when charger becomes available.
  4. Reminders:
  • When a charger is available for more than 10 minutes, EV Concierge will notify the room about precious time being wasted.
  • When a user has been charging for more than 2.5 hours, EV Concierge will (politely) ask him or her to move their car to let others partake in the experience.

In fact, EV Concierge has been getting so smart, people sometimes talk back to it, not realizing it is a robot. :-)

How we built it

If you are intrigued by this creative solution to a common workplace problem, you can build your own EV Concierge relatively easily. We are working to open source our implementation, but in the meantime, here is how to do it.

ChargePoint API

Charge Point publishes their Web Services API and it can be found here

If your company owns the chargers, most likely you have a support agreement with ChargePoint and your facilities manager has the API key that you will need to integrate with the API. There are two ways to talk to ChargePoint: SOAP API and XMPP protocol. We use a combination of both because they expose different levels of information about drivers and their sessions. In fact, the level of detail you get in the API is highly dependent on your corporate support agreement with ChargePoint and will control how sophisticated of a system you can build. If you are a Java developer, Smack API is an easy to use library for XMPP listener.

HipChat Integration

There are many ways to integrate with HipChat. For on-premise installations, you can extend HipChat with HUBOT. It is a tiny process that can listen for special words and execute commands. It uses CoffeeScript and is relatively easy to use. For cloud versions, you can use a feature called “slash” which allows you to map anything that starts with a “slash” (duh!) to a REST API call. Finally, to programmatically post messages to HipChat from EV Concierge, you can use the simple REST interface that HipChat supports out of the box. For extra fun, you can extend HipChat with custom icons and make your EV Concierge messages include some branding (or character).

If your company uses Slack, Yammer, or Google Hangouts instead of HipChat — no worries. The same type of integration can be achieved with any of these systems. The key is to try not to introduce yet another communications interface in your workplace. If you want high adoption, stick with existing tools.

Queue Persistence

This can be done in a thousand different ways, but if you have access to the AWS ecosystem, it is an obvious choice. You can use a document storage DB like AWS Dynamo, put the persistence logic in an AWS Lambda function, slap a REST interface on top of it through AWS API Gateway and be done in a day or less. This was a hackathon project, so I know for a fact that it can be done in less than a day, even if you have never heard of Lambda or Dynamo before.

EV Concierge

Finally, the heart of the logic is implemented as a standalone Java program. It loads the initial charger status via ChargePoint SOAP API on start up and then goes into listening mode for events. With every event, it keeps track of who is plugged in, who is finished and who should be notified. To make HipChat messaging personal, you will need to map ChargePoint user ids that you get through the API to your internal HipChat user ids. This will allow you to automatically manage the queue when a driver is recognized and also send direct messages using HipChat “@” feature.

EV Concierge is deployed on Amazon cloud via Elastic Beanstalk, which simplifies deployment and management of the process. One caveat to note is that we noticed that XMPP connection gets stale after prolonged use (12+ hours), so we had to build an automated restart at 6AM every morning to renew it. It works fine for us because EV Concierge can sleep at night ahead of a busy working day.


EV Concierge has been a fun little project to work on. It’s great to have a problem that is so well defined and actionable that it begs to be solved. It’s also a great feeling to build something that your fellow colleagues can use and enjoy on a daily basis. As I mentioned, since we adopted EV Concierge, many more drivers get a chance to charge and the process is much smoother and more fun for everyone. The list of proposed features is also steadily growing. Oh, if one can only find enough time…

As part of the hackathon, we put together a little presentation that describes EV Concierge in 3 minutes and shows it in action. Here is the video for your to enjoy.